Mitochondrial Protein UCP2 Controls Pancreas Development

Yunvjian decoction mitigates hyperglycemia in rats induced by a high-fat diet and streptozotocin via reducing oxidative stress in pancreatic beta cells

ETHNOPHARMACOLOGICAL RELEVANCE

Yunvjian (YNJ), a traditional Chinese herbal formula first reported in Jing Yue Quan Shu, is commonly used in the clinical treatment of type 2 diabetes mellitus (T2DM). However, the mechanism by which YNJ affects T2DM remains unclear.

AIM OF THE STUDY

This study aimed to assess the therapeutic effects of YNJ on T2DM and explore the potential mechanism involved.

MATERIALS AND METHODS

High-performance liquid chromatography (HPLC) was used to identify the chemical compounds of YNJ. The anti-T2DM effects of YNJ were observed in a high-fat diet/streptozotocin induced rat model. The type 2 diabetic rats were prepared as follows: rats were fed a high-fat diet for four weeks and then intraperitoneally injected with a low dose (30 mg/kg) of streptozotocin. YNJ and the positive control metformin were used in these experiments. Biochemical assays were implemented to determine the fasting blood glucose, glucose tolerance, insulin sensitivity, serum lipid levels, and oxidative stress index of the pancreas. Hematoxylin-eosin (H&E) staining was used to assess histopathological alterations in the pancreas. The mechanism by which YNJ affects T2DM was evaluated in INS-1 cells treated with glucose and high sodium palmitate. YNJ-supplemented serum was used in these experiments. Methyl thiazolyl tetrazolium assays, enzyme-linked immunosorbent assays, Nile red staining, flow cytometric analysis, and Western blotting were used to assess apoptosis, insulin secretion, lipid accumulation, reactive oxygen species production, and protein levels.

RESULTS

Five major compounds were identified in YNJ. In high-fat diet/streptozotocin-induced diabetic rats, YNJ-M notably decreased fasting blood glucose and lipid levels; ameliorated glucose tolerance, insulin sensitivity, and islet morphology; reduced Malondialdehyde levels; and restored superoxide dismutase activity in the pancreatic islets. Furthermore, the effect of YNJ-M was significantly greater than that of YNJ-L, and YNJ-H had little effect on diabetic rats. In vitro experiments revealed that YNJ-supplemented serum (10%, 15%, and 20%) dramatically suppressed apoptosis, mitigated intracellular lipid accumulation and reduced intracellular oxidative stress levels in a dose-dependent manner. Additionally, YNJ-supplemented serum increased the protein expression of Nuclear factor erythroid 2-related factor 2, Heme oxygenase-1, and superoxide dismutase 1 and inhibited the protein expression of Kelch-like ECH-associated protein 1.

CONCLUSION

YNJ ameliorates high-fat diet/streptozotocin induced experimental T2DM. The underlying mechanism involves reducing oxidative stress in pancreatic beta cells. The findings of this study provide scientific justification for the application of the traditional medicine YNJ in treating T2DM.

Mitochondrial Energy Metabolism in the Regulation of Thermogenic Brown Fats and Human Metabolic Diseases

Brown fats specialize in thermogenesis by increasing the utilization of circulating blood glucose and fatty acids. Emerging evidence suggests that brown adipose tissue (BAT) prevents the incidence of obesity-associated metabolic diseases and several types of cancers in humans. Mitochondrial energy metabolism in brown/beige adipocytes regulates both uncoupling protein 1 (UCP1)-dependent and -independent thermogenesis for cold adaptation and the utilization of excess nutrients and energy. Many studies on the quantification of human BAT indicate that mass and activity are inversely correlated with the body mass index (BMI) and visceral adiposity. Repression is caused by obesity-associated positive and negative factors that control adipocyte browning, de novo adipogenesis, mitochondrial energy metabolism, UCP1 expression and activity, and noradrenergic response. Systemic and local factors whose levels vary between lean and obese conditions include growth factors, inflammatory cytokines, neurotransmitters, and metal ions such as selenium and iron. Modulation of obesity-associated repression in human brown fats is a promising strategy to counteract obesity and related metabolic diseases through the activation of thermogenic capacity. In this review, we highlight recent advances in mitochondrial metabolism, thermogenic regulation of brown fats, and human metabolic diseases.

UCP2 as a Cancer Target through Energy Metabolism and Oxidative Stress Control

Despite numerous therapies, cancer remains one of the leading causes of death worldwide due to the lack of markers for early detection and response to treatment in many patients. Technological advances in tumor screening and renewed interest in energy metabolism have allowed us to identify new cellular players in order to develop personalized treatments. Among the metabolic actors, the mitochondrial transporter uncoupling protein 2 (UCP2), whose expression is increased in many cancers, has been identified as an interesting target in tumor metabolic reprogramming. Over the past decade, a better understanding of its biochemical and physiological functions has established a role for UCP2 in (1) protecting cells from oxidative stress, (2) regulating tumor progression through changes in glycolytic, oxidative and calcium metabolism, and (3) increasing antitumor immunity in the tumor microenvironment to limit cancer development. With these pleiotropic roles, UCP2 can be considered as a potential tumor biomarker that may be interesting to target positively or negatively, depending on the type, metabolic status and stage of tumors, in combination with conventional chemotherapy or immunotherapy to control tumor development and increase response to treatment. This review provides an overview of the latest published science linking mitochondrial UCP2 activity to the tumor context.

Activating PPARβ/δ Protects against Endoplasmic Reticulum Stress-Induced Astrocytic Apoptosis via UCP2-Dependent Mitophagy in Depressive Model

As energy metabolism regulation factor, peroxisome proliferator-activated receptor (PPAR) is thought to be a potential target for the treatment of depression. The present study was performed to evaluate the effects of activating PPARβ/δ, the most highly expressed subtype in the brain, in depressive in vivo and in vitro models. We observed that PPARβ/δ agonist GW0742 significantly alleviated depressive behaviors in mice and promoted the formation of autophagosomes around the damaged mitochondria in hippocampal astrocytes. Our in vitro experiments showed that GW0742 could reduce mitochondrial oxidative stress, and thereby attenuate endoplasmic reticulum (ER) stress-mediated apoptosis pathway via inhibiting IRE1α phosphorylation, subsequently protect against astrocytic apoptosis and loss. Furthermore, we found that PPARβ/δ agonist induces astrocytic mitophagy companied with the upregulated UCP2 expressions. Knocking down UCP2 in astrocytes could block the anti-apoptosis and pro-mitophagy effects of GW0742. In conclusion, our findings reveal PPARβ/δ activation protects against ER stress-induced astrocytic apoptosis via enhancing UCP2-mediated mitophagy, which contribute to the anti-depressive action. The present study provides a new insight for depression therapy.

Skeletal Muscle Uncoupling Proteins in Mice Models of Obesity

Obesity and accompanying type 2 diabetes are among major and increasing worldwide problems that occur fundamentally due to excessive energy intake during its expenditure. Endotherms continuously consume a certain amount of energy to maintain core body temperature via thermogenic processes, mainly in brown adipose tissue and skeletal muscle. Skeletal muscle glucose utilization and heat production are significant and directly linked to body glucose homeostasis at rest, and especially during physical activity. However, this glucose balance is impaired in diabetic and obese states in humans and mice, and manifests as glucose resistance and altered muscle cell metabolism. Uncoupling proteins have a significant role in converting electrochemical energy into thermal energy without ATP generation. Different homologs of uncoupling proteins were identified, and their roles were linked to antioxidative activity and boosting glucose and lipid metabolism. From this perspective, uncoupling proteins were studied in correlation to the pathogenesis of diabetes and obesity and their possible treatments. Mice were extensively used as model organisms to study the physiology and pathophysiology of energy homeostasis. However, we should be aware of interstrain differences in mice models of obesity regarding thermogenesis and insulin resistance in skeletal muscles. Therefore, in this review, we gathered up-to-date knowledge on skeletal muscle uncoupling proteins and their effect on insulin sensitivity in mouse models of obesity and diabetes.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

Diet-induced prediabetes: Effects on the activity of the renin-angiotensin-aldosterone system (RAAS) in selected organs

Derangements often observed with type 2 diabetes (T2D) are associated with disturbances in renin-angiotensin-aldosterone system (RAAS) activity. A positive correlation between local RAAS activity and the complications observed in T2D has been noted. However, the detrimental ramifications due to moderate hyperglycemia noted in prediabetes and the affected organ system and mechanistic pathways are not elucidated. Hence, this study investigated the effects of diet-induced prediabetes on RAAS in various organs.

MATERIALS AND METHODS

Male Sprague-Dawley rats were separated into two groups: non-pre-diabetic (NPD) through exposure to standard rat chow and diet-induced prediabetic (PD) group by exposure to a high-fat high carbohydrate diet for 32 weeks. RAAS activity in the skeletal muscle, adipose tissue, liver, pancreas and heart was determined through the analysis of RAAS components such as; renin, angiotensinogen, angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT1R) via PCR as well as the quantification of angiotensin II and aldosterone concentration. Furthermore, NADPH oxidase, SOD and GPx1 concentrations were determined in the skeletal muscle, pancreas and heart in addition to the hepatic triglycerides.

RESULTS

The RAAS components were elevated in the PD group when compared to the NPD. This was further accompanied by increased NADPH oxidase and reduced SOD and GPx1 concentrations in the selected organs, in addition to the elevated hepatic triglycerides concentration in the PD by comparison to NPD.

CONCLUSION

Due to these observed changes, we suggest that local RAAS activity in the prediabetic state in selected organs elicits the derangements noted in T2D.

Type 2 Diabetes Mellitus Intersects With Pancreatic Cancer Diagnosis and Development

The relationship between type 2 diabetes mellitus (T2DM) and pancreatic cancer (PC) is complex. Diabetes is a known risk factor for PC, and new-onset diabetes (NOD) could be an early manifestation of PC that may be facilitate the early diagnosis of PC. Metformin offers a clear benefit of inhibiting PC, whereas insulin therapy may increase the risk of PC development. No evidence has shown that novel hypoglycemic drugs help or prevent PC. In this review, the effects of T2DM on PC development are summarized, and novel strategies for the prevention and treatment of T2DM and PC are discussed.

Metformin Perturbs Pancreatic Differentiation From Human Embryonic Stem Cells

Metformin is becoming a popular treatment before and during pregnancy, but current literature on in utero exposure to metformin lacks long-term clinical trials and mechanistic studies. Current literature on the effects of metformin on mature pancreatic β-cells highlights its dual, opposing, protective, or inhibitory effects, depending on metabolic environment. However, the impact of metformin on developing human pancreatic β-cells remains unknown. In this study, we investigated the potential effects of metformin exposure on human pancreatic β-cell development and function in vitro. In the absence of metabolic challenges such as high levels of glucose and fatty acids, metformin exposure impaired the development and function of pancreatic β-cells, with downregulation of pancreatic genes and dysfunctional mitochondrial respiration. It also affected the insulin secretion function of pancreatic β-cells. These findings call for further in-depth evaluation of the exposure of human embryonic and fetal tissue during pregnancy to metformin and its implications for long-term offspring health.

Klotho inhibits H2 O2 -induced oxidative stress and apoptosis in periodontal ligament stem cells by regulating UCP2 expression

Periodontitis, a human chronic inflammatory disease, has affected the lives of millions of individuals. Periodontal ligament stem cells (PDLSCs), derived from the periodontal ligament, exhibit tissue specificity and impaired differentiation ability and are closely associated with tissue regeneration in periodontitis. Klotho, a single-pass transmembrane protein, has been reported to positively affect H₂ O₂ -induced oxidative stress and inflammation in PDLSCs. The ultimate damage of oxidative stress stimulation in PDLSCs was cell apoptosis, which was also the major lesion in periodontitis. Thus, the present study aimed to figure out the effect of klotho on H₂ O₂ -injured PDLSCs and its underlying mechanism to provide new therapeutic targets in periodontitis. The expression of klotho and uncoupling protein 2 (UCP2) was investigated in the gingival tissues, gingival crevicular fluid (GCF), and periodontal ligament stem cells (PDLSCs) in patients with chronic periodontitis. Then, under klotho treatment, oxidative stress was evaluated by measuring SOD and GSH-PX levels. Cell apoptosis and cell necrosis were also detected by measuring the cell death-relevant proteins, including Caspase-3, BAX, Bcl, MLKL, RIP1, and RIP3. Finally, a rescue assay was performed by inhibiting the expression of UCP2. The results showed that klotho and UCP2 were downregulated in patients with chronic periodontitis. In addition, klotho upregulated the production of UCP2 in H₂ O₂ -treated PDLSCs. Klotho inhibited H₂ O₂ -induced oxidative stress and cellular loss in PDLSCs, moreover, the rescue assay suggested that UCP2 knockdown suppressed the effects of klotho on PDLSCs. In conclusion, this study showed that klotho inhibits H₂ O₂ -induced oxidative stress and apoptosis in PDLSCs by regulating UCP2 expression. This novel discovery might provide a potential target for chronic periodontitis treatment.

Transcriptome analysis reveals brown adipogenic reprogramming in chemical compound-induced brown adipocytes converted from human dermal fibroblasts

Brown adipogenesis contributes to controlling systemic energy balance by enhancing glucose and lipid consumptions. We have previously reported chemical compound-induced brown adipocytes (ciBAs) directly converted from human dermal fibroblasts using a serum-free medium. In this study, genome-wide transcriptional analysis was performed in ciBAs in comparison with the control fibroblasts. A broad range of integrated gene expression was enhanced in functional groups including tricarboxylic acid cycle, electron transfer chain, triglycerides metabolism, fatty acid and glucose metabolism, and adaptive thermogenesis. The results suggested that the chemical conversion underwent metabolic and mitochondrial reprogramming closely associated with functions in brown/beige adipocytes. Moreover, we also compared the transcriptional changes to those of adipocyte browning in adipose tissue-derived mesenchymal stem cells (AdMSCs). Transcriptome analysis indicated that the same sets of metabolic and mitochondria-related genes were similarly changed in the adipocyte browning. Interestingly, ciBAs more expressed Ucp1, while AdMSC-derived adipocytes predominantly expressed Ucp2. UCP1 protein was also more expressed in ciBAs than in AdMSC-derived adipocytes. Based on the evidence that UCP1, but not UCP2, is responsible for adrenergic thermogenesis, ciBAs could be a promising model for human beige adipocytes applicable for basic research, drug development, and clinical uses.

Mitochondrial dysfunction and pancreatic islet β-cell failure (Review)

Pancreatic β-cells are the only source of insulin in humans. Mitochondria uses pyruvate to produce ATP as an intermediate link between glucose intake and insulin secretion in β-cells, in a process known as glucose-stimulated insulin secretion (GSIS). Previous studies have demonstrated that GSIS is negatively regulated by various factors in the mitochondria, including tRNA^Leu mutations, high p58 expression, reduced nicotinamide nucleotide transhydrogenase activity, abnormal levels of uncoupling proteins and reduced expression levels of transcription factors A, B1 and B2. Additionally, oxidative stress damages mitochondria and impairs antioxidant defense mechanisms, leading to the increased production of reactive oxygen species, which induces β-cell dysfunction. Inflammation in islets can also damage β-cell physiology. Inflammatory cytokines trigger the release of cytochrome c from the mitochondria via the NF-κB pathway. The present review examined the potential factors underlying mitochondrial dysfunction and their association with islet β-cell failure, which may offer novel insights regarding future strategies for the preservation of mitochondrial function and enhancement of antioxidant activity for individuals with diabetes mellitus.

Brain Overexpression of Uncoupling Protein-2 (UCP2) Delays Renal Damage and Stroke Occurrence in Stroke-Prone Spontaneously Hypertensive Rats

The downregulation of uncoupling protein-2 (UCP2) is associated with increased brain and kidney injury in stroke-prone spontaneously hypertensive rats (SHRSP) fed with a Japanese style hypersodic diet (JD). Systemic overexpression of UCP2 reduces organ damage in JD-fed SHRSP. We examined the effect of brain-specific UCP2 overexpression on blood pressure (BP), stroke occurrence and kidney damage in JD-fed SHRSP. Rats received a single i.c.v. injection of a lentiviral vector encoding UCP2 (LV-UCP2), or an empty vector. The brain delivery of LV-UCP2 significantly delayed the occurrence of stroke and kidney damage. The large reduction of proteinuria observed after LV-UCP2 injection was unexpected, because BP levels were unchanged. At the time of stroke, rats treated with LV-UCP2 still showed a large UCP2 upregulation in the striatum, associated with increases in OPA1 and FIS1 protein levels, and reductions in PGC1-α, SOD2, TNFα mRNA levels and NRF2 protein levels. This suggested UCP2 overexpression enhanced mitochondrial fusion and fission and reduced oxidative damage and inflammation in the striatum of JD-fed SHRSP rats. Our data suggest the existence of central mechanisms that may protect against hypertension-induced organ damage independently of BP, and strengthen the suitability of strategies aimed at enhancing UCP2 expression for the treatment of hypertensive damage.

Resveratrol protects against ethanol-induced impairment of insulin secretion in INS-1 cells through SIRT1-UCP2 axis

SIRT1 has been proposed to enhance insulin secretion in β-cell through repressing the expression of uncoupling protein2 (UCP2), but whether ethanol-induced β-cell dysfunction is mediated by the disrupted SIRT1-UCP2 axis remains unknown. This study was conducted to explore the underlying mechanisms by which ethanol resulted in β-cell dysfunction and the potential protective effects of resveratrol in this process. INS-1 cells (rat pancreatic β-cell line) were cultured with ethanol in the presence or absence of resveratrol (2.5, 12.5 μmol/L). The results showed that ethanol exposure reduced glucose-stimulated insulin secretion, ATP production and SIRT1 expression but increased UCP2 expression, while supplementation with resveratrol restored the function of INS-1 cell by upregulating SIRT1 and inhibiting UCP2. Moreover, the critical role of SIRT1-UCP2 axis was further supported by the results that SIRT1 activator SRT1720 reversed ethanol-induced impairment of glucose-stimulated insulin secretion by decreasing UCP2, while SIRT1 inhibitor Ex527 abolished the beneficial effects of resveratrol. Meanwhile, NAD⁺ booster nicotinamide mononucleotide also counteracted the deleterious effects of ethanol by increasing SIRT1, suggesting the regulation of SIRT1-UCP2 axis may be associated with cellular NAD⁺/NADH ratio. In conclusion, our observations imply that ethanol induces impaired insulin secretion from INS-1 cell through disrupting SIRT1-UCP2 axis, while resveratrol may reverse this process by augmenting SIRT1 and inhibiting UCP2.

Interplay Between Diabetes and Pancreatic Ductal Adenocarcinoma and Insulinoma: The Role of Aging, Genetic Factors, and Obesity

Epidemiologic analyses have shed light on an association between type 2 diabetes (T2D) and pancreatic ductal adenocarcinoma (PDAC). Recent data also suggest a potential relationship between T2D and insulinoma. Under rare circumstances, type 1 diabetes (T1D) can also be implicated in tumorigenesis. The biological mechanisms underlying such relationships are extremely complex. Some genetic factors contributing to the development of T2D are shared with pancreatic exocrine and endocrine tumors. Obesity and overweight can also contribute to the initiation and severity of T2D, while aging may influence both endocrine and exocrine tumors. Finally, pharmacological treatments of T2D may have an impact on PDAC. On the other hand, some treatments for insulinoma can trigger diabetes. In the present minireview, we discuss the cellular and molecular mechanisms that could explain these interactions. This analysis may help to define new potential therapeutic strategies.

Stanniocalcin-1 ameliorates cerebral ischemia by decrease oxidative stress and blood brain barrier permeability

Blood brain barrier (BBB) permeability and oxidative stress have been reported to be important mechanisms for brain damage following ischemic stroke and stanniocalcin-1 (STC-1), a neuroprotective protein, has anti-inflammatory and anti-oxidative stress properties. Herein, we report the effect of STC-1 on BBB permeability and brain oxidative stress after stroke in an animal model. Male Wistar received an intracerebroventricularly injection of human recombinant STC-1 (100 ng/kg) or saline and were subjected to sham procedure or global cerebral ischemia/reperfusion (I/R) model. Six and 24 h after I/R, neurological evaluation was performed; at 24 h brain water content was evaluated in the total brain, and BBB permeability, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the hippocampus, cortex, prefrontal cortex, striatum and cerebellum. Rats exhibited neurological deficit at 6 and 24 h after I/R and STC-1 reduction at 24 h. After I/R there were an increase of brain water content, BBB permeability in the hippocampus, cortex and pre-frontal cortex and N/N in the hippocampus, and STC-1 decreased this level only in the hippocampus. STC-1 decreased lipid peroxidation in the hippocampus, cortex and prefrontal cortex and protein oxidative damage in the hippocampus and cortex. SOD activity decreased in the hippocampus, cortex and prefrontal cortex after I/R and STC-1 reestablished these levels in the hippocampus and cortex. CAT activity decreased only in the hippocampus and cortex and STC-1 increased the CAT activity in the hippocampus. Our data provide the first experimental demonstration that STC-1 reduced brain dysfunction associated with cerebral I/R in rats, by decreasing BBB permeability and oxidative stress parameters.

Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes

Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.

Hippo/Mst1 overexpression induces mitochondrial death in head and neck squamous cell carcinoma via activating β-catenin/Drp1 pathway

Mammalian Ste20-like kinase 1 (Mst1) is associated with cell apoptosis. In the current study, we explored the regulatory effects of Mst1 on squamous cell carcinoma of the head and neck (SCCHN) in vitro. SCCHN Cal27 cells and Tu686 cells were transfected with adenovirus-loaded Mst1 to detect the role of Mst1 in cell viability. Then, siRNA against Drp1 was transfected into cells to evaluate the influence of mitochondrial fission in cancer survival. Our data illustrated that Mst1 overexpression promoted SCCHN Cal27 cell and Tu686 cell death via activating mitochondria-related apoptosis. Cells transfected with adenovirus-loaded Mst1 have increased expression of DRP1 and higher DRP1 promoted mitochondrial fission. Active mitochondrial fission mediated mitochondrial damage, as evidenced by increased mitochondrial oxidative stress, decreased mitochondrial energy production, and reduced mitochondrial respiratory complex function. Moreover, Mst1 overexpression triggered mitochondria-dependent cell apoptosis via DRP1-related mitochondrial fission. Further, we found that Mst1 overexpression controlled mitochondrial fission via the β-catenin/DRP1 pathways; inhibition of β-catenin and/or knockdown of DRP1 abolished the pro-apoptotic effects of Mst1 overexpression on SCCHN Cal27 cells and Tu686 cells, leading to the survival of cancer cells in vitro. In sum, our results illustrate that Mst1/β-catenin/DRP1 axis affects SCCHN Cal27 cell and Tu686 cell viability via controlling mitochondrial dynamics balance. This finding identifies Mst1 activation might be an effective therapeutic target for the treatment of SCCHN.

Mst1 deletion reduces septic cardiomyopathy via activating Parkin-related mitophagy

Cardiomyocyte function and viability are highly modulated by mammalian Ste20-like kinase 1 (Mst1)-Hippo pathway and mitochondria. Mitophagy, a kind of mitochondrial autophagy, is a protective program to attenuate mitochondrial damage. However, the relationship between Mst1 and mitophagy in septic cardiomyopathy has not been explored. In the present study, Mst1 knockout mice were used in a lipopolysaccharide (LPS)-induced septic cardiomyopathy model. Mitophagy activity was measured via immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay. Pathway blocker and small interfering RNA were used to perform the loss-of-function assay. The results demonstrated that Mst1 was rapidly increased in response to LPS stress. Knockout of Mst1 attenuated LPS-mediated inflammation damage, reduced cardiomyocyte death, and improved cardiac function. At the molecular levels, LPS treatment activated mitochondrial damage, such as mitochondrial respiratory dysfunction, mitochondrial potential reduction, mitochondrial ATP depletion, and caspase family activation. Interestingly, in response to mitochondrial damage, Mst1 deletion activated mitophagy which attenuated LPS-mediated mitochondrial damage. However, inhibition of mitophagy via inhibiting parkin mitophagy abolished the protective influences of Mst1 deletion on mitochondrial homeostasis and cardiomyocyte viability. Overall, our results demonstrated that septic cardiomyopathy is linked to Mst1 upregulation which is followed by a drop in the protective mitophagy.

Mst1 deletion reduces hyperglycemia-mediated vascular dysfunction via attenuating mitochondrial fission and modulating the JNK signaling pathway

Diabetes is a leading cause of microvascular complications, such as nephropathy and retinopathy. Recent studies have proposed that hyperglycemia-induced endothelial cell dysfunction is modulated by mitochondrial stress. Therefore, our experiment was to detect the upstream mediator of mitochondrial stress in hyperglycemia-treated endothelial cells with a focus on macrophage-stimulating 1 (Mst1) and mitochondrial fission. Our data illuminated that hyperglycemia incubation reduced cell viability, as well as increased apoptosis ratio in endothelial cell, and this alteration seemed to be associated with Mst1 upregulation. Inhibition of Mst1 via transfection of Mst1 siRNA into an endothelial cell could sustain cell viability and maintain mitochondrial function. At the molecular levels, endothelial cell death was accompanied with the activation of mitochondrial oxidative stress, mitochondrial apoptosis, and mitochondrial fission. Genetic ablation of Mst1 could reduce mitochondrial oxidative injury, block mitochondrial apoptosis, and repress mitochondrial fission. Besides, we also found Mst1 triggered mitochondrial dysfunction as well as endothelial cell damage through augmenting JNK pathway. Suppression of JNK largely ameliorated the protective actions of Mst1 silencing on hyperglycemia-treated endothelial cells and sustain mitochondrial function. The present study identifies Mst1 as a primary key mediator for hyperglycemia-induced mitochondrial damage and endothelial cell dysfunction. Increased Mst1 impairs mitochondrial function and activates endothelial cell death via opening mitochondrial death pathway through JNK.

Sirt3 modulate renal ischemia-reperfusion injury through enhancing mitochondrial fusion and activating the ERK-OPA1 signaling pathway

Mitochondrial fusion is linked to heart and liver ischemia-reperfusion (IR) insult. Unfortunately, there is no report to elucidate the detailed influence of mitochondrial fusion in renal IR injury. This study principally investigated the mechanism by which mitochondrial fusion protected kidney against IR injury. Our results indicated that sirtuin 3 (Sirt3) was inhibited after renal IR injury in vivo and in vitro. Overexpression of Sirt3 improved kidney function, modulated oxidative injury, repressed inflammatory damage, and reduced tubular epithelial cell apoptosis. The molecular investigation found that Sirt3 overexpression attenuated IR-induced mitochondrial damage in renal tubular epithelial cells, as evidenced by decreased reactive oxygen species production, increased antioxidants sustained mitochondrial membrane potential, and inactivated mitochondria-initiated death signaling. In addition, our information also illuminated that Sirt3 maintained mitochondrial homeostasis against IR injury by enhancing optic atrophy 1 (OPA1)-triggered fusion of mitochondrion. Inhibition of OPA1-induced fusion repressed Sirt3 overexpression-induced kidney protection, leading to mitochondrial dysfunction. Further, our study illustrated that OPA1-induced fusion could be affected through ERK; inhibition of ERK abolished the regulatory impacts of Sirt3 on OPA1 expression and mitochondrial fusion, leading to mitochondrial damage and tubular epithelial cell apoptosis. Altogether, our results suggest that renal IR injury is closely associated with Sirt3 downregulation and mitochondrial fusion inhibition. Regaining Sirt3 and/or activating mitochondrial fission by modifying the ERK-OPA1 cascade may represent new therapeutic modalities for renal IR injury.

Mst1 contributes to nasal epithelium inflammation via augmenting oxidative stress and mitochondrial dysfunction in a manner dependent on Nrf2 inhibition

Nasal epithelium inflammation plays an important role in transmitting and amplifying damage signals for the lower airway. However, the molecular basis of nasal epithelium inflammation damage has not been fully addressed. Mst1 is reported to modulate inflammation via multiple effects. Thus, the aim of our study is to understand the pathological mechanism underlying Mst1-related nasal epithelium inflammation in vitro. Our result indicated that Mst1 expression was rapidly increased in response to tumor necrosis factor-α (TNF-α) treatment in vitro and this effect was a dose-dependent manner. Interestingly, knockdown of Mst1 via transfecting small interfering RNA markedly reversed cell viability in the presence of TNF-α. Further, we found that Mst1 deficiency reduced cellular oxidative stress and attenuated mitochondrial dysfunction, as evidenced by reversed mitochondrial complex-I activity, decreased mitochondrial permeability transition pore opening rate, and stabilized mitochondrial membrane potential. Besides, we found that Nrf2 expression was increased after deletion of Mst1 whereas silencing of Nrf2 abolished the protective effects of Mst1 deletion on nasal epithelium survival and mitochondrial homeostasis. Moreover, Nrf2 overexpression also protected nasal epithelium against TNF-α-induced inflammation damage. Altogether, our data confirm that the Mst1 activation and Nrf2 downregulation seem to be the potential mechanisms responsible for the inflammation-mediated injury in nasal epithelium via mediating mitochondrial damage and cell oxidative stress.

Active Vitamin D and Vitamin D Receptor Help Prevent High Glucose Induced Oxidative Stress of Renal Tubular Cells via AKT/UCP2 Signaling Pathway

Background

It has been documented that vitamin D supplementation showed an improvement of symptoms of diabetic nephropathy; however, the underlying mechanisms remain unknown. We here tested the hypothesis that active vitamin D is able to up-regulate AKT/UCP2 signaling to alleviate oxidative stress of renal tubular cell line HK2.

Methods

There are eight groups in the present study: normal glucose, osmotic control (5.5 mmol/L D-glucose+24.5 mmol/L D-mannitol), NAC control (30 mmol/L D-glucose + 1.0 mmol/L N-Methylcysteine), high glucose, high glucose+VD, high glucose (HG)+VD+siVDR, HG+VD+AKT inhibitor (AI), and high glucose+VD+UCP2 inhibitor (Gelipin). Concentration of superoxide dismutase (SOD) and malondialdehyde (MDA) was analyzed by ELISA. Reactive oxygen species (ROS), mitochondrial membrane potential and apoptosis were measured by flow cytometry. JC-1 was evaluated by flow cytometry. The presence of VDR, AKT, and UCP2 in HK cells was assessed using RT-PCR and western blot analyses.

Results

VD administration significantly upregulated the SOD activation and downregulated MDA levels compared to HG group. siVDR, AKT inhibitor, and UCP2 inhibitor significantly suppressed the activation of SOD and increased the expression of MDA compared to VD group. ROS generation and apoptosis of HK2 cells in HG+VD group were significantly lower than those in HG, HG+VD+siVDR, HG+VD+AI, and HG+VD+Gelipin group. ΔΨm in HG+VD group was obviously higher than those in HG, HG+VD+siVDR, HG+VD+AI, and HG+VD+Gelipin group. Decreased mRNA and protein levels of VDR, p-AKT, and UCP2 were observed in HG+VD+siVDR, HG+VD+AI, and HG+VD+Gelipin group compared to those in HG+VD group.

Conclusions

siVDR, AKT inhibitor, and UCP2 inhibitor elevated the ROS and apoptosis of HK2 cells while attenuating the mitochondrial membrane potential, suggesting that vitamin D protects renal tubular cell from high glucose by AKT/UCP2 signaling pathway.

Bromodomain and Extra Terminal Protein Inhibitors Promote Pancreatic Endocrine Cell Fate

Bromodomain and extraterminal (BET) proteins are epigenetic readers that interact with acetylated lysines of histone tails. Recent studies have demonstrated their role in cancer progression because they recruit key components of the transcriptional machinery to modulate gene expression. However, their role during embryonic development of the pancreas has never been studied. Using mouse embryonic pancreatic explants and human induced pluripotent stem cells (hiPSCs), we show that BET protein inhibition with I-BET151 or JQ1 enhances the number of neurogenin3 (NEUROG3) endocrine progenitors. In mouse explants, BET protein inhibition further led to increased expression of β-cell markers but in the meantime, strongly downregulated Ins1 expression. Similarly, although acinar markers, such as Cpa1 and CelA, were upregulated, Amy expression was repressed. In hiPSCs, BET inhibitors strongly repressed C-peptide and glucagon during endocrine differentiation. Explants and hiPSCs were then pulsed with BET inhibitors to increase NEUROG3 expression and further chased without inhibitors. Endocrine development was enhanced in explants with higher expression of insulin and maturation markers, such as UCN3 and MAFA. In hiPSCs, the outcome was different because C-peptide expression remained lower than in controls, but ghrelin expression was increased. Altogether, by using two independent models of pancreatic development, we show that BET proteins regulate multiple aspects of pancreatic development.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.