Mitochondrial ROS and the Effectors of the Intrinsic Apoptotic Pathway in Aging Cells: The Discerning Killers!

The glyoxylate shunt protein ICL-1 protects from mitochondrial superoxide stress through activation of the mitochondrial unfolded protein response

Disrupting mitochondrial superoxide dismutase (SOD) causes neonatal lethality in mice and death of flies within 24 h after eclosion. Deletion of mitochondrial sod genes in C. elegans impairs fertility as well, but surprisingly is not detrimental to survival of progeny generated. The comparison of metabolic pathways among mouse, flies and nematodes reveals that mice and flies lack the glyoxylate shunt, a shortcut that bypasses part of the tricarboxylic acid (TCA) cycle. Here we show that ICL-1, the sole protein that catalyzes the glyoxylate shunt, is critical for protection against embryonic lethality resulting from elevated levels of mitochondrial superoxide. In exploring the mechanism by which ICL-1 protects against ROS-mediated embryonic lethality, we find that ICL-1 is required for the efficient activation of mitochondrial unfolded protein response (UPRmt) and that ATFS-1, a key UPRmt transcription factor and an activator of icl-1 gene expression, is essential to limit embryonic/neonatal lethality in animals lacking mitochondrial SOD. In sum, we identify a biochemical pathway that highlights a molecular strategy for combating toxic mitochondrial superoxide consequences in cells.

Age-Dependent Surface Receptor Expression Patterns in Immature Versus Mature Platelets in Mouse Models of Regenerative Thrombocytopenia

Aging is a multifaceted process that unfolds at both the individual and cellular levels, resulting in changes in platelet count and platelet reactivity. These alterations are influenced by shifts in platelet production, as well as by various environmental factors that affect circulating platelets. Aging also triggers functional changes in platelets, including a reduction in RNA content and protein production capacity. Older individuals and RNA-rich immature platelets often exhibit hyperactivity, contributing significantly to pathologic conditions such as cardiovascular diseases, sepsis, and thrombosis. However, the impact of aging on surface receptor expression of circulating platelets, particularly whether these effects vary between immature and mature platelets, remains largely unexplored. Thus, we investigated the expression of certain surface and activation receptors on platelets from young and old mice as well as on immature and mature platelets from mouse models of regenerative thrombocytopenia by flow cytometry. Our findings indicate that aged mice show an upregulated expression of the platelet endothelial cell adhesion molecule-1 (CD31), tetraspanin-29 (CD9), and Toll-like receptor 2 (TLR2) compared to their younger counterparts. Interestingly, when comparing immature and mature platelets in both young and old mice, no differences were observed in mature platelets. However, immature platelets from young mice displayed higher surface expression compared to immature platelets from old mice. Additionally, in mouse models of regenerative thrombocytopenia, the majority of receptors were upregulated in immature platelets. These results suggest that distinct surface receptor expressions are increased on platelets from old mice and immature platelets, which may partially explain their heightened activity and contribute to an increased thrombotic risk.

MTH1 protects platelet mitochondria from oxidative damage and regulates platelet function and thrombosis

Human MutT Homolog 1 (MTH1) is a nucleotide pool sanitization enzyme that hydrolyzes oxidized nucleotides to prevent their mis-incorporation into DNA under oxidative stress. Expression and functional roles of MTH1 in platelets are not known. Here, we show MTH1 expression in platelets and its deficiency impairs hemostasis and arterial/venous thrombosis in vivo. MTH1 deficiency reduced platelet aggregation, phosphatidylserine exposure and calcium mobilization induced by thrombin but not by collagen-related peptide (CRP) along with decreased mitochondrial ATP production. Thrombin but not CRP induced Ca2+-dependent mitochondria reactive oxygen species generation. Mechanistically, MTH1 deficiency caused mitochondrial DNA oxidative damage and reduced the expression of cytochrome c oxidase 1. Furthermore, MTH1 exerts a similar role in human platelet function. Our study suggests that MTH1 exerts a protective function against oxidative stress in platelets and indicates that MTH1 could be a potential therapeutic target for the prevention of thrombotic diseases.

Mitochondrial Oxidative Metabolism: An Emerging Therapeutic Target to Improve CKD Outcomes

Chronic kidney disease (CKD) predisposes one toward end-stage renal disease (ESRD) and its associated morbidity and mortality. Significant metabolic perturbations in conjunction with alterations in redox status during CKD may induce increased production of reactive oxygen species (ROS), including superoxide (O₂^●-) and hydrogen peroxide (H₂O₂). Increased O₂^●- and H₂O₂ may contribute to the overall progression of renal injury as well as catalyze the onset of comorbidities. In this review, we discuss the role of mitochondrial oxidative metabolism in the pathology of CKD and the recent developments in treating CKD progression specifically targeted to the mitochondria. Recently published results from a Phase 2b clinical trial by our group as well as recently released data from a ROMAN: Phase 3 trial (NCT03689712) suggest avasopasem manganese (AVA) may protect kidneys from cisplatin-induced CKD. Several antioxidants are under investigation to protect normal tissues from cancer-therapy-associated injury. Although many of these antioxidants demonstrate efficacy in pre-clinical models, clinically relevant novel compounds that reduce the severity of AKI and delay the progression to CKD are needed to reduce the burden of kidney disease. In this review, we focus on the various metabolic pathways in the kidney, discuss the role of mitochondrial metabolism in kidney disease, and the general involvement of mitochondrial oxidative metabolism in CKD progression. Furthermore, we present up-to-date literature on utilizing targets of mitochondrial metabolism to delay the pathology of CKD in pre-clinical and clinical models. Finally, we discuss the current clinical trials that target the mitochondria that could potentially be instrumental in advancing the clinical exploration and prevention of CKD.

Mitochondrial Dysfunction: At the Nexus between Alcohol-Associated Immunometabolic Dysregulation and Tissue Injury

Alcohol misuse, directly or indirectly as a result of its metabolism, negatively impacts most tissues, including four with critical roles in energy metabolism regulation: the liver, pancreas, adipose, and skeletal muscle. Mitochondria have long been studied for their biosynthetic roles, such as ATP synthesis and initiation of apoptosis. However, current research has provided evidence that mitochondria participate in myriad cellular processes, including immune activation, nutrient sensing in pancreatic β-cells, and skeletal muscle stem and progenitor cell differentiation. The literature indicates that alcohol impairs mitochondrial respiratory capacity, promoting reactive oxygen species (ROS) generation and disrupting mitochondrial dynamics, leading to dysfunctional mitochondria accumulation. As discussed in this review, mitochondrial dyshomeostasis emerges at a nexus between alcohol-disrupted cellular energy metabolism and tissue injury. Here, we highlight this link and focus on alcohol-mediated disruption of immunometabolism, which refers to two distinct, yet interrelated processes. Extrinsic immunometabolism involves processes whereby immune cells and their products influence cellular and/or tissue metabolism. Intrinsic immunometabolism describes immune cell fuel utilization and bioenergetics that affect intracellular processes. Alcohol-induced mitochondrial dysregulation negatively impacts immunometabolism in immune cells, contributing to tissue injury. This review will present the current state of literature, describing alcohol-mediated metabolic and immunometabolic dysregulation from a mitochondrial perspective.

Microarrays, Enzymatic Assays, and MALDI-MS for Determining Specific Alterations to Mitochondrial Electron Transport Chain Activity, ROS Formation, and Lipid Composition in a Monkey Model of Parkinson’s Disease

Multiple evidences suggest that mitochondrial dysfunction is implicated in the pathogenesis of Parkinson’s disease via the selective cell death of dopaminergic neurons, such as that which occurs after prolonged exposure to the mitochondrial electron transport chain (ETC) complex I inhibitor, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrine (MPTP). However, the effects of chronic MPTP on the ETC complexes and on enzymes of lipid metabolism have not yet been thoroughly determined. To face these questions, the enzymatic activities of ETC complexes and the lipidomic profile of MPTP-treated non-human primate samples were determined using cell membrane microarrays from different brain areas and tissues. MPTP treatment induced an increase in complex II activity in the olfactory bulb, putamen, caudate, and substantia nigra, where a decrease in complex IV activity was observed. The lipidomic profile was also altered in these areas, with a reduction in the phosphatidylserine (38:1) content being especially relevant. Thus, MPTP treatment not only modulates ETC enzymes, but also seems to alter other mitochondrial enzymes that regulate the lipid metabolism. Moreover, these results show that a combination of cell membrane microarrays, enzymatic assays, and MALDI-MS provides a powerful tool for identifying and validating new therapeutic targets that might accelerate the drug discovery process.

Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans

Mitochondria preserve metabolic homeostasis and integrate stress signals, to trigger cytoprotective, or cell death pathways. Mitochondrial homeostasis and function decline with age. The mechanisms underlying the deterioration of mitochondrial homeostasis during ageing, or in age-associated pathologies, remain unclear. Here, we show that CISD-1, a mitochondrial iron-sulfur cluster binding protein, implicated in the pathogenesis of Wolfram neurodegenerative syndrome type 2, modulates longevity in the nematode Caenorhabditis elegans by engaging autophagy and the mitochondrial intrinsic apoptosis pathway. The anti-apoptotic protein CED-9 is the downstream effector that mediates CISD-1-dependent effects on proteostasis, neuronal integrity and lifespan. Moreover, intracellular iron abundance is critical for CISD-1 function, since mild iron supplementation is sufficient to decelerate ageing and partly ameliorate the disturbed mitochondrial bioenergetics and proteostasis of CISD-1 deficient animals. Our findings reveal that CISD-1 serves as a mechanistic link between autophagy and the apoptotic pathway in mitochondria to differentially modulate organismal proteostasis and ageing, and suggest novel approaches which could facilitate the treatment of Wolfram Syndrome or related diseases.

Transcriptome Profiling of the Liver in Nellore Cattle Phenotypically Divergent for RFI in Two Genetic Groups

The identification and selection of genetically superior animals for residual feed intake (RFI) could enhance productivity and minimize environmental impacts. The aim of this study was to use RNA-seq data to identify the differentially expressed genes (DEGs), known non-coding RNAs (ncRNAs), specific biomarkers and enriched biological processes associated with RFI of the liver in Nellore cattle in two genetic groups. In genetic group 1 (G1), 24 extreme RFI animals (12 low RFI (LRFI) versus 12 high RFI (HRFI)) were selected from a population of 60 Nellore bulls. The RNA-seq of the samples from their liver tissues was performed using an Illumina HiSeq 2000. In genetic group 2 (G2), 20 samples of liver tissue of Nellore bulls divergent for RFI (LRFI, n = 10 versus HRFI, n = 10) were selected from 83 animals. The raw data of the G2 were chosen from the ENA repository. A total of 1811 DEGs were found for the G1 and 2054 for the G2 (p-value ≤ 0.05). We detected 88 common genes in both genetic groups, of which 33 were involved in the immune response and in blocking oxidative stress. In addition, seven (B2M, ADSS, SNX2, TUBA4A, ARHGAP18, MECR, and ABCF3) possible gene biomarkers were identified through a receiver operating characteristic analysis (ROC) considering an AUC > 0.70. The B2M gene was overexpressed in the LRFI group. This gene regulates the lipid metabolism protein turnover and inhibits cell death. We also found non-coding RNAs in both groups. MIR25 was up-regulated and SNORD16 was down-regulated in the LRFI for G1. For G2, up-regulated RNase_MRP and SCARNA10 were found. We highlight MIR25 as being able to act by blocking cytotoxicity and oxidative stress and RMRP as a blocker of mitochondrial damage. The biological pathways associated with RFI of the liver in Nellore cattle in the two genetic groups were for energy metabolism, protein turnover, redox homeostasis and the immune response. The common transcripts, biomarkers and metabolic pathways found in the two genetic groups make this unprecedented work even more relevant, since the results are valid for different herds raised in different ways. The results reinforce the biological importance of these known processes but also reveal new insights into the complexity of the liver tissue transcriptome of Nellore cattle.

A mitochondrion-free eukaryote contains proteins capable of import into an exogenous mitochondrion-related organelle

The endobiotic flagellate Monocercomonoides exilis is the only known eukaryote to have lost mitochondria and all its associated proteins in its evolutionary past. This final stage of the mitochondrial evolutionary pathway may serve as a model to explain events at their very beginning such as the initiation of protein import. We have assessed the capability of proteins from this eukaryote to enter emerging mitochondria using a specifically designed in vitro assay. Hydrogenosomes (reduced mitochondria) of Trichomonas vaginalis were incubated with a soluble protein pool derived from a cytosolic fraction of M. exilis, and proteins entering hydrogenosomes were subsequently detected by mass spectrometry. The assay detected 19 specifically and reproducibly imported proteins, and in 14 cases the import was confirmed by the overexpression of their tagged version in T. vaginalis. In most cases, only a small portion of the signal reached the hydrogenosomes, suggesting specific but inefficient transport. Most of these proteins represent enzymes of carbon metabolism, and none exhibited clear signatures of proteins targeted to hydrogenosomes or mitochondria, which is consistent with their inefficient import. The observed phenomenon may resemble a primaeval type of protein import which might play a role in the establishment of the organelle and shaping of its proteome in the initial stages of endosymbiosis.

Mitochondrial transplantation attenuates traumatic neuropathic pain, neuroinflammation, and apoptosis in rats with nerve root ligation

Traumatic neuropathic pain (TNP) is caused by traumatic damage to the somatosensory system and induces the presentation of allodynia and hyperalgesia. Mitochondrial dysfunction, neuroinflammation, and apoptosis are hallmarks in the pathogenesis of TNP. Recently, mitochondria-based therapy has emerged as a potential therapeutic intervention for diseases related to mitochondrial dysfunction. However, the therapeutic effectiveness of mitochondrial transplantation (MT) on TNP has rarely been investigated. Here, we validated the efficacy of MT in treating TNP. Both in vivo and in vitro TNP models by conducting an L5 spinal nerve ligation in rats and exposing the primary dorsal root ganglion (DRG) neurons to capsaicin, respectively, were applied in this study. The MT was operated by administrating 100 µg of soleus-derived allogeneic mitochondria into the ipsilateral L5 DRG in vivo and the culture medium in vitro. Results showed that the viable transplanted mitochondria migrated into the rats' spinal cord and sciatic nerve. MT alleviated the nerve ligation-induced mechanical and thermal pain hypersensitivity. The nerve ligation-induced glial activation and the expression of pro-inflammatory cytokines and apoptotic markers in the spinal cord were also repressed by MT. Consistently, exogenous mitochondria reversed the capsaicin-induced reduction of mitochondrial membrane potential and expression of pro-inflammatory cytokines and apoptotic markers in the primary DRG neurons in vitro. Our findings suggest that MT mitigates the spinal nerve ligation-induced apoptosis and neuroinflammation, potentially playing a role in providing neuroprotection against TNP.

The interplay of dopamine metabolism abnormalities and mitochondrial defects in the pathogenesis of schizophrenia

Dopamine (DA) is a major monoamine neurotransmitter in the brain and has essential roles in higher functions of the brain. Malfunctions of dopaminergic signaling have been implicated in various mental disorders such as addiction, attention deficit/hyperactivity disorder, Huntington's disease, Parkinson's disease (PD), and schizophrenia. The pathogenesis of PD and schizophrenia involves the interplay of mitochondrial defect and DA metabolism abnormalities. This article focuses on this issue in schizophrenia. It started with the introduction of metabolism, behavioral action, and physiology of DA, followed by reviewing evidence for malfunctions of dopaminergic signaling in patients with schizophrenia. Then it provided an overview of multiple facets of mitochondrial physiology before summarizing mitochondrial defects reported in clinical studies with schizophrenia patients. Finally, it discussed the interplay between DA metabolism abnormalities and mitochondrial defects and outlined some clinical studies showing effects of combination therapy of antipsychotics and antioxidants in treating patients with schizophrenia. The update and integration of these lines of information may advance our understanding of the etiology, pathogenesis, phenomenology, and treatment of schizophrenia.

ROS: Basic Concepts, Sources, Cellular Signaling, and its Implications in Aging Pathways

Reactive oxygen species (ROS) are bioproducts of cellular metabolism. There is a range of molecules with oxidizing properties known as ROS. Despite those molecules being implied negatively in aging and numerous diseases, their key role in cellular signaling is evident. ROS control several biological processes such as inflammation, proliferation, and cell death. The redox signaling underlying these cellular events is one characteristic of the new generation of scientists aimed at defining the role of ROS in the cellular environment. The control of redox potential, which includes the balance of the sources of ROS and the antioxidant system, implies an important target for understanding the cells' fate derived from redox signaling. In this review, we summarized the chemical, the redox balance, the signaling, and the implications of ROS in biological aging.

Programmed cell death process in freshwater Microcystis aeruginosa and marine Phaeocystis globosa induced by a plant derived allelochemical

Harmful algal blooms (HAB) are a serious problem worldwide. Allelochemicals from natural plants were recently thought to be promising anti-algaecide in controlling harmful algae. However, the programmed cell death (PCD) process of algae under allelopathic pressure induced by 5,4'-dihydroxyflavone (5,4'-DHF) was poorly understood. In this study, two common and worldwide distributed microalgae, Microcystis aeruginosa and Phaeocystis globosa were selected as target algae, and the PCD processes induced by 5,4'-DHF were cross-compared between the two species. Both algae species were inhibited significantly by 5,4'-DHF with the relative sensitivity of 0.11. To uncover the PCD progress systematically, signals for PCD triggering, antioxidant enzyme activity, photosynthetic ability variation, caspase-like activities and typical indicators were investigated. In both species, typical indicators of PCD - phosphatidylserine externalization and chromatin condensation - were detected. The intracellular reactive oxygen species (ROS), nitric oxide (NO) and H₂O₂ were the potential signal molecules to stimulate PCD, and caspase-like activities were activated with an elevation of cytochrome c indicating the initiation of PCD in both species. However, P. globosa responded to 5,4'-DHF immediately after 3 h with the elevation of ROS and not in M. aeruginosa. Antioxidant enzyme activities of superoxide dismutase (SOD) and catalase (CAT) in M. aeruginosa and P. globosa also showed different patterns on day 3. Specifically, SOD activity in M. aeruginosa increased significantly while it decreased significantly in P. globosa, CAT activity in M. aeruginosa decreased significantly while it increased significantly in P. globosa (p < 0.05). Malondialdehyde (MDA) content in P. globosa increased significantly (p < 0.001) while it showed no variation in M. aeruginosa. Overall, this study is one of the earliest studies to explore the inhibition and action mechanism of plant derived flavonoids on harmful algae from the perspective of PCD, and provide new insights into the antialgal mechanism of allelochemicals.

Translocator protein (18kDa) TSPO: a new diagnostic or therapeutic target for stress-related disorders?

Efficient treatment of stress-related disorders, such as depression, is still a major challenge. The onset of antidepressant drug action is generally quite slow, while the anxiolytic action of benzodiazepines is considerably faster. However, their long-term use is impaired by tolerance development, abuse liability and cognitive impairment. Benzodiazepines act as positive allosteric modulators of ɣ-aminobutyric acid type A (GABA_A) receptors. 3α-reduced neurosteroids such as allopregnanolone also are positive allosteric GABA_A receptor modulators, however, through a site different from that targeted by benzodiazepines. Recently, the administration of neurosteroids such as brexanolone or zuranolone has been shown to rapidly ameliorate symptoms in post-partum depression or major depressive disorder. An attractive alternative to the administration of exogenous neurosteroids is promoting endogenous neurosteroidogenesis via the translocator protein 18k Da (TSPO). TSPO is a transmembrane protein located primarily in mitochondria, which mediates numerous biological functions, e.g., steroidogenesis and mitochondrial bioenergetics. TSPO ligands have been used in positron emission tomography (PET) studies as putative markers of microglia activation and neuroinflammation in stress-related disorders. Moreover, TSPO ligands have been shown to modulate neuroplasticity and to elicit antidepressant and anxiolytic therapeutic effects in animals and humans. As such, TSPO may open new avenues for understanding the pathophysiology of stress-related disorders and for the development of novel treatment options.

The pentacyclic triterpenoid phytosterol lupeol promotes antioxidant response in the nematode C. elegans

Plants of the Mimosa genus are studied and used for their bioactive properties. Among bioactive phytochemicals are quercetin and myricetin, which have been demonstrated to act as antioxidants in many contexts (Taheri et al. 2020; Xu et al. 2019), including in C. elegans (Buchter et al. 2013; Grünz et al. 2012; Sugawara and Sakamoto 2020). Other phytochemicals from these plants, such as the triterpenoid phytosterol lupeol, have been shown to have antioxidant properties but have not been as extensively characterized in model organisms (Liu et al. 2021; Shai et al. 2009). Here we employed the nematode C. elegans to assess whether lupeol elicits antioxidant response in vivo . Using reporter assays for oxidative stress, we find that treatment of animals with lupeol rescues some of the effects resulting from treatment with the prooxidant paraquat. Our results demonstrate that lupeol displays antioxidant properties in vivo in C. elegans .

The effect of postmortem pH decline rate on caspase-3 activation and tenderness of bovine skeletal muscle during aging

This study aimed to investigate the effect of postmortem pH decline rate on caspase-3 activity and bovine muscle tenderness during aging. Protein denaturation, reactive oxygen species (ROS) levels, mitochondrial apoptosis factors, and shear force were assessed in bovine muscles with different pH decline rates. The results showed that, compared with the slow group, the fast pH decline group had a 1.79% and 1.39% higher sarcoplasmic protein denaturation at 6 and 12 h, respectively (p < .05), and a significantly or extremely significantly higher ROS levels at 6-24 (p < .05, p < .01). Moreover, the fast group had a 14.05%, 22.39%,18.34%, and 25.28% of higher mitochondrial dysfunction at 6, 12, 24, and 72 h, respectively (p < .05); a 16.71%, 23.39%, 17.05%, and 26.61% of lower cytochrome c reduction levels at 6, 12, 24, and 120 h, respectively (p < .05); a significantly increased caspase-3 activity and proportion of apoptotic nuclei at 12-168 and 24-168 h, respectively (p < .05); and a 5.70%, 7.24%, 12.16%, 10.10% and 10.49% decreased shear force at 12, 24, 72,120, and 168 h, respectively (p < .05). These results demonstrated that the fast postmortem pH decline enhanced caspase-3 activation and bovine muscle tenderization by mitochondrial dysfunction-induced apoptosis during aging. PRACTICAL APPLICATIONS: Beef tenderness has long been one of the most important concerns for consumers and the meat industry. To date, the postmortem aging process has been an effective way to improve the tenderness of chilled beef. However, changes in many of the elements in a cattle's muscle after slaughter might actually determine the final tenderness of the meat. The present study suggested that the fast postmortem pH decline could promote the activation of caspase-3 and improve the tenderness of beef during aging. This finding can provide a basis for the meat processing industry to produce beef with high tenderness. In the future, beef tenderness could even be improved by adjusting the glycolytic rate and pH of muscle for a short time after slaughter.

Early Effects of Extracellular Vesicles Secreted by Adipose Tissue Mesenchymal Cells in Renal Ischemia Followed by Reperfusion: Mechanisms Rely on a Decrease in Mitochondrial Anion Superoxide Production

Acute kidney injury (AKI) caused by ischemia followed by reperfusion (I/R) is characterized by intense anion superoxide (O₂^•−) production and oxidative damage. We investigated whether extracellular vesicles secreted by adipose tissue mesenchymal cells (EVs) administered during reperfusion can suppress the exacerbated mitochondrial O₂^•− formation after I/R. We used Wistar rats subjected to bilateral renal arterial clamping (30 min) followed by 24 h of reperfusion. The animals received EVs (I/R + EVs group) or saline (I/R group) in the kidney subcapsular space. The third group consisted of false-operated rats (SHAM). Mitochondria were isolated from proximal tubule cells and used immediately. Amplex Red™ was used to measure mitochondrial O₂^•− formation and MitoTracker™ Orange to evaluate inner mitochondrial membrane potential (Δψ). In vitro studies were carried out on human renal proximal tubular cells (HK-2) co-cultured or not with EVs under hypoxic conditions. Administration of EVs restored O₂^•− formation to SHAM levels in all mitochondrial functional conditions. The gene expression of catalase and superoxide dismutase-1 remained unmodified; transcription of heme oxygenase-1 (HO-1) was upregulated. The co-cultures of HK-2 cells with EVs revealed an intense decrease in apoptosis. We conclude that the mechanisms by which EVs favor long-term recovery of renal structures and functions after I/R rely on a decrease of mitochondrial O₂^•− formation with the aid of the upregulated antioxidant HO-1/Nuclear factor erythroid 2-related factor 2 system, thus opening new vistas for the treatment of AKI.

Adiponectin promotes repair of renal tubular epithelial cells by regulating mitochondrial biogenesis and function

BACKGROUND

Mitochondrial biogenesis and dysfunction are associated with renal tubular epithelial cell injury and the pathophysiological development of diabetic nephropathy (DN). Adiponectin (APN) is a plasma hormone protein specifically secreted by adipocytes. In the present study, we studied the effects of APN on mitochondrial biogenesis and function in renal tubular epithelial cells and examined the mechanisms underlying its actions.

MATERIALS

A rat model of type 2 diabetes mellitus (T2DM) was established using streptozotocin (STZ), and an NRK-52E culture model exposed to high glucose was also used. We found that APN treatment alleviated kidney histopathological injury in T2DM rats, reduced fasting blood glucose (FBG) and postprandial blood glucose (PBG) levels, maintained stable animal weight, promoted cell viability, inhibited apoptosis and the formation of autophagosomes, and also increased mitochondrial mass, mitochondrial DNA (mtDNA) content and mitochondrial membrane potential (MMP) in vivo and in vitro.

RESULTS

We found that the expression of AdipoR1/CREB/PGC-1α/TFAM pathway proteins and respiratory chain complex subunits CO1, CO2, CO3, ATP6 and ATP8 were significantly increased after APN treatment. We also found that inhibition of cAMP response element binding protein (CREB) weakened the effects of APN in NRK-52E cells treated with high glucose. Coimmunoprecipitation experiments showed that AdipoR1 interacted with CREB.

CONCLUSION

APN promoted mitochondrial biogenesis and function in renal tubular epithelial cells by regulating the AdipoR1/CREB/PGC-1α/TFAM pathway. APN has the potential to serve as an effective drug for the treatment of DN.

Comparison of cytotoxicity effects induced by four different types of nanoparticles in human corneal and conjunctival epithelial cells

The impact of particulate matter (PM) on ocular surface health has attracted increased attention in recent years. Previous studies have reported that differences in the chemical composition of PM can affect the toxicological response. However, available information on the toxic effects of chemical components of PM on the ocular surface is insufficient. In this paper, we aimed to investigate the toxicity effects of chemical components of PM on the ocular surface, focusing on the effects of four different types of nanoparticles (NPs) in human corneal epithelial cells (HCECs) and human conjunctival epithelial cells (HCjECs), which include titanium dioxide (TiO2), carbon black (CB), zinc dioxide (ZnO), and silicon dioxide (SiO2). We found that the in vitro cytotoxic effects of CB, ZnO, and SiO2 NPs are dependent on particle properties and cell type as well as the exposure concentration and time. Here, the order of increasing toxicity was SiO2 → CB → ZnO, while TiO2 demonstrated no toxicity. Moreover, toxic effects appearing more severe in HCECs than HCjECs. Reactive oxygen species (ROS)-mediated oxidative stress plays a key role in the toxicity of these three NPs in HCECs and HCjECs, leading to apoptosis and mitochondrial damage, which are also important contributors to aging. Sirtuin1 (SIRT1) as an NAD+-dependent protein deacetylase that seems to play a potential protective role in this process. These findings implied that ROS and/or SIRT1 may become a potential target of clinical treatment of PM- or NP-related ocular surface diseases.

Mitochondrial DNA copy number as a prognostic marker is age-dependent in adult glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive form of glioma. GBM frequently displays chromosome (chr) 7 gain, chr 10 loss and/or EGFR amplification (chr7+/chr10-/EGFRamp). Overall survival (OS) is 15 months after treatment. In young adults, IDH1/2 mutations are associated with longer survival. In children, histone H3 mutations portend a dismal prognosis. Novel reliable prognostic markers are needed in GBM. We assessed the prognostic value of mitochondrial DNA (mtDNA) copy number in adult GBM.

METHODS

mtDNA copy number was assessed using real-time quantitative PCR in 232 primary GBM. Methylation of POLG and TFAM genes, involved in mtDNA replication, was assessed by bisulfite-pyrosequencing in 44 and 51 cases, respectively.

RESULTS

Median age at diagnosis was 56.6 years-old and median OS, 13.3 months. 153/232 GBM (66 %) displayed chr7+/chr10-/EGFRamp, 23 (9.9 %) IDH1/2 mutation, 3 (1.3 %) H3 mutation and 53 (22.8 %) no key genetic alterations. GBM were divided into two groups, "Low" (n = 116) and "High" (n = 116), according to the median mtDNA/nuclear DNA ratio (237.7). There was no significant difference in OS between the two groups. By dividing the whole cohort according to the median age at diagnosis, OS was longer in the "High" vs "Low" subgroup (27.3 vs 15 months, P = .0203) in young adult GBM (n = 117) and longer in the "Low" vs "High" subgroup (14.5 vs 10.2 months, P = .0116) in older adult GBM (n = 115). POLG was highly methylated, whereas TFAM remained unmethylated.

CONCLUSION

mtDNA copy number may be a novel prognostic biomarker in GBM, its impact depending on age.

Mitochondrial DNA in innate immune responses against infectious diseases

Mitochondrial DNA (mtDNA) can initiate an innate immune response when mislocalized in a compartment other than the mitochondrial matrix. mtDNA plays significant roles in regulating mitochondrial dynamics as well as mitochondrial unfolded protein response (UPR). The mislocalized extra-mtDNA can elicit innate immune response via cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) pathway, inducing the expression of the interferon-stimulated genes (ISGs). Also, cytosolic damaged mtDNA is cleared up by various pathways which are responsible for participating in the activation of inflammatory responses. Four pathways of extra-mitochondrial mtDNA clearance are highlighted in this review - the inflammasome activation mechanism, neutrophil extracellular traps formation, recognition by Toll-like receptor 9 and transfer of mtDNA between cells packaged into extracellular vesicles. Anomalies in these pathways are associated with various diseases. We posit our review in the present pandemic situation and discuss how mtDNA elicits innate immune responses against different viruses and bacteria. This review gives a comprehensive picture of the role of extra-mitochondrial mtDNA in infectious diseases and speculates that research towards its understanding would help establish its therapeutic potential.

Maintenance of complex I and its supercomplexes by NDUF-11 is essential for mitochondrial structure, function and health

Mitochondrial supercomplexes form around a conserved core of monomeric complex I and dimeric complex III; wherein a subunit of the former, NDUFA11, is conspicuously situated at the interface. We identified nduf-11 (B0491.5) as encoding the Caenorhabditis elegans homologue of NDUFA11. Animals homozygous for a CRISPR-Cas9-generated knockout allele of nduf-11 arrested at the second larval (L2) development stage. Reducing (but not eliminating) expression using RNAi allowed development to adulthood, enabling characterisation of the consequences: destabilisation of complex I and its supercomplexes and perturbation of respiratory function. The loss of NADH dehydrogenase activity was compensated by enhanced complex II activity, with the potential for detrimental reactive oxygen species (ROS) production. Cryo-electron tomography highlighted aberrant morphology of cristae and widening of both cristae junctions and the intermembrane space. The requirement of NDUF-11 for balanced respiration, mitochondrial morphology and development presumably arises due to its involvement in complex I and supercomplex maintenance. This highlights the importance of respiratory complex integrity for health and the potential for its perturbation to cause mitochondrial disease. This article has an associated First Person interview with Amber Knapp-Wilson, joint first author of the paper.

Knockdown of Gastrin Promotes Apoptosis of Gastric Cancer Cells by Decreasing ROS Generation

Overexpressed gastrin is reported to promote oncogenesis and development of gastric cancer by inhibiting apoptosis of cancer cells; however, the underlying mechanism remains unclear. Our study is aimed at revealing the mechanism underlying the effect of gastrin on apoptosis of gastric cancer cells. Gastrin-interfering cell line was constructed by stably transfecting gastrin-specific pshRNA plasmid to gastric cancer cell line BGC-823. Then, differentially expressed proteins between untreated BGC-823 and gastrin-interfering BGC-823 cell lines were detected by the iTRAQ technique. GO and KEGG analysis was used to analyze the differentially expressed genes that code these differentially expressed proteins. The Annexin V-FITC staining assay was used to detect gastric cancer cell apoptosis. The DCFH-DA fluorescent probe staining assay was used to measure intracellular ROS. Mitochondrial membrane potential was detected by flow cytometry. Western blot was used to analyze the mitochondria respiratory chain proteins and apoptosis-related proteins. A total of 107 differentially expressed proteins were identified by iTRAQ. GO and KEGG analysis showed that proteins coded by the corresponding differentially expressed genes were mainly enriched in the mitochondrial oxidative respiratory chain, and the expression of three proteins (COX17, COX5B, ATP5J) was upregulated. The three proteins with higher scores were verified by Western blot. The apoptosis rate of the gastrin knockdown cancer cell was significantly increased; meanwhile, gastrin knockdown leads to increase of membrane potential and decrease of intracellular ROS production. Additionally, Bax was significantly increased, whereas NF-κB-p65 and Bcl-2 were downregulated after knockdown of gastrin. Concomitantly, pretreatment with NAC reversed the effect of gastrin on the Bax and Bcl-2 expression. Gastrin promotes the production of ROS from mitochondria, activates NF-κB, and inhibits apoptosis via modulating the expression level of Bcl-2 and Bax.

Madecassoside protects retinal pigment epithelial cells against hydrogen peroxide-induced oxidative stress and apoptosis through the activation of Nrf2/HO-1 pathway

Age-related macular degeneration (AMD) is a progressive and degenerative ocular disease associated with oxidative stress. Madecassoside (MADE) is a major bioactive triterpenoid saponin that possesses antioxidative activity. However, the role of MADE in AMD has never been investigated. In the current study, we aimed to evaluate the protective effect of MADE on retinal pigment epithelium (RPE) cells under oxidative stress condition. We used hydrogen peroxide (H₂O₂) to induce oxidative damage in human RPE cells (ARPE-19 cells). Our results showed that H₂O₂-caused significant decrease in cell viability and increase in lactate dehydrogenase (LDH) release were dose-dependently attenuated by MADE. MADE treatment also attenuated H₂O₂-induced reactive oxygen species (ROS) and malondialdehyde (MDA) production in RPE cells. The reduced glutathione (GSH) level and superoxide dismutase (SOD) activity in H₂O₂-induced ARPE-19 cells were elevated after MADE treatment. MADE also suppressed caspase-3 activity and bax expression, as well as increased bcl-2 expression. Furthermore, H₂O₂-induced increase in expression levels of HO-1 and nuclear Nrf2 were enhanced by MADE treatment. Finally, knockdown of Nrf2 reversed the protective effects of MADE on H₂O₂-induced ARPE-19 cells. In conclusion, these findings demonstrated that MADE protected ARPE-19 cells from H₂O₂-induced oxidative stress and apoptosis by inducing the activation of Nrf2/HO-1 signaling pathway.

Melanocortin 1 receptor attenuates early brain injury following subarachnoid hemorrhage by controlling mitochondrial metabolism via AMPK/SIRT1/PGC-1α pathway in rats

Mitochondria-mediated oxidative stress and apoptosis contribute greatly to early brain injury (EBI) following subarachnoid hemorrhage (SAH). This study hypothesized that activation of melanocortin 1 receptor (MC1R), using BMS-470539, attenuates EBI by controlling mitochondrial metabolism after SAH. Methods: We utilized BMS-470539, MSG-606, selisistat, and PGC-1α to verify the neuroprotective effects of MC1R. We evaluated short- and long-term neurobehavior after SAH. Western blotting, immunofluorescence, and Golgi staining techniques were performed to assess changes in protein levels. Results: The results of western blotting suggested that the expression of SIRT1 and PGC-1α were increased, reaching their peaks at 24 h following SAH. Moreover, BMS-470539 treatment notably attenuated neurological deficits, and also reduced long-term spatial learning and memory impairments caused by SAH. The underlying neuroprotective mechanisms of the BMS-470539/MC1R system were mediated through the suppression of oxidative stress, apoptosis, and mitochondrial fission by increasing the levels of SIRT1, PGC-1α, UCP2, SOD, GPx, Bcl-2, cyto-Drp1, and ATP, while decreasing the levels of cleaved caspase-3, Bax, mito-Drp1, ROS, GSH/GSSG, and NADPH/NADP+ ratios. The neuroprotective effects of the BMS-470539/MC1R system were significantly abolished by MSG-606, selisistat, and PGC-1α siRNA. Conclusions: The activation of MC1R with BMS-470539 significantly attenuated EBI after SAH by suppressing the oxidative stress, apoptosis, and mitochondrial fission through the AMPK/SIRT1/PGC-1α signaling pathway.

Evaluation of catacholase mimicking activity and apoptosis in human colorectal carcinoma cell line by activating mitochondrial pathway of copper(II) complex coupled with 2-(quinolin-8-yloxy)(methyl)benzonitrile and 8-hydroxyquinoline

To evaluate the cytotoxic potential of metal-based chemotherapeutic candidate towards the colorectal cancer, we have synthesized a new copper(II) complex [Cu(qmbn)(q)(Cl)] (1) (where, qmbn = 2-(quinolin-8-yloxy)(methyl)benzonitrile and q = 8-hydroxyquinoline) and structurally characterized by single crystal X-ray, Powder-XRD, FTIR and thermogravimetric analysis (TGA). The structural analysis reveals that copper(II) ions exist in a distorted square pyramidal (τ = ~0.1), with ligation of a chloride ion, oxygen atom and two nitrogen atoms at equatorial position and one oxygen atom at apical position. The cytotoxicity potential of complex 1 was executed against human colorectal cell lines (HCT116), which showed that 1 induces mitochondrion-mediated apoptotic cell death via activation of the Bax (pro-apoptotic protein) caspases-3 and 9 proteins. Interestingly, complex 1 was found to be a good candidate as electron-transfer catalyst which mimics catacholase with high turnover frequency (k_cat = 1.03 × 10² h^-1) for the conversion of the model substrate 3,5-di-tertbutylcatechol (3,5-DTBC) to 3,5-di-tertbutylquinone (3,5-DTBQ). Furthermore, molecular docking studies revealed that complex 1 was successfully localized inside the binding pocket of protein kinase (Akt), which validate the mechanism and mode of interaction of 1 that displayed cytotoxic activity experimentally. The obtained outcomes reveal that the complex 1 could be utilized as an encouraging perspective in the development of new therapeutic candidate for colon cancer.

Immunotoxicity of nickel: Pathological and toxicological effects

Nickel (Ni) is a widely distributed metal in the environment and an important pollutant because of its many industrial applications. With increasing incidences of Ni contamination, Ni toxicity has become a global public health concern and recent evidence suggests that Ni adversely affects the immune system. Hence, this paper reviews the literature on immune-related effects of Ni exposure, the immunotoxicological effects of Ni, and the underlying mechanism of Ni immunotoxicity. The main focus was on the effect of Ni on the development of organs of immune system, lymphocyte subpopulations, cytokines, immunoglobulins, natural killer (NK) cells, and macrophages. Moreover, Ni toxicity also induces inflammation and several studies demonstrated that Ni could induce immunotoxicity. Excessive Ni exposure can inhibit the development of immune organs by excessively inducing apoptosis and inhibiting proliferation. Furthermore, Ni can decrease T and B lymphocytes, the specific mechanism of which requires further research. The effects of Ni on immunoglobulin A (IgA), IgG, and IgM remain unknown and while Ni inhibited IgA, IgG, and IgM levels in an animal experiment, the opposite result was found in research on humans. Ni inhibits the production of cytokines in non-inflammatory responses. Cytokine levels increased in Ni-induced inflammation responses, and Ni activates inflammation through toll like (TL)4-mediated nuclear factor-κB (NF-κB) and signal transduction cascades mitogen-activated protein kinase (MAPK) pathways. Ni has been indicated to inactivate NK cells and macrophages both in vitro and in vivo. Identifying the mechanisms underlying the Ni-induced immunotoxicity may help to explain the growing risk of infections and cancers in human populations that have been exposed to Ni for a long time. Such knowledge may also help to prevent and treat Ni-related carcinogenicity and toxicology.

Identification of chemical compounds as an inhibitor of mitochondrial ATP synthesis, leading to an increased stress resistance and an extended lifespan in C. elegans

It is well known that the disruption of the mitochondrial respiratory components prolongs lifespan in many species. The mitochondrial stress response can lead to an increased survival rate through the restoration of the cellular homeostasis. Therefore, developing pharmacological interventions that induce mitochondrial stress response may be desirable to delay the onset of age-related diseases and promote a healthy life. In this study, we present chemical compounds, revealed by systematic screening of chemical libraries, which inhibit mitochondrial ATP synthesis in mammalian cells. Our study demonstrates that these compounds alter the body length and promote the oxidative stress response which leads to an increased longevity in Caenorhabditis elegans. Thus, our study identifies chemical compounds that may have potential therapeutic applications through affecting the mitochondrial function.

Cytotoxicity of Saikosaponin A targets HEKa cell through apoptosis induction by ROS accumulation and inflammation suppression via NF-κB pathway

Saikosaponin A (SSA) is a triterpenoid saponin extracted from oriental medicinal plant Radix bupleuri, possessing various biological functions such as anti-inflammatory, immune regulation and anti-virus. This study aimed to explore therapeutic effects of SSA on psoriasis in both vitro and vivo. Our results showed that SSA increased reactive oxygen species (ROS) generation, and decreased mitochondrial membrane potential (MMP) and M5-induced inflammatory cytokines levels in HEKa cells in a dose-dependent manner. In addition, SSA promoted apoptosis and suppressed phosphorylation of NF-κB in vitro, which were restored by the ROS scavenger N-acetylcysteine (NAC). In imiquimod (IMQ)-induced mice, gavage with SSA markedly decreased Psoriasis Area and Severity Index (PASI) score and ameliorated epidermal hyperplasia through inhibition of NF-κB and NLRP3 signaling pathway. In conclusion, our studies demonstrate that SSA induces apoptosis and suppresses inflammation in HEKa cells and ameliorates IMQ-induced psoriasis in mice, making it a therapeutic candidate for psoriasis.

Discovery of fifteen new geroprotective plant extracts and identification of cellular processes they affect to prolong the chronological lifespan of budding yeast

In a quest for previously unknown geroprotective natural chemicals, we used a robust cell viability assay to search for commercially available plant extracts that can substantially prolong the chronological lifespan of budding yeast. Many of these plant extracts have been used in traditional Chinese and other herbal medicines or the Mediterranean and other customary diets. Our search led to a discovery of fifteen plant extracts that significantly extend the longevity of chronologically aging yeast not limited in calorie supply. We show that each of these longevity-extending plant extracts is a geroprotector that decreases the rate of yeast chronological aging and promotes a hormetic stress response. We also show that each of the fifteen geroprotective plant extracts mimics the longevity-extending, stress-protecting, metabolic and physiological effects of a caloric restriction diet but if added to yeast cultured under non-caloric restriction conditions. We provide evidence that the fifteen geroprotective plant extracts exhibit partially overlapping effects on a distinct set of longevity-defining cellular processes. These effects include a rise in coupled mitochondrial respiration, an altered age-related chronology of changes in reactive oxygen species abundance, protection of cellular macromolecules from oxidative damage, and an age-related increase in the resistance to long-term oxidative and thermal stresses.

Cypermethrin-induced cortical neurons apoptosis via the Nrf2/ARE signaling pathway

Pesticide residue is a common problem worldwide. Cypermethrin is a type II pyrethroid pesticide that has been widely used in recent years. It has become a widespread residual pesticide in the environment and agricultural products. The neurotoxicity of cypermethrin remains a matter of concern. However, few studies have evaluated its toxicity on cerebral cortical neurons. As the center of the nervous system, the cerebral cortex is involved in a series of biological processes, such as learning, memory, emotions, and movement. The Nrf2/ARE signaling pathway has been considered to play a protective role in several central nervous system (CNS) diseases. We investigated whether this pathway plays a protective role in cypermethrin-induced apoptosis of the cortical neurons. We established a cypermethrin-induced apoptosis model in the cortical neurons using different cypermethrin doses and different incubation periods. The changes in Nrf2 protein and mRNA expression and its downstream genes HO-1 and NQO1 were detected by quantitative real-time PCR and Western blotting to study the role of the Nrf2/ARE pathway in cypermethrin-induced apoptosis of the cortical neurons. The results showed that the Nrf2/ARE signaling pathway has a protective effect in cypermethrin-induced apoptosis of the cortical neurons. However, this protective effect of the Nrf2/ARE pathway is very limited and is dependent on the exposure dose and exposure period of cypermethrin.

Bacopa monnieri inhibits apoptosis and senescence through mitophagy in human astrocytes

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon, is a potent neurotoxic agent that is responsible for impaired neuronal development and is associated with aging. Here, it was demonstrated that extracts of Bacopa monnieri (BM), a traditional Ayurvedic medicine, diminished the B[a]P-induced apoptosis and senescence in human astrocytes. BM was demonstrated to protect the immortalized primary fetal astrocytes (IMPHFA) from B[a]P-induced apoptosis and senescence by reducing the damaged mitochondria that produced reactive oxygen species (ROS). Furthermore, it was shown that B[a]P-triggered G2 arrest could be altered by BM, thus indicating that BM could reverse the cell cycle arrest and mediate a normal cell cycle in IMPHFA cells. In addition, the lifespan of Caenorhabditis elegans was assessed, which confirmed these effects in the presence of BM, compared to the B[a]P-treated group. Furthermore, the anti-senescence and anti-apoptotic activities of BM were observed to be mediated through the protective effect of mitophagy, and inhibition of mitophagy could not protect the astrocytes from mitochondrial ROS-induced apoptosis and senescence in BM-treated cells. Moreover, it was revealed that BM induced Parkin-dependent mitophagy to exert its cytoprotective activity in IMPHFA cells. In conclusion, the anti-senescence and anti-apoptotic effects of BM in astrocytes could combat pollution and aging-related neurological disorders.

In vivo hyperglycaemia exposure elicits distinct period-dependent effects on human pancreatic progenitor differentiation, conveyed by oxidative stress

AIM

The loss of insulin-secreting β-cells, ultimately characterizing most diabetes forms, demands the development of cell replacement therapies. The common endpoint for all ex vivo strategies is transplantation into diabetic patients. However, the effects of hyperglycaemia environment on the transplanted cells were not yet properly assessed. Thus, the main goal of this study was to characterize global effect of brief and prolonged in vivo hyperglycaemia exposure on the cell fate acquisition and maintenance of transplanted human pancreatic progenitors.

METHODS

To rigorously study the effect of hyperglycaemia, in vitro differentiated human-induced pluripotent stem cells (hiPSC)-derived pancreatic progenitors were xenotransplanted in normoglycaemic and diabetic NSG rat insulin promoter (RIP)-diphtheria toxin receptor (DTR) mice. The transplants were retrieved after 1-week or 1-month exposure to overt hyperglycaemia and analysed by large-scale microscopy or global proteomics. For this study we pioneer the use of the NSG RIP-DTR system in the transplantation of hiPSC, making use of its highly reproducible specific and absolute β-cell ablation property in the absence of inflammation or other organ toxicity.

RESULTS

Here we show for the first time that besides the presence of an induced oxidative stress signature, the cell fate and proteome landscape response to hyperglycaemia was different, involving largely different mechanisms, according to the period spent in the hyperglycaemic environment. Surprisingly, brief hyperglycaemia exposure increased the bihormonal cell number by impeding the activity of specific islet lineage determinants. Moreover, it activated antioxidant and inflammation protection mechanisms signatures in the transplanted cells. In contrast, the prolonged exposure was characterized by decreased numbers of hormone + cells, low/absent detoxification signature, augmented production of oxygen reactive species and increased apoptosis.

CONCLUSION

Hyperglycaemia exposure induced distinct, period-dependent, negative effects on xenotransplanted human pancreatic progenitor, affecting their energy homeostasis, cell fate acquisition and survival.

Do You Remember Mitochondria?

Dementia is one among the consequences of aging, and amnesia is often one of the most common symptoms. The lack of memory, as a consequence of both “healthy” aging or neurodegenerative conditions, such as in Alzheimer’s disease, has a dramatic impact on the patient’s lifestyle. In fact, the inability to recall information made by a previous experience could not only alter the interaction with the environment, but also lead to a loss of identity. Mitochondria are key regulators of brain’s activity; thanks to their “dynamic organelles” nature they constantly rearrange in the cell body and move along axons and dendrites, changing in dimension, shape, and location, accordingly to the cell’s energy requirements. Indeed, the energy they can provide is essential to maintain synaptic plasticity and to ensure transmission through presynaptic terminals and postsynaptic spines. Stressful conditions, like the ones found in neurodegenerative diseases, seriously impair mitochondria bioenergetic, leading to both loss of proper neuronal interaction and of neuron themselves. Here, we highlighted the current knowledge about the role of mitochondria and mitochondrial dynamics in relation to neurodegenerative disorders linked to aging. Furthermore, we discuss the obstacles as well as the future perspectives aimed to enlarge our knowledge about mitochondria as target for new therapeutic strategies to slow down aging and neurodegenerative disease’s symptoms.

Comparative Evaluation of the Effectiveness of Novel Hyaluronic Acid-Polynucleotide Complex Dermal Filler

HA (Hyaluronic acid) filler, the most commonly used dermal filler, causes several side effects. HA-PN (Hyaluronic acid-Polynucleotide), a new composite filler, has excellent biocompatibility and induces tissue regeneration. In this study, we compare the efficacies and safety profiles of these fillers. The characteristics of HA and HA-PN fillers were compared using scanning electron microscopy and rheometry. No morphological difference was noted between the fillers. However, the latter had higher viscosity and elasticity values. The HA-PN filler induced higher cell migration than the HA filler in a wound healing assay. It was also found to stimulate better collagen synthesis in human and mouse fibroblasts. The HA and HA-PN fillers were injected into SKH1 hairless mice to determine changes in their volume for up to 24 weeks. Increased cell migration and collagen synthesis were observed in mice injected with the HA-PN complex filler. Although the safety and durability of the HA and HA-PN fillers were similar, the latter induced a lower transient receptor potential vanilloid 4 expression and caused less stimulation upon injection. In conclusion, HA-PN complex fillers can stimulate fibroblast growth and facilitate volume growth and skin regeneration.

Defective arginine metabolism impairs mitochondrial homeostasis in Caenorhabditiselegans

Arginine catabolism involves enzyme-dependent reactions in both mitochondria and the cytosol, defects in which may lead to hyperargininemia, a devastating developmental disorder. It is largely unknown if defective arginine catabolism has any effects on mitochondria. Here we report that normal arginine catabolism is essential for mitochondrial homeostasis in Caenorhabditiselegans. Mutations of the arginase gene argn-1 lead to abnormal mitochondrial enlargement and reduced adenosine triphosphate (ATP) production in C. elegans hypodermal cells. ARGN-1 localizes to mitochondria and its loss causes arginine accumulation, which disrupts mitochondrial dynamics. Heterologous expression of human ARG1 or ARG2 rescued the mitochondrial defects of argn-1 mutants. Importantly, genetic inactivation of the mitochondrial basic amino acid transporter SLC-25A29 or the mitochondrial glutamate transporter SLC-25A18.1 fully suppressed the mitochondrial defects caused by argn-1 mutations. These findings suggest that mitochondrial damage probably contributes to the pathogenesis of hyperargininemia and provide clues for developing therapeutic treatments for hyperargininemia.

[Cypermethrin induces cell injury in primary cortical neurons of C57BL/6 mice by inhibiting Nrf2/ARE signaling pathway]

OBJECTIVE

To study the role of Nrf2/ARE signaling pathway in cypermethrin-induced oxidative stress and apoptosis of cerebral cortex neurons in C57BL/6 mice.

METHODS

The cortical neurons of C57BL/6 mice were cultured and identified, and a cypermethrin-induced cell injury model was established by treating the cells with 0, 25, 50 and 100 μmol/L of cypermethrin for 48 h. CCK-8 assay was used to analyze the effects of cypermethrin on the cell viability, and the fluorescence probe DCFH-DA was used for detecting intracellular reactive oxygen species (ROS); flow cytometry was performed for determining the apoptosis rate of the cells. The mRNA and protein expression levels of Nrf2 and its downstream genes HO-1 and NQO1 were detected using qPCR and Western blotting.

RESULTS

Exposure to cypermethrin at different doses inhibited the viability of the cultured cortical neurons. With the increase of cypermethrin dose, the viability of the neurons decreased progressively, the intracellular ROS and the cell apoptosis rate increased, and the neuronal injury worsened. At the dose of 50 and 100 μmol/L, cypermethrin significantly down-regulated the expressions of HO-1, NQO1 and Nrf2 at both the mRNA and protein levels in the cells (P < 0.01).

CONCLUSIONS

Cypermethrin exposure shows a dose-dependent neurotoxicity by inhibiting Nrf2/ARE signaling pathway, down-regulating the expression of Nrf2 and its downstream genes HO-1, NQO1 mRNA and protein, and inducing oxidative damage and apoptosis in primary mouse cortical neurons, .

Role of Platelet Mitochondria: Life in a Nucleus-Free Zone

Platelets are abundant, small, anucleate circulating cells, serving many emerging pathophysiological roles beyond hemostasis; including active critical roles in thrombosis, injury response, and immunoregulation. In the absence of genomic DNA transcriptional regulation (no nucleus), platelets require strategic prepackaging of all the needed RNA and organelles from megakaryocytes, to sense stress (e.g., hyperglycemia), to protect themselves from stress (e.g., mitophagy), and to communicate a stress response to other cells (e.g., granule and microparticle release). Distinct from avian thrombocytes that have a nucleus, the absence of a nucleus allows the mammalian platelet to maintain its small size, permits morphological flexibility, and may improve speed and efficiency of protein expression in response to stress. In the absence of a nucleus, platelet lifespan of 7–10 days, is largely determined by the mitochondria. The packaging of 5–8 mitochondria is critical in aerobic respiration and yielding metabolic substrates needed for function and survival. Mitochondria damage or dysfunction, as observed with several disease processes, results in greatly attenuated platelet survival and increased risk for thrombovascular events. Here we provide insights into the emerging roles of platelets despite the lack of a nucleus, and the key role played by mitochondria in platelet function and survival both in health and disease.

The Overcrowded Crossroads: Mitochondria, Alpha-Synuclein, and the Endo-Lysosomal System Interaction in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide, mainly affecting the elderly. The disease progresses gradually, with core motor presentations and a multitude of non-motor manifestations. There are two neuropathological hallmarks of PD, the dopaminergic neuronal loss and the alpha-synuclein-containing Lewy body inclusions in the substantia nigra. While the exact pathomechanisms of PD remain unclear, genetic investigations have revealed evidence of the involvement of mitochondrial function, alpha-synuclein (α-syn) aggregation, and the endo-lysosomal system, in disease pathogenesis. Due to the high energy demand of dopaminergic neurons, mitochondria are of special importance acting as the cellular powerhouse. Mitochondrial dynamic fusion and fission, and autophagy quality control keep the mitochondrial network in a healthy state. Should defects of the organelle occur, a variety of reactions would ensue at the cellular level, including disrupted mitochondrial respiratory network and perturbed calcium homeostasis, possibly resulting in cellular death. Meanwhile, α-syn is a presynaptic protein that helps regulate synaptic vesicle transportation and endocytosis. Its misfolding into oligomeric sheets and fibrillation is toxic to the mitochondria and neurons. Increased cellular oxidative stress leads to α-syn accumulation, causing mitochondrial dysfunction. The proteasome and endo-lysosomal systems function to regulate damage and unwanted waste management within the cell while facilitating the quality control of mitochondria and α-syn. This review will analyze the biological functions and interactions between mitochondria, α-syn, and the endo-lysosomal system in the pathogenesis of PD.

Targeting pro-senescence mitogen activated protein kinase (Mapk) enzymes with bioactive natural compounds

Aging is a multifactorial universal process characterized by a gradual decrease in physiological and biochemical functions. Given that life expectancy is on the rise, a better understanding of molecular mechanisms of the aging process is necessary in order to develop anti-aging interventions. Uncontrolled cellular senescence promotes persistent inflammation and accelerates the aging process by decreasing tissue renewal, repair and regeneration. Senescence of immune cells, immunesenescence, is another hallmark of aging. Targeting pro-senescent enzymes increases survival and therefore the lifespan. Although the upregulation of Mitogen Activated Protein Kinases (MAPK) enzymes in aging is still controversial, increasing evidence shows that dysregulation of those enzymes are associated with biological processes that contribute to aging such as irreversible senescence. In this manuscript components of the MAPK pathway will be summarized, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38, as well as natural flavonoids, phenolic and diterpenoids with anti-senescence activity that shows positive effects on longevity and MAPK inhibition. Although more studies using additional aging models are needed, we suggest that these selected natural bioactive compounds that regulate MAPK enzymes and reduce senescent cells can be potentially used to improve longevity and prevent/treat age-related diseases.

Potential role of E4orf1 protein in aging-associated impairment in glycemic control

Aging constitutes a major risk factor for the development of type-2 diabetes (T2D) where glucose tolerance declines with age, resulting in a high prevalence of T2D and impaired glucose tolerance in the elderly population. Currently more than half of the 20 million U.S. adults with T2D are above the age of 60, and the largest increase in T2D prevalence is expected in the elderly. Obesity is a causative factor for T2D associated insulin resistance and hyperglycemia. Furthermore, the aging process is accelerated by hyperglycemia and effective treatment options are limited for the vulnerable aging population. One of the mechanisms contributing to aging associated hyperglycemia is resistance to insulin-mediated glucose disposal. Chronic hyperglycemia also accelerates aging by increasing pro-inflammatory milieu leading to impaired immune function. Although currently available anti-diabetic agents improve glycemic control, they have potential serious side effects in some cases. Therefore, additional and better drugs are urgently needed for treatment of insulin resistance and aging associated health risk factors. This review presents the novel use of a microbial protein, E4orf1 as a potential anti-diabetic agent, which functions independent of insulin and obesity, highlighting the role of unique sources for future drug development.

Antioxidant Characterization and Biological Effects of Grape Pomace Extracts Supplementation in Caenorhabditis elegans

The aim of this work was to evaluate the biological activity of four grape pomace (GP) extracts that are rich in polyphenols using C. elegans as an in vivo model. Different concentrations of the GP extracts were assessed for their effects on the resistance of C. elegans against thermally induced oxidative stress, accumulation of reactive oxygen species (ROS), and lifespan. The cultivation of C. elegans with relatively low concentrations of GP extracts increased their resistance against thermal stress and prolonged their lifespan, while high levels displayed detrimental effects. In the studied extracts, maximum protection was observed for levels of polyphenols around 7 to 9 µg gallic acid equivalents per cultivation plate. The obtained results suggested that small changes in the ROS levels could have beneficial effects, although further studies are required to fully understand the impact of the extracts and assayed doses on ROS levels to explain the mechanism that is involved in the observed effects.

The Neuroprotector Benzothiazepine CGP37157 Extends Lifespan in C. elegans Worms

The benzothiazepine CGP37157 has shown neuroprotective effects in several in vitro models of excitotoxicity involving dysregulation of intracellular Ca²⁺ homeostasis. Although its mechanism of neuroprotection is unclear, it is probably related with some of its effects on Ca²⁺ homeostasis. CGP37157 is a well-known inhibitor of the mitochondrial Na⁺/Ca²⁺ exchanger (mNCX). However, it is not very specific and also blocks several other Ca²⁺ channels and transporters, including voltage-gated Ca²⁺ channels, plasma membrane Na⁺/Ca²⁺ exchanger and the Ca²⁺ homeostasis modulator 1 channel (CALHM1). In the present work, we have studied if CGP37157 could also induce changes in life expectancy. We now report that CGP37157 extends C. elegans lifespan by 10%–15% with a bell-shaped concentration-response, with high concentrations producing no effect. The effect was even larger (25% increase in life expectancy) in worms fed with heat-inactivated bacteria. The worm CGP37157 concentration producing maximum effect was measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and was close to the IC₅₀ for inhibition of the Na⁺/Ca²⁺ exchanger. CGP37157 also extended the lifespan in eat-2 mutants (a model for caloric restriction), suggesting that caloric restriction is not involved in the mechanism of lifespan extension. Actually, CGP37157 produced no effect in mutants of the TOR pathway (daf15/unc24) or the insulin/insulin-like growth factor-1 (IGF-1) pathway (daf-2), indicating that the effect involves these pathways. Moreover, CGP37157 was also ineffective in nuo-6 mutants, which have a defect in the mitochondrial respiratory chain complex I. Since it has been described that neuroprotection by this compound in cell cultures is abolished by mitochondrial inhibitors, this suggests that life extension in C. elegans and neuroprotection in cell cultures may share a similar mechanism involving mitochondria.

New drugs for pharmacological extension of replicative life span in normal and progeroid cells

A high-throughput anti-aging drug screen was developed that simultaneously measures senescence-associated β-galactosidase activity and proliferation. Applied to replicatively pre-aged fibroblasts, this screen yielded violuric acid (VA) and 1-naphthoquinone-2-monoxime (N2N1) as its top two hits. These lead compounds extended the replicative life spans of normal and progeroid human cells in a dose-dependent manner and also extended the chronological life spans of mice and C. elegans. They are further shown here to function as redox catalysts in oxidations of NAD(P)H. They thus slow age-related declines in NAD(P)⁺/NAD(P)H ratios. VA participates in non-enzymatic electron transfers from NAD(P)H to oxidized glutathione or peroxides. N2N1 transfers electrons from NAD(P)H to cytochrome c or CoQ₁₀ via NAD(P)H dehydrogenase (quinone) 1 (NQO1). Our results indicate that pharmacologic manipulation of NQO1 activity via redox catalysts may reveal mechanisms of senescence and aging.

Two drugs were discovered that can extend the life spans of normally aged human cells and thus potentially slow human aging. The anti-aging drugs were identified using a novel method that screens drugs across a two-dimensional endpoint space of senescence-associated galactosidase activity as a general axis of aging and ATP as an axis representing proliferation. The two most potent substances were, likely more than coincidentally, electrons carriers that transfer electrons from NAD(P)H to molecules and cellular structures that demand reducing power to repair oxidative damage that accumulates with aging. Treatment of single cells and whole organisms with these new anti-aging drugs increased their lifespans. The mechanism of the drug action may advance our understanding of the complex, yet resolvable, biological process of aging.

Cytotoxicity induced by iodinated haloacetamides via ROS accumulation and apoptosis in HepG-2 cells

Iodinated haloacetamides (I-HAcAms) are emerging disinfection by-products and have received great concern due to their extremely high health risk. Previous studies have demonstrated the cytotoxicity of I-HAcAms, but the biological mechanism remained unclear. In this study, cytotoxicity mechanisms of 4 I-HAcAms species were preliminarily examined using HepG-2 cells. The results showed that the cytotoxicity could be ranked as follows: diiodoacetamide (DIAcAm)> iodoacetamide (IAcAm)> bromoiodoacetamide (BIAcAm)> chloroiodoacetamide (CIAcAm). Reactive oxygen species (ROS) and apoptosis played an important role in the cytotoxicity for all I-HAcAms species. Moreover, the ROS and cytotoxicity could be completely reversed by the addition of an antioxidant (N-acetylcysteine (NAC)), but the apoptosis could not. Specifically, the apoptosis induced by DIAcAm and IAcAm was partially reversed by NAC, suggesting that in addition to ROS, other pathways were also possible; While For BIAcAm and CIAcAm, the apoptosis was not reversed by NAC at all, which is potentially due to ROS-independent pathways. The apoptosis mechanisms were further analyzed via Bax and Bcl-2 gene expression and the corresponding protein expression in HepG-2 cells, that mitochondrial pathway was important in the apoptosis of HepG-2 cells induced by all I-HAcAms species. Overall, the mitochondrial pathway provided a potential explanation for BIAcAm and CIAcAm-induced apoptosis, while both ROS and mitochondrial pathways explained DIAcAm and IAcAm-induced apoptosis.

Cellular mechanism of resistance of human colorectal adenocarcinoma cells against apoptosis-induction by Russell's Viper venom l-amino acid oxidase (Rusvinoxidase)

The present study highlights the cellular mechanism of resistance in human adenocarcinoma (Colo-205) cells against apoptosis induction by Rusvinoxidase, an l-amino acid oxidase purified from Russell's Viper venom (RVV). The significantly lower cytotoxicity as well as apoptotic activity of Rusvinoxidase towards Colo-205 cells (compared to MCF-7 breast cancer cells) is correlated with lower depletion of cellular glutathione content and increased down-regulation of catalase activity of Colo-205 cells following Rusvinoxidase treatment. Exposure to Rusvinoxidase subsequently diminished reactive oxygen species (ROS) production and failed to impair mitochondrial membrane potential, resulting in apoptosis induction resistance in Colo-205 cells. Further, higher expression levels of caspase 8, compared to caspase 9, indicate that Rusvinoxidase preferentially triggers the extrinsic pathway of apoptosis in Colo-205 cells. A time-dependent lower ratio of the relative expression of Bax and Bcl-xL (pro- and anti-apoptotic proteins) in Colo-205 cells, compared to our previous study on MCF-7 cells, unambiguously supports a higher cellular resistance mechanism in Colo-205 cells against Rusvinoxidase-induced apoptosis.

Prolonged Growth Hormone/Insulin/Insulin-like Growth Factor Nutrient Response Signaling Pathway as a Silent Killer of Stem Cells and a Culprit in Aging

The dream of slowing down the aging process has always inspired mankind. Since stem cells are responsible for tissue and organ rejuvenation, it is logical that we should search for encoded mechanisms affecting life span in these cells. However, in adult life the hierarchy within the stem cell compartment is still not very well defined, and evidence has accumulated that adult tissues contain rare stem cells that possess a broad trans-germ layer differentiation potential. These most-primitive stem cells-those endowed with pluripotent or multipotent differentiation ability and that give rise to other cells more restricted in differentiation, known as tissue-committed stem cells (TCSCs) - are of particular interest. In this review we present the concept supported by accumulating evidence that a population of so-called very small embryonic-like stem cells (VSELs) residing in adult tissues positively impacts the overall survival of mammals, including humans. These unique cells are prevented in vertebrates from premature depletion by decreased sensitivity to growth hormone (GH), insulin (INS), and insulin-like growth factor (IGF) signaling, due to epigenetic changes in paternally imprinted genes that regulate their resistance to these factors. In this context, we can envision nutrient response GH/INS/IGF signaling pathway as a lethal factor for these most primitive stem cells and an important culprit in aging.

Long-lived rodents reveal signatures of positive selection in genes associated with lifespan

The genetics of lifespan determination is poorly understood. Most research has been done on short-lived animals and it is unclear if these insights can be transferred to long-lived mammals like humans. Some African mole-rats (Bathyergidae) have life expectancies that are multiple times higher than similar sized and phylogenetically closely related rodents. To gain new insights into genetic mechanisms determining mammalian lifespans, we obtained genomic and transcriptomic data from 17 rodent species and scanned eleven evolutionary branches associated with the evolution of enhanced longevity for positively selected genes (PSGs). Indicating relevance for aging, the set of 250 identified PSGs showed in liver of long-lived naked mole-rats and short-lived rats an expression pattern that fits the antagonistic pleiotropy theory of aging. Moreover, we found the PSGs to be enriched for genes known to be related to aging. Among these enrichments were “cellular respiration” and “metal ion homeostasis”, as well as functional terms associated with processes regulated by the mTOR pathway: translation, autophagy and inflammation. Remarkably, among PSGs are RHEB, a regulator of mTOR, and IGF1, both central components of aging-relevant pathways, as well as genes yet unknown to be aging-associated but representing convincing functional candidates, e.g. RHEBL1, AMHR2, PSMG1 and AGER. Exemplary protein homology modeling suggests functional consequences for amino acid changes under positive selection. Therefore, we conclude that our results provide a meaningful resource for follow-up studies to mechanistically link identified genes and amino acids under positive selection to aging and lifespan determination.

As an adaption to different environments rodents have evolved a wide range of lifespans. While most rodents are short-lived, along several phylogenetic branches long-lived species evolved. This provided us a unique opportunity to search for genes that are associated with enhanced longevity in mammals. Towards this, we computationally compared gene sequences of exceptional long-lived rodent species (like the naked mole-rat and chinchilla) and short-lived rodents (like rat and mouse) and identified those which evolved exceptional fast. As natural selection acts in parallel on a multitude of phenotypes, only a subset of the identified genes is probably associated with enhanced longevity. Applying several tests, we ensured that the dataset is related to aging. We conclude that lifespan extension in rodents can be attributed to changes in their defense against free radicals, iron homeostasis as well as cellular respiration and translation as central parts of the growth program. This confirms aging theories assuming a tradeoff between fast growth and long lifespan. Moreover, our study offers a meaningful resource of targets, i.e. genes and specific positions therein, for functional follow-up studies on their potential roles in the determination of lifespan–regardless whether they are currently known to be aging-related or not.

Cell Biology of the Mitochondrion

Mitochondria are best known for harboring pathways involved in ATP synthesis through the tricarboxylic acid cycle and oxidative phosphorylation. Major advances in understanding these roles were made with Caenorhabditiselegans mutants affecting key components of the metabolic pathways. These mutants have not only helped elucidate some of the intricacies of metabolism pathways, but they have also served as jumping off points for pharmacology, toxicology, and aging studies. The field of mitochondria research has also undergone a renaissance, with the increased appreciation of the role of mitochondria in cell processes other than energy production. Here, we focus on discoveries that were made using C. elegans, with a few excursions into areas that were studied more thoroughly in other organisms, like mitochondrial protein import in yeast. Advances in mitochondrial biogenesis and membrane dynamics were made through the discoveries of novel functions in mitochondrial fission and fusion proteins. Some of these functions were only apparent through the use of diverse model systems, such as C. elegans Studies of stress responses, exemplified by mitophagy and the mitochondrial unfolded protein response, have also benefitted greatly from the use of model organisms. Recent developments include the discoveries in C. elegans of cell autonomous and nonautonomous pathways controlling the mitochondrial unfolded protein response, as well as mechanisms for degradation of paternal mitochondria after fertilization. The evolutionary conservation of many, if not all, of these pathways ensures that results obtained with C. elegans are equally applicable to studies of human mitochondria in health and disease.