Acute mental stress induces mitochondrial bioenergetic crisis and hyper-fission along with aberrant mitophagy in the gut mucosa in rodent model of stress-related mucosal disease

Mitochondrial Functioning: Front and Center in Defining Psychosomatic Mechanisms of Allostasis in Health and Disease

There is increased awareness among basic and clinical scientists that psychological and social stress can have detrimental effects on physical, cognitive, and mental health. Data have been published indicating that social, economic, psychological, and physical environmental stress can influence behavior that has biological and physiological consequences-yet there are major gaps in understanding the physiological and cellular processes that drive increased morbidity and mortality. The potential role of mitochondria has been highlighted in psychosomatic medicine, as their functionality in various biological and physiological processes has earned recognition. This review outlines the essential role of mitochondria by considering the numerous intracellular, extracellular, and physiological functions it regulates that position the organelle as a central mediator in responses to psychological stress. We then connect these functions to mitochondrial allostasis and allostatic load for further examination of the limitations of mitochondria to an adaptive psychological stress response where mitochondrial allostatic load may eventually lead to systemic pathophysiology. This review emphasizes how chronic social, economic, and psychological stress can contribute to mitochondrial dysfunction and predispose individuals to poorer health outcomes and death. Mitochondrial capacity, function, and activity may therefore serve as biomarkers for identifying individuals at high risk for developing comorbid conditions related to their psychosocial environment.

A Comprehensive Pan-Cancer Analysis of Cytochrome C Oxidase Assembly Factor 1 (COA1) Reveals Instrumental Role of Mitochondrial Protein Assembly in Cancer that Modulates Disease Progression and Prognostic Outcome

Cytochrome c oxidase assembly factor 1 (COA1), a mitochondrial respiratory chain complex assembly factor protein of inner mitochondrial membrane (IMM), is involved in translating many mitochondrial components and assembling nuclear-encoded components within mitochondria. Given the lack of extensive research on COA1 in cancer, this study undertakes a comprehensive pan-cancer analysis of COA1, which is overexpressed across various cancer types, shedding light on its multifaceted role in tumorigenesis, prognosis, and tumor microenvironment (TME) modulation. Leveraging bioinformatics tools and public databases, we elucidated its potential as a diagnostic cancer biomarker as well as a target for novel anti-cancer therapeutics. Gene expression analysis using "TIMER2.0", "UALCAN" and "GEPIA2" platforms, supported by protein expression data, revealed a significant correlation between COA1 upregulation and poor prognosis in Kaplan-Meir analysis, underscoring its clinical relevance. Additionally, genetic mutation analysis of COA1 with the help of "cBioPortal" warrants further exploration into its functional significance. Moreover, our investigation of the tumor microenvironment unveiled the interplay of COA1 with fibroblast and T cell infiltration implicating the role of COA1 in the tumor immune microenvironment. Furthermore, COA1-related gene enrichment study in "GeneMANIA" and pathway cross-talk analysis with Gene Ontology (GO) gene sets established comprehensive clarifications about the molecular pathways and protein networks associated with COA1 deregulation. Overall, this study lays a sturdy foundation to support future research endeavors targeting COA1, unraveling the molecular mechanisms underlying COA1 deregulation, and exploring its therapeutic potential in cancer.

PINK1 insufficiency can be exploited as a specific target for drug combinations inducing mitochondrial pathology-mediated cell death in gastric adenocarcinoma

There exist very limited non-hazardous therapeutic strategies except for surgical resection and lymphadenectomy against gastric cancer (GC) despite being the third leading cause of cancer deaths worldwide. This study proposes an innovative treatment approach against GC using a drug combination strategy that manipulates mitochondrial dynamics in conjunction with the induction of mitochondrial pathology-mediated cell death. Comparative analysis was done with gastric adenocarcinoma and normal cells by qPCR, western blot, microscopic immunocytochemistry, and live cell imaging. In this study, impairment of dynamin-related protein 1 (Drp1)-mediated mitochondrial fission by Mdivi-1 created an imbalance in mitochondrial structural dynamics in indomethacin-treated AGS cells in which mitophagy-regulator protein PINK1 is downregulated. These drug combinations with the individual sub-lethal doses ultimately led to the activation of cell death machinery upregulating pro-apoptotic proteins like Bax, Puma, and Noxa. Interestingly, this combinatorial therapy did not affect normal gastric epithelial cells significantly and also no significant upregulation of death markers was observed. Moreover, the drug combination strategy also retarded cell migration and reduced stemness in GC cells. In summary, this study offers a pioneering specific therapeutic strategy for GC treatment, sparing normal cells providing opportunities for minimal drug-mediated toxicity utilizing mitochondria as a viable and specific target for anti-cancer therapy in gastric cancer.

From macroautophagy to mitophagy: Unveiling the hidden role of mitophagy in gastrointestinal disorders

In this editorial, we comment on an article titled "Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases", which was published in a recent issue of the World Journal of Gastroenterology. We focused on the statement that "autophagy is closely related to the digestion, secretion, and regeneration of gastrointestinal cells". With advancing research, autophagy, and particularly the pivotal role of the macroautophagy in maintaining cellular equilibrium and stress response in the gastrointestinal system, has garnered extensive study. However, the significance of mitophagy, a unique selective autophagy pathway with ubiquitin-dependent and independent variants, should not be overlooked. In recent decades, mitophagy has been shown to be closely related to the occurrence and development of gastrointestinal diseases, especially inflammatory bowel disease, gastric cancer, and colorectal cancer. The interplay between mitophagy and mitochondrial quality control is crucial for elucidating disease mechanisms, as well as for the development of novel treatment strategies. Exploring the pathogenesis behind gastrointestinal diseases and providing individualized and efficient treatment for patients are subjects we have been exploring. This article reviews the potential mechanism of mitophagy in gastrointestinal diseases with the hope of providing new ideas for diagnosis and treatment.

The effects of restraint stress on ceramide metabolism disorders in the rat liver: the role of CerS6 in hepatocyte injury

BACKGROUND

Stress is implicated in various pathological conditions leading to liver injury. Existing evidence suggests that excessive stress can induce mitochondrial damage in hepatocytes, yet the underlying mechanism remains unclear. Ceramide synthase 6 (CerS6)-derived C16:0 ceramide is recognised as a lipotoxic substance capable of causing mitochondrial damage. However, the role of CerS6 in stress has received insufficient attention. This study aimed to explore the involvement of CerS6 in stress-induced hepatic damage and its associated mechanisms.

METHODS

The rat restraint stress model and a corticosterone (CORT)-induced hepatocyte stress model were employed for in vivo and in vitro experimental analyses, respectively. Changes in mitochondrial damage and ceramide metabolism in hepatocytes induced by stress were evaluated. The impact of CORT on mitochondrial damage and ceramide metabolism in hepatocytes was assessed following CerS6 knockdown. Mitochondria were isolated using a commercial kit, and ceramides in liver tissue and hepatocytes were detected by LC-MS/MS.

RESULTS

In comparison to the control group, rats subjected to one week of restraint exhibited elevated serum CORT levels. The liver displayed significant signs of mitochondrial damage, accompanied by increased CerS6 and mitochondrial C16:0 ceramide, along with activation of the AMPK/p38 MAPK pathway. In vitro studies demonstrated that CORT treatment of hepatocytes resulted in mitochondrial damage, concomitant with elevated CerS6 and mitochondrial C16:0 ceramide. Furthermore, CORT induced sequential phosphorylation of AMPK and p38 MAPK proteins, and inhibition of the p38 MAPK pathway using SB203580 mitigated the CORT-induced elevation in CerS6 protein. Knocking down CerS6 in hepatocytes inhibited both the increase in C16:0 ceramide and the release of mitochondrial cytochrome c induced by CORT.

CONCLUSIONS

CerS6-associated C16:0 ceramide plays a mediating role in stress-induced mitochondrial damage in hepatocytes. The molecular mechanism is linked to CORT-induced activation of the AMPK/p38 MAPK pathway, leading to upregulated CerS6.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Mitochondria as a sensor, a central hub and a biological clock in psychological stress-accelerated aging

The theory that oxidative damage caused by mitochondrial free radicals leads to aging has brought mitochondria into the forefront of aging research. Psychological stress that encompasses many different experiences and exposures across the lifespan has been identified as a catalyst for accelerated aging. Mitochondria, known for their dynamic nature and adaptability, function as a highly sensitive stress sensor and central hub in the process of accelerated aging. In this review, we explore how mitochondria as sensors respond to psychological stress and contribute to the molecular processes in accelerated aging by viewing mitochondria as hormonal, mechanosensitive and immune suborganelles. This understanding of the key role played by mitochondria and their close association with accelerated aging helps us to distinguish normal aging from accelerated aging, correct misconceptions in aging studies, and develop strategies such as exercise and mitochondria-targeted nutrients and drugs for slowing down accelerated aging, and also hold promise for prevention and treatment of age-related diseases.

Mitochondrial dysfunction: A fatal blow in depression

Mitochondria maintain the normal physiological function of nerve cells by producing sufficient cellular energy and performing crucial roles in maintaining the metabolic balance through intracellular Ca2+ homeostasis, oxidative stress, and axonal development. Depression is a prevalent psychiatric disorder with an unclear pathophysiology. Damage to the hippocampal neurons is a key component of the plasticity regulation of synapses and plays a critical role in the mechanism of depression. There is evidence suggesting that mitochondrial dysfunction is associated with synaptic impairment. The maintenance of mitochondrial homeostasis includes quantitative maintenance and quality control of mitochondria. Mitochondrial biogenesis produces new and healthy mitochondria, and mitochondrial dynamics cooperates with mitophagy to remove damaged mitochondria. These processes maintain mitochondrial population stability and exert neuroprotective effects against early depression. In contrast, mitochondrial dysfunction is observed in various brain regions of patients with major depressive disorders. The accumulation of defective mitochondria accelerates cellular nerve dysfunction. In addition, impaired mitochondria aggravate alterations in the brain microenvironment, promoting neuroinflammation and energy depletion, thereby exacerbating the development of depression. This review summarizes the influence of mitochondrial dysfunction and the underlying molecular pathways on the pathogenesis of depression. Additionally, we discuss the maintenance of mitochondrial homeostasis as a potential therapeutic strategy for depression.

Honokiol, an inducer of sirtuin-3, protects against non-steroidal anti-inflammatory drug-induced gastric mucosal mitochondrial pathology, apoptosis and inflammatory tissue injury

BACKGROUND AND PURPOSE

Mitochondrial oxidative stress, inflammation and apoptosis primarily underlie gastric mucosal injury caused by the widely used non-steroidal anti-inflammatory drugs (NSAIDs). Alternative gastroprotective strategies are therefore needed. Sirtuin-3 pivotally maintains mitochondrial structural integrity and metabolism while preventing oxidative stress; however, its relevance to gastric injury was never explored. Here, we have investigated whether and how sirtuin-3 stimulation by the phytochemical, honokiol, could rescue NSAID-induced gastric injury.

EXPERIMENTAL APPROACH

Gastric injury in rats induced by indomethacin was used to assess the effects of honokiol. Next-generation sequencing-based transcriptomics followed by functional validation identified the gastroprotective function of sirtuin-3. Flow cytometry, immunoblotting, qRT-PCR and immunohistochemistry were used measure effects on oxidative stress, mitochondrial dynamics, electron transport chain function, and markers of inflammation and apoptosis. Sirtuin-3 deacetylase activity was also estimated and gastric luminal pH was measured.

KEY RESULTS

Indomethacin down-regulated sirtuin-3 to induce oxidative stress, mitochondrial hyperacetylation, 8-oxoguanine DNA glycosylase 1 depletion, mitochondrial DNA damage, respiratory chain defect and mitochondrial fragmentation leading to severe mucosal injury. Indomethacin dose-dependently inhibited sirtuin-3 deacetylase activity. Honokiol prevented mitochondrial oxidative damage and inflammatory tissue injury by attenuating indomethacin-induced depletion of both sirtuin-3 and its transcriptional regulators PGC1α and ERRα. Honokiol also accelerated gastric wound healing but did not alter gastric acid secretion, unlike lansoprazole.

CONCLUSIONS AND IMPLICATIONS

Sirtuin-3 stimulation by honokiol prevented and reversed NSAID-induced gastric injury through maintaining mitochondrial integrity. Honokiol did not affect gastric acid secretion. Sirtuin-3 stimulation by honokiol may be utilized as a mitochondria-based, acid-independent novel gastroprotective strategy against NSAIDs.

3-Methyladenine ameliorates surgery-induced anxiety-like behaviors in aged mice by inhibiting autophagy-induced excessive oxidative stress

BACKGROUND

Postoperative anxiety is a common surgical complication in older patients. Research has recently linked excessive autophagy to several neurological disorders, including anxiety. This study aimed to determine whether 3-Methyladenine (3-MA) administration reduced anxiety-like behaviors in a mouse model following abdominal exploratory laparotomy.

METHODS

An abdominal exploratory laparotomy model of postoperative anxiety was established using male C57BL/6 mice aged 20 months. 3-MA (6, 30, and 150 mg/ml) was administered via intracerebroventricular immediately following surgery. The mice were assessed 14 days after surgery using the marble burying, elevated plus maze tests, and local field potential recording in the amygdala. The levels of expression of phosphorylated-Akt, Beclin-1, LC3B, nuclear factor erythroid 2-related factor 2 (Nrf2)-occupied regions in NeuN-positive cells, superoxide dismutase (SOD) activity, malondialdehyde (MDA), and glutathione (GSH) were measured at 24 h after surgery.

RESULTS

The injection of 3-MA reversed the increased number of marbles buried, decreased time spent in the open arm, and enhanced θ oscillation power after 14 days of abdominal exploratory laparotomy. In addition, administration of 3-MA reduced the ratio of phosphorylated- to total-Akt, decreased expression in Beclin-1 and LC3B, attenuated MDA levels, and increased the ratio of Nrf2-occupied areas in NeuN-positive cells, SOD activity, and GSH levels under abdominal exploratory laparotomy conditions.

CONCLUSIONS

3-MA improved anxiety-like behaviors in aged mice undergoing abdominal exploratory laparotomy by inhibiting excessive autophagy-induced oxidative stress. These results suggest that 3-MA could be an effective treatment for postoperative anxiety.

Pathophysiological involvement of host mitochondria in SARS-CoV-2 infection that causes COVID-19: a comprehensive evidential insight

SARS-CoV-2 is a positive-strand RNA virus that infects humans through the nasopharyngeal and oral route causing COVID-19. Scientists left no stone unturned to explore a targetable key player in COVID-19 pathogenesis against which therapeutic interventions can be initiated. This article has attempted to review, coordinate and accumulate the most recent observations in support of the hypothesis predicting the altered state of mitochondria concerning mitochondrial redox homeostasis, inflammatory regulations, morphology, bioenergetics and antiviral signalling in SARS-CoV-2 infection. Mitochondria is extremely susceptible to physiological as well as pathological stimuli, including viral infections. Recent studies suggest that SARS-CoV-2 pathogeneses alter mitochondrial integrity, in turn mitochondria modulate cellular response against the infection. SARS-CoV-2 M protein inhibited mitochondrial antiviral signalling (MAVS) protein aggregation in turn hinders innate antiviral response. Viral open reading frames (ORFs) also play an instrumental role in altering mitochondrial regulation of immune response. Notably, ORF-9b and ORF-6 impair MAVS activation. In aged persons, the NLRP3 inflammasome is over-activated due to impaired mitochondrial function, increased mitochondrial reactive oxygen species (mtROS), and/or circulating free mitochondrial DNA, resulting in a hyper-response of classically activated macrophages. This article also tries to understand how mitochondrial fission-fusion dynamics is affected by the virus. This review comprehends the overall mitochondrial attribute in pathogenesis as well as prognosis in patients infected with COVID-19 taking into account pertinent in vitro, pre-clinical and clinical data encompassing subjects with a broad range of severity and morbidity. This endeavour may help in exploring novel non-canonical therapeutic strategies to COVID-19 disease and associated complications.

Possible Pathogenesis and Prevention of Long COVID: SARS-CoV-2-Induced Mitochondrial Disorder

Patients who have recovered from coronavirus disease 2019 (COVID-19) infection may experience chronic fatigue when exercising, despite no obvious heart or lung abnormalities. The present lack of effective treatments makes managing long COVID a major challenge. One of the underlying mechanisms of long COVID may be mitochondrial dysfunction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can alter the mitochondria responsible for energy production in cells. This alteration leads to mitochondrial dysfunction which, in turn, increases oxidative stress. Ultimately, this results in a loss of mitochondrial integrity and cell death. Moreover, viral proteins can bind to mitochondrial complexes, disrupting mitochondrial function and causing the immune cells to over-react. This over-reaction leads to inflammation and potentially long COVID symptoms. It is important to note that the roles of mitochondrial damage and inflammatory responses caused by SARS-CoV-2 in the development of long COVID are still being elucidated. Targeting mitochondrial function may provide promising new clinical approaches for long-COVID patients; however, further studies are needed to evaluate the safety and efficacy of such approaches.

Selenium alleviates cadmium-induced mitophagy through FUNDC1-mediated mitochondrial quality control pathway in the lungs of sheep

Cadmium (Cd) is a poisonous metal element that causes mitochondrial dysfunction. Selenium (Se) can reduce the damage of Cd to various organs of animals, but the protective mechanism of Se in Cd-induced lung injury has not been fully elucidated. For purpose of further illustrating the specific mechanism of Se alleviated Cd-triggered pulmonary toxicity, 48 sheep were divided into 4 groups, of which the sheep in the treatment group were taken 1 mg/kg body weight (BW) of Cd, 0.34 mg/kg BW of Se, and 0.34 mg Se + 1 mg/kg BW of Cd by intragastric administration for 50 d, respectively. The results indicated that Cd caused inflammatory cell infiltration and alveolar wall thickening, which facilitated mitochondrial vacuolation and formation of mitophagosomes in lung tissues. Simultaneously, Cd treatment impaired the antioxidant capacity of sheep lung tissue. Additionally, Cd treatment down-regulated the expression levels of mitochondrial biogenesis and mitochondrial fusion, but up-regulated the levels of mitochondrial fission and mitophagy mediated by FUNDC1. Moreover, the immunofluorescence co-localization puncta of LC3B/COX IV, LC3B/FUNDC1 were increased after Cd treatment. Nevertheless, co-treatment with Se improved effectively the above variation caused by Cd exposure. In summary, Se could mitigate Cd-generated mitophagy through FUNDC1-mediated mitochondrial quality control pathway in the lungs of sheep.

Glucagon-like Peptide 1 Receptor Activation Inhibits Microglial Pyroptosis via Promoting Mitophagy to Alleviate Depression-like Behaviors in Diabetic Mice

Depression is a frequent and serious comorbidity associated with diabetes which adversely affects prognosis and quality of life. Glucagon-like peptide-1 receptor (GLP-1R) agonists, widely used in the treatment of diabetes, are reported to exert neuroprotective effects in the central nervous system. Thus, we aim to evaluate whether GLP-1R agonist exendin-4 (EX-4) could alleviate depression-like behaviors in diabetic mice and to explore its underlying mechanism. The antidepressant effects of EX-4 were evaluated using behavioral tests in db/db mice. The effects of EX-4 on microglial pyroptosis and neuroinflammation were assessed in N9 microglial cells. EX-4 administration alleviated depression-like behaviors in diabetic db/db mice. GLP-1R activation by EX-4 significantly suppressed microglial pyroptosis and neuroinflammation by downregulation of gasdermin D (GSDMD) and interleukin (IL)-1β in diabetic mice and lipopolysaccharide (LPS)-primed N9 microglia. Mechanistically, GLP-1R activation improved mitochondrial function and promoted mitophagy by decreasing the accumulation of mitochondrial reactive oxygen species (mtROS) and intracellular ROS production. EX-4 exhibits antidepressant effects in depression associated with diabetes in diabetic mice, which may be mediated by inhibiting microglial pyroptisis via promoting mitophagy. It is supposed that GLP-1R agonists may be a promising therapy in depression associated with diabetes.

The Nervous System as a Regulator of Cancer Hallmarks: Insights into Therapeutic Implications

Simple Summary

The nervous system communicates with the whole organism, regulating several physiological pathways. The modification of nerve activity could deregulate the state of cellular and tissue homeostasis which could drive cancer development. This paper provides the current state of knowledge, in an evidence-oriented manner, that the nervous system is able to participate in the carcinogenesis process by inducing biochemical, physiological, and cellular modifications involved in the hallmarks of cancer.

Abstract

The involvement of the nervous system in the development of cancer is controversial. Several authors have shown opinions and conflicting evidence that support the early effect of the nervous system on the carcinogenic process. For about a century, research has not been enough, questions remain open, ideas are not discarded, and although more research is still needed to answer all the questions, there is now enough evidence to support the theories and give hope of finding one more possible form of treatment. It is clear that malignant neoplasms have endogenous characteristics that allow them to establish and progress. Some of these characteristics known as hallmarks of cancer, are damage mechanisms in the pathology but necessary during other physiological processes which show some nerve dependence. The nervous system communicates with the whole organism, regulating physiological processes necessary to respond to external stimuli and for the maintenance of homeostasis. The modification of nerve activity could generate an overload and deregulate the state of cellular and tissue homeostasis; this could drive cancer development. In this review, we will address the issue in an evidence-oriented manner that supports that the nervous system is able to participate in the initial and progressive process of carcinogenesis by inducing biochemical, physiological, and cellular modifications involved in the hallmarks of cancer.

Emerging role of mitochondrial DAMPs, aberrant mitochondrial dynamics and anomalous mitophagy in gut mucosal pathogenesis

Gastroduodenal inflammation and ulcerative injuries are increasing due to expanding socio-economic stress, unhealthy food habits-lifestyle, smoking, alcoholism and usage of medicines like non-steroidal anti-inflammatory drugs. In fact, gastrointestinal (GI) complications, associated with the prevailing COVID-19 pandemic, further, poses a challenge to global healthcare towards safeguarding the GI tract. Emerging evidences have discretely identified mitochondrial dysfunctions as common etiological denominators in diseases. However, it is worth realizing that mitochondrial dysfunctions are not just consequences of diseases. Rather, damaged mitochondria severely aggravate the pathogenesis thereby qualifying as perpetrable factors worth of prophylactic and therapeutic targeting. Oxidative and nitrosative stress due to endogenous and exogenous stimuli triggers mitochondrial injury causing production of mitochondrial damage associated molecular patterns (mtDAMPs), which, in a feed-forward loop, inflicts inflammatory tissue damage. Mitochondrial structural dynamics and mitophagy are crucial quality control parameters determining the extent of mitopathology and disease outcomes. Interestingly, apart from endogenous factors, mitochondria also crosstalk and in turn get detrimentally affected by gut pathobionts colonized during luminal dysbiosis. Although mitopathology is documented in various pre-clinical/clinical studies, a comprehensive account appreciating the mitochondrial basis of GI mucosal pathologies is largely lacking. Here we critically discuss the molecular events impinging on mitochondria along with the interplay of mitochondria-derived factors in fueling mucosal pathogenesis. We specifically emphasize on the potential role of aberrant mitochondrial dynamics, anomalous mitophagy, mitochondrial lipoxidation and ferroptosis as emerging regulators of GI mucosal pathogenesis. We finally discuss about the prospect of mitochondrial targeting for next-generation drug discovery against GI disorders.

Graphene quantum dots alleviate ROS-mediated gastric damage

The gastrointestinal (GI) tract is one of the major sites for reactive oxygen species generation (ROS). Physiological ROS, lower than the threshold concentration, is beneficial for human physiology to preserve gut functional integrity. However, ROS generated in large quantities in presence of external stimuli overwhelms the cellular antioxidant defense mechanism and results in oxidative damage and associated physiological disorder. Graphene quantum dots (GQDs) are a class of carbon-based nanomaterials that have attracted tremendous attention not only for their tunable optical properties but also for their broad-spectrum antioxidant properties. In this report we have shown that GQDs are highly efficient in scavenging ROS and suppressing stress-induced gastric ulcers by targeting the MMP-9 pathway and reducing the inflammatory burden by suppressing excessive oxidative stress by inducing high caspase activity, overproduction of Bax, and downregulation of BCL2.

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The gastrointestinal tract is one of the major sites for ROS generation

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Graphene quantum dots (GQDs) have broad-spectrum antioxidant properties

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GQDs scavenge the ROS and suppress gastric ulcers by targeting the MMP-9 pathway

Redox Implications of Extreme Task Performance: The Case in Driver Athletes

Redox homeostasis and redox-mediated signaling mechanisms are fundamental elements of human biology. Physiological levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) modulate a range of functional processes at the cellular, tissue, and systemic levels in healthy humans. Conversely, excess ROS or RNS activity can disrupt function, impairing the performance of daily activities. This article analyzes the impact of redox mechanisms on extreme task performance. Such activities (a) require complex motor skills, (b) are physically demanding, (c) are performed in an extreme environment, (d) require high-level executive function, and (e) pose an imminent risk of injury or death. The current analysis utilizes race car driving as a representative example. The physiological challenges of this extreme task include physical exertion, g loading, vibration, heat exposure, dehydration, noise, mental demands, and emotional factors. Each of these challenges stimulates ROS signaling, RNS signaling, or both, alters redox homeostasis, and exerts pro-oxidant effects at either the tissue or systemic levels. These redox mechanisms appear to promote physiological stress during race car driving and impair the performance of driver athletes.

Omeprazole prevents stress induced gastric ulcer by direct inhibition of MMP-2/TIMP-3 interactions

The healing of damaged tissues in gastric tract starts with the extracellular matrix (ECM) remodeling by the action of matrix metalloproteinases (MMPs). Particularly, MMP-2 (gelatinase-A) maintains ECM structure and function by degrading type IV collagen, the major component of basement membranes and by clearing denatured collagen. The proteolytic activities of MMPs are critically balanced by endogenous tissue inhibitors of metalloproteinases (TIMPs) and disruption of this balance results in several diseases. The well-known drug omeprazole is a proton pump inhibitor used for curing gastric ulcer. However, the action of omeprazole in ECM remodeling on gastroprotection has never been explored. Herein, using rat model of gastric ulcer, we report that restraint cold stress caused increase apoptosis to surface epithelia of gastric tissues along with TIMP-3 upregulation and inhibition of MMP-2 activity thereon. In contrast, omeprazole treatment suppressed TIMP-3 while increasing MMP-2 activity and thereby, restoring MMP-2/TIMP-3 balance. Additionally, nanomolar binding constant (K_d = 318 nM) of omeprazole with purified MMP-2 indicates a direct effect of omeprazole in restoring MMP-2 activity. Further in silico simulations revealed a plausible mechanism of action of omeprazole for TIMP-3 deactivation. Altogether, omeprazole restores MMP-2 activity and reduces apoptosis while preventing acute stress-induced gastric ulcer that occurs via suppression of nuclear factor kappa B (NF-κB) activity and peroxisome proliferator-activated receptor gamma activity (PPAR-γ). This represents an unprecedented correlation between physical docking of drug molecule to a protease and the severity of organ injury and provides a novel therapeutic approach to prevent stress induced tissue damage.

Enterocyte synthesizes and secrets uric acid as antioxidant to protect against oxidative stress via the involvement of Nrf pathway

The gut is an important site to excreting uric acid (UA) in addition to the kidney. The gastrointestinal tract is constantly exposed to various potentially harmful substances, triggering intestinal oxidative damage. In the present study, the hypothesis that UA is can be synthesized to function as an antioxidant in the gut is evaluated. The synthesis and secretion of UA by enterocytes were analyzed in the presence of inosine, a precursor of UA, febuxostat (Fx), an inhibitor of xanthine oxidase (XOR), and H₂O₂. The regulation of Nrf2 pathway on UA secretion and transport were evaluated in the present of agonist (TBHQ) and inhibitor (ML385) of Nrf2. The in vivo result showed that UA and its oxidation product allantoin were presented in gut contents along the gastrointestinal tract and the highest level of UA and allantoin were detected in duodenum and jejunum respectively. The genes in the de novo purine nucleotide synthesis and salvage-catabolism pathways, and UA transporters were expressed in the intestinal tract. In the in vitro cultured enterocytes and everted gut sacs, inosine stimulated UA synthesis and secretion. H₂O₂ stimulated UA synthesis and secretion and meanwhile induced oxidative damage. UA attenuated H₂O₂-induced oxidative damage by Nrf2 pathway. UA secretion and transport were reduced by blocking Nrf2 with ML385, while increased by activating Nrf2 with TBHQ. This study provides new insights into the antioxidant effects if UA on intestinal lumen. The result suggests that activation of Nrf2 pathway is involved in the transportation and secretion of UA.

Mitophagy in depression: Pathophysiology and treatment targets

Mitochondria, the 'powerhouse' of eukaryotic cells, play a key role in cellular homeostasis. However, defective mitochondria increase mitochondrial ROS (mtROS) production and cell-free mitochondrial DNA (mtDNA) release, leading to increased inflammation. Mitophagy is a vital pathway, which selectively removes defective mitochondria through the process of autophagy. Thus, an impairment in the mitophagy pathway might trigger the gradual accumulation of defective mitochondria. Accumulating evidence suggest that inflammation and mitochondrial dysfunction are linked to the pathogenesis of depression. In this article, we have reviewed the role of impaired mitophagy as a contributing factor in depression pathophysiology. Further, we have discussed the potential therapeutic interventions aimed at modulating mitophagy in depression.

Glucocorticoid impairs mitochondrial quality control in neurons

Neurons are particularly vulnerable to mitochondrial dysfunction due to high energy demand and an inability to proliferate. Therefore, dysfunctional mitochondria cause various neuropathologies. Mitochondrial damage induces maintenance pathways to repair or eliminate damaged organelles. This mitochondrial quality control (MQC) system maintains appropriate morphology, localization, and removal/replacement of mitochondria to sustain brain homeostasis and counter progression of neurological disorders. Glucocorticoid release is an essential response to stressors for adaptation; however, it often culminates in maladaptation if neurons are exposed to chronic and severe stress. Long-term exposure to high levels of glucocorticoids induces mitochondrial dysfunction via genomic and nongenomic mechanisms. Glucocorticoids induce abnormal mitochondrial morphology and dysregulate fusion and fission. Moreover, mitochondrial trafficking is arrested by glucocorticoids and dysfunctional mitochondria are subsequently accumulated around the soma. These alterations lead to energy deficiency, particularly for synaptic transmission that requires large amounts of energy. Glucocorticoids also impair mitochondrial clearance by preventing mitophagy of damaged organelle and suppress mitochondrial biogenesis, resulting in the reduced number of healthy mitochondria. Failure to maintain MQC degrades brain function and contributes to neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. However, mechanisms of glucocorticoid action on the regulation of MQC during chronic stress conditions are not well understood. The present review discusses pathways involved in the impairment of MQC and the clinical significance of high glucocorticoid blood levels for neurodegenerative diseases.

Saikosaponin A improved depression-like behavior and inhibited hippocampal neuronal apoptosis after cerebral ischemia through p-CREB/BDNF pathway

Post-stroke depression(PSD) is a common complication and associates with poor physical recovery, low quality of life and high mortality after cerebral infarction. However, the pathogenesis of PSD have not been elucidated thoroughly now, and there is a lack of effective therapy in clinic. It reported that Saikosaponin A, one of the main constituents from Chinese herb Bupleurum chinense, has pharmacological activity in anti-depression. Thus, this study aimed to elucidate the potential effects and mechanisms of Saikosaponin A on the depression-like behavior after cerebral ischemic injury in rats. The rat model of PSD was induced by middle cerebral artery occlusion(MCAO) combined with chronic unpredictable mild stress(CUMS) and isolation. Behavior tests including open field test, beam-walking test, sucrose preference and forced swimming tests were performed. Western blot and immunohistochemistry were adopted to evaluate expression of phosphorylated cAMP response element binding protein(p-CREB), brain derived neurotrophic factor(BDNF) and apoptosis-related molecules in the dentate gyrus region of rat hippocampus. The TUNEL assay was used to determine neuronal apoptosis. We found that the rats subjected to MCAO combined with CUMS and isolation experienced significant depressive-like behavior. Administration of Saikosaponin A significantly ameliorated depressive-like behavior, and inhibited neuronal apoptosis, enhanced the level of p-CREB, BDNF and Bcl-2, reduced the level of Bax, Caspase-3 in the hippocampus of PSD rats. These results revealed that Saikosaponin A improved depression-like behavior and inhibited hippocampal neuronal apoptosis after cerebral ischemia, presumably through increasing the expression of BDNF, p-CREB and Bcl-2, as well as decreasing the level of Bax, Caspase-3.

Mediators of mitophagy that regulate mitochondrial quality control play crucial role in diverse pathophysiology

Mitochondria are double membrane-bound cellular work-horses constantly functioning to regulate vital aspects of cellular metabolism, bioenergetics, proliferation and death. Biogenesis, homeostasis and regulated turnover of mitochondria are stringently regulated to meet the bioenergetic requirements. Diverse external and internal stimuli including oxidative stress, diseases, xenobiotics and even age profoundly affect mitochondrial integrity. Damaged mitochondria need immediate segregation and selective culling to maintain physiological homeostasis. Mitophagy is a specialised form of macroautophagy that constantly checks mitochondrial quality followed by elimination of rogue mitochondria by lysosomal targeting through multiple pathways tightly regulated and activated in context-specific manners. Mitophagy is implicated in diverse oxidative stress-associated metabolic, proliferating and degenerative disorders owing to the centrality of mitopathology in diseases as well as the common mandate to eliminate damaged mitochondria for restoring physiological homeostasis. With improved health care and growing demand for precision medicine, specifically targeting the keystone factors in pathogenesis, more exploratory studies are focused on mitochondrial quality control as underlying guardian of cellular pathophysiology. In this context, mitophagy emerged as a promising area to focus biomedical research for identifying novel therapeutic targets against diseases linked with physiological redox perturbation. The present review provides a comprehensive account of the recent developments on mitophagy along with precise discussion on its impact on major diseases and possibilities of therapeutic modulation.

Novel insights into stress-induced susceptibility to influenza: corticosterone impacts interferon-β responses by Mfn2-mediated ubiquitin degradation of MAVS

Although stress has been known to increase the susceptibility of pathogen infection, the underlying mechanism remains elusive. In this study, we reported that restraint stress dramatically enhanced the morbidity and mortality of mice infected with the influenza virus (H1N1) and obviously aggravated lung inflammation. Corticosterone (CORT), a main type of glucocorticoids in rodents, was secreted in the plasma of stressed mice. We further found that this stress hormone significantly boosted virus replication by restricting mitochondrial antiviral signaling (MAVS) protein-transduced IFN-β production without affecting its mRNA level, while the deficiency of MAVS abrogated stress/CORT-induced viral susceptibility in mice. Mechanistically, the effect of CORT was mediated by proteasome-dependent degradation of MAVS, thereby resulting in the impediment of MAVS-transduced IFN-β generation in vivo and in vitro. Furthermore, RNA-seq assay results indicated the involvement of Mitofusin 2 (Mfn2) in this process. Gain- and loss-of-function experiments indicated that Mfn2 interacted with MAVS and recruited E3 ligase SYVN1 to promote the polyubiquitination of MAVS. Co-immunoprecipitation experiments clarified an interaction between any two regions of Mfn2 (HR1), MAVS (C-terminal/TM) and SYVN1 (TM). Collectively, our findings define the Mfn2-SYVN1 axis as a new signaling cascade for proteasome-dependent degradation of MAVS and a 'fine tuning' of antiviral innate immunity in response to influenza infection under stress.

Oxidative stress is important in the pathogenesis of stress-related mucosal disease

Stress-related mucosal disease (SRMD) is a common complication in patients in the intensive care unit (ICU). The aim of the present study was to investigate the possible mechanisms for the pathogenesis of SRMD. In total, 38 patients with SRMD were enrolled from an ICU, as well as 15 healthy volunteers. The disease severity of patients in ICU was evaluated using the Acute Physiology and Chronic Health Evaluation (APACHE) II score. Gastric mucosa with the most severe lesions were biopsied for hematoxylin and eosin staining and then assessed by pathological damage scoring. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD) and ischemic modified albumin (IMA) were also detected. In addition, claudin-3 and inducible nitric oxide (NO) synthase (iNOS) in the gastric mucosa were assessed by western blotting and immunohistochemistry. The average APACHE II score of the patients with SRMD was significantly higher compared with the controls. Moreover, the levels of MDA (4.74±2.89 nmol/ml) and IMA (93.61±10.78 U/ml) in patients with SRMD were significantly higher compared with the controls (P<0.001), while those of SOD (89.66±12.85 U/ml) in the patients with SRMD were significantly lower compared with the controls (P<0.001). Furthermore, compared with the control, iNOS expression was significantly higher (P=0.034), while the expression of claudin-3 was significantly lower in patients with SRMD (P<0.001). The results indicated that APACHE II score was positively correlated with pathological damage score (r=0.639, P<0.001) and levels of MDA (r=0.743, P<0.001), but negatively correlated with the level of SOD (r=-0.392, P=0.015). In addition, MDA was positively correlated with IMA (r=0.380, P=0.018), but negatively correlated with claudin-3 (r=-0.377, P=0.020). Therefore, it was speculated that oxidative stress may play an important role in the pathogenesis of SRMD, and NO levels and cell membrane permeability are altered during this process.

Chronic Restraint Stress Induces Gastric Mucosal Inflammation with Enhanced Oxidative Stress in a Murine Model

Background

Although the underlying mechanisms of chronic stress are still unknown, this condition has been related to the pathophysiology of gastric mucosal inflammation, whose development is accelerated by oxidative stress. The present study investigates how chronic stress influences gastric mucosal oxidative stress and inflammation.

Methods

Eight-week-old C57BL/6J male mice were subjected to two-week intermittent restraint stress. The expressions of CD11b (a specific for monocyte/macrophage), monocyte/macrophage cell surface markers (CD68 and F4/80), NADPH oxidase-4 (Nox-4) and 8-hydroxy-2’-deoxyguanosine (8-OHdG, a sensitive biomarker of oxidative stress) were determined using immunohistochemistry, RT-PCR, and enzyme-linked immunosorbent assay, respectively. The expressions of antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, were examined by RT-PCR and Western blotting. The expressions of proinflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), were determined using immunohistochemistry and RT-PCR, respectively.

Results

Chronic stress increased the lymphocytic infiltration and inflammation within the gastric mucosa of mice. Stress remarkably increased the expression levels of CD11b and mRNA expression levels of CD68 and F4/80 in the mucosa of the stomach of stressed mice. Stress remarkably increased both mRNA and plasma concentrations of Nox-4 and 8-OHdG; and markedly reduced gastric mRNA and protein expression levels of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. The expressions of proinflammatory cytokines (MCP-1, IL-1β, and TNF-α) were predominantly observed in the gastric mucosal layers of the stressed mice. Furthermore, stress remarkably elevated the gastric mucosal mRNA expression levels of MCP-1, IL-1β, and TNF-α.

Conclusion

Two weeks of restraint stress induced gastric inflammation in the murine model with enhanced oxidative stress and reduced anti-oxidative system.

Activation of the kynurenine pathway and mitochondrial respiration to face allostatic load in a double-hit model of stress

Allostasis is the process by which the body's physiological systems adapt to environmental changes. Chronic stress increases the allostatic load to the body, producing wear and tear that could, over time, become pathological. In this study, young adult male Wistar Kyoto rats were exposed to an unpredictable chronic mild stress (uCMS) protocol to increase allostatic load. First, physiological systems which may be affected by extended uCMS exposure were assessed. Secondly, 5 weeks of uCMS were used to investigate early adaptations in the previously selected systems. Adverse experiences during developmentally sensitive periods like adolescence are known to severely alter the individual stress vulnerability with long-lasting effects. To elucidate how early life adversity impacts stress reactivity in adulthood, an additional group with juvenile single-housing (JSH) prior to uCMS was included in the second cohort. The aim of this work was to assess the impact of chronic stress with or without adversity during adolescence on two domains known to be impacted in numerous stress-related disorders: mitochondrial energy metabolism and the immune system. Both, uCMS and adolescence stress increased kynurenine and kynurenic acid in plasma, suggesting a protective, anti-oxidant response from the kynurenine pathway. Furthermore, uCMS resulted in a down-regulation of immediate early gene expression in the prefrontal cortex and hippocampus, while only rats with the double-hit of adolescent stress and uCMS demonstrated increased mitochondrial activity in the hippocampus. These results suggest that early life adversity may impact on allostatic load by increasing energetic requirements in the brain.

Astragaloside IV Protects Ethanol-Induced Gastric Mucosal Injury by Preventing Mitochondrial Oxidative Stress and the Activation of Mitochondrial Pathway Apoptosis in Rats

Alcohol consumption affects gastric mucosa by multiple and complex mechanisms depending either by direct contact of ethanol or by indirect biological damage induced by its metabolite acetaldehyde. The present study aims at further investigating the mechanism of ethanol-induced gastric mucosa injury and the protective effect of astragaloside IV (AS-IV) in an aspect of mitochondrial oxidative stress and mitochondrial pathway of apoptosis. Using an array of experimental approaches, we have shown that the development of mitochondrial oxidative stress and associated apoptosis play crucial roles in the pathogenesis of gastric injury induced by ethanol. AS-IV inhibits mitochondrial oxidative stress by scavenging accumulation of malondialdehyde and decreasing the consumption of glutathione. AS-IV also prevents ethanol-induced apoptosis by modulating the activity of caspase-3 and caspase-9, the expression of Bax/Bcl-2, and the release of cytochrome C and apoptosis inducing factor. Moreover, AS-IV reduces ethanol-mediated activation of caspase-8 and breakage of Bid. This study thus indicates that AS-IV prevented ethanol-induced gastric damage by blocking activation of mitochondrial oxidative stress and mitochondrial pathway of apoptosis induced by ethanol in the gastric mucosa.

Hypertension linked to allostatic load: from psychosocial stress to inflammation and mitochondrial dysfunction

Although a large number of available treatments and strategies, the prevalence of cardiovascular diseases continues to grow worldwide. Emerging evidence supports the notion of counteracting stress as a critical component of a comprehensive therapeutic strategy for cardiovascular disease. Indeed, an unhealthy lifestyle is a burden to biological variables such as plasma glucose, lipid profile, and blood pressure control. Recent findings identify allostatic load as a new paradigm for an integrated understanding of the importance of psychosocial stress and its impact on the development and maintenance of cardiovascular disease. Allostasis complement homeostasis and integrates behavioral and physiological mechanisms by which genes, early experiences, environment, lifestyle, diet, sleep, and physical exercise can modulate and adapt biological responses at the cellular level. For example, variability is a physiological characteristic of blood pressure necessary for survival and the allostatic load in hypertension can contribute to its related cardiovascular morbidity and mortality. Therefore, the current review will focus on the mechanisms that link hypertension to allostatic load, which includes psychosocial stress, inflammation, and mitochondrial dysfunction. We will describe and discuss new insights on neuroendocrine-immune effects linked to allostatic load and its impact on the cellular and molecular responses; the links between allostatic load, inflammation, and endothelial dysfunction; the epidemiological evidence supporting the pathophysiological origins of hypertension; and the biological embedding of allostatic load and hypertension with an emphasis on mitochondrial dysfunction.

Macrophage migration inhibitory factor regulates mitochondrial dynamics and cell growth of human cancer cell lines through CD74-NF-κB signaling

The indispensable role of macrophage migration inhibitory factor (MIF) in cancer cell proliferation is unambiguous, although which specific roles the cytokine plays to block apoptosis by preserving cell growth is still obscure. Using different cancer cell lines (AGS, HepG2, HCT116, and HeLa), here we report that the silencing of MIF severely deregulated mitochondrial structural dynamics by shifting the balance toward excess fission, besides inducing apoptosis with increasing sub-G₀ cells. Furthermore, enhanced mitochondrial Bax translocation along with cytochrome c release, down-regulation of Bcl-xL, and Bcl-2 as well as up-regulation of Bad, Bax, and p53 indicated the activation of a mitochondrial pathway of apoptosis upon MIF silencing. The data also indicate a concerted down-regulation of Opa1 and Mfn1 along with a significant elevation of Drp1, cumulatively causing mitochondrial fragmentation upon MIF silencing. Up-regulation of Drp1 was found to be further coupled with fissogenic serine 616 phosphorylation and serine 637 dephosphorylation, thus ensuring enhanced mitochondrial translocation. Interestingly, MIF silencing was found to be associated with decreased NF-κB activation. In fact, NF-κB knockdown in turn increased mitochondrial fission and cell death. In addition, the silencing of CD74, the cognate receptor of MIF, remarkably increased mitochondrial fragmentation in addition to preventing cell proliferation, inducing mitochondrial depolarization, and increasing apoptotic cell death. This indicates the active operation of a MIF-regulated CD74-NF-κB signaling axis for maintaining mitochondrial stability and cell growth. Thus, we propose that MIF, through CD74, constitutively activates NF-κB to control mitochondrial dynamics and stability for promoting carcinogenesis via averting apoptosis.

Mitochondria and Mood: Mitochondrial Dysfunction as a Key Player in the Manifestation of Depression

Human and animal studies suggest an intriguing link between mitochondrial diseases and depression. Although depression has historically been linked to alterations in monoaminergic pharmacology and adult hippocampal neurogenesis, new data increasingly implicate broader forms of dampened plasticity, including plasticity within the cell. Mitochondria are the cellular powerhouse of eukaryotic cells, and they also regulate brain function through oxidative stress and apoptosis. In this paper, we make the case that mitochondrial dysfunction could play an important role in the pathophysiology of depression. Alterations in mitochondrial functions such as oxidative phosphorylation (OXPHOS) and membrane polarity, which increase oxidative stress and apoptosis, may precede the development of depressive symptoms. However, the data in relation to antidepressant drug effects are contradictory: some studies reveal they have no effect on mitochondrial function or even potentiate dysfunction, whereas other studies show more beneficial effects. Overall, the data suggest an intriguing link between mitochondrial function and depression that warrants further investigation. Mitochondria could be targeted in the development of novel antidepressant drugs, and specific forms of mitochondrial dysfunction could be identified as biomarkers to personalize treatment and aid in early diagnosis by differentiating between disorders with overlapping symptoms.