Neuroprotective Efficacy of Mitochondrial Antioxidant MitoQ in Suppressing Peroxynitrite-Mediated Mitochondrial Dysfunction Inflicted by Lead Toxicity in the Rat Brain

The mitochondria-targeted antioxidant MitoQ ameliorates inorganic arsenic-induced DCs/Th1/Th2/Th17/Treg differentiation partially by activating PINK1-mediated mitophagy in murine liver

Inorganic arsenic is a well-established environmental toxicant linked to acute liver injury, fibrosis, and cancer. While oxidative stress, pyroptosis, and ferroptosis are known contributors, the role of PTEN-induced kinase 1 (PINK1)-mediated mitophagy in arsenic-induced hepatic immunotoxicity remains underexplored. Our study revealed that acute arsenic exposure prompts differentiation of hepatic dendritic cells (DCs) and T helper (Th) 1, Th2, Th17, and regulatory T (Treg) cells, alongside increased transcription factors and cytokines. Inorganic arsenic triggered liver redox imbalance, leading to elevated alanine transaminase (ALT), hydrogen peroxide (H2O2), malondialdehyde (MDA), and activation of nuclear factor erythroid 2-related factor (Nrf2)/heme oxygenase-1 (HO-1) pathway. PINK1-mediated mitophagy was initiated, and its inhibition exacerbates H2O2 accumulation while promoting DCs/Th1/Th2/Treg differentiation in the liver of arsenic-exposed mice. Mitoquinone (MitoQ) pretreatment relieved arsenic-induced acute liver injury and immune imbalance by activating Nrf2/HO-1 and PINK1-mediated mitophagy. To our knowledge, this is the first report identifying PINK1-mediated mitophagy as a protective factor against inorganic arsenic-induced hepatic DCs/Th1/Th2 differentiation. This study has provided new insights on the immunotoxicity of inorganic arsenic and established a foundation for exploring preventive and therapeutic strategies targeting PINK1-mediated mitophagy in acute liver injury. Consequently, the application of mitochondrial antioxidant MitoQ may offer a promising treatment for the metalloid-induced acute liver injury.

Heavy Metal Exposure: Molecular Pathways, Clinical Implications, and Protective Strategies

Heavy metals are often found in soil and can contaminate drinking water, posing a serious threat to human health. Molecular pathways and curation therapies for mitigating heavy metal toxicity have been studied for a long time. Recent studies on oxidative stress and aging have shown that the molecular foundation of cellular damage caused by heavy metals, namely, apoptosis, endoplasmic reticulum stress, and mitochondrial stress, share the same pathways as those involved in cellular senescence and aging. In recent aging studies, many types of heavy metal exposures have been used in both cellular and animal aging models. Chelation therapy is a traditional treatment for heavy metal toxicity. However, recently, various antioxidants have been found to be effective in treating heavy metal-induced damage, shifting the research focus to investigating the interplay between antioxidants and heavy metals. In this review, we introduce the molecular basis of heavy metal-induced cellular damage and its relationship with aging, summarize its clinical implications, and discuss antioxidants and other agents with protective effects against heavy metal damage.

Oyster (Crassostrea gigas) ferritin relieves lead-induced liver oxidative damage via regulating the mitophagy

Lead can induce oxidative stress and increase lipid peroxidation in biofilms, leading to liver damage and physiological dysfunction. This study aimed to investigate how oyster ferritin (GF1) attenuates lead-induced oxidative damage to the liver in vitro and in vivo. Animal experiments have confirmed that lead exposure can lead to oxidative damage and lipid peroxidation of the liver, and ferritin can regulate the activity of antioxidant enzymes and alleviate pathological changes in the liver. At the same time, oyster ferritin can regulate the expression of oxidative stress-related genes and reduce the expression of inflammasome-related genes. In addition, lead can induce apoptosis and mitophagy, leading to overproduction of reactive oxygen species and cell death, which can be effectively alleviated by oyster ferritin. Overall, this study provides a theoretical foundation for the use of oyster ferritin as a means of mitigating and preventing lead-induced damage.

Targeting mitophagy for neurological disorders treatment: advances in drugs and non-drug approaches

Mitochondria serve as a vital energy source for nerve cells. The mitochondrial network also acts as a defense mechanism against external stressors that can threaten the stability of the nervous system. However, excessive accumulation of damaged mitochondria can lead to neuronal death. Mitophagy is an essential pathway in the mitochondrial quality control system and can protect neurons by selectively removing damaged mitochondria. In most neurological disorders, dysfunctional mitochondria are a common feature, and drugs that target mitophagy can improve symptoms. Here, we reviewed the role of mitophagy in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, stroke, and traumatic brain injuries. We also summarized drug and non-drug approaches to promote mitophagy and described their therapeutic role in neurological disorders in order to provide valuable insight into the potential therapeutic agents available for neurological disease treatment. However, most studies on mitophagy regulation are based on preclinical research using cell and animal models, which may not accurately reflect the effects in humans. This poses a challenge to the clinical application of drugs targeting mitophagy. Additionally, these drugs may carry the risk of intolerable side effects and toxicity. Future research should focus on the development of safer and more targeted drugs for mitophagy.

Recent insights into autophagy and metals/nanoparticles exposure

Some anthropogenic pollutants, such as heavy metals and nanoparticles (NPs), are widely distributed and a major threat to environmental safety and public health. In particular, lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) have systemic toxicity even at extremely low concentrations, so they are listed as priority metals in relation to their significant public health burden. Aluminum (Al) is also toxic to multiple organs and is linked to Alzheimer's disease. As the utilization of many metal nanoparticles (MNPs) gradually gain traction in industrial and medical applications, they are increasingly being investigated to address potential toxicity by impairing certain biological barriers. The dominant toxic mechanism of these metals and MNPs is the induction of oxidative stress, which subsequently triggers lipid peroxidation, protein modification, and DNA damage. Notably, a growing body of research has revealed the linkage between dysregulated autophagy and some diseases, including neurodegenerative diseases and cancers. Among them, some metals or metal mixtures can act as environmental stimuli and disturb basal autophagic activity, which has an underlying adverse health effect. Some studies also revealed that specific autophagy inhibitors or activators could modify the abnormal autophagic flux attributed to continuous exposure to metals. In this review, we have gathered recent data about the contribution of the autophagy/mitophagy mediated toxic effects and focused on the involvement of some key regulatory factors of autophagic signaling during exposure to selected metals, metal mixtures, as well as MNPs in the real world. Besides this, we summarized the potential significance of interactions between autophagy and excessive reactive oxygen species (ROS)-mediated oxidative damage in the regulation of cell survival response to metals/NPs. A critical view is given on the application of autophagy activators/inhibitors to modulate the systematic toxicity of various metals/MNPs.

Exposure of combination of environmental pollutant, lead (Pb) and β-amyloid peptides causes mitochondrial dysfunction and oxidative stress in human neuronal cells

Exposure to the environmental pollutant lead (Pb) has been linked to Alzheimer's disease (AD), in which mitochondrial dysfunction is a pathological consequence of neuronal degeneration. The toxicity of Pb in combination with β-amyloid peptides (1-40) and (25-35) causes selective death in neuronal cells. However, the precise mechanism through which Pb induces Alzheimer's disease, particularly mitochondrial damage, is unknown. Changes in mitochondrial mass, membrane potential, mitochondrial complex activities, mitochondrial DNA and oxidative stress were examined in neuronal cells of human origin exposed to Pb and β-amyloid peptides (1-40) and (25-35) individually and in different combinations. The results showed depolarization of mitochondrial membrane potential, decrease in mitochondrial mass, ATP levels and mtDNA copy number in Pb and β-amyloid peptides (1-40) and (25-35) exposed cells. Also, significant reductions in the expression of mitochondrial electron transport chain (ETC) complex proteins (ATP5A, COXIV, UQCRC2, SDHB, NDUFS3), as well as down regulation of ETC complex gene expressions such as COXIV, ATP5F1 and NDUFS3 and antioxidant gene expressions like MnSOD and Gpx4 were observed in exposed cells. Furthermore, Pb and β-amyloid peptides exposure resulted in elevated mitochondrial malondialdehyde levels and a decrease in mitochondrial GSH levels. Our findings suggest that Pb toxicity could be one of the causative factors for the mitochondrial dysfunction and oxidative stress in Alzheimer's disease progression.

The role of oxidative stress in the pathogenesis of infections with coronaviruses

Coronaviruses can cause serious respiratory tract infections and may also impact other end organs such as the central nervous system, the lung and the heart. The coronavirus disease 2019 (COVID-19) has had a devastating impact on humanity. Understanding the mechanisms that contribute to the pathogenesis of coronavirus infections, will set the foundation for development of new treatments to attenuate the impact of infections with coronaviruses on host cells and tissues. During infection of host cells, coronaviruses trigger an imbalance between increased production of reactive oxygen species (ROS) and reduced antioxidant host responses that leads to increased redox stress. Subsequently, increased redox stress contributes to reduced antiviral host responses and increased virus-induced inflammation and apoptosis that ultimately drive cell and tissue damage and end organ disease. However, there is limited understanding how different coronaviruses including SARS-CoV-2, manipulate cellular machinery that drives redox responses. This review aims to elucidate the redox mechanisms involved in the replication of coronaviruses and associated inflammation, apoptotic pathways, autoimmunity, vascular dysfunction and tissue damage that collectively contribute to multiorgan damage.

Defective mitophagy and induction of apoptosis by the depleted levels of PINK1 and parkin in Pb and β-amyloid peptide induced toxicity

Exposure to lead (Pb), an environmental pollutant, is closely associated with the development of neurodegenerative disorders through oxidative stress induction and alterations in mitochondrial function. Damaged mitochondria could be one of the reasons for the progression of Alzheimer's Disease (AD). Mitophagy is vital in keeping the cell healthy. To know its role in Pb-induced AD, we investigated the PINK1/parkin dependent pathway by studying specific mitophagy marker proteins such as PINK1 and parkin in differentiated SH-SY5Y cells. Our data have indicated a significant reduction in the levels of PINK1 and parkin in cells exposed to Pb and β-amyloid peptides, both Aβ (25-35) and Aβ (1-40) individually and in different combinations, resulting in defective mitophagy. Also, the study unravels the status of mitochondrial permeability transition pore (MPTP), mitochondrial mass, mitochondrial membrane potential (MMP) and mitochondrial ROS production in cells treated with individual and different combination of Pb and Aβ peptides. An increase in mitochondrial ROS production, enhanced MPTP opening, depolarization of membrane potential and reduced mitochondrial mass in the exposed groups were observed. Also, in the present study, we found that Pb and β-amyloid peptides could trigger apoptosis by activating the Bak protein, which releases the cytochrome c from mitochondria through MPTP that further activates the AIF (apoptosis inducing factor) and caspase-3 proteins in the cytosol. The above findings reveal the potential role of mechanisms like PINK1/parkin mediated mitophagy and dysfunctional mitochondria mediated apoptosis in Pb induced neurotoxicity.

Systemic delivery of a mitochondria targeted antioxidant partially preserves limb muscle mass and grip strength in response to androgen deprivation

Muscle mass is important for health. Decreased testicular androgen production (hypogonadism) contributes to the loss of muscle mass, with loss of limb muscle being particularly debilitating. Androgen replacement is the only pharmacological treatment, which may not be feasible for everyone. Prior work showed that markers of reactive oxygen species and markers of mitochondrial degradation pathways were higher in the limb muscle following castration. Therefore, we tested whether an antioxidant preserved limb muscle mass in male mice subjected to a castration surgery. Subsets of castrated mice were treated with resveratrol (a general antioxidant) or MitoQ (a mitochondria targeted antioxidant). Relative to the non-castrated control mice, lean mass, limb muscle mass, and grip strength were partially preserved only in castrated mice treated with MitoQ. Independent of treatment, markers of mitochondrial degradation pathways remained elevated in all castrated mice. Therefore, a mitochondrial targeted antioxidant may partially preserve limb muscle mass in response to hypogonadism.

Pb induced mitochondrial fission of fibroblast cells via ATM activation

Previous study showed that lead (Pb) could induce ATM-dependent mitophagy. However, whether Pb has any impact on mitochondrial fusion and fission, the upstream events of mitophagy, and how ATM connects to these processes remain unclear. In this study, we found that Pb can disrupt mitochondrial network morphology as indicated by increased percentage of shortened mitochondria and by decreased mitochondrial footprints. Correspondingly, the expression of fission protein Drp1 and its association with mitochondrial marker Hsp60 were significantly increased, while those of fusion proteins Mfn2 and Opa1 and their co-localization with Hsp60 were drastically attenuated. Notably, the expression of p-Drp1 (Ser616) and its translocation to mitochondria were dramatically elevated. Moreover, a small amount of ATM could be detected in the cytoplasm around mitochondria in response to Pb, and the co-localization of p-ATM (Ser1981) with Drp1 and p-Drp1 (Ser616) was obviously increased while its co-localization with Mfn2 and Opa1 was dramatically decreased. Furthermore, siRNA silencing of ATM evidently promoted greater fission in response to Pb stress, indicating that ATM is involved in mitochondrial fragmentation. Our results suggest that cytoplasmic ATM is an important regulator of Pb-induced mitochondrial fission.

Substance P failed to reverse dextran sulfate sodium-induced murine colitis mediated by mitochondrial dysfunction: implications in ulcerative colitis

As controversy exists about the efficacy of substance P (SP) in treating ulcerative colitis (UC) with no previous study highlighting the impact of SP on mitochondrial dysfunction in this diseased condition, it became logical to perform the present study. C57BL/6 J mice were administered with DSS @ 3.5%/gm body weight for 3 cycles of 5 days each followed by i.v. dose of SP @ 5nmole per kg for consecutive 7 days. Histopathological features were noticed in the affected colon along with colonic mitochondrial dysfunction, alterations in mitochondrial stress variables and enhanced colonic cell death. Interestingly, SP failed to reverse colitic features and proved ineffective in inhibiting mitochondrial dysfunction. Unexpectedly SP alone seemed to impart detrimental effects on some of the mitochondrial functions, enhanced lipid peroxidation and increased staining intensities for caspases 3 and 9 in the normal colon. To substantiate in vivo findings and to assess free radical scavenging property of SP, Caco-2 cells were exposed to DSS with or without SP in the presence and absence of specific free radical scavengers and antioxidants. Interestingly, in vitro treatment with SP failed to restore mitochondrial functions and its efficacy proved below par compared to SOD and DMSO indicating involvement of O2 •- and •OH in the progression of UC. Besides, catalase, L-NAME and MEG proved ineffective indicating non-involvement of H2O2, NO and ONOO- in UC. Thus, SP may not be a potent anti-colitogenic agent targeting colonic mitochondrial dysfunction for maintenance of colon epithelial tract as it lacks free radical scavenging property.

Cognitive Impairment Induced by Lead Exposure during Lifespan: Mechanisms of Lead Neurotoxicity

Lead (Pb) is considered a strong environmental toxin with human health repercussions. Due to its widespread use and the number of people potentially exposed to different sources of this heavy metal, Pb intoxication is recognized as a public health problem in many countries. Exposure to Pb can occur through ingestion, inhalation, dermal, and transplacental routes. The magnitude of its effects depends on several toxicity conditions: lead speciation, doses, time, and age of exposure, among others. It has been demonstrated that Pb exposure induces stronger effects during early life. The central nervous system is especially vulnerable to Pb toxicity; Pb exposure is linked to cognitive impairment, executive function alterations, abnormal social behavior, and fine motor control perturbations. This review aims to provide a general view of the cognitive consequences associated with Pb exposure during early life as well as during adulthood. Additionally, it describes the neurotoxic mechanisms associated with cognitive impairment induced by Pb, which include neurochemical, molecular, and morphological changes that jointly could have a synergic effect on the cognitive performance.

Involvement of nitrosative stress cytotoxicity induced by CdTe quantum dots in human vascular endothelial cells

Quantum dots (QDs) are new types of fluorescent nanomaterials which can be utilized as ideal agents for intracellular tracking, drug delivery, biomedical imaging and diagnosis. It is urgent to understand their potential toxicity and the interactions with the toxin-susceptible vascular system, especially vascular endothelial cells. In this study, we intended to explore whether the cytotoxicity of CdTe (cadmium telluride) QDs was partly induced by nitrosative stress in vascular endothelial cells. Our results showed that the intracellular amount of CdTe QDs was gradually increased in a dose- and time-dependent manner, and a concentration-dependent decrease in viability were observed when incubated with CdTe QDs of 20-80 nM. The peroxynitrite level was significantly up-regulated by QDs treatment, which indicated the nitrosative stress was activated. Furthermore, nitrotyrosine level was increased after 24 hr CdTe QDs exposure in a dose-dependent manner, which suggested that CdTe QDs-induced nitrosative stress was associated with tyrosine nitration in EA.hy926. In addition, CdTe QDs induced EA.hy926 apoptosis, and the percentage of cells with low Δψm was increased after CdTe QDs treatment, indicating the mitochondrion depolarization was induced. The increased ROS fluorescence was observed in a QDs dose-dependent manner, which suggested that the oxidative stress was also involved in the CdTe QDs-induced endothelial cytotoxicity. Our work provided experimental evidence into QDs toxicity and potential vascular risks induced by nitrosative stress for the future applications of QDs.

Role of free radical scavenging activity of vasoactive intestinal peptide in the attenuation of mitochondrial dysfunction to ameliorate dextran sulphate sodium-induced colitis in mice: Implications in ulcerative colitis

OBJECTIVE

To evaluate the efficacy of vasoactive intestinal peptide (VIP) in treating ulcerative colitis (UC), targeting colonic mitochondrial dysfunction by virtue of its free radical scavenging properties for maintenance of colon mucosal integrity.

METHODS

A murine model was administered with dextran sodium sulfate (DSS) to induce colitis in C57BL/6J mice at 3.5%/g bodyweight for 3 cycles of 5 days each, followed by an intraperitoneal dose of VIP at 0.5 nmol/L per mouse per day for 10 days. The post-treatment mice were sacrificed and their colon samples were utilized for further analysis. To substantiate the in vivo findings and identify the reactive species involved in progression of UC, Caco-2 cells were subjected to DSS (5%) for 24 hours at 37 °C with or without VIP (10 nmol/L) in the presence or absence of specific free radical scavengers and antioxidants.

RESULTS

Treatment with VIP reduced histopathological severity of colitis and cell death markers in murine model, leading to partial recovery of inhibited mitochondrial respiratory complexes, altered mitochondrial membrane potential and lowered adenosine triphosphate generation. Interestingly, in vitro treatment with VIP restored mitochondrial functions and its efficacy was equal to super oxide dismutase and dimethyl sulfoxide, indicating involvement of superoxide free radical (O₂ ^•-) and hydroxyl radical (^•OH) in progression of UC. However, catalase, N_ω-nitro-l-arginine methyl ester and mercaptoethylguanidine were ineffective, indicating non-involvement of hydrogen peroxide, nitric oxide and ONOO^- in UC.

CONCLUSION

By virtue of its free radical scavenging properties VIP can act as a potent anti-colitogenic agent, reversing colonic mitochondrial dysfunction for treating UC.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Protective role of mitoquinone against impaired mitochondrial homeostasis in metabolic syndrome

Mitochondria control various processes in cellular metabolic homeostasis, such as adenosine triphosphate production, generation and clearance of reactive oxygen species, control of intracellular Ca²⁺ and apoptosis, and are thus a critical therapeutic target for metabolic syndrome (MetS). The mitochondrial targeted antioxidant mitoquinone (MitoQ) reduces mitochondrial oxidative stress, prevents impaired mitochondrial dynamics, and increases mitochondrial turnover by promoting autophagy (mitophagy) and mitochondrial biogenesis, which ultimately contribute to the attenuation of MetS conditions, including obesity, insulin resistance, hypertension and cardiovascular disease. The regulatory effect of MitoQ on mitochondrial homeostasis is mediated through AMPK and its downstream signaling pathways, including MTOR, SIRT1, Nrf2 and NF-κB. However, there are few reviews focusing on the critical role of MitoQ as a therapeutic agent in the treatment of MetS. The purpose of this review is to summarize the mitochondrial role in the pathogenesis of MetS, especially in obesity and type 2 diabetes, and discuss the effect and underlying mechanism of MitoQ on mitochondrial homeostasis in MetS.

Alleviation of Simvastatin-Induced Myopathy in Rats by the Standardized Extract of Ginkgo Biloba (EGb761): Insights into the Mechanisms of Action

Statins are the most widely prescribed cholesterol-lowering drugs to reduce the risk of cardiovascular diseases. Statin-induced myopathy is the major side effect of this class of drugs. Here, we studied whether standardized leaf extracts of ginkgo biloba (EGb761) would improve simvastatin (SIM)-induced muscle changes. Sixty Wistar rats were allotted into six groups: control group, vehicle group receiving 0.5% carboxymethyl cellulose (CMC) for 30 days, SIM group receiving 80 mg/kg/day SIM in 0.5% CMC orally for 30 days, SIM withdrawal group treated with SIM for 16 days and sacrificed 14 days later, and EGb761-100 and EGb761-200 groups posttreated with either 100 or 200 mg/kg/day EGb761 orally. Muscle performance on the rotarod, serum creatine kinase (CK), coenzyme Q10 (CoQ10), serum and muscle nitrite, muscle malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were estimated. Additionally, muscle samples were processed for histopathological evaluation. We found that SIM decreased muscle performance on the rotarod, serum CoQ10, as well as muscle SOD and CAT activities while it increased serum CK, serum and muscle nitrite, as well as muscle MDA levels. SIM also induced sarcoplasmic vacuolation, splitting of myofibers, disorganization of sarcomeres, and disintegration of myofilaments. In contrast, posttreatment with EGb761 increased muscle performance, serum CoQ10, as well as muscle SOD and CAT activities while it reduced serum CK as well as serum and muscle nitrite levels in a dose-dependent manner. Additionally, EGb761 reversed SIM-induced histopathological changes with better results obtained by its higher dose. Interestingly, SIM withdrawal increased muscle performance on the rotarod, reduce serum CK and CoQ10, and reduced serum and muscle nitrite while it reversed SIM-induced histopathological changes. However, SIM withdrawal was not effective enough to restore their normal values. Additionally, SIM withdrawal did not improve SIM-induce muscle MDA, SOD, or CAT activities during the period studied. Our results suggest that EGb761 posttreatment reversed SIM-induces muscle changes possibly through its antioxidant effects, elevation of CoQ10 levels, and antagonizing mitochondrial damage.

Gut bacteria signaling to mitochondria in intestinal inflammation and cancer

The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.

Neuroprotective role of luteolin against lead acetate-induced cortical damage in rats

Luteolin (LUT) is a glycosylated flavonoid compound that has multiple beneficial pharmacological and biological impacts. The current investigation was undertaken to evaluate the putative neuroprotective potency of LUT against neuronal damage induced by lead acetate (PbAc). Twenty-eight rats were placed into four equal groups. Group 1: served as the control group, group 2: rats were supplemented orally with LUT (50 mg kg^-1), group 3: rats were intraperitoneally injected with PbAc (20 mg kg^-1), and group 4: rats were pretreated with LUT before PbAc injection with the same doses. All animals were treated for 7 days. The exposure to PbAc increased the concentration of lead in the cortical tissue, neuronal lipid peroxidation, and nitric oxide (NO) production and decreased the antioxidant enzymes. Additionally, PbAc enhanced a neuroinflammatory response in the cortical tissue through increasing the pro-inflammatory cytokines secretion and inducible NO synthase expression. Moreover, cortical cell death was recorded following PbAc intoxication as evidenced by the enhancement of the proapoptotic and inhibiting the antiapoptotic markers. Interestingly, LUT supplementation reversed the cortical adverse reactions induced by PbAc. Taken together, these findings may suggest that LUT may be useful for attenuating neuronal damage induced by PbAc through inhibiting the oxidative damage, neuroinflammation, and the cortical cell death.

Mitophagy Reduces Oxidative Stress Via Keap1 (Kelch-Like Epichlorohydrin-Associated Protein 1)/Nrf2 (Nuclear Factor-E2-Related Factor 2)/PHB2 (Prohibitin 2) Pathway After Subarachnoid Hemorrhage in Rats

Background and Purpose- Mitoquinone has been reported as a mitochondria-targeting antioxidant to promote mitophagy in various chronic diseases. Here, our aim was to study the role of mitoquinone in mitophagy activation and oxidative stress-induced neuronal death reduction after subarachnoid hemorrhage (SAH) in rats. Methods- Endovascular perforation was used for SAH model of male Sprague-Dawley rats. Exogenous mitoquinone was injected intraperitoneally 1 hour after SAH. ML385, an inhibitor of Nrf2 (nuclear factor-E2-related factor 2), was given intracerebroventricularly 24 hours before SAH. Small interfering RNA for PHB2 (prohibitin 2) was injected intracerebroventricularly 48 hours before SAH. Nuclear, mitochondrial, and cytoplasmic fractions were gathered using nucleus and mitochondria isolation kits. SAH grade evaluation, short- and long- term neurological function tests, oxidative stress, and apoptosis measurements were performed. Pathway related proteins were investigated with Western blot and immunofluorescence staining. Results- Expression of Keap1 (Kelch-like epichlorohydrin-associated protein 1, 2.84× at 24 hours), Nrf2 (2.78× at 3 hours), and LC3II (light chain 3-II; 1.94× at 24 hours) increased, whereas PHB2 (0.46× at 24 hours) decreased after SAH compared with sham group. Mitoquinone treatment attenuated oxidative stress and neuronal death, both short-term and long-term. Administration of mitoquinone resulted in a decrease in expression of Keap1 (0.33×), Romo1 (reactive oxygen species modulator 1; 0.24×), Bax (B-cell lymphoma-2 associated X protein; 0.31×), Cleaved Caspase-3 (0.29×) and an increase in Nrf2 (2.13×), Bcl-xl (B-cell lymphoma-extra large; 1.67×), PINK1 (phosphatase and tensin-induced kinase 1; 1.67×), Parkin (1.49×), PHB2 (1.60×), and LC3II (1.67×) proteins compared with SAH+vehicle group. ML385 abolished the treatment effects of mitoquinone on behavior and protein levels. PHB2 small interfering RNA reversed the outcomes of mitoquinone administration through reduction in protein expressions downstream of PHB2. Conclusions- Mitoquinone inhibited oxidative stress-related neuronal death by activating mitophagy via Keap1/Nrf2/PHB2 pathway after SAH. Mitoquinone may serve as a potential treatment to relieve brain injury after SAH.

The Neuroprotective Role of Coenzyme Q10 Against Lead Acetate-Induced Neurotoxicity Is Mediated by Antioxidant, Anti-Inflammatory and Anti-Apoptotic Activities

Heavy metal exposure, in lead (Pb) particularly, is associated with severe neuronal impairment though oxidative stress mediated by reactive oxygen species, and antioxidants may be used to abolish these adverse effects. This study investigated the potential neuroprotective role of coenzyme Q10 (CoQ₁₀) against lead acetate (PbAc)-induced neurotoxicity. Twenty-eight male Wistar albino rats were divided into four equal groups (n = 7) and treated as follows: the control group was injected with physiological saline (0.9% NaCl); the CoQ₁₀ group was injected with CoQ₁₀ (10 mg/kg); PbAc group was injected with PbAc (20 mg/kg); PbAc + CoQ₁₀ group was injected first with PbAc, and after 1 h with CoQ₁₀. All groups were injected intraperitoneally for seven days. PbAc significantly increased cortical lipid peroxidation, nitrate/nitrite levels, and inducible nitric oxide synthase expression, and decreased glutathione content, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase activity and mRNA expression, as well as nuclear factor erythroid 2–related factor 2 (Nrf2) and homoxygenase-1 (HO-1) expression. PbAc also promoted the secretion of interleukin-1ß and tumor necrosis factor-α, inhibited interleukin-10 production, triggered the activation of pro-apoptotic proteins, and suppressed anti-apoptotic proteins. Additionally, PbAc increased the cortical levels of serotonin, dopamine, norepinephrine, GABA, and glutamate, and decreased the level of ATP. However, treatment with CoQ₁₀ rescued cortical neurons from PbAc-induced neurotoxicity by restoring the balance between oxidants and antioxidants, activating the Nrf2/HO-1 pathway, suppressing inflammation, inhibiting the apoptotic cascade, and modulating cortical neurotransmission and energy metabolism. Altogether, our findings indicate that CoQ₁₀ has beneficial effects against PbAc-induced neuronal damage through its antioxidant, anti-inflammatory, anti-apoptotic, and neuromodulatory activities.

Rapid peroxynitrite reduction by human peroxiredoxin 3: Implications for the fate of oxidants in mitochondria

Mitochondria are main sites of peroxynitrite formation. While at low concentrations mitochondrial peroxynitrite has been associated with redox signaling actions, increased levels can disrupt mitochondrial homeostasis and lead to pathology. Peroxiredoxin 3 is exclusively located in mitochondria, where it has been previously shown to play a major role in hydrogen peroxide reduction. In turn, reduction of peroxynitrite by peroxiredoxin 3 has been inferred from its protective actions against tyrosine nitration and neurotoxicity in animal models, but was not experimentally addressed so far. Herein, we demonstrate the human peroxiredoxin 3 reduces peroxynitrite with a rate constant of 1 × 10⁷ M^-1 s^-1 at pH 7.8 and 25 °C. Reaction with hydroperoxides caused biphasic changes in the intrinsic fluorescence of peroxiredoxin 3: the first phase corresponded to the peroxidatic cysteine oxidation to sulfenic acid. Peroxynitrite in excess led to peroxiredoxin 3 hyperoxidation and tyrosine nitration, oxidative post-translational modifications that had been previously identified in vivo. A significant fraction of the oxidant is expected to react with CO₂ and generate secondary radicals, which participate in further oxidation and nitration reactions, particularly under metabolic conditions of active oxidative decarboxylations or increased hydroperoxide formation. Our results indicate that both peroxiredoxin 3 and 5 should be regarded as main targets for peroxynitrite in mitochondria.

Differential response to lead toxicity in rat primary microglia and astrocytes

Lead (Pb) is one of the most widely studied occupational and environmental toxins. Chronic exposure to Pb affects neural function in the central nervous system (CNS). Glial cells in the CNS, such as microglia and astrocytes, respond differently to Pb-induced toxicity. However, the underlying mechanism has not yet been identified. We measured the cell viability and intracellular Pb uptake in rat primary microglia and astrocytes using the CCK-8 assay and inductively coupled plasma mass spectrometry, and found that Pb decreased microglial viability at lower dosages than in astrocytes, while Pb uptake was greater in astrocytes. Pb-induced oxidative stress in microglia results in increased production of reactive oxygen species, down-regulation of glutathione, and enhanced Nrf2 protein expression, while there was no obvious change in astrocytes. The role of Nrf2 in Pb-induced oxidative stress has also been confirmed in primary microglia with the use of Nrf2 small interfering RNA and an Nrf2 agonist. These data indicate that primary microglia were more sensitive to Pb exposure than astrocytes, which is associated with an obvious oxidative stress response and up-regulation of Nrf2 might be involved in this process.

Mitochondrial regulation by pyrroloquinoline quinone prevents rotenone-induced neurotoxicity in Parkinson's disease models

Pyrroloquinoline quinone (PQQ), a redox cofactor in the mitochondrial respiratory chain, has been reported to protect SH-SY5Y cells from cytotoxicity induced by rotenone, a mitochondrial complex I inhibitor. In this study, we aimed to investigate the mitochondrial mechanisms involved in the neuroprotection of PQQ both in vitro and in vivo. The cultured human SH-SY5Y neuroblastoma cells were exposed to different concentrations of PQQ after which the cells were treated with rotenone. Electron microscopy images showed that PQQ could prevent the mitochondrial morphology damage. The down-regulation of mitochondrial biogenesis related genes (PGC-1alpha and TFAM) and mitochondrial fission and fusion related genes (Drp1and Mfn2) in rotenone-injured SH-SY5Y cells could be inhibited by PQQ. PQQ could also promote the transposition of Drp1 and Mfn2 from cytosol to mitochondria. In addition, rotenone was injected into the left medial forebrain bundle of SD rats to establish a Parkinson's disease (PD) model in vivo, after which different doses of PQQ or Edaravone were given intraperitoneally once daily for 8 weeks. PQQ could up-regulate the mRNA levels of PGC-1alpha, TFAM, Drp-1 and Mfn2 in the midbrain of PD rats. Our findings indicated that PQQ could prevent mitochondrial dysfunction by promoting mitochondrial biogenesis and regulating mitochondrial fission and fusion, which might contribute to its neuroprotective effect in PD models.

A Hypothesis of the Interaction of the Nitrergic and Serotonergic Systems in Aggressive Behavior Induced by Exposure to Lead

The effects caused by exposure to lead (Pb) are still considered as a relevant health risk despite public policies aimed to restricting the use of this element. The toxicity limit in the blood (10 μg/dL, established by the Center for Disease Control and Prevention) has been insufficient to prevent adverse effects and even lower values have been related to neurobehavioral dysfunctions in children. Currently, there is not a safe limit of exposure to Pb. A large body of evidence points to environmental pollutant exposure as the cause of predisposition to violent behavior, among others. Considering the evidence by our group and others, we propose that Pb exposure induces alterations in the brain vasculature, specifically in nitric oxide synthases (NOS), affecting in turn the serotonergic system and leading to heightened aggressive behavior in the exposed individuals. This review article describes the consequences of Pb exposure on the nitrergic and serotonergic systems as well as its relationship with aggressive behavior. In addition, it summarizes the available therapy to prevent damage in gestation and among infants.

The Effect of MitoQ on Aging-Related Biomarkers: A Systematic Review and Meta-Analysis

Mitochondria are metabolically active organelles that produce significant reactive oxygen species, linked with aging and degenerative diseases. In recent years, particular focus has been put on mitochondria-targeted antioxidants, to decrease the concentration of reactive oxygen species and help alleviate the accumulation of oxidative damage and associated aging. MitoQ is a mitochondria-targeted antioxidant of which is reported to support healthy aging. The aim of this systematic review is to investigate the effects of MitoQ on oxidative outcomes related to the aging process. A predeveloped search strategy was run against MEDLINE (Ovid), EMBASE (Ovid), and CINAHL databases, which identified 10,255 articles of interest, with 27 of these finalised for use after screening. Three outcomes had sufficient data to meta-analyse nitrotyrosine concentration (190 animals, SMD -0.67, 95% CI (-1.30, -0.05), p = 0.04), membrane potential (63 animals, MD 11.44, 95% CI (1.28-21.60), p = 0.03), and protein carbonyl concentration (182 animals, SMD -0.13, 95% CI (-0.44, 0.18), p = 0.41). MitoQ intervention produced a statistically significant reduction in nitrotyrosine concentration and increased membrane potential. MitoQ may be of some benefit in alleviating oxidative stress related to aging.

Mitigating peroxynitrite mediated mitochondrial dysfunction in aged rat brain by mitochondria-targeted antioxidant MitoQ

Although reactive oxygen species mediated oxidative stress is a well-documented mechanism of aging, recent evidences indicate involvement of nitrosative stress in the same. As mitochondrial dysfunction is considered as one of the primary features of aging, the present study was designed to understand the involvement of nitrosative stress by studying the impact of a mitochondria-targeted antioxidant MitoQ, a peroxynitrite (ONOO^-) scavenger, on mitochondrial functions. Four groups of rats were included in this study: Group I: Young-6 months (-MitoQ), Group II: Aged-22 months (- MitoQ), Group III: Young-6 months (+ MitoQ), Group IV: Aged-22 months (+ MitoQ). The rats belonging to group III and IV were treated with oral administration of MitoQ (500 μM) daily through drinking water for 5 weeks. MitoQ efficiently suppressed synaptosomal lipid peroxidation and protein oxidation accompanied by diminution of nitrite production and protein bound 3-nitrotyrosine. MitoQ normalized enhanced caspase 3 and 9 activities in aged rat brains and efficiently reversed ONOO^- mediated mitochondrial complex I and IV inhibition, restored mitochondrial ATP production and lowered mitochondrial membrane potential loss. To ascertain these findings, a mitochondrial in vitro model (iron/ascorbate) was used involving different free radical scavengers and anti-oxidants. MitoQ provided better protection compared to mercaptoethylguanidine, N-nitro-L-arginine-methyl ester and superoxide dismutase establishing the predominancy of ONOO^- in the process compared to ^•NO and O ₂^•- . These results clearly highlight the involvement of nitrosative stress in aging process with MitoQ having therapeutic potential to fight against ONOO^- mediated aging deficits.

Targeting Mitochondria to Counteract Age-Related Cellular Dysfunction

Senescence is related to the loss of cellular homeostasis and functions, which leads to a progressive decline in physiological ability and to aging-associated diseases. Since mitochondria are essential to energy supply, cell differentiation, cell cycle control, intracellular signaling and Ca²⁺ sequestration, fine-tuning mitochondrial activity appropriately, is a tightrope walk during aging. For instance, the mitochondrial oxidative phosphorylation (OXPHOS) ensures a supply of adenosine triphosphate (ATP), but is also the main source of potentially harmful levels of reactive oxygen species (ROS). Moreover, mitochondrial function is strongly linked to mitochondrial Ca²⁺ homeostasis and mitochondrial shape, which undergo various alterations during aging. Since mitochondria play such a critical role in an organism’s process of aging, they also offer promising targets for manipulation of senescent cellular functions. Accordingly, interventions delaying the onset of age-associated disorders involve the manipulation of mitochondrial function, including caloric restriction (CR) or exercise, as well as drugs, such as metformin, aspirin, and polyphenols. In this review, we discuss mitochondria’s role in and impact on cellular aging and their potential to serve as a target for therapeutic interventions against age-related cellular dysfunction.