A Comprehensive Review on Oxysterols and Related Diseases

Oxysterols, age-related-diseases and nutritherapy: Focus on 7-ketocholesterol and 7β-hydroxycholesterol

Age-related diseases are often associated with a disruption of RedOx balance that can lead to lipid peroxidation with the formation of oxysterols, especially those oxidized on carbon-7: 7-ketocholesterol (also known as 7-oxo-cholesterol) and 7β-hydroxycholesterol. Like cholesterol, these oxysterols have 27 carbons, they are composed of a sterane nucleus and have a hydroxyl function in position 3. The oxysterols 7-ketocholesterol and 7β-hydroxycholesterol are mainly formed by cholesterol autoxidation and are biomarkers of oxidative stress. These two oxysterols are frequently found at increased levels in the biological fluids (plasma, cerebrospinal fluid), tissues and/or organs (arterial wall, retina, brain) of patients with age-related diseases, especially cardiovascular diseases, neurodegenerative diseases (mainly Alzheimer's disease), ocular diseases (cataract, age-related macular degeneration), and sarcopenia. Depending on the cell type considered, 7-ketocholesterol and 7β-hydroxycholesterol induce either caspase- dependent or -independent types of cell death associated with mitochondrial and peroxisomal dysfunctions, autophagy and oxidative stress. The caspase dependent type of cell death associated with oxidative stress and autophagy is defined as oxiapoptophagy. These two oxysterols are also inducers of inflammation. These biological features associated with the toxicity of 7-ketocholesterol, and 7β-hydroxycholesterol are often observed in patients with age-related diseases, suggesting an involvement of these oxysterols in the pathophysiology of these disorders. The cytotoxic effects of 7-ketocholesterol and 7β-hydroxycholesterol are counteracted on different cell models by representative nutrients of the Mediterranean diet: ω3 and ω9 fatty acids, polyphenols, and tocopherols. There are also evidences, mainly in cardiovascular diseases, of the benefits of α-tocopherol and phenolic compounds. These in vitro and in vivo observations on 7-ketocholesterol and 7β-hydroxycholesterol, which are frequently increased in age-related diseases, reinforce the interest of nutritherapeutic treatments to prevent and/or cure age-related diseases currently without effective therapies.

Oxysterols Modulate Protein-Sterol Interactions to Impair CXCR4 Signaling in Aging Cells

Organismal aging is accompanied by the accumulation of senescent cells in the body, which drives tissue dysfunction. Senescent cells have a distinctive profile, including proliferation arrest, resistance to apoptosis, altered gene expression, and high inflammation. Despite global signaling and metabolic dysregulation during senescence, the underlying reasons for changes in signaling remain unclear. GPCRs are pivotal in cellular signaling, dynamically mediating the complex interplay between cells and their surrounding environment to maintain cellular homeostasis. The chemokine receptor CXCR4 plays a crucial role in modulating immune responses and inflammation. It has been shown that the expression of CXCR4 increases in cells undergoing senescence, which enhances inflammation postactivation. Here, we examine CXCR4 signaling in deeply senescent cells (aged cells), where cholesterol and its oxidized derivatives, oxysterols, affect receptor function. We report elevated oxysterol levels in senescent cells, which altered classical CXCL12-mediated CXCR4 signaling. Tail-oxidized sterols disrupted signaling more than ring-oxidized counterparts. Molecular dynamics simulations revealed that 27-hydroxycholesterol displaces cholesterol and binds strongly to alter the conformation of critical signaling residues, modifying the sterol-CXCR4 interaction landscape. Our study provides a molecular view of the observed mitigated GPCR signaling in the presence of oxysterols, which switched G-protein signaling from Gαi/o to Gαs class. Overall, we present an altered paradigm of GPCR signaling, where cholesterol oxidation alters the signaling outcome in aged cells.

Nutritional Status Is Associated with Mortality but Not Appropriate Discharge of Implantable Cardioverter Defibrillators in Patients with Heart Failure

Objective: To investigate the predictive value of nutritional status in heart failure (HF) patients with an implantable cardioverter defibrillator (ICD), and to identify factors associated with ICD discharge and mortality. Methods: This retrospective study was conducted by analyzing data from 2017 to 2021. HF patients who underwent ICD implantation for primary prevention were included. Follow-up visits were continued until December 2022. Patients were examined based on ICD shock occurrence (ICD-A: appropriate shock), ICD non-discharge (ICD-X), and mortality. Nutritional status was assessed by the Prognostic Nutritional Index (PNI) and the Controlling Nutritional Status (CONUT) scores. Results: A total of 221 patients were included in the study, 86 of whom were in the ICD-A group (135 in the ICD-X group). Age and sex distribution were similar in these groups. The all-cause mortality rate was 20.36%. A PNI with a cut-off value of <47.25 and a CONUT score with a cut-off value of >2.5 were able to significantly predict all-cause mortality. The PNI had a greater area under the curve compared to the CONUT. Non-ischemic cardiomyopathy and high left-ventricle end-systolic diameter (ESD) were independently associated with appropriate ICD shock. Low systolic blood pressure, high ESD, low sodium, low total cholesterol, low (<47.25) PNI, and ICD shock were independently associated with all-cause mortality. Conclusions: Malnutrition appears to be associated with mortality in patients with primary-prevention ICDs, and the PNI appears to be a more useful indicator than the CONUT for determining the risk of mortality in these patients.

Major heme proteins hemoglobin and myoglobin with respect to their roles in oxidative stress - a brief review

Oxidative stress is considered as the root-cause of different pathological conditions. Transition metals, because of their redox-active states, are capable of free radical generation contributing oxidative stress. Hemoglobin and myoglobin are two major heme proteins, involved in oxygen transport and oxygen storage, respectively. Heme prosthetic group of heme proteins is a good reservoir of iron, the most abundant transition metal in human body. Although iron is tightly bound in the heme pocket of these proteins, it is liberated under specific circumstances yielding free ferrous iron. This active iron can react with H2O2, a secondary metabolite, forming hydroxyl radical via Fenton reaction. Hydroxyl radical is the most harmful free radical among all the reactive oxygen species. It causes oxidative stress by damaging lipid membranes, proteins and nucleic acids, activating inflammatory pathways and altering membrane channels, resulting disease conditions. In this review, we have discussed how heme-irons of hemoglobin and myoglobin can promote oxidative stress under different pathophysiological conditions including metabolic syndrome, diabetes, cardiovascular, neurodegenerative and renal diseases. Understanding the association of heme proteins to oxidative stress may be important for knowing the complications as well as therapeutic management of different pathological conditions.

The relationship of ulnar variance with pathologies detected by magnetic resonance imaging in patients with chronic or subacute wrist pain

Background

This study aims to determine whether ulnar variance (UV) types are associated with chronic or subacute ulnar-side wrist pain using 3 Tesla (T) magnetic resonance imaging (MRI), and to investigate potential relationships between UV, clinical data, and MRI-detected findings.

Methods

This retrospective study included patients who presented with ulnar-side wrist pain for at least one month and underwent 3T MRI between January 2020 and October 2023. All demographic and clinical data, wrist radiography, and MRI images were obtained from computerized records. The patients were classified as having neutral-UV, negative-UV, and positive-UV.

Results

In total, 272 patients were included in the analysis. Mean age was 40.57 ± 13.18 years and 63.60% (n = 173) of the subjects were female. Neutral UV was detected in 147 (54.04%) patients, negative UV in 106 (38.97%), and positive UV in 19 (6.99%). Patients in the negative-UV group were significantly younger than those in the neutral-UV and positive-UV groups (p = 0.013); however, the sex distribution was similar in all groups (p = 0.653). All patients with ulnar impingement were in the negative-UV group, whereas all subjects with ulnar impaction were in the positive-UV group (p < 0.001). Finally, triangular fibrocartilage complex (TFCC) ruptures were significantly more common in the positive-UV group (p = 0.023).

Conclusion

There is a significant relationship between UV changes and ulnar impingement syndrome, ulnar impaction syndrome, and TFCC tears, which can be easily detected by MRI. The previously reported relationships between UV, sex, and other pathologies were not supported by our findings.

Interactions of sphingomyelin with biologically crucial side chain-hydroxylated cholesterol derivatives

Oxysterols are interesting molecules due to their dual nature, reflecting beneficial and harmful effects on the body. An issue that still needs to be solved is how slight modification of their structure owing to the location of the additional polar group in the molecules affects their biological activity. With this in mind, we selected three side chain-hydroxylated oxysterols namely: 20(S)-hydroxycholesterol (20(S)-OH), 24(S)-hydroxycholesterol (24(S)-OH), and 27-hydroxycholesterol (27-OH), and examined their behavior in mixtures with the bioactive sphingolipid - sphingomyelin (SM). Our research was based on the Langmuir monolayer technique supplemented with molecular dynamics (MD) and microscopic observation of the films texture (Brewster angle microscopy, BAM, and atomic force microscopy, AFM). Additionally, since 20(S)-hydroxycholesterol has not been studied so far, we thoroughly characterized this oxysterol in one-component monolayers. Our studies showed differences in the interactions of the studied oxysterols and sphingomyelin. Namely, it was found that 20(S)-OH binds to SM, unlike 24(S)-OH and 27-OH, which both weakly interact with SM. This distinct behavior was interpreted within the molecular dynamics as being due to weak intermolecular interactions between 20(S)-OH molecules, which allowed easy incorporation of SM into the 20(S)-OH monolayer. In contrast, the strong oxysterol-oxysterol interactions occurring in monolayers with 24(S)-OH or 27-OH make this process more difficult. This may be important in the process of bone formation/resorption. Other aspects derived from our study are: (i) the tendency of oxysterols to incorporate into lipid rafts (leading to their modification in structure and function), as well as (ii) the formation of multilayer structures, in which oxysterols are arranged in the characteristic forms of "strings of beads", which may facilitate their transport across the membrane.

Impact of Anemia and Acquired Anemia on in-Hospital Mortality of Acute Coronary Syndrome Patients

Objective

To investigate the associations of anemia-related parameters, with in-hospital mortality after acute coronary syndrome (ACS), as well as factors associated with prior anemia (PA) and hospital-acquired anemia (HAA) in patients with ACS.

Methods

This was a retrospective cohort study conducted between June 2021 and May 2023. The data of patients diagnosed with ACS who were hospitalized and treated in our hospital were recorded, including age and sex, smoking and comorbidity status, laboratory findings, CHA2DS2-VASc scores, prior medication use, left ventricular ejection fraction, ACS type, the synergy between percutaneous intervention with taxus drug-eluting stents and cardiac surgery (SYNTAX) scores, stent thrombosis status and mortality status. Mortality was assessed according to in-hospital death. Patients were grouped based on anemia presence (PA and HAA).

Results

A total of 329 patients were included in the study. Of these, 219 (66.56%) were in the no anemia group, 58 (17.63%) in the PA group, and 52 (15.81%) in the HAA group. The mean age of all participants was 61.27±12.45 years and 76.29% of them were male. 14 (4.26%) patients died during hospitalization. Multivariable logistic regression analysis had revealed that, prior coronary artery disease (OR: 3.779, 95% CI: 1.141-12.508, p=0.030), PA (OR: 7.043, 95% CI: 1.574-31.517, p = 0.011), HAA (OR: 5.857, 95% CI: 1.260-27.236, p=0.024) and high WBC (OR: 1.190, 95% CI: 1.028-1.378, p=0.020) were independently associated with the increased risk of in-hospital mortality.

Conclusion

Consequently, the risk of in-hospital mortality is higher in patients with a previous history of coronary artery disease, PA, HAA and high WBC, and additional precautions should be taken in these patients.

The Uric Acid-to-High-Density Lipoprotein Cholesterol Ratio: A New Biomarker for Predicting Arrhythmia Recurrence After Atrial Fibrillation Ablation

Background: We aimed to assess the uric acid-to-high-density lipoprotein cholesterol (HDL-C) ratio (UHR) and several other parameters with respect to their performance in detecting recurrence among patients with atrial fibrillation (AF) who underwent ablation. Methods: This retrospective cohort study analyzed data from patients who underwent radiofrequency or cryoablation for paroxysmal, persistent, or long persistent AF between September 2021 and September 2023. After ablation, patients were monitored for 24 h, with an ECG Holter used for symptomatic cases. Follow-up visits occurred at 1, 3, and 12 months. Collected data included demographics, comorbidities, echocardiographic measurements, clinical data, ablation type, medication use, and a comprehensive set of laboratory findings. Results: The study included 163 patients, with AF recurrence in 39 (23.93%) patients. Mean age was 57.49 ± 11.22 years, and 59.51% of participants were male. There was no significant difference between recurrent and non-recurrent groups in terms of age or sex distribution. Univariate analysis showed that recurrent patients had significantly larger left atrium diameter, higher percentages of persistent/long AF, and elevated levels of CRP, uric acid, UHR, and uric acid-to-creatinine ratio (UCR). Logistic regression analysis revealed that high left atrium diameter, long persistent AF presence, high CRP and uric acid levels, and high UCR and UHR values greater than 15.1 were independent predictors of AF recurrence. A UHR value of >15.1 was found to predict recurrence with 61.54% sensitivity and 70.97% specificity. Conclusions: Despite low sensitivity, UHR appears to be an independent biomarker that can predict AF recurrence. Including UHR in future risk assessment tools may be beneficial to enhance their accuracy.

Isoflavones obtained from red clover improve both dyslipidemia and menopausal symptoms in menopausal women: a prospective randomized placebo-controlled trial

OBJECTIVE

This study aimed to investigate the effects of red clover isoflavones on menopausal symptoms and the lipid profile in menopausal females.

METHODS

This study included postmenopausal women with dyslipidemia. The red clover group (n = 39) received 40 mg isoflavone red clover capsule twice daily for 6 months, while placebo (n = 36) was 40 mg starch capsule twice daily. Data were collected at baseline, 3 months and 6 months. The Menopause Rating Scale (MRS) was applied to calculate subdimension and total scores.

RESULTS

The two groups were similar in terms of age, MRS and lipid profile at baseline. In the red clover group, MRS scores decreased significantly at both 3 and 6 months. Similarly, total cholesterol, low-density lipoprotein cholesterol (LDL-C) and triglyceride levels decreased at both 3 months and 6 months. High-density lipoprotein cholesterol increased significantly from baseline to 3 months and 6 months. Except for LDL-C and MRS urogenital score at 3 months, the improvements were significantly in favor of red clover isoflavone treatment.

CONCLUSIONS

Red clover treatment for 3-6 months demonstrated significant improvements in lipid profiles and menopausal symptoms. While promising, further research is crucial to ascertain long-term safety and recommend the use of red clover isoflavones during menopause.

Lipidomic profiling in patients with familial hypercholesterolemia: Abnormalities in glycerolipids and oxysterols

OBJECTIVES AND AIM

This study aimed to identify precise biomarkers and develop targeted therapeutic strategies for preventing premature atherosclerotic cardiovascular disease in patients with familial hypercholesterolemia (FH) by investigating the quantitative and qualitative abnormalities in the metabolic network of lipids in these patients using an advanced lipidomics platform.

DESIGN & METHODS

The study population comprised 18 homozygous (HoFH), 18 heterozygous (HeFH) FH patients, and 20 healthy controls. Cholesterol oxidation products (oxysterol, COPs) and main lipid classes were determined using gas chromatography-mass spectrometry. Results were expressed as percentages of total fat matter for lipid classes and percentages of total COPs for oxysterols. The principal component analysis (PCA) was also carried out, to highlight the correlation between studied parameters and groups investigated.

RESULTS

Patients (both HoFH and HeFH) showed lower content of free fatty acids (FFAs) and greater values of triacylglycerols (TAGs) in comparison to controls. HoFH showed lower monoacylglycerols (P<0.01) and higher free cholesterol (FC) (P<0.05) when compared to HeFH and controls. The total content of COPs ranged from 1.96 to 4.25 mg/dL, from 2.27 to 4.05 mg/dL, and from 0.79 to 4.12 mg/dL in healthy controls, HoFH and HeFH groups, respectively, with no significant differences between patients and controls. In general, the 7α-hydroxycholesterol (7α-HC) was greater than other COPs. However, no significant differences were found between the three studied groups. Moreover, an opposite trend was observed between 7α-HC and 7-ketocholesterol (7-KC). Additionally, when PCA was carried out, the first two PCs explained 92.13 % of the total variance, of which the PC1 describes 53.94 % of variance mainly correlated to TAGs, diacylglycerols (DAGs), and 7-KC. On the other hand, the PC2 was correlated primarily for FFAs, FC and esterified sterols (E-STE).

CONCLUSIONS

In conclusion, abnormal levels of TAGs, DAGs and 7-KC were associated with HeFH while HoFH was associated with the abnormal amount of E-STE.

The Effect of Local Papaverine Use in an Experimental High-Risk Colonic Anastomosis Model: Reduced Inflammatory Findings and Less Necrosis

Objectives: To assess the impact of topical papaverine administration in complete and incomplete colonic anastomosis, by examining bursting pressure, hydroxyproline concentration, collagen content, inflammation levels, inflammatory cell infiltration, neoangiogenesis, and necrosis grades. Methods: We performed an experimental study on rats, in which they were divided into the following 4 groups of 16 subjects each. Group 1 [complete anastomosis (CA) without papaverine (CA -P) group], Group 2 [CA with papaverine (CA +P) group], Group 3 [incomplete anastomosis (ICA) without papaverine (ICA -P) group], and Group 4 [ICA with papaverine (ICA +P) group]. Results: The lymphocyte infiltration score of the ICA +P3 (day 3) group was significantly higher compared to the ICA -P3 group (p = 0.018). The median Ehrlich-Hunt score (p = 0.012), inflammation score (p = 0.026), and neutrophil infiltration score (p = 0.041) of the CA +P7 (day 7) group were significantly lower than the corresponding data of the CA -P7 group. Additionally, the necrosis score of the ICA +P7 group was significantly lower than that of the ICA -P7 group (p = 0.014). Conclusions: Data from the current study reveal that, although topical papaverine seems to suppress inflammation in anastomosis tissue and reduce necrosis at 7 days, definite conclusions regarding its impact on anastomotic leak cannot be drawn without further studies investigating anastomotic wound healing and anastomotic leak, preferably with both shorter- and longer-term evaluations.

Impact of Methylated Cyclodextrin KLEPTOSE® CRYSMEB on Inflammatory Responses in Human In Vitro Models

KLEPTOSE® CRYSMEB methylated cyclodextrin derivative displays less methylated group substitution than randomly methylated cyclodextrin. It has demonstrated an impact on atherosclerosis and neurological diseases, linked in part to cholesterol complexation and immune response, however, its impact on inflammatory cascade pathways is not clear. Thus, the impact of KLEPTOSE® CRYSMEB on various pharmacological targets was assessed using human umbilical vein endothelial cells under physiological and inflammatory conditions, followed by screening against twelve human primary cell-based systems designed to model complex human tissue and disease biology of the vasculature, skin, lung, and inflammatory tissues using the BioMAP® Diversity PLUS® panel. Finally, its anti-inflammatory mechanism was investigated on peripheral blood mononuclear cells to evaluate anti-inflammatory or pro-resolving properties. The results showed that KLEPTOSE® CRYSMEB can modulate the immune system in vitro and potentially manage vascular issues by stimulating the expression of molecules involved in the crosstalk between immune cells and other cell types. It showed anti-inflammatory effects that were driven by the inhibition of pro-inflammatory cytokine secretion and could have different impacts on different tissue types. Moreover, this cyclodextrin showed no clear impact on pro-resolving lipid mediators. Additionally, it appeared that the mechanism of action of KLEPTOSE® CRYSMEB seems to not be shared by other well-known anti-inflammatory molecules. Finally, KLEPTOSE® CRYSMEB may have an anti-inflammatory impact, which could be due to its effect on receptors such as TLR or direct complexation with LPS or PGE2, and conversely, this methylated cyclodextrin could stimulate a pro-inflammatory response involving lipid mediators and on proteins involved in communication with immune cells, probably via interaction with membrane cholesterol.

Gout and erectile dysfunction: Increased carotid intima-media thickness is independently associated with greater likelihood for erectile dysfunction

Objectives

The study aimed to compare gout patients and healthy subjects in terms of erectile dysfunction, carotid intima-media thickness (CIMT), and other variables and to investigate the relationship between CIMT and erectile dysfunction.

Patients and methods

This cross-sectional study was conducted with 134 male gout patients (median age: 56 years; range, 48 to 62 years) and 104 healthy males (median age: 47 years; range, 40.5 to 54.5 years) between September 2022 and June 2023. Age, comorbidities, height, weight, laboratory results, gout treatment data, insulin resistance evaluated by the homeostatic model assessment for insulin resistance, presence and severity of erectile dysfunction evaluated by the six-item International Index of Erectile Function erectile function domain (IIEF-EF), and CIMT measured by ultrasound were assessed.

Results

Hypertension, hyperlipidemia, greater insulin resistance, erectile dysfunction, and bilaterally increased CIMT were significantly more common in the gout group. The mean IIEF-EF score of gout patients was significantly lower than that of controls. Multivariable logistic regression revealed increased CIMT as the sole parameter independently associated with erectile dysfunction (p=0.010). When both groups were categorized into CIMT-based subsets, erectile dysfunction was present in 97.9% of patients with coexistence of gout and increased CIMT (≥0.9 mm), a significantly higher proportion compared to the other three subsets (p<0.001).

Conclusion

Increased CIMT was the only factor independently associated with a greater likelihood of erectile dysfunction in patients with and without gout; however, coexistence of gout and increased CIMT appears to result in a significantly elevated risk for erectile dysfunction.

Oxidized Cholesterol Derivatives in Fraction B Prepared from Gulf Catfish (Arius bilineatus, Val.) Skin Regulate Calcium Response and Neutrophil Extracellular Traps (NETs) Formation

In this study, we present in vitro actions of pure commercial preparations of oxidized and/or dehydrated metabolites of cholesterol (OS) identified in the lipid fraction of Fraction B (FB) prepared from a catfish skin preparation on calcium transients and on the formation of human neutrophil extracellular traps (NETs). These investigations are part of an ongoing effort to understand the important roles these compounds play as components of FB when FB is applied to accelerate the healing of wounds and the healing of highly infected non-healing diabetic foot ulcers, without the use of antibiotics. Our aim was to determine potential therapeutic interventions for various disease states. Our results reveal interesting findings, demonstrating specific actions of the individual compounds. Compounds 7α-hydroxy-cholesterol (S3), Cholestane-3,5,6-triol (S5), 5-cholesten-3β-ol-7-one (S8) and Cholesta-3,5 dien-7-one (S10) are inhibitory, while Cholesterol 5β,6β-epoxide (S4) and 5α-cholestane-3,6-dione (S11) activate the response for calcium influx in human neutrophils. A somewhat similar response is observed in dHL60 cell lines, where S3, S5, S7, S8, and cholesta-2,4-diene (S14) inhibit the calcium influx, although S4, S10, and S11 activate the response in this cell line. Furthermore, we observed a relationship between actions against NETosis and calcium transients. Interestingly, relative to the vehicle control, S3, Cholesta-3,5 diene (S9), and S14 appeared to significantly stimulate DNA release (NETosis), while S2, 7α-hydroxy-cholesterol (S6) and cholesta-3,5 dien-7-one (S10) caused lesser stimulation. We provide the IC50 activities for each compound tested in each assay. Calcium influx and NETs formation (NETosis) correlate with diseases exacerbation. These findings offer valuable insights into the potential therapeutic applications of individual OS for various diseases, highlighting their importance in future interventions.

Evaluation of Sarcopenia in Patients with Monoclonal Gammopathy of Undetermined Significance

Background: We aimed to determine the prevalence of sarcopenia in patients with monoclonal gammopathy of undetermined significance (MGUS) and to evaluate the links between MGUS and sarcopenia. Methods: Eighty-two patients with a diagnosis of MGUS were enrolled in the study. Muscle strength was measured using the handgrip dynamometer. Physical performance was assessed by assessing gait speed over a 6-minute walking test. Muscle mass was determined using a bioelectrical impedance analyzer. Results: Sarcopenia was confirmed in 34.15% of patients. Male predominance was demonstrated in MGUS subjects with sarcopenia, particularly patients with low hand grip strength, low appendicular skeletal muscle mass (ASMM), or low ASMM index (p < 0.001, 0.013, and 0.001, respectively). Higher age and lower serum free light-chain Lambda levels were shown in MGUS patients with low muscle function scores compared to normal scores (p < 0.001, and 0.014, respectively). In addition, having a low ASMM score was related to low body mass index and high-risk group (p = 0.020, 0.033, respectively). Conclusions: We demonstrated that the frequency of sarcopenia is high in patients with MGUS. Whether sarcopenia has a possible role as a factor contributing to the pathogenesis of MGUS should be supported by further studies containing longitudinal data.

Outcomes of Mulligan Concept Applications in Obese Individuals with Chronic Mechanical Low Back Pain: A Randomized Controlled Trial

BACKGROUND

Various treatment modalities have been employed for mechanical low back pain (MLBP), but evidence of their efficacy varies greatly. Objectıve: This randomized controlled trial aimed to assess the outcomes of Mulligan concept applications, including sustained natural apophyseal glides (SNAGS) and natural apophyseal glides (NAGS), in obese patients with MLBP.

METHODS

The study, conducted between January 2021 and June 2022 at a tertiary hospital, involved randomizing patients into two groups. Both groups underwent six sessions of stretching and strengthening exercises every other day. The Mulligan group received additional intervention with SNAG and NAGS techniques. Measurements were made regarding the Visual Analog Scale (VAS) score, Oswestry Disability Index (ODI) score and range of motion (ROM) for the patients' MLBP level.

RESULTS

Post-interventions, both groups exhibited positive changes in flexion ROM, extension ROM, right and left rotation ROM, right and left lateral flexion ROM, VAS score, and ODI score compared to pre-intervention (p < 0.001 for both groups and variables). The Mulligan group showed a higher increase in ROM and a more significant decrease in VAS and ODI scores. Conclusıons: Mulligan mobilization techniques prove significantly beneficial for enhancing ROM in all directions, reducing pain levels, and alleviating disability in obese individuals with MLBP.

Molecular mechanism of renal lipid accumulation in diabetic kidney disease

Diabetic kidney disease (DKD) is a leading cause of end stage renal disease with unmet clinical demands for treatment. Lipids are essential for cell survival; however, renal cells have limited capability to metabolize overloaded lipids. Dyslipidaemia is common in DKD patients and renal ectopic lipid accumulation is associated with disease progression. Unveiling the molecular mechanism involved in renal lipid regulation is crucial for exploring potential therapeutic targets. In this review, we focused on the mechanism underlying cholesterol, oxysterol and fatty acid metabolism disorder in the context of DKD. Specific regulators of lipid accumulation in different kidney compartment and TREM2 macrophages, a lipid-related macrophages in DKD, were discussed. The role of sodium-glucose transporter 2 inhibitors in improving renal lipid accumulation was summarized.

Cholestane-3β,5α,6β-triol Induces Multiple Cell Death in A549 Cells via ER Stress and Autophagy Activation

Cholestane-3β,5α,6β-triol (CT) and its analogues are abundant in natural sources and are reported to demonstrate cytotoxicity toward different kinds of tumor cells without a deep probe into their mechanism of action. CT is also one of the major metabolic oxysterols of cholesterol in mammals and is found to accumulate in various diseases. An extensive exploration of the biological roles of CT over the past few decades has established its identity as an apoptosis inducer. In this study, the effects of CT on A549 cell death were investigated through cell viability assays. RNA-sequencing analysis and western blot of CT-treated A549 cells revealed the role of CT in inducing endoplasmic reticulum (ER) stress response and enhancing autophagy flux, suggesting a putative mechanism of CT-induced cell-death activation involving reactive oxygen species (ROS)-mediated ER stress and autophagy. It is reported for the first time that the upregulation of autophagy induced by CT can serve as a cellular cytotoxicity response in accelerating CT-induced cell death in A549 cells. This research provides evidence for the effect of CT as an oxysterol in cell response to oxidative damage and allows for a deep understanding of cholesterol in its response in an oxidative stress environment that commonly occurs in the progression of various diseases.

Adipose tissue peroxisomal lipid synthesis orchestrates obesity and insulin resistance through LXR-dependent lipogenesis

OBJECTIVE

Adipose tissue mass is maintained by a balance between lipolysis and lipid storage. The contribution of adipose tissue lipogenesis to fat mass, especially in the setting of high-fat feeding, is considered minor. Here we investigated the effect of adipose-specific inactivation of the peroxisomal lipid synthetic protein PexRAP on fatty acid synthase (FASN)-mediated lipogenesis and its impact on adiposity and metabolic homeostasis.

METHODS

To explore the role of PexRAP in adipose tissue, we metabolically phenotyped mice with adipose-specific knockout of PexRAP. Bulk RNA sequencing was used to determine transcriptomic responses to PexRAP deletion and 14C-malonyl CoA allowed us to measure de novo lipogenic activity in adipose tissue of these mice. In vitro cell culture models were used to elucidate the mechanism of cellular responses to PexRAP deletion.

RESULTS

Adipose-specific PexRAP deletion promoted diet-induced obesity and insulin resistance through activation of de novo lipogenesis. Mechanistically, PexRAP inactivation inhibited the flux of carbons to ethanolamine plasmalogens. This increased the nuclear PC/PE ratio and promoted cholesterol mislocalization, resulting in activation of liver X receptor (LXR), a nuclear receptor known to be activated by increased intracellular cholesterol. LXR activation led to increased expression of the phospholipid remodeling enzyme LPCAT3 and induced FASN-mediated lipogenesis, which promoted diet-induced obesity and insulin resistance.

CONCLUSIONS

These studies reveal an unexpected role for peroxisome-derived lipids in regulating LXR-dependent lipogenesis and suggest that activation of lipogenesis, combined with dietary lipid overload, exacerbates obesity and metabolic dysregulation.

The Chemical Reactivity of Membrane Lipids

It is well-known that aqueous dispersions of phospholipids spontaneously assemble into bilayer structures. These structures have numerous applications across chemistry and materials science and form the fundamental structural unit of the biological membrane. The particular environment of the lipid bilayer, with a water-poor low dielectric core surrounded by a more polar and better hydrated interfacial region, gives the membrane particular biophysical and physicochemical properties and presents a unique environment for chemical reactions to occur. Many different types of molecule spanning a range of sizes, from dissolved gases through small organics to proteins, are able to interact with membranes and promote chemical changes to lipids that subsequently affect the physicochemical properties of the bilayer. This Review describes the chemical reactivity exhibited by lipids in their membrane form, with an emphasis on conditions where the lipids are well hydrated in the form of bilayers. Key topics include the following: lytic reactions of glyceryl esters, including hydrolysis, aminolysis, and transesterification; oxidation reactions of alkenes in unsaturated fatty acids and sterols, including autoxidation and oxidation by singlet oxygen; reactivity of headgroups, particularly with reactive carbonyl species; and E/Z isomerization of alkenes. The consequences of reactivity for biological activity and biophysical properties are also discussed.

Cytoprotective effects of α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol on 7-ketocholesterol - Induced oxiapoptophagy: Major roles of PI3-K / PDK-1 / Akt signaling pathway and glutathione peroxidase activity in cell rescue

On murine N2a cells, 7-ketocholesterol induced an oxiapotophagic mode of cell death characterized by oxidative stress (reactive oxygen species overproduction on whole cells and at the mitochondrial level; lipid peroxidation), apoptosis induction (caspase-9, -3 and -7 cleavage, PARP degradation) and autophagy (increased ratio LC3-II / LC3-I). Oxidative stress was strongly attenuated by diphenyleneiodonium chloride which inhibits NAD(P)H oxidase. Mitochondrial and peroxisomal morphological and functional changes were also observed. Down regulation of PDK1 / Akt signaling pathways as well as of GSK3 / Mcl-1 and Nrf2 pathways were simultaneously observed in 7-ketocholesterol-induced oxiapoptophagy. These events were prevented by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by LY-294002, a PI3-K inhibitor, demonstrated an essential role of PI3-K in cell rescue. The rupture of oxidative stress in 7-ketocholesterol-induced oxiapoptophagy was also associated with important modifications of glutathione peroxidase, superoxide dismutase and catalase activities as well as of glutathione peroxidase-1, superoxide dismutase-1 and catalase level and expression. These events were also counteracted by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by mercaptosuccinic acid, a glutathione peroxidase inhibitor, showed an essential role of this enzyme in cell rescue. Altogether, our data support that the reactivation of PI3-K and glutathione peroxidase activities by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol are essential to prevent 7KC-induced oxiapoptophagy.

Impact of Oxysterols in Age-Related Disorders and Strategies to Alleviate Adverse Effects

Oxysterols or cholesterol oxidation products are a class of molecules with the sterol moiety, derived from oxidative reaction of cholesterol through enzymatic and non-enzymatic processes. They are widely reported in animal-origin foods and prove significant involvement in the regulation of cholesterol homeostasis, lipid transport, cellular signaling, and other physiological processes. Reports of oxysterol-mediated cytotoxicity are in abundance and thus consequently implicated in several age-related and lifestyle disorders such as cardiovascular diseases, bone disorders, pancreatic disorders, age-related macular degeneration, cataract, neurodegenerative disorders such as Alzheimer's and Parkinson's disease, and some types of cancers. In this chapter, we attempt to review a selection of physiologically relevant oxysterols, with a focus on their formation, properties, and roles in health and disease, while also delving into the potential of natural and synthetic molecules along with bacterial enzymes for mitigating oxysterol-mediated cell damage.

Oxysterols as Biomarkers of Aging and Disease

Oxysterols derive from either enzymatic or non-enzymatic oxidation of cholesterol. Even though they are produced as intermediates of bile acid synthesis pathway, they are recognised as bioactive compounds in cellular processes. Therefore, their absence or accumulation have been shown to be associated with disease phenotypes. This chapter discusses the contribution of oxysterol to ageing, age-related diseases such as neurodegeneration and various disorders such as cancer, cardiovascular disease, diabetes, metabolic and ocular disorders. It is clear that oxysterols play a significant role in development and progression of these diseases. As a result, oxysterols are being investigated as suitable markers for disease diagnosis purposes and some drug targets are in development targeting oxysterol pathways. However, further research will be needed to confirm the suitability of these potentials.

Therapeutic Applications of Oxysterols and Derivatives in Age-Related Diseases, Infectious and Inflammatory Diseases, and Cancers

Oxysterols, resulting from the oxidation of cholesterol, are formed either by autoxidation, enzymatically, or by both processes. These molecules, which are provided in more or less important quantities depending on the type of diet, are also formed in the body and their presence is associated with a normal physiological activity. Their increase and decrease at the cellular level and in biological fluids can have significant consequences on health due or not to the interaction of some of these molecules with different types of receptors but also because oxysterols are involved in the regulation of RedOx balance, cytokinic and non-cytokinic inflammation, lipid metabolism, and induction of cell death. Currently, various pathologies such as age-related diseases, inflammatory and infectious diseases, and several cancers are associated with abnormal levels of oxysterols. Due to the important biological activities of oxysterols, their interaction with several receptors and their very likely implications in several diseases, this review focuses on these molecules and on oxysterol derivatives, which are often more efficient, in a therapeutic context. Currently, several oxysterol derivatives are developed and are attracting a lot of interest.

In Vitro Evaluation of the Effects of 7-Ketocholesterol and 7β-Hydroxycholesterol on the Peroxisomal Status: Prevention of Peroxisomal Damages and Concept of Pexotherapy

7-Ketocholesterol and 7β-hydroxycholesterol are most often derived from the autoxidation of cholesterol. Their quantities are often increased in the body fluids and/or diseased organs of patients with age-related diseases such as cardiovascular diseases, Alzheimer's disease, age-related macular degeneration, and sarcopenia which are frequently associated with a rupture of RedOx homeostasis leading to a high oxidative stress contributing to cell and tissue damages. On murine cells from the central nervous system (158N oligodendrocytes, microglial BV-2 cells, and neuronal N2a cells) as well as on C2C12 murine myoblasts, these two oxysterols can induce a mode of cell death which is associated with qualitative, quantitative, and functional modifications of the peroxisome. These changes can be revealed by fluorescence microscopy (apotome, confocal microscopy), transmission electron microscopy, flow cytometry, quantitative reverse transcription polymerase chain reaction (RT-qPCR), and gas chromatography-coupled with mass spectrometry (GC-MS). Noteworthy, several natural molecules, including ω3 fatty acids, polyphenols, and α-tocopherol, as well as several Mediterranean oils [argan and olive oils, Milk-thistle (Sylibum marianum) and Pistacia lenticus seed oils], have cytoprotective properties and attenuate 7-ketocholesterol- and 7β-hydroxycholesterol-induced peroxisomal modifications. These observations led to the concept of pexotherapy.

Role of Oxysterols in Ocular Degeneration Mechanisms and Involvement of P2X7 Receptor

Ocular degeneration, including cataracts, glaucoma, macular degeneration, and diabetic retinopathy, is a major public health challenge, as it affects the quality of life of millions of people worldwide and, in its advanced stages, leads to blindness. Ocular degeneration, although it can affect different parts of the eye, shares common characteristics such as oxysterols and the P2X7 receptor. Indeed, oxysterols, which are cholesterol derivatives, are associated with ocular degeneration pathogenesis and trigger inflammation and cell death pathways. Activation of the P2X7 receptor is also linked to ocular degeneration and triggers the same pathways. In age-related macular degeneration, these two key players have been associated, but further studies are needed to extrapolate this interrelationship to other ocular degenerations.

27-hydroxycholesterol causes cognitive deficits by disturbing Th17/Treg balance and the related immune responses in mild cognitive impairment patients and C57BL/6J mice

BACKGROUND

Cognitive impairment is associated with dysregulated immune responses. Emerging evidence indicates that Th17 cells and their characteristic cytokine-IL-17 are receiving growing interest in the pathogenesis of cognitive decline. Here, we focus on the involvement of Th17 cells in mild cognitive impairment (MCI) and the possible mechanism of cholesterol metabolite-27-hydroxycholesterol (27-OHC).

METHODS

100 individuals were recruited into the nested case-control study who completed cognition assessment and the detection of oxysterols and Th17-related cytokines in serum. In addition, mice were treated with 27-OHC and inhibitors of RORγt and Foxp3 (Th17 and Treg transcription factors), and the factors involved in Th17/Treg balance and amyloidosis were detected.

RESULTS

Our results showed there was enhanced 27-OHC level in serum of MCI individuals. The Th17-related cytokines homeostasis was altered, manifested as increased IL-17A, IL-12p70, IL-23, GM-CSF, MIP-3α and TNF-α but decreased IL-13, IL-28A and TGF-β1. Further, in vivo experiments showed that 27-OHC induced higher immunogenicity, which increased Th17 proportion but decreased Treg cells in peripheral blood mononuclear cells (PBMCs); Th17 proportions in hippocampus, and IL-17A level in serum and brain were also higher than control mice. The fluorescence intensity of amyloid-β (Aβ) and the precursor of amyloid A amyloidosis-serum amyloid A (SAA) was increased in the brain of 27-OHC-treated mice, and worse learning and memory performance was supported by water maze test results. While by inhibiting RORγt in 27-OHC-loaded mice, Th17 proportions in both PBMCs and hippocampus were reduced, and expressions of IL-17A and TGF-β1 were down- and up-regulated, respectively, along with a decreased amyloidosis in brain and improved learning and memory decline.

CONCLUSIONS

Altogether, our results demonstrate that excessive 27-OHC aggravates the amyloidosis and leads to cognitive deficits by regulating RORγt and disturbing Th17/Treg balance.

Glycemic variability leads to higher levels of auto-oxidized oxysterol species in patients with type 1 diabetes mellitus

PURPOSE

Hyperglycemia and glycemic variability (GV) are associated with oxidative stress in patients with diabetes mellitus (DM). Oxysterol species, produced by the non-enzymatic oxidation of cholesterol, are potential biomarkers of oxidative stress. This study examined the relationship between auto-oxidized oxysterols and GV in patients with type 1 DM.

METHODS

Thirty patients with type 1 DM using a continuous subcutaneous insulin infusion pump therapy and a healthy control group (n = 30) were included in this prospective study. A Continuous Glucose Monitoring System device was applied for 72 h. Blood samples were taken for oxysterols produced by non-enzymatic oxidation [7-ketocholesterol (7-KC) and cholestane-3β, 5α, 6β-triol (Chol-Triol)] levels at 72 h. Short-term glycemic variability parameters, mean amplitude of glycemic excursions (MAGE), the standard deviation of glucose measurements (Glucose-SD), and mean of daily differences (MODD) were calculated with continuous glucose monitoring data. HbA1c was used to evaluate glycemic control and HbA1c-SD (the SD of HbA1c over the past year) for long-term glycemic variability.

RESULTS

7-KC and Chol-triol levels were significantly higher in the study group than in the control group. Strong positive correlations were found between 7-KC with MAGE(24-48 h) and Glucose-SD(24-48 h). 7-KC was positively correlated with MAGE(0-72 h) and Glucose-SD(0-72 h). No significant correlation was found between HbA1c and HbA1c -SD with oxysterol levels. The regression models showed that SD(24-48 h) and MAGE(24-48 h) predicted 7-KC levels while HbA1c did not.

CONCLUSIONS

Glycemic variability leads to higher levels of auto-oxidized oxysterol species in patients with type 1 DM independent of long-term glycemic control.

Development and validation of a liquid chromatography-tandem mass spectrometry assay to quantify plasma 24(S)-hydroxycholesterol and 27-hydroxycholesterol: A new approach integrating the concept of ion ratio

Accurate quantification of 24(S)-hydroxycholesterol and 27-hydroxycholesterol holds substantial biological significance due to their involvement in pivotal cellular processes, encompassing cholesterol homeostasis, inflammatory responses, neuronal signaling, and their potential as disease biomarkers. The plasma determination of these oxysterols is challenging considering their low concentrations and similarities in terms of empirical formulae, molecular structure, and physicochemical properties across all human endogenous plasma oxysterols. To overcome these sensitivity and specificity issues, we developed and validated a quantification method using liquid chromatography coupled to a tandem mass spectrometry instrument. Validation studies were designed inspired by Clinical and Laboratory Standards Institute (CLSI) C62-A Guidelines. The linearity ranged between 20 and 300 nM for both oxysterols with limits of quantification at 20 nM and 30 nM for 24(S)-OHC and 27-OHC, respectively. Inter-day precision coefficient variations (CV) were lower than 10% for both oxysterols. An optimal separation of 25-OHC was obtained from 24(S)-OHC and 27-OHC with a resolution (Rs) > 1.25. The determination and validation of ion ratios for 24(S)-OHC and 27-OHC enabled another quality check in identifying interferents that could impact the quantification. Our developed and validated LC-MS/MS method allows consistent and reliable quantification of human plasmatic 24(S)-OHC and 27-OHC that is warranted in fundamental and clinical research projects.

7β-Hydroxycholesterol and 7-ketocholesterol: New oxidative stress biomarkers of sarcopenia inducing cytotoxic effects on myoblasts and myotubes

Aging is a complex biological process which can be associated with skeletal muscle degradation leading to sarcopenia. The aim of this study consisted i) to determine the oxidative and inflammatory status of sarcopenic patients and ii) to clarify the impact of oxidative stress on myoblasts and myotubes. To this end, various biomarkers of inflammation (C-reactive protein (CRP), TNF-α, IL-6, IL-8, leukotriene B4 (LTB4)) and oxidative stress (malondialdehyde, conjugated dienes, carbonylated proteins and antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase) as well as oxidized derivatives of cholesterol formed by cholesterol autoxidation (7-ketocholesterol, 7β-hydroxycholesterol), were analyzed. Apelin, a myokine which contributes to muscle strength, was also quantified. To this end, a case-control study was conducted to evaluate the RedOx and inflammatory status in 45 elderly subjects (23 non-sarcopenic; 22 sarcopenic) from 65 years old and higher. SARCopenia-Formular (SARC-F) and Timed Up and Go (TUG) tests were used to distinguish between sarcopenic and non-sarcopenic subjects. By using red blood cells, plasma and/or serum, we observed in sarcopenic patients an increased activity of major antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase) associated with lipid peroxidation and protein carbonylation (increased level of malondialdehyde, conjugated dienes and carbonylated proteins). Higher levels of 7-ketocholesterol and 7β-hydroxycholesterol were also observed in the plasma of sarcopenic patients. Significant differences were only observed with 7β-hydroxycholesterol. In sarcopenic patients comparatively to non-sarcopenic subjects, significant increase of CRP, LTB4 and apelin were observed whereas similar levels of TNF-α, IL-6 and IL-8 were found. The increased plasma level of 7-ketocholesterol and 7β-hydroxycholesterol in sarcopenic patients led us to study the cytotoxic effect of these oxysterols on undifferentiated (myoblasts) and differentiated (myotubes) murine C2C12 cells. With the fluorescein diacetate and sulforhodamine 101 assays, an induction of cell death was observed both on undifferentiated and differentiated cells: the cytotoxic effects were less pronounced with 7-ketocholesterol. In addition, IL-6 secretion was never detected whatever the culture conditions, TNF-α secretion was significantly increased on undifferentiated and differentiated C2C12 cells treated with 7-ketocholesterol- and 7β-hydroxycholesterol, and IL-8 secretion was increased on differentiated cells. 7-ketocholesterol- and 7β-hydroxycholesterol-induced cell death was strongly attenuated by α-tocopherol and Pistacia lentiscus L. seed oil both on myoblasts and/or myotubes. TNF-α and/or IL-8 secretions were reduced by α-tocopherol and Pistacia lentiscus L. seed oil. Our data support the hypothesis that the enhancement of oxidative stress observed in sarcopenic patients could contribute, especially via 7β-hydroxycholesterol, to skeletal muscle atrophy and inflammation via cytotoxic effects on myoblasts and myotubes. These data bring new elements to understand the pathophysiology of sarcopenia and open new perspectives for the treatment of this frequent age-related disease.

Accumulation of oxysterols in the erythrocytes of COVID-19 patients as a biomarker for case severity

BACKGROUND

Due to the high risk of COVID-19 patients developing thrombosis in the circulating blood, atherosclerosis, and myocardial infarction, it is necessary to study the lipidome of erythrocytes. Specifically, we examined the pathogenic oxysterols and acylcarnitines in the erythrocyte homogenate of COVID-19 patients. These molecules can damage cells and contribute to the development of these diseases.

METHODS

This study included 30 patients and 30 healthy volunteers. The erythrocyte homogenate extract was analyzed using linear ion trap mass spectrometry combined with high-performance liquid chromatography. The concentrations of oxysterols and acylcarnitines in erythrocyte homogenates of healthy individuals and COVID-19 patients were measured. Elevated levels of toxic biomarkers in red blood cells could initiate oxidative stress, leading to a process known as Eryptosis.

RESULTS

In COVID-19 patients, the levels of five oxysterols and six acylcarnitines in erythrocyte homogenates were significantly higher than those in healthy individuals, with a p-value of less than 0.05. The mean total concentration of oxysterols in the red blood cells of COVID-19 patients was 23.36 ± 13.47 μg/mL, while in healthy volunteers, the mean total concentration was 4.92 ± 1.61 μg/mL. The 7-ketocholesterol and 4-cholestenone levels were five and ten times higher, respectively, in COVID-19 patients than in healthy individuals. The concentration of acylcarnitines in the red blood cell homogenate of COVID-19 patients was 2 to 4 times higher than that of healthy volunteers on average. This finding suggests that these toxic biomarkers may cause the red blood cell death seen in COVID-19 patients.

CONCLUSIONS

The abnormally high levels of oxysterols and acylcarnitines found in the erythrocytes of COVID-19 patients were associated with the severity of the cases, complications, and the substantial risk of thrombosis. The concentration of oxysterols in the erythrocyte homogenate could serve as a diagnostic biomarker for COVID-19 case severity.

The Janus-Faced Role of Lipid Droplets in Aging: Insights from the Cellular Perspective

It is widely accepted that nine hallmarks-including mitochondrial dysfunction, epigenetic alterations, and loss of proteostasis-exist that describe the cellular aging process. Adding to this, a well-described cell organelle in the metabolic context, namely, lipid droplets, also accumulates with increasing age, which can be regarded as a further aging-associated process. Independently of their essential role as fat stores, lipid droplets are also able to control cell integrity by mitigating lipotoxic and proteotoxic insults. As we will show in this review, numerous longevity interventions (such as mTOR inhibition) also lead to strong accumulation of lipid droplets in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and mammalian cells, just to name a few examples. In mammals, due to the variety of different cell types and tissues, the role of lipid droplets during the aging process is much more complex. Using selected diseases associated with aging, such as Alzheimer's disease, Parkinson's disease, type II diabetes, and cardiovascular disease, we show that lipid droplets are "Janus"-faced. In an early phase of the disease, lipid droplets mitigate the toxicity of lipid peroxidation and protein aggregates, but in a later phase of the disease, a strong accumulation of lipid droplets can cause problems for cells and tissues.

Exhaustion-associated cholesterol deficiency dampens the cytotoxic arm of antitumor immunity

The concept of targeting cholesterol metabolism to treat cancer has been widely tested in clinics, but the benefits are modest, calling for a complete understanding of cholesterol metabolism in intratumoral cells. We analyze the cholesterol atlas in the tumor microenvironment and find that intratumoral T cells have cholesterol deficiency, while immunosuppressive myeloid cells and tumor cells display cholesterol abundance. Low cholesterol levels inhibit T cell proliferation and cause autophagy-mediated apoptosis, particularly for cytotoxic T cells. In the tumor microenvironment, oxysterols mediate reciprocal alterations in the LXR and SREBP2 pathways to cause cholesterol deficiency of T cells, subsequently leading to aberrant metabolic and signaling pathways that drive T cell exhaustion/dysfunction. LXRβ depletion in chimeric antigen receptor T (CAR-T) cells leads to improved antitumor function against solid tumors. Since T cell cholesterol metabolism and oxysterols are generally linked to other diseases, the new mechanism and cholesterol-normalization strategy might have potential applications elsewhere.

Eight-Hour Time-Restricted Feeding: A Strong Candidate Diet Protocol for First-Line Therapy in Polycystic Ovary Syndrome

We aimed to investigate the effects of a 6-week program of 8 h time-restricted feeding (TRF) diet in polycystic ovary syndrome (PCOS), as determined by anthropometric, hormonal, metabolic profiles, and fecal calprotectin level. Thirty women diagnosed with PCOS underwent a 6-week 8 h TRF diet intervention. Age, anthropometric features (body mass index (BMI), waist-to-hip ratio (WHR)) and biochemical results were recorded. Free androgen index (FAI, defining hyperandrogenism) and the homeostatic model assessment-insulin resistance (HOMA-IR) were calculated. Baseline (pre-diet) and 6-week post-diet findings were compared. Mean age was 25.57 ± 2.67 years. BMI (p < 0.001) and WHR (p = 0.001) were found to have significantly decreased after the diet, as well as the percentage of patients defined to have hyperandrogenism (p = 0.016). Reproductive hormone levels, FAI (p < 0.001) and HOMA-IR (p < 0.001) were improved significantly. Metabolic parameters associated with glucose and lipid profiles were also significantly improved after the diet. Additionally, fecal calprotectin levels demonstrated a significant decrease from pre-diet to post-diet (p < 0.001). In conclusion, a 6-week diet intervention with 8 h TRF may be a suitable and effective intermittent fasting protocol that can be used as a first-line option in PCOS.

Higher concentration of 25-hydroxycholesterol in treatment-naïve patients with type 2 diabetes compared to healthy individuals

BACKGROUND

Oxysterols are cholesterol oxidation derivatives with diverse biological activities. However, little is known about the oxysterol levels in treatment-naïve patients with type 2 diabetes.

OBJECTIVE

We utilized gas chromatography-mass spectrometry to investigate the potential association between oxysterol concentrations and type 2 diabetes and atherosclerosis in treatment-naïve patients diagnosed with type 2 diabetes.

METHODS

This case-control study enrolled 53 eligible patients with type 2 diabetes and 50 healthy volunteers. We compared serum oxysterol concentrations between the two groups; we examined the correlation between the oxysterol concentrations and the carotid plaque score in the type 2 diabetes group.

RESULTS

Univariate analysis revealed significant differences in the concentrations of oxysterols (i.e., cholesterol-5α, 6α-epoxide; cholesterol-5β, 6β-epoxide; 7β-hydroxycholesterol; and 25-hydroxycholesterol [25-HC]) and other cardiovascular risk factors between the two groups. The 25-HC concentration was almost twofold greater in the type 2 diabetes group than in the healthy volunteers (median [interquartile range]: 8.52 [6.37-11.26] vs. 4.58 [3.45-5.44] ng/mL). After adjusting for multiple covariates, such as age, body mass index, mean arterial pressure, and triglyceride, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol levels, only the concentration of 25-HC showed a significant association with type 2 diabetes. However, the univariate analysis failed to demonstrate any significant correlation between oxysterol concentrations and the carotid plaque score among individuals with type 2 diabetes.

CONCLUSIONS

The levels of various oxysterols differ between treatment-naïve patients with type 2 diabetes and healthy individuals; the 25-HC level differs the most prominently.

Identification and characterization of select oxysterols as ligands for GPR17

BACKGROUND AND PURPOSE

G-protein coupled receptor 17 (GPR17) is an orphan receptor involved in the process of myelination, due to its ability to inhibit the maturation of oligodendrocyte progenitor cells (OPCs) into myelinating oligodendrocytes. Despite multiple claims that the biological ligand has been identified, it remains an orphan receptor.

EXPERIMENTAL APPROACH

Seventy-seven oxysterols were screened in a cell-free [³⁵ S]GTPγS binding assay using membranes from cells expressing GPR17. The positive hits were characterized using adenosine 3',5' cyclic monophosphate (cAMP), inositol monophosphate (IP1) and calcium mobilization assays, with results confirmed in rat primary oligodendrocytes. Rat and pig brain extracts were separated by high-performance liquid chromatography (HPLC) and endogenous activator(s) were identified in receptor activation assays. Gene expression studies of GPR17, and CYP46A1 (cytochrome P450 family 46 subfamily A member 1) enzymes responsible for the conversion of cholesterol into specific oxysterols, were performed using quantitative real-time PCR.

KEY RESULTS

Five oxysterols were able to stimulate GPR17 activity, including the brain cholesterol, 24(S)-hydroxycholesterol (24S-HC). A specific brain fraction from rat and pig extracts containing 24S-HC activates GPR17 in vitro. Expression of Gpr17 during mouse brain development correlates with the expression of Cyp46a1 and the levels of 24S-HC itself. Other active oxysterols have low brain concentrations below effective ranges.

CONCLUSIONS AND IMPLICATIONS

Oxysterols, including but not limited to 24S-HC, could be physiological activators for GPR17 and thus potentially regulate OPC differentiation and myelination through activation of the receptor.

Plasma levels of oxysterols 7-ketocholesterol and cholestane-3β, 5α, 6β-triol in patients with allergic asthma

The prevalence of allergic asthma is increasing on a global scale, reflecting changes in air pollution, climatic changes, and other environmental stimulants. In allergic conditions, oxidative stress occurs as a result of immune system activation. Oxidation of cholesterol leads to the formation of oxysterols. The main purpose of the study was to compare plasma levels of two oxysterols, namely 7-ketocholesterol (7-KC) and cholestane-3β, 5α, 6β-triol (C-triol), and a lipid peroxidation product, malondialdehyde (MDA) in allergic asthma patients with those of healthy controls, in order to provide information about the involvement of lipid peroxidation in allergic asthma.

Oxysterols were quantified by LC-MS/MS in plasma samples of 120 asthma patients (90 females + 30 males) and 120 healthy controls (matched by age and sex). Plasma MDA level was analyzed by a spectrophotometric method.

Plasma 7-KC (39.45 ± 20.37 ng/mL) and C-triol (25.61 ± 10.13 ng/mL) levels in patients were significantly higher than in healthy subjects (17.84 ± 4.26 ng/mL and 10.00 ± 3.90 ng/mL, respectively) (P < 0.001). Plasma MDA levels were also higher in asthmatic patients (4.98 ± 1.77 nmol/mL) than in healthy controls (1.14 ± 0.31 nmol/mL) (P < 0.001). All data support that lipid peroxidation products are involved in allergic asthma.

Oxysterols were quantified for the first time in allergic asthma. Since the high plasma 7-KC and C-triol levels of allergic asthma patients correlate with high IgE levels, detection of these oxysterols by LC-MS/MS may be helpful in the clinical monitoring of allergic asthma. Current data may also lead to new approaches for the prevention, diagnosis, and treatment of the disease.

Supplemental data for this article is available online at at.

Oxiapoptophagy in Age-Related Diseases. Comment on Ouyang et al. 7-Ketocholesterol Induces Oxiapoptophagy and Inhibits Osteogenic Differentiation in MC3T3-E1 Cells. Cells 2022, 11, 2882

Due to the increase in life span and life expectancy, which can, however, be more or less pronounced depending on the economic, social and cultural context [...].

Alteration of cholesterol distribution at the plasma membrane of cancer cells: From evidence to pathophysiological implication and promising therapy strategy

Cholesterol-enriched domains are nowadays proposed to contribute to cancer cell proliferation, survival, death and invasion, with important implications in tumor progression. They could therefore represent promising targets for new anticancer treatment. However, although diverse strategies have been developed over the years from directly targeting cholesterol membrane content/distribution to adjusting sterol intake, all approaches present more or less substantial limitations. Those data emphasize the need to optimize current strategies, to develop new specific cholesterol-targeting anticancer drugs and/or to combine them with additional strategies targeting other lipids than cholesterol. Those objectives can only be achieved if we first decipher (i) the mechanisms that govern the formation and deformation of the different types of cholesterol-enriched domains and their interplay in healthy cells; (ii) the mechanisms behind domain deregulation in cancer; (iii) the potential generalization of observations in different types of cancer; and (iv) the specificity of some alterations in cancer vs. non-cancer cells as promising strategy for anticancer therapy. In this review, we will discuss the current knowledge on the homeostasis, roles and membrane distribution of cholesterol in non-tumorigenic cells. We will then integrate documented alterations of cholesterol distribution in domains at the surface of cancer cells and the mechanisms behind their contribution in cancer processes. We shall finally provide an overview on the potential strategies developed to target those cholesterol-enriched domains in cancer therapy.

Cytoprotective activities of representative nutrients from the Mediterranean diet and of Mediterranean oils against 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity: Application to age-related diseases and civilization diseases

7-ketocholesterol and 7β-hydroxycholesterol are two oxysterols mainly formed by the autoxidation of cholesterol. These two molecules are interconvertible via specific enzymes. These two oxysterols are often observed at increased amounts in biological fluids as well as tissues and organs affected during age-related diseases and in diseases of civilization such as cardiovascular, neurodegenerative, and ocular diseases as well as type 2 diabetes and metabolic syndrome. Noteworthy, 7-ketocholesterol and 7β-hydroxycholesterol induce oxidative stress and inflammation, which are frequently observed in patients with age-related and civilization diseases. For this reason, the involvement of these two oxysterols in the pathophysiology of these diseases is widely suspected. In addition, the toxicity of these oxysterols can lead to death by oxiapoptophagy characterized by oxidative stress, apoptosis induction and autophagy criteria. To prevent, or even treat, certain age-related or civilization diseases associated with increased levels of 7-ketocholesterol and 7β-hydroxycholesterol, the identification of molecules or mixtures of molecules attenuating or inhibiting the toxic effects of these oxysterols allows to consider new treatments. In this context, many nutrients present in significant amounts in the Mediterranean diet, especially tocopherols, fatty acids, and polyphenols, have shown cytoprotective activities as well as several Mediterranean oils (argan and olive oils, milk thistle seed oil, and pistacia lentiscus seed oil). Consequently, a nutraceutical approach, rich in nutrients present in the Mediterranean diet, could thus make it possible to counteract certain age-related and civilization diseases associated with increased levels of 7-ketocholesterol and 7β-hydroxycholesterol.

GPR183 Regulates 7α,25-Dihydroxycholesterol-Induced Oxiapoptophagy in L929 Mouse Fibroblast Cell

7α,25-dihydroxycholesterol (7α,25-DHC) is an oxysterol synthesized from 25-hydroxycholesterol by cytochrome P450 family 7 subfamily B member 1 (CYP7B1) and is a monooxygenase (oxysterol-7α-hydroxylase) expressed under inflammatory conditions in various cell types. In this study, we verified that 7α,25-DHC-induced oxiapoptophagy is mediated by apoptosis, oxidative stress, and autophagy in L929 mouse fibroblasts. MTT assays and live/dead cell staining revealed that cytotoxicity was increased by 7α,25-DHC in L929 cells. Consequentially, cells with condensed chromatin and altered morphology were enhanced in L929 cells incubated with 7α,25-DHC for 48 h. Furthermore, apoptotic population was increased by 7α,25-DHC exposure through the cascade activation of caspase-9, caspase-3, and poly (ADP-ribose) polymerase in the intrinsic pathway of apoptosis in these cells. 7α,25-DHC upregulated reactive oxygen species (ROS) in L929 cells. Expression of autophagy biomarkers, including beclin-1 and LC3, was significantly increased by 7α,25-DHC treatment in L929 cells. 7α,25-DHC inhibits the phosphorylation of Akt associated with autophagy and increases p53 expression in L929 cells. In addition, inhibition of G-protein-coupled receptor 183 (GPR183), a receptor of 7α,25-DHC, using GPR183 specific antagonist NIBR189 suppressed 7α,25-DHC-induced apoptosis, ROS production, and autophagy in L929 cells. Collectively, GPR183 regulates 7α,25-DHC-induced oxiapoptophagy in L929 cells.

Protective effects of milk thistle (Sylibum marianum) seed oil and α-tocopherol against 7β-hydroxycholesterol-induced peroxisomal alterations in murine C2C12 myoblasts: Nutritional insights associated with the concept of pexotherapy

Peroxisomes play an important role in regulating cell metabolism and RedOx homeostasis. Peroxisomal dysfunctions favor oxidative stress and cell death. The ability of 7β-hydroxycholesterol (7β-OHC; 50 μM, 24 h), known to be increased in patients with age-related diseases such as sarcopenia, to trigger oxidative stress, mitochondrial and peroxisomal dysfunction was studied in murine C2C12 myoblasts. The capacity of milk thistle seed oil (MTSO, 100 μg/mL) as well as α-tocopherol (400 µM; reference cytoprotective agent) to counteract the toxic effects of 7β-OHC, mainly at the peroxisomal level were evaluated. The impacts of 7β-OHC, in the presence or absence of MTSO or α-tocopherol, were studied with complementary methods: measurement of cell density and viability, quantification of reactive oxygen species (ROS) production and transmembrane mitochondrial potential (ΔΨm), evaluation of peroxisomal mass as well as topographic, morphologic and functional peroxisomal changes. Our results indicate that 7β-OHC induces a loss of cell viability and a decrease of cell adhesion associated with ROS overproduction, alterations of mitochondrial ultrastructure, a drop of ΔΨm, and several peroxisomal modifications. In the presence of 7β-OHC, comparatively to untreated cells, important quantitative and qualitative peroxisomal modifications were also identified: a) a reduced number of peroxisomes with abnormal sizes and shapes, mainly localized in cytoplasmic vacuoles, were observed; b) the peroxisomal mass was decreased as indicated by lower protein and mRNA levels of the peroxisomal ABCD3 transporter; c) lower mRNA level of Pex5 involved in peroxisomal biogenesis as well as higher mRNA levels of Pex13 and Pex14, involved in peroxisomal biogenesis and/or pexophagy, was found; d) lower levels of ACOX1 and MFP2 enzymes, implicated in peroxisomal β-oxidation, were detected; e) higher levels of very-long-chain fatty acids, which are substrates of peroxisomal β-oxidation, were found. These different cytotoxic effects were strongly attenuated by MTSO, in the same range of order as with α-tocopherol. These findings underline the interest of MTSO and α-tocopherol in the prevention of peroxisomal damages (pexotherapy).

Non-enzymatic electrochemical determination of cholesterol in dairy products on boron-doped diamond electrode

Determination of cholesterol in food matrices is essential for quality control concerning the health of consumers. Herein, a simple electrochemical approach for cholesterol quantitation in dairy products is evaluated. The newly developed differential pulse voltammetric method using acetonitrile-perchloric acid mixture as a supporting electrolyte is statistically compared to GC-MS and HPLC-UV. Oxidation signals of cholesterol at +1.5 V and +1.4 V (vs. Ag/AgNO₃ in acetonitrile) provide detection limits of 4.9 µM and 6.1 µM on boron-doped diamond and glassy carbon electrodes, respectively. A simple liquid-liquid extraction procedure from dairy products into hexane resulted in a recovery rate of (74.8 ± 3.8)%. The method provides results in close agreement (at a 95% confidence level) with GC-MS, while HPLC-UV resulted in a significant difference in estimated cholesterol concentrations for all samples. This newly developed method is a simpler, faster and cheaper alternative to instrumentally demanding MS-based methods and clearly outperforms HPLC-UV.

Cholesterol metabolism in aging simultaneously altered in liver and nervous system

In humans, aging, triggers increased plasma concentrations of triglycerides, cholesterol, low-density lipoproteins and lower capacity of high-density lipoproteins to remove cellular cholesterol. Studies in rodents showed that aging led to cholesterol accumulation in the liver and decrease in the brain with reduced cholesterol synthesis and increased levels of cholesterol 24-hydroxylase, an enzyme responsible for removing cholesterol from the brain. Liver diseases are also related to brain aging, inducing changes in cholesterol metabolism in the brain and liver of rats. It has been suggested that late onset Alzheimer's disease is associated with metabolic syndrome. Non-alcoholic fatty liver is associated with lower total brain volume in the Framingham Heart Study offspring cohort study. Furthermore, disorders of cholesterol homeostasis in the adult brain are associated with neurological diseases such as Niemann-Pick, Alzheimer, Parkinson, Huntington and epilepsy. Apolipoprotein E (apoE) is important in transporting cholesterol from astrocytes to neurons in the etiology of sporadic Alzheimer's disease, an aging-related dementia. Desmosterol and 24S-hydroxycholesterol are reduced in ApoE KO hypercholesterolemic mice. ApoE KO mice have synaptic loss, cognitive dysfunction, and elevated plasma lipid levels that can affect brain function. In contrast to cholesterol itself, there is a continuous uptake of 27- hydroxycholesterol in the brain as it crosses the blood-brain barrier and this flow can be an important link between intra- and extracerebral cholesterol homeostasis. Not surprisingly, changes in cholesterol metabolism occur simultaneously in the liver and nervous tissues and may be considered possible biomarkers of the liver and nervous system aging.

Oxysterols: From redox bench to industry

More and more attention is nowadays given to the possible translational application of a great number of biochemical and biological findings with the involved molecules. This is also the case of cholesterol oxidation products, redox molecules over the last years deeply investigated for their implication in human pathophysiology. Oxysterols of non-enzymatic origin, the excessive increase of which in biological fluids and tissues is of toxicological relevance for their marked pro-oxidant and pro-inflammatory properties, are increasingly applied in clinical biochemistry as molecular markers in the diagnosis and monitoring of several human and veterinary diseases. Conversely, oxysterols of enzymatic origin, the production of which is commonly under physiological regulation, could be considered and tested as promising pharmaceutical agents because of their antiviral, pro-osteogenic and antiadipogenic properties of some of them. Very recently, the quantification of oxysterols of non-enzymatic origin has been adopted in a systematic way to evaluate, monitor and improve the quality of cholesterol-based food ingredients, that are prone to auto-oxidation, as well as their industrial processing and the packaging and the shelf life of the finished food products. The growing translational value of oxysterols is here reviewed in its present and upcoming applications in various industrial fields.

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

Dietary cholesterol oxidation products (COPs) are heterogeneous compounds formed during the processing and storage of cholesterol-rich foods, such as seafood, meat, eggs, and dairy products. With the increased intake of COPs-rich foods, the concern about health implications of dietary COPs is rising. Dietary COPs may exert deleterious effects on human health to induce several inflammatory diseases including atherosclerosis, neurodegenerative diseases, and inflammatory bowel diseases. Thus, knowledge regarding the effects of processing and storage conditions leading to formation of COPs is needed to reduce the levels of COPs in foods. Efficient methodologies to determine COPs in foods are also essential. More importantly, the biological roles of dietary COPs in human health and effects of phytochemicals on dietary COPs-induced diseases need to be established. This review summarizes the recent information on dietary COPs including their formation in foods during their processing and storage, analytical methods of determination of COPs, metabolic fate, implications for human health, and beneficial interventions by phytochemicals. The formation of COPs is largely dependent on the heating temperature, storage time, and food matrices. Alteration of food processing and storage conditions is one of the potent strategies to restrict hazardous dietary COPs from forming, including maintaining relatively low temperatures, shorter processing or storage time, and the appropriate addition of antioxidants. Once absorbed into the circulation, dietary COPs can contribute to the progression of several inflammatory diseases, where the absorbed dietary COPs may induce inflammation, apoptosis, and autophagy in cells in the target organs or tissues. Improved intake of phytochemicals may be an effective strategy to reduce the hazardous effects of dietary COPs.

Antioxidant Properties and Cytoprotective Effect of Pistacia lentiscus L. Seed Oil against 7β-Hydroxycholesterol-Induced Toxicity in C2C12 Myoblasts: Reduction in Oxidative Stress, Mitochondrial and Peroxisomal Dysfunctions and Attenuation of Cell Death

Aging is characterized by a progressive increase in oxidative stress, which favors lipid peroxidation and the formation of cholesterol oxide derivatives, including 7β-hydroxycholesterol (7β-OHC). This oxysterol, which is known to trigger oxidative stress, inflammation, and cell death, could contribute to the aging process and age-related diseases, such as sarcopenia. Identifying molecules or mixtures of molecules preventing the toxicity of 7β-OHC is therefore an important issue. This study consists of determining the chemical composition of Tunisian Pistacia lentiscus L. seed oil (PLSO) used in the Tunisian diet and evaluating its ability to counteract the cytotoxic effects induced by 7β-OHC in murine C2C12 myoblasts. The effects of 7β-OHC (50 µM; 24 h), associated or not with PLSO, were studied on cell viability, oxidative stress, and on mitochondrial and peroxisomal damages induction. α-Tocopherol (400 µM) was used as the positive control for cytoprotection. Our data show that PLSO is rich in bioactive compounds; it contains polyunsaturated fatty acids, and several nutrients with antioxidant properties: phytosterols, α-tocopherol, carotenoids, flavonoids, and phenolic compounds. When associated with PLSO (100 µg/mL), the 7β-OHC-induced cytotoxic effects were strongly attenuated. The cytoprotection was in the range of those observed with α-tocopherol. This cytoprotective effect was characterized by prevention of cell death and organelle dysfunction (restoration of cell adhesion, cell viability, and plasma membrane integrity; prevention of mitochondrial and peroxisomal damage) and attenuation of oxidative stress (reduction in reactive oxygen species overproduction in whole cells and at the mitochondrial level; decrease in lipid and protein oxidation products formation; and normalization of antioxidant enzyme activities: glutathione peroxidase (GPx) and superoxide dismutase (SOD)). These results provide evidence that PLSO has similar antioxidant properties than α-tocopherol used at high concentration and contains a mixture of molecules capable to attenuate 7β-OHC-induced cytotoxic effects in C2C12 myoblasts. These data reinforce the interest in edible oils associated with the Mediterranean diet, such as PLSO, in the prevention of age-related diseases, such as sarcopenia.

7-Ketocholesterol: Effects on viral infections and hypothetical contribution in COVID-19

7-Ketocholesterol, which is one of the earliest cholesterol oxidization products identified, is essentially formed by the auto-oxidation of cholesterol. In the body, 7-ketocholesterol is both provided by food and produced endogenously. This pro-oxidant and pro-inflammatory molecule, which can activate apoptosis and autophagy at high concentrations, is an abundant component of oxidized Low Density Lipoproteins. 7-Ketocholesterol appears to significantly contribute to the development of age-related diseases (cardiovascular diseases, age-related macular degeneration, and Alzheimer's disease), chronic inflammatory bowel diseases and to certain cancers. Recent studies have also shown that 7-ketocholesterol has anti-viral activities, including on SARS-CoV-2, which are, however, lower than those of oxysterols resulting from the oxidation of cholesterol on the side chain. Furthermore, 7-ketocholesterol is increased in the serum of moderately and severely affected COVID-19 patients. In the case of COVID-19, it can be assumed that the antiviral activity of 7-ketocholesterol could be counterbalanced by its toxic effects, including pro-oxidant, pro-inflammatory and pro-coagulant activities that might promote the induction of cell death in alveolar cells. It is therefore suggested that this oxysterol might be involved in the pathophysiology of COVID-19 by contributing to the acute respiratory distress syndrome and promoting a deleterious, even fatal outcome. Thus, 7-ketocholesterol could possibly constitute a lipid biomarker of COVID-19 outcome and counteracting its toxic effects with adjuvant therapies might have beneficial effects in COVID-19 patients.

Oxidative Stress and Antioxidant Pathway in Allergic Rhinitis

Oxidative stress is the cause and consequence of redox metabolism in various physiological and pathological conditions. Understanding the molecular pathways underlying oxidative stress and the role of antioxidants could serve as the key to helping treat associated diseases. Allergic rhinitis is a condition that deteriorates the daily function and quality of life of afflicted individuals and is associated with a high socioeconomic burden and prevalence. Recent studies have focused on the role of oxidative stress and antioxidants in allergic rhinitis. This review discusses animal and clinical studies on oxidative markers and the potential therapeutic dietary antioxidants for allergic rhinitis.

Attenuation of 7-ketocholesterol- and 7β-hydroxycholesterol-induced oxiapoptophagy by nutrients, synthetic molecules and oils: Potential for the prevention of age-related diseases

Age-related diseases for which there are no effective treatments include cardiovascular diseases; neurodegenerative diseases such as Alzheimer's disease; eye disorders such as cataract and age-related macular degeneration; and, more recently, Severe Acute Respiratory Syndrome (SARS-CoV-2). These diseases are associated with plasma and/or tissue increases in cholesterol derivatives mainly formed by auto-oxidation: 7-ketocholesterol, also known as 7-oxo-cholesterol, and 7β-hydroxycholesterol. The formation of these oxysterols can be considered as a consequence of mitochondrial and peroxisomal dysfunction, leading to increased in oxidative stress, which is accentuated with age. 7-ketocholesterol and 7β-hydroxycholesterol cause a specific form of cytotoxic activity defined as oxiapoptophagy, including oxidative stress and induction of death by apoptosis associated with autophagic criteria. Oxiaptophagy is associated with organelle dysfunction and in particular with mitochondrial and peroxisomal alterations involved in the induction of cell death and in the rupture of redox balance. As the criteria characterizing 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity are often simultaneously observed in major age-related diseases (cardiovascular diseases, age-related macular degeneration, Alzheimer's disease) the involvement of these oxysterols in the pathophysiology of the latter seems increasingly likely. It is therefore important to better understand the signalling pathways associated with the toxicity of 7-ketocholesterol and 7β-hydroxycholesterol in order to identify pharmacological targets, nutrients and synthetic molecules attenuating or inhibiting the cytotoxic activities of these oxysterols. Numerous natural cytoprotective compounds have been identified: vitamins, fatty acids, polyphenols, terpenes, vegetal pigments, antioxidants, mixtures of compounds (oils, plant extracts) and bacterial enzymes. However, few synthetic molecules are able to prevent 7-ketocholesterol- and/or 7β-hydroxycholesterol-induced cytotoxicity: dimethyl fumarate, monomethyl fumarate, the tyrosine kinase inhibitor AG126, memantine, simvastatine, Trolox, dimethylsufoxide, mangafodipir and mitochondrial permeability transition pore (MPTP) inhibitors. The effectiveness of these compounds, several of which are already in use in humans, makes it possible to consider using them for the treatment of certain age-related diseases associated with increased plasma and/or tissue levels of 7-ketocholesterol and/or 7β-hydroxycholesterol.