Sphingosine-1-phosphate induces myocyte autophagy after myocardial infarction through mTOR inhibition

SEW2871 attenuates myocyte necroptosis in heart failure through inhibition of oxidative stress and inflammatory cytokines

BACKGROUND AND PURPOSE

Sphingosine-1-phosphate (S1P)/S1P receptor signalling exerts cardioprotective effects. However, the effect of the selective S1P1 receptor agonist SEW2871 on myocyte necroptosis in heart failure and the underlying mechanisms are unknown. In the present study, we tested the hypothesis that SEW2871 attenuates myocyte necroptosis in heart failure through inhibition of oxidative stress and inflammatory cytokines.

EXPERIMENTAL APPROACH

Eight-week-old male C57BL/6J mice underwent myocardial infarction (MI) or sham operation. The animals were randomized to receive SEW2871 (5 mg·kg-1·day-1, i.p) or placebo for 4 weeks.

KEY RESULTS

MI mice exhibited the increases in left ventricular (LV) end-diastolic dimension, LV end-systolic dimension, LV mass and lung weight and a decrease in LV ejection fraction, indicating LV dilation, LV systolic dysfunction and lung congestion, and these alterations were attenuated by the SEW2871 treatment. Myocardial expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, inflammatory cytokines tumour necrosis factor-α (TNF-α), interleukin-1β and interleukin-6, and phosphorylated RIPK1 (p-RIPK1), p-RIPK3 and p-MLKL, reflective of their respective kinase activities, markers of necroptosis, was markedly increased in the MI placebo group, and the increase was abolished by the SEW2871 treatment. Similarly, intracellular levels of reactive oxygen species, inflammatory cytokines, p-RIPK1, p-RIPK3 and p-MLKL protein expression were increased in H9C2 cardiomyocytes under mimic ischaemia and the increases were prevented by the SEW2871 treatment.

CONCLUSION AND IMPLICATIONS

The selective S1P1 receptor agonist SEW2871 attenuates myocyte necroptosis through inhibition of oxidative stress and inflammatory cytokines, leading to improvement of LV remodelling and function in heart failure.

Chaihu Guizhi Ganjiang Decoction ameliorates chronic pancreatitis by modulating the SK1/S1P signaling pathway

Chronic pancreatitis (CP) is a progressive disease characterized by injury on pancreatic acinar cells (PACs), ongoing fibrosis, and gradual loss of exocrine and endocrine functions. Sphingosine kinase 1 (SK1) expression is elevated in injured PACs, and its metabolite sphingosine-1-phosphate (S1P) promotes the activation of pancreatic stellate cell (PSC) through autophagy and pyroptosis. Chaihu Guizhi Ganjiang Decoction (CGGD), a traditional Chinese medicine is widely used in the clinical treatment of digestive diseases. However, whether CCGD affects the SK1/S1P axis and relieves pancreatic damage through this pathway remains unknown. In this study, CP rats were treated with CGGD, individually or in combination with S1P and SKI-178 for four weeks to assess the effect of CGGD on pancreatic injury, fibrosis, autophagy and pyroptosis. The results showed that SK1, S1P and S1PR2 levels were increased in the pancreatic tissues of CP rats, while CGGD reduced these levels. Treatment with S1P exacerbated histological damage, promoted fibrosis, accelerated autophagy, and induced pyroptosis. Conversely, SKI-178 suppressed these effects. Notably, CGGD mitigated histological damage, decreased serum amylase and lipase levels, and alleviated pancreatic fibrosis induced by S1P. Furthermore, CGGD downregulated autophagy and pyroptosis induced by S1P, exhibiting an effect comparable to SKI-178 in CP. In conclusion, CGGD ameliorates pancreatic damage by reducing fibrosis, inhibiting autophagy, and suppressing pyroptosis through the SK1/S1P axis.

Exploring the association between osteoporosis and kidney stones: a clinical to mechanistic translational study based on big data and bioinformatics

BACKGROUND

Osteoporosis and kidney stones share several common pathophysiological risk factors, and their association is well-established. However, previous studies have primarily focused on environmental mediators, such as diet, and the precise mechanism linking these two conditions remains unclear.

METHODS

The relationship between osteoporosis and kidney stones was analyzed using weighted multivariate logistic regression, employing data from five cycles of the National Health and Nutrition Examination Survey (NHANES) from 2007-2010, 2013-2014, and 2017-2020. Gene expression data from the Gene Expression Omnibus (GEO) microarray database were integrated with machine learning techniques to identify key genes involved in both osteoporosis and kidney stones. Common targets were then identified through the Comparative Toxicogenomics Database (CTD) and GeneCards. GMFA enrichment analysis was performed to identify shared biological pathways. Additionally, drug prediction and molecular docking were employed to further investigate the pharmacological relevance of these targets.

RESULTS

Analysis of the NHANES database confirmed a strong association between osteoporosis and kidney stones. Weighted multivariate logistic regression showed that osteoporosis (OR: 1.41; 95% CI 1.11-1.79; P < 0.001) and bone loss (OR: 1.24; 95% CI 1.08-1.43; P < 0.001) were significantly correlated with an increased risk of kidney stones. Three hub genes-WNT1, AKT1, and TNF-were identified through various analytical methods. GMFA revealed that the mTOR signaling pathway is a key shared pathway. Molecular docking studies further confirmed the pharmacological relevance of these targets, demonstrating strong binding affinity between drugs and the proteins involved, consistent with previous findings.

CONCLUSION

Bone loss is associated with an increased risk of kidney stones. Targeting the mTOR signaling pathway may offer a potential therapeutic approach for treating both osteoporosis and kidney stones.

Aloperine Regulates Inflammation, Apoptosis, and Autophagy in H9C2 Rat Cardiomyoblast Cells After Excessive Hypoxia

Myocardial infarction (MI) is a cardiovascular condition that leads to increased morbidity and mortality, impacting the quality of life of individuals. Aloperine (ALO), derived from Sophora alopecuroides L, has been recognized for its beneficial effects in treating various diseases by showcasing therapeutic properties. However, the precise protective mechanisms of ALO on hypoxia/reoxygenation (H/R) -induced damage in cardiomyocytes in vitro remain unclear. In this study, it was manifested that cell proliferation was weakened after H/R treatment, but this impact was offset after ALO treatment. Furthermore, cell apoptosis was heightened after H/R treatment, but this phenomenon was neutralized after ALO treatment. ALO relieved inflammation in H/R-treated H9C2 rat cardiomyoblast cells. Moreover, ALO strengthened autophagy in H/R-triggered H9C2 rat cardiomyoblast cells through enhancing the LC3II/LC3I level and the LC3B fluorescence intensity. Lastly, it was testified that ALO can rescue the weakened autophagy, the heightened cell apoptosis, and the augmented inflammation after CC treatment in H/R-mediated H9C2 rat cardiomyoblast cells. In conclusion, ALO regulated inflammation, apoptosis, and autophagy through AMPK/Nrf2 pathway in H9C2 rat cardiomyoblast cells after excessive hypoxia. This study suggested that ALO may be an underlying drug for MI therapy.

Sphingosine-1-phosphate alleviates Sjögren's syndrome-like symptoms via inducing autophagy and regulating status of Treg cells in NOD mice

BACKGROUND

Sjögren' s syndrome (SS) is a chronic autoimmune disease that causes multiple lesions. Regulatory T (Treg) cells play an important role in the maintenance of immune homeostasis. Weakened Treg-cell-mediated immunosuppression may aggravate SS symptoms by inducing lymphocyte infiltration into the salivary glands. Although Treg cell egress from such glands requires sphingosine-1-phosphate (S1P), the specific effects of S1P on SS-like symptoms remain unclear.

AIMS

To examine the effect of S1P on SS-like symptoms and the crosstalk between such symptoms and autophagy in non-obese diabetic (NOD) mice.

METHODS

NOD mice were taken as SS model mice. Balb/c mice served as controls. Serum anti-SSA and anti-SSB antibodies were quantitated via ELISA. Submandibular gland tissues were subjected to haematoxylin-and-eosin staining, and extracts thereof to reverse transcription-polymerase chain reaction. The numbers of Treg cells; and the levels of cytokines, LC3, and SPHK1 were measured via flow cytometry (FCM). The Treg immunosuppression capacity was assessed in co-culture experiments.

RESULT

Compared to untreated NOD mice, mice treated with S1P exhibited milder disease, and higher numbers of functional Treg cells. FCM revealed that S1P restored LC3 expression in Treg cells, but had little effect on the LC3 levels of Teff cells. RT-PCR showed that S1P increased the expression levels of mRNAs encoding Foxp-3, SPHK1, S1PR1, and LC3 in submandibular glands (SMGs). After administration of PF-543, the disease became aggravated; lymphocyte infiltration into SMGs increased and LC3 expression fell.

CONCLUSION

S1P therapy alleviated SS-like symptoms in NOD mice by increasing the number of Treg cells, by restoring Treg cell function, and by positively regulating autophagy via crosstalk. Such therapy may be a new and valuable SS treatment option.

NADPH oxidase 2 mediates cardiac sympathetic denervation and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced cardiomyopathy

Doxorubicin has been used extensively as a potent anticancer agent, but its clinical use is limited by its cardiotoxicity. However, the underlying mechanisms remain to be fully elucidated. In this study, we tested whether NADPH oxidase 2 (Nox2) mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced heart failure. Nox2 knockout (KO) and wild-type (WT) mice were randomly assigned to receive a single injection of doxorubicin (15 mg/kg, i.p.) or saline. WT doxorubicin mice exhibited the decreases in survival rate, left ventricular (LV) wall thickness and LV fractional shortening and the increase in the lung wet-to-dry weight ratio 1 week after the injections. These alterations were attenuated in Nox2 KO doxorubicin mice. In WT doxorubicin mice, myocardial oxidative stress was increased, myocardial noradrenergic nerve fibers were reduced, myocardial expression of PGP9.5, GAP43, tyrosine hydroxylase and norepinephrine transporter was decreased, and these changes were prevented in Nox2 KO doxorubicin mice. Myocyte autophagy was increased and myocyte size was decreased in WT doxorubicin mice, but not in Nox2 KO doxorubicin mice. Nox2 mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy-both of which contribute to cardiac atrophy and failure after doxorubicin treatment.

NADPH oxidase 2 inhibitor GSK2795039 prevents doxorubicin-induced cardiac atrophy by attenuating cardiac sympathetic nerve terminal abnormalities and myocyte autophagy

Doxorubicin is widely used for the treatment of human cancer, but its clinical use is limited by a cumulative dose-dependent cardiotoxicity. However, the mechanism of doxorubicin-induced cardiac atrophy and failure remains to be fully understood. In this study, we tested whether the specific NADPH oxidase 2 (Nox2) inhibitor GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, leading to the amelioration of cardiac atrophy and dysfunction in chronic doxorubicin-induced cardiomyopathy. Mice were randomized to receive saline, doxorubicin (2.5 mg/kg, every other day, 6 times) or doxorubicin plus GSK2795039 (2.5 mg/kg, twice a day, 9 weeks). Left ventricular (LV) total wall thickness and LV ejection fraction were decreased in doxorubicin-treated mice compared with saline-treated mice and the decreases were prevented by the treatment of the specific Nox2 inhibitor GSK2795039. The ratio of total heart weight to tibia length and myocyte cross-sectional area were decreased in doxorubicin-treated mice, and the decreases were attenuated by the GSK2795039 treatment. In doxorubicin-treated mice, myocardial Nox2 and 4-hydroxynonenal levels were increased, myocardial expression of GAP43, tyrosine hydroxylase and norepinephrine transporter, markers of sympathetic nerve terminals, was decreased, and these changes were prevented by the GSK2795039 treatment. The ratio of LC3 II/I, a marker of autophagy, and Atg5, Atg12 and Atg12-Atg5 conjugate proteins were increased in doxorubicin-treated mice, and the increases were attenuated by the GSK2795039 treatment. These findings suggest that inhibition of Nox2 by GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, thereby ameliorating cardiac atrophy and dysfunction after chronic doxorubicin treatment.

Metabolic signatures in post-myocardial infarction heart failure, including insights into prediction, intervention, and prognosis

Heart failure (HF) is a prevalent long-term complication of myocardial infarction (MI). The incidence of post-MI HF is high, and patients with the condition have a poor prognosis. Accurate identification of individuals at high risk for post-MI HF is crucial for implementation of a protective and ideally personalized strategy to prevent fatal events. Post-MI HF is characterized by adverse cardiac remodeling, which results from metabolic changes in response to long-term ischemia. Moreover, various risk factors, including genetics, diet, and obesity, can influence metabolic pathways in patients. This review focuses on the metabolic signatures of post-MI HF that could serve as non-invasive biomarkers for early identification in high-risk populations. We also explore how metabolism participates in the pathophysiology of post-MI HF. Furthermore, we discuss the potential of metabolites as novel targets for treatment of post-MI HF and as biomarkers for prognostic evaluation. It is expected to provide valuable suggestions for the clinical prevention and treatment of post-MI HF from a metabolic perspective.

Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes to Fibrosis of Chronic Pancreatitis via Inducing Autophagy and Activation of Pancreatic Stellate Cells

BACKGROUND & AIMS

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.

METHODS

Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1-/- mice or PACs-specific SPHK1-knockdown mice with recombinant adeno-associated virus serotypes 9-SPHK1-knockdown, as well as in mice treated with inhibitor of SPHK1 and S1P receptor 2 (S1PR2).

RESULTS

SPHK1/S1P was remarkably increased in iPACs and acinar cells in pancreatic tissues of CP mice. Meanwhile, the pathogenesis, fibrosis, and PSCs activation of CP was significantly prevented in SPHK1-/- mice and recombinant adeno-associated virus serotypes 9-SPHK1-knockdown mice. Meanwhile, iPACs obviously activated PSCs, which was prevented by SPHK1 knockdown in iPACs. Moreover, iPACs-derived S1P specifically combined to S1PR2 of PSCs, by which modulated 5' adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway and consequently induced autophagy and activation of PSCs. Furthermore, hypoxia-inducible factor 1-α and -2α promoted SPHK1 transcription of PACs under hypoxia conditions, which is a distinct characteristic of the CP microenvironment. Coincidently, inhibition of SPHK1 and S1PR2 activity with inhibitor PF-543 and JTE-013 obviously impeded pancreatic fibrogenesis of CP mice.

CONCLUSIONS

The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

The role of sphingosine-1-phosphate in autophagy and related disorders

S1P, also referred to as sphingosine-1-phosphate, is a lipid molecule with bioactive properties involved in numerous cellular processes such as cell growth, movement, programmed cell death, self-degradation, cell specialization, aging, and immune system reactions. Autophagy is a meticulously controlled mechanism in which cells repurpose their elements to maintain cellular balance. There are five stages in autophagy: initiation, nucleation, elongation and maturation, fusion, and degradation. New research has provided insight into the complex connection between S1P and autophagy, uncovering their interaction in both normal and abnormal circumstances. Gaining knowledge about the regulatory mechanism of S1P signaling on autophagy can offer a valuable understanding of its function in well-being and illness, potentially leading to innovative therapeutic concepts for diverse ailments. Hence, this review analyzes the essential stages in mammalian autophagy, with a specific emphasis on recent research exploring the control of each stage by S1P. Additionally, it sheds light on the roles of S1P-induced autophagy in various disorders.

Dysregulation of sphingosine-1-phosphate (S1P) and S1P receptor 1 signaling in the 5xFAD mouse model of Alzheimer's disease

Sphingolipid-1-phosphate (S1P) signaling through the activation S1P receptors (S1PRs) plays critical roles in cellular events in the brain. Aberrant S1P metabolism has been identified in the brains of Alzheimer's disease (AD) patients. Our recent studies have shown that treatment with fingolimod, an analog of sphingosine, provides neuroprotective effects in five familiar Alzheimer disease (5xFAD) transgenic mice, resulting in the reduction of amyloid-β (Aβ) neurotoxicity, inhibition of activation of microglia and astrocytes, increased hippocampal neurogenesis, and improved learning and memory. However, the pathways by which dysfunctional S1P and S1PR signaling may associate with the development of AD-like pathology remain unknown. In this study, we investigated the alteration of signaling of S1P/S1P receptor 1 (S1PR1), the most abundant S1PR subtype in the brain, in the cortex of 5xFAD transgenic mice at 3, 8, and 14 months of age. Compared to non-transgenic wildtype (WT) littermates, we found significant decreased levels of sphingosine kinases (SphKs), increased S1P lyase (S1PL), and increased S1PR1 in 8- and 14-month-old, but not in 3-month-old 5xFAD mice. Furthermore, we detected increased activation of the S1PR1 downstream pathway of Akt/mTor/Tau signaling in aging 5xFAD mice. Treatment with fingolimod from 1 to 8 months of age reversed the levels of SphKs, S1PL, and furthermore, those of S1PR1 and its downstream pathway of Akt/mTor/Tau signaling. Together the data reveal that dysregulation of S1P and S1PR signaling may associate with the development of AD-like pathology through Akt/mTor/Tau signaling.

Sphingolipid metabolism and signaling in cardiovascular diseases

Sphingolipids are a structural component of the cell membrane, derived from sphingosine, an amino alcohol. Its sphingoid base undergoes various types of enzymatic transformations that lead to the formation of biologically active compounds, which play a crucial role in the essential pathways of cellular signaling, proliferation, maturation, and death. The constantly growing number of experimental and clinical studies emphasizes the pivotal role of sphingolipids in the pathophysiology of cardiovascular diseases, including, in particular, ischemic heart disease, hypertension, heart failure, and stroke. It has also been proven that altering the sphingolipid metabolism has cardioprotective properties in cardiac pathologies, including myocardial infarction. Recent studies suggest that selected sphingolipids may serve as valuable biomarkers useful in the prognosis of cardiovascular disorders in clinical practice. This review aims to provide an overview of the current knowledge of sphingolipid metabolism and signaling in cardiovascular diseases.

Cyclic mechanical strain with high-tensile triggers autophagy in growth plate chondrocytes

Background

Mechanical loading has been widely considered to be essential for growth plate to maintain metabolism and development. Cyclic mechanical strain has been demonstrated to induce autophagy, whereas the relationship between cyclic tensile strain (CTS) and autophagy in growth plate chondrocytes (GPCs) is not clear. The objective of this study was to investigate whether CTS can regulate autophagy in GPCs in vitro and explore the potential mechanisms of this regulation.

Methods

The 2-week-old Sprague–Dawley rat GPCs were subjected to CTS of varying magnitude and duration at a frequency of 2.0 Hz. The mRNA levels of autophagy-related genes were measured by RT-qPCR. The autophagy in GPCs was verified by transmission electron microscopy (TME), immunofluorescence and Western blotting. The fluorescence-activated cell sorting (FACS) was employed to detect the percentage of apoptotic and necrotic cells.

Results

In GPCs, CTS significantly increased the mRNA and protein levels of autophagy-related genes, such as LC3, ULK1, ATG5 and BECN1 in a magnitude- and time-dependent manner. There was no significant difference in the proportion of apoptotic and necrotic cells between control group and CTS group. The autophagy inhibitors, 3-methyladenine (3MA) and chloroquine (CQ) reversed the CTS-induced autophagy via promoting the formation of autophagosomes. Cytochalasin D (cytoD), an inhibitor of G-actin polymerization into F-actin, could effectively block the CTS-induced autophagy in GPCs.

Conclusion

Cyclic mechanical strain with high-tensile triggers autophagy in GPCs, which can be suppressed by 3MA and CQ, and cytoskeletal F-actin microfilaments organization plays a key role in chondrocytes’ response to mechanical loading.

Signaling pathways and targeted therapy for myocardial infarction

Although the treatment of myocardial infarction (MI) has improved considerably, it is still a worldwide disease with high morbidity and high mortality. Whilst there is still a long way to go for discovering ideal treatments, therapeutic strategies committed to cardioprotection and cardiac repair following cardiac ischemia are emerging. Evidence of pathological characteristics in MI illustrates cell signaling pathways that participate in the survival, proliferation, apoptosis, autophagy of cardiomyocytes, endothelial cells, fibroblasts, monocytes, and stem cells. These signaling pathways include the key players in inflammation response, e.g., NLRP3/caspase-1 and TLR4/MyD88/NF-κB; the crucial mediators in oxidative stress and apoptosis, for instance, Notch, Hippo/YAP, RhoA/ROCK, Nrf2/HO-1, and Sonic hedgehog; the controller of myocardial fibrosis such as TGF-β/SMADs and Wnt/β-catenin; and the main regulator of angiogenesis, PI3K/Akt, MAPK, JAK/STAT, Sonic hedgehog, etc. Since signaling pathways play an important role in administering the process of MI, aiming at targeting these aberrant signaling pathways and improving the pathological manifestations in MI is indispensable and promising. Hence, drug therapy, gene therapy, protein therapy, cell therapy, and exosome therapy have been emerging and are known as novel therapies. In this review, we summarize the therapeutic strategies for MI by regulating these associated pathways, which contribute to inhibiting cardiomyocytes death, attenuating inflammation, enhancing angiogenesis, etc. so as to repair and re-functionalize damaged hearts.