UVB-induced inactivation of manganese-containing superoxide dismutase promotes mitophagy via ROS-mediated mTORC2 pathway activation

TIMP3 deficiency accelerates UVB-induced HaCaT cell senescence by regulating ferroptosis

Prolonged exposure to ultraviolet B (UVB) light leads to the accumulation of reactive oxygen species (ROS), a key contributor to skin aging. Previous studies have demonstrated that UVB exposure results in a deficiency in the expression of TIMP3 in keratinocytes. The objective of this study was to investigate the specific role of TIMP3 in keratinocytes. UVB-treated HaCaT cells were utilized to establish a cellular photoaging model. We found that UVB significantly increased levels of ROS, promoted senescence and ferroptosis, and inhibited the expression of TIMP3 in HaCaT. This inhibition was notably alleviated by Fer-1, a ferroptosis inhibitor. In addition, the knockdown of TIMP3 in HaCaT enhanced senescence by inducing the ferroptosis. Mechanistically, UVB exposure also led to a decrease in the expression of KLF4, a transcription factor that regulated TIMP3 expression. Futhermore, UVB-induced reduced expression of KLF4 and TIMP3 in vivo. Our results suggest that deletion of the KLF4/TIMP3 axis promotes HaCaT cell senescence by facilitating the progression of ferroptosis. TIMP3 may serve as an effective therapeutic target for preventing skin photoaging.

FUNDC1-mediated mitophagy regulates photodamage independently of the PINK1/Parkin-dependent pathway

BACKGROUND

Ultraviolet B(UVB) triggers a pro-survival response through mitophagy, but the role of FUNDC1-mediated mitophagy in photodamaged skin remains unexplored.

OBJECTIVES

To clarify the function of mitophagy in UVB-induced photodamaged skin.

METHODS

To investigate the role of FUNDC1-mediated mitophagy in UVB-induced mitochondrial damage and cell apoptosis, FUNDC1 knockdown in C57BL/6 mice was performed using adeno-associated virus. Additionally, FUNDC1 overexpression and knockdown in HaCaT cells were conducted using lentivirus. A comprehensive analysis was conducted on a panel of human sun-exposed skin samples, alongside control samples, to assess the expression levels of FUNDC1.

RESULTS

In UVB-induced C57BL/6 mice, the dorsal skin showed photodamage including erythema, scaling, erosion, and scabs. The expression levels of PINK1, Parkin, and BNIP3 did not show significant changes, while FUNDC1 expression consistently declined along with LC3B. Cytochrome C, Bax, and cleaved-caspase3 were upregulated, while Bcl2 was downregulated. UVB-induced HaCaT cells showed mitochondrial damage, accompanied by FUNDC1 downregulation and BNIP3 upregulation, while PINK1 and Parkin showed no significant changes. FUNDC1 overexpression led to an increase in mtROS and a decrease in mitochondrial membrane potential and ATP levels, indicating complete mitochondrial clearance and exacerbated cell death. FUNDC1 knockdown protected against UVB-induced photodamage in mice and mitigated mitochondrial damage and apoptosis in HaCaT cells by activating compensatory PINK1/Parkin-dependent mitophagy, which was evidenced by upregulation of PINK1 and Bcl2 and downregulation of Bax. In human sun-exposed skin samples, there was a decrease in the number of FUNDC1+ cells compared with non-sun-exposed controls.

CONCLUSIONS

FUNDC1-mediated mitophagy regulates skin photodamage and provides a novel mechanism for resisting photodamage, presenting a potential target for future therapeutic interventions.

Imperative connotation of SODs in cancer: Emerging targets and multifactorial role of action

Superoxide dismutase (SOD) is a crucial enzyme responsible for the redox homeostasis inside the cell. As a part of the antioxidant defense system, it plays a pivotal role in the dismutation of the superoxide radicals (O 2 - ) generated mainly by the oxidative phosphorylation, which would otherwise bring out the redox dysregulation, leading to higher reactive oxygen species (ROS) generation and, ultimately, cell transformation, and malignancy. Several studies have shown the involvement of ROS in a wide range of human cancers. As SOD is the key enzyme in regulating ROS, any change, such as a transcriptional change, epigenetic remodeling, functional alteration, and so forth, either activates the proto-oncogenes or aberrant signaling cascades, which results in cancer. Interestingly, in some cases, SODs act as tumor promoters instead of suppressors. Furthermore, SODs have also been known to switch their role during tumor progression. In this review, we have tried to give a comprehensive account of SODs multifactorial role in various human cancers so that SODs-based therapeutic strategies could be made to thwart cancers.

Elimination of damaged mitochondria during UVB-induced senescence is orchestrated by NIX-dependent mitophagy

Skin aging is the result of two types of aging, "intrinsic aging" an inevitable consequence of physiologic and genetically determined changes and "extrinsic aging," which is dependent on external factors such as exposure to sunlight, smoking, and dietary habits. UVB causes skin injury through the generation of free radicals and other oxidative byproducts, also contributing to DNA damage. Appearance and accumulation of senescent cells in the skin are considered one of the hallmarks of aging in this tissue. Mitochondria play an important role for the development of cellular senescence, in particular stress-induced senescence of human cells. However, many aspects of mitochondrial physiology relevant to cellular senescence and extrinsic skin aging remain to be unraveled. Here, we demonstrate that mitochondria damaged by UVB irradiation of human dermal fibroblasts (HDF) are eliminated by NIX-dependent mitophagy and that this process is important for cell survival under these conditions. Additionally, UVB-irradiation of human dermal fibroblasts (HDF) induces the shedding of extracellular vesicles (EVs), and this process is significantly enhanced in UVB-irradiated NIX-depleted cells. Our findings establish NIX as the main mitophagy receptor in the process of UVB-induced senescence and suggest the release of EVs as an alternative mechanism of mitochondrial quality control in HDF.

A novel MTORC2-AKT-ROS axis triggers mitofission and mitophagy-associated execution of colorectal cancer cells upon drug-induced activation of mutant KRAS

RAS is one of the most commonly mutated oncogenes associated with multiple cancer hallmarks. Notably, RAS activation induces intracellular reactive oxygen species (ROS) generation, which we previously demonstrated as a trigger for autophagy-associated execution of mutant KRAS-expressing cancer cells. Here we report that drug (merodantoin; C1)-induced activation of mutant KRAS promotes phospho-AKT S473-dependent ROS-mediated S616 phosphorylation and mitochondrial localization of DNM1L/DRP1 (dynamin 1 like) and cleavage of the fusion-associated protein OPA1 (OPA1 mitochondrial dynamin like GTPase). Interestingly, accumulation of the outer mitochondrial membrane protein VDAC1 (voltage dependent anion channel 1) is observed in mutant KRAS-expressing cells upon exposure to C1. Conversely, silencing VDAC1 abolishes C1-induced mitophagy, and gene knockdown of either KRAS, AKT or DNM1L rescues ROS-dependent VDAC1 accumulation and stability, thus suggesting an axis of mutant active KRAS-phospho-AKT S473-ROS-DNM1L-VDAC1 in mitochondrial morphology change and cancer cell execution. Importantly, we identified MTOR (mechanistic target of rapamycin kinsase) complex 2 (MTORC2) as the upstream mediator of AKT phosphorylation at S473 in our model. Pharmacological or genetic inhibition of MTORC2 abrogated C1-induced phosphorylation of AKT S473, ROS generation and mitophagy induction, as well as rescued tumor colony forming ability and migratory capacity. Finally, increase in thermal stability of KRAS, AKT and DNM1L were observed upon exposure to C1 only in mutant KRAS-expressing cells. Taken together, our work has unraveled a novel mechanism of selective targeting of mutant KRAS-expressing cancers via MTORC2-mediated AKT activation and ROS-dependent mitofission, which could have potential therapeutic implications given the relative lack of direct RAS-targeting strategies in cancer.Abbreviations: ACTB/ß-actin: actin beta; AKT: AKT serine/threonine kinase; C1/merodantoin: 1,3-dibutyl-2-thiooxo-imidazoldine-4,5-dione; CAT: catalase; CETSA: cellular thermal shift assay; CHX: cycloheximide; DKO: double knockout; DNM1L/DRP1: dynamin 1 like; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; H2O2: hydrogen peroxide; HSPA1A/HSP70-1: heat shock protein family A (Hsp70) member 1A; HSP90AA1/HSP90: heat shock protein 90 alpha family class A member 1; KRAS: KRAS proto-oncogene, GTPase; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; LC3B-I: unlipidated form of LC3B; LC3B-II: phosphatidylethanolamine-conjugated form of LC3B; MAPKAP1/SIN1: MAPK associated protein 1; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; MFI: mean fluorescence intensity; MiNA: Mitochondrial Network Analysis; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin kinase complex 1; MTORC2: mechanistic target of rapamycin kinase complex 2; O2.-: superoxide; OMA1: OMA1 zinc metallopeptidase; OPA1: OPA1 mitochondrial dynamin like GTPase; RICTOR: RPTOR independent companion of MTOR complex 2; ROS: reactive oxygen species; RPTOR/raptor: regulatory associated protein of MTOR complex 1; SOD1: superoxide dismutase 1; SOD2: superoxide dismutase 2; SQSTM1/p62: sequestosome 1; VDAC1: voltage dependent anion channel 1; VDAC2: voltage dependent anion channel 2.

NEAT1 Confers Radioresistance to Hepatocellular Carcinoma Cells by Inducing PINK1/Parkin-Mediated Mitophagy

A long noncoding RNA, nuclear paraspeckle assembly transcript 1 (NEAT1) variant 1 (NEAT1v1), confers radioresistance to hepatocellular carcinoma (HCC) cells by inducing autophagy via γ-aminobutyric acid A receptor-associated protein (GABARAP). Radiation induces oxidative stress to damage cellular components and organelles, but it remains unclear how NEAT1v1 protects HCC cells from radiation-induced oxidative stress via autophagy. To address this, we precisely investigated NEAT1v1-induced autophagy in irradiated HCC cell lines. X-ray irradiation significantly increased cellular and mitochondrial oxidative stress and mitochondrial DNA content in HCC cells while NEAT1v1 suppressed them. NEAT1v1 concomitantly induced the phosphatase and tensin homolog-induced kinase 1 (PINK1)/parkin-mediated mitophagy. Interestingly, parkin expression was constitutively upregulated in NEAT1v1-overexpressing HCC cells, leading to increased mitochondrial parkin levels. Superoxide dismutase 2 (SOD2) was also upregulated by NEAT1v1, and GABARAP or SOD2 knockdown in NEAT1v1-overexpressing cells increased mitochondrial oxidative stress and mitochondrial DNA content after irradiation. Moreover, it was suggested that SOD2 was involved in NEAT1v1-induced parkin expression, and that GABARAP promoted parkin degradation via mitophagy. This study highlights the unprecedented roles of NEAT1v1 in connecting radioresistance and mitophagy in HCC.

mTORC2 protects the heart from high-fat diet-induced cardiomyopathy through mitochondrial fission in Drosophila

High-fat diet (HFD)-induced obesity has become the major risk factor for the development of cardiovascular diseases, but the underlying mechanisms remain poorly understood. Here, we use Drosophila as a model to study the role of mTORC2 in HFD-induced mitochondrial fission and cardiac dysfunction. We find that knockdown of mTORC2 subunit rictor blocks HFD-induced mitochondrial fragmentation and Drp1 recruitment. Knockdown of rictor further impairs cardiac contractile function under HFD treatment. Surprisingly, knockdown of Akt, the major effector of mTORC2, did not affect HFD-induced mitochondrial fission. Similar to mTORC2 inhibition, knockdown of Drp1 blocks HFD-induced mitochondrial fragmentation and induces contractile defects. Furthermore, overexpression of Drp1 restored HFD-induced mitochondrial fragmentation in rictor knockdown flies. Thus, we uncover a novel function of mTORC2 in protecting the heart from HFD treatment through Drp1-dependent mitochondrial fission.

Role of mitochondria on UV-induced skin damage and molecular mechanisms of active chemical compounds targeting mitochondria

Mitochondria are the principal place of energy metabolism and ROS production, leading to mtDNA being especially sensitive to the impacts of oxidative stress. Our review aims to elucidate and update the mechanisms of mitochondria in UV-induced skin damage. The mitochondrial deteriorative response to UV manifests morphological and functional alterations, including mitochondrial fusion and fission, mitochondrial biogenesis, mitochondrial energy metabolism and mitophagy. Additionally, we conclude the effect and molecular mechanisms of active chemical components to protect skin from UV-induced damage via mitochondrial protection which have been described in the last five years, showing prospective prospects in cosmetics as new therapeutic targets.

The potential inhibitory effect of ginsenoside Rh2 on mitophagy in UV-irradiated human dermal fibroblasts

Background

In addition to its use as a health food, ginseng is used in cosmetics and shampoo because of its extensive health benefits. The ginsenoside, Rh2, is a component of ginseng that inhibits tumor cell proliferation and differentiation, promotes insulin secretion, improves insulin sensitivity, and shows antioxidant effects.

Methods

The effects of Rh2 on cell survival, extracellular matrix (ECM) protein expression, and cell differentiation were examined. The antioxidant effects of Rh2 in UV-irradiated normal human dermal fibroblast (NHDF) cells were also examined. The effects of Rh2 on mitochondrial function, morphology, and mitophagy were investigated in UV-irradiated NHDF cells.

Results

Rh2 treatment promoted the proliferation of NHDF cells. Additionally, Rh2 increased the expression levels of ECM proteins and growth-associated immediate-early genes in ultraviolet (UV)-irradiated NHDF cells. Rh2 also affected antioxidant protein expression and increased total antioxidant capacity. Furthermore, treatment with Rh2 ameliorated the changes in mitochondrial morphology, induced the recovery of mitochondrial function, and inhibited the initiation of mitophagy in UV-irradiated NHDF cells.

Conclusion

Rh2 inhibits mitophagy and reinstates mitochondrial ATP production and membrane potential in NHDF cells damaged by UV exposure, leading to the recovery of ECM, cell proliferation, and antioxidant capacity.

Mitochondrial superoxide targets energy metabolism to modulate epigenetic regulation of NRF2-mediated transcription

Mitochondria are central to the metabolic circuitry that generates superoxide radicals/anions (O2•-) as a by-product of oxygen metabolism. By regulating superoxide levels, manganese superoxide dismutase plays important roles in numerous biochemical and molecular events essential for the survival of aerobic life. In this study, we used MitoParaquat (mPQ) to generate mitochondria-specific O2•- and stable isotope-resolved metabolomics tracing in primary human epidermal keratinocytes to investigate how O2•- generated in mitochondria regulates gene expression. The results reveal that isocitrate is blocked from conversion to α-ketoglutarate and that acetyl-coenzyme A (CoA) accumulates, which is consistent with a reduction in oxygen consumption rate and inactivation of isocitrate dehydrogenase (IDH) activity. Since acetyl-CoA is linked to histone acetylation and gene regulation, we determined the effect of mPQ on histone acetylation. The results demonstrate an increase in histone H3 acetylation at lysines 9 and 14. Suppression of IDH increased histone acetylation, providing a direct link between metabolism and epigenetic alterations. The activity of histone acetyltransferase p300 increased after mPQ treatment, which is consistent with histone acetylation. Importantly, mPQ selectively increased the nuclear levels and activity of the oxidative stress-sensitive nuclear factor erythroid 2-related factor 2. Together, the results establish a new paradigm that recognizes O2•- as an initiator of metabolic reprogramming that activates epigenetic regulation of gene transcription in response to mitochondrial dysfunction.

Regulation of mitochondrial dynamics in skin: role in pathophysiology

Skin is a dynamic interface between the external environment and internal organs. It has high turnover that allows the renewal of dead skin cells, thus maintaining a healthy skin homeostasis. Mitochondria fulfills all the energy needs for these cells. In addition, mitochondria are an active source of free radicals that have been determined as crucially important in skin health and disease. The common notion of limited role of mitochondria as merely the cellular powerhouse has drastically changed. Several extracellular stressors have proved to induce impairment in the dynamic properties of mitochondria such as fusion and fission, which further leads to an activation of selective autophagic response known as mitophagy. Altered mitochondrial dynamics have been lately associated with skin photodamage and cutaneous manifestations of several diseased states, thereby suggesting it to be an effective therapeutic target. This review summarizes the molecular mechanisms involved with impaired mitochondrial dynamics and its potential role in skin health and disease.

Autophagy Contributes to the Quality Control of Leaf Mitochondria

In autophagy, cytoplasmic components of eukaryotic cells are transported to lysosomes or the vacuole for degradation. Autophagy is involved in plant tolerance to the photooxidative stress caused by ultraviolet B (UVB) radiation, but its roles in plant adaptation to UVB damage have not been fully elucidated. Here, we characterized organellar behavior in UVB-damaged Arabidopsis (Arabidopsis thaliana) leaves and observed the occurrence of autophagic elimination of dysfunctional mitochondria, a process termed mitophagy. Notably, Arabidopsis plants blocked in autophagy displayed increased leaf chlorosis after a 1-h UVB exposure compared to wild-type plants. We visualized autophagosomes by labeling with a fluorescent protein-tagged autophagosome marker, AUTOPHAGY8 (ATG8), and found that a 1-h UVB treatment led to increased formation of autophagosomes and the active transport of mitochondria into the central vacuole. In atg mutant plants, the mitochondrial population increased in UVB-damaged leaves due to the cytoplasmic accumulation of fragmented, depolarized mitochondria. Furthermore, we observed that autophagy was involved in the removal of depolarized mitochondria when mitochondrial function was disrupted by mutation of the FRIENDLY gene, which is required for proper mitochondrial distribution. Therefore, autophagy of mitochondria functions in response to mitochondrion-specific dysfunction as well as UVB damage. Together, these results indicate that autophagy is centrally involved in mitochondrial quality control in Arabidopsis leaves.

Mechanistic study of mtROS-JNK-SOD2 signaling in bupivacaine-induced neuron oxidative stress

Manganese superoxide dismutase (SOD2) is a key enzyme to scavenge free radical superoxide in the mitochondrion. SOD2 deficiency leads to oxidative injury in cells. Bupivacaine, a local anesthetic commonly used in clinic, could induce neurotoxic injury via oxidative stress. The role and the mechanism of SOD2 regulation in bupivacaine-induced oxidative stress remains unclear. Here, bupivacaine was used to treat Sprague-Dawley rats with intrathecal injection and culture human neuroblastoma cells for developing vivo injury model and vitro injury model. The results showed that bupivacaine caused the over-production of mitochondrial reactive oxygen species (mtROS), the activation of C-Jun N-terminal kinase (JNK), and the elevation of SOD2 transcription. Decrease of mtROS with N-acetyl-L-cysteine attenuated the activation of JNK and the increase of SOD2 transcription. Inhibition of JNK signaling with a small interfering RNA (siRNA) or with sp600125 down-regulated the increase of SOD2 transcription. SOD2 gene knock-down exacerbated bupivacaine-induced mtROS generation and neurotoxic injury but had no effect on JNK phosphorylation. Mito-TEMPO (a mitochondria-targeted antioxidant) could protect neuron against bupivacaine-induced toxic injury. Collectively, our results confirm that mtROS stimulates the transcription of SOD2 via activating JNK signaling in bupivacaine-induced oxidative stress. Enhancing antioxidant ability of SOD2 might be crucial in combating bupivacaine-induced neurotoxic injury.

3-Nitrotyrosine and related derivatives in proteins: precursors, radical intermediates and impact in function

Oxidative post-translational modification of proteins by molecular oxygen (O2)- and nitric oxide (•NO)-derived reactive species is a usual process that occurs in mammalian tissues under both physiological and pathological conditions and can exert either regulatory or cytotoxic effects. Although the side chain of several amino acids is prone to experience oxidative modifications, tyrosine residues are one of the preferred targets of one-electron oxidants, given the ability of their phenolic side chain to undergo reversible one-electron oxidation to the relatively stable tyrosyl radical. Naturally occurring as reversible catalytic intermediates at the active site of a variety of enzymes, tyrosyl radicals can also lead to the formation of several stable oxidative products through radical-radical reactions, as is the case of 3-nitrotyrosine (NO2Tyr). The formation of NO2Tyr mainly occurs through the fast reaction between the tyrosyl radical and nitrogen dioxide (•NO2). One of the key endogenous nitrating agents is peroxynitrite (ONOO-), the product of the reaction of superoxide radical (O2•-) with •NO, but ONOO--independent mechanisms of nitration have been also disclosed. This chemical modification notably affects the physicochemical properties of tyrosine residues and because of this, it can have a remarkable impact on protein structure and function, both in vitro and in vivo. Although low amounts of NO2Tyr are detected under basal conditions, significantly increased levels are found at pathological states related with an overproduction of reactive species, such as cardiovascular and neurodegenerative diseases, inflammation and aging. While NO2Tyr is a well-established stable oxidative stress biomarker and a good predictor of disease progression, its role as a pathogenic mediator has been laboriously defined for just a small number of nitrated proteins and awaits further studies.

Photochemical reactions between 1,4-benzoquinone and O2•

The superoxide anion radical (O2•-) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O2•- was generated by irradiating riboflavin in an O2-saturated solution using an ultraviolet lamp (λem = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone (p-BQ) by O2•- was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p-BQ was influenced by the riboflavin concentration, p-BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p-BQ, forming reduced BQ radicals (BQ•-) with a second-order rate constant of 1.1 × 109 L mol-1 s-1. The main product of the photochemical reaction between p-BQ and O2•- was hydroquinone (H2Q). The present work suggests that the reaction with O2•- is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.

Nanoformulation of the superoxide dismutase mimic, MnTnBuOE-2-PyP5+, prevents its acute hypotensive response

Scavenging superoxide (O₂^•-) via overexpression of superoxide dismutase (SOD) or administration of SOD mimics improves outcomes in multiple experimental models of human disease including cardiovascular disease, neurodegeneration, and cancer. While few SOD mimics have transitioned to clinical trials, MnTnBuOE-2-PyP⁵⁺ (BuOE), a manganese porphyrin SOD mimic, is currently in clinical trials as a radioprotector for cancer patients; thus, providing hope for the use of SOD mimics in the clinical setting. However, BuOE transiently alters cardiovascular function including a significant and precipitous decrease in blood pressure. To limit BuOE's acute hypotensive action, we developed a mesoporous silica nanoparticle and lipid bilayer nanoformulation of BuOE (nanoBuOE) that allows for slow and sustained release of the drug. Herein, we tested the hypothesis that unlike native BuOE, nanoBuOE does not induce an acute hypotensive response, as the nanoformulation prevents BuOE from scavenging O₂^•- while the drug is still encapsulated in the formulation. We report that intact nanoBuOE does not effectively scavenge O₂^•-, whereas BuOE released from the nanoformulation does retain SOD-like activity. Further, in mice, native BuOE, but not nanoBuOE, rapidly, acutely, and significantly decreases blood pressure, as measured by radiotelemetry. To begin exploring the physiological mechanism by which native BuOE acutely decreases blood pressure, we recorded renal sympathetic nerve activity (RSNA) in rats. RSNA significantly decreased immediately following intravenous injection of BuOE, but not nanoBuOE. These data indicate that nanoformulation of BuOE, a SOD mimic currently in clinical trials in cancer patients, prevents BuOE's negative side effects on blood pressure homeostasis.

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MnTnBuOE-2-PyP⁵⁺ (BuOE) induces a rapid and significant decrease in blood pressure.

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BuOE's hypotensive response is concomitant with reduced sympathetic nerve activity.

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Nanoformulated BuOE (nanoBuOE) release of active drug is slow and sustained.

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nanoBuOE prevents the BuOE-induced hypotensive and sympathoinhibition responses.

Inhibitory Effect of Ursolic Acid on Ultraviolet B Radiation-Induced Oxidative Stress and Proinflammatory Response-Mediated Senescence in Human Skin Dermal Fibroblasts

Ultraviolet radiation is an environmental carcinogenic agent that enhances inflammation and immunological reactions in the exposed human skin cells leading to oxidative photoaging of the epidermal and dermal segment. In the present study, we investigated the protective role of ursolic acid (UA) against ultraviolet B (UVB) radiation- induced photoaging an in vitro model of human skin dermal fibroblasts. UA-pretreated human skin dermal fibroblast (HDF) cells were exposed to UVB radiation to evaluated cell viability, reactive oxygen species (ROS), mitochondrial membrane potential, lipid peroxidation, antioxidant status, DNA damage, proinflammatory response, apoptotic induction, and matrix metalloproteinase (MMP) alteration. The UA pretreatment of HDFs mitigated the UVB irradiation-induced cytotoxicity, ROS generation, and mitochondrial membrane potential alteration and lipid peroxidation, depletion of antioxidant status, DNA damage, and apoptotic induction. UA pretreatment of HDFs also attenuated the UVB-induced expression of inflammatory (TNF-α and NF-κB) and apoptotic (p53, Bax, and caspase-3) and MMPs (MMP-2 and MMP-9) and enhanced the Bcl-2 protein levels in 20 μM UA treatment, when compared to concentrations. Hence, these results revealed that UA has the potential to mitigate UVB-induced extracellular damage by interfering with the ROS-mediated apoptotic induction and photoaging senescence and thus is a potential therapeutic agent to protect the skin against UVB-irradiation induced photooxidative damage.

Nitric Oxide-Dependent Protein Post-Translational Modifications Impair Mitochondrial Function and Metabolism to Contribute to Neurodegenerative Diseases

Significance: Most brains affected by neurodegenerative diseases manifest mitochondrial dysfunction as well as elevated production of reactive oxygen species and reactive nitrogen species (RNS), contributing to synapse loss and neuronal injury. Recent Advances: Excessive production of RNS triggers nitric oxide (NO)-mediated post-translational modifications of proteins, such as S-nitrosylation of cysteine residues and nitration of tyrosine residues. Proteins thus affected impair mitochondrial metabolism, mitochondrial dynamics, and mitophagy in the nervous system. Critical Issues: Identification and better characterization of underlying molecular mechanisms for NO-mediated mitochondrial dysfunction will provide important insights into the pathogenesis of neurodegenerative disorders. In this review, we highlight recent discoveries concerning S-nitrosylation of the tricarboxylic acid cycle enzymes, mitochondrial fission GTPase dynamin-related protein 1, and mitophagy-related proteins Parkin and phosphatase and tensin homolog-induced putative kinase protein 1. We delineate signaling cascades affected by pathologically S-nitrosylated proteins that diminish mitochondrial function in neurodegenerative diseases. Future Directions: Further elucidation of the pathological events resulting from aberrant S-nitrosothiol or nitrotyrosine formation may lead to new therapeutic approaches to ameliorate neurodegenerative disorders.

The emerging, multifaceted role of mitophagy in cancer and cancer therapeutics

Mitophagy is an evolutionarily conserved cellular process which selectively eliminates dysfunctional mitochondria by targeting them to the autophagosome for degradation. Dysregulated mitophagy results in the accumulation of damaged mitochondria, which plays an important role in carcinogenesis and tumor progression. The role of mitophagy receptors and adaptors including PINK1, Parkin, BNIP3, BNIP3L/NIX, and p62/SQSTM1, and the signaling pathways that govern mitophagy are impaired in cancer. Furthermore, the contribution of mitophagy in regulating the metabolic switch may establish a balance between aerobic glycolysis and oxidative phosphorylation for cancer cell survival. Moreover, ROS-driven mitophagy achieves different goals depending on the stage of tumorigenesis. Mitophagy promotes plasticity in the cancer stem cell through the metabolic reconfiguration for better adaption to the tumor microenvironment. In addition, the present review sheds some light on the role of mitophagy in stemness and differentiation during the transition of cell's fate, which could have a crucial role in cancer progression and metastasis. In conclusion, this review deals with the detailed molecular mechanisms underlying mitophagy, along with highlighting the dual role of mitophagy in different aspects of cancer, suggesting it as a possible target in the mitophagy-modulated cancer therapy.