Carbon monoxide releasing molecule-A1 improves nonalcoholic steatohepatitis via Nrf2 activation mediated improvement in oxidative stress and mitochondrial function

Model organisms for investigating the functional involvement of NRF2 in non-communicable diseases

Non-communicable chronic diseases (NCDs) are most commonly characterized by age-related loss of homeostasis and/or by cumulative exposures to environmental factors, which lead to low-grade sustained generation of reactive oxygen species (ROS), chronic inflammation and metabolic imbalance. Nuclear factor erythroid 2-like 2 (NRF2) is a basic leucine-zipper transcription factor that regulates the cellular redox homeostasis. NRF2 controls the expression of more than 250 human genes that share in their regulatory regions a cis-acting enhancer termed the antioxidant response element (ARE). The products of these genes participate in numerous functions including biotransformation and redox homeostasis, lipid and iron metabolism, inflammation, proteostasis, as well as mitochondrial dynamics and energetics. Thus, it is possible that a single pharmacological NRF2 modulator might mitigate the effect of the main hallmarks of NCDs, including oxidative, proteostatic, inflammatory and/or metabolic stress. Research on model organisms has provided tremendous knowledge of the molecular mechanisms by which NRF2 affects NCDs pathogenesis. This review is a comprehensive summary of the most commonly used model organisms of NCDs in which NRF2 has been genetically or pharmacologically modulated, paving the way for drug development to combat NCDs. We discuss the validity and use of these models and identify future challenges.

Vascular endothelial cell injury: causes, molecular mechanisms, and treatments

Vascular endothelial cells form a single layer of flat cells that line the inner surface of blood vessels, extending from large vessels to the microvasculature of various organs. These cells are crucial metabolic and endocrine components of the body, playing vital roles in maintaining circulatory stability, regulating vascular tone, and preventing coagulation and thrombosis. Endothelial cell injury is regarded as a pivotal initiating factor in the pathogenesis of various diseases, triggered by multiple factors, including infection, inflammation, and hemodynamic changes, which significantly compromise vascular integrity and function. This review examines the causes, underlying molecular mechanisms, and potential therapeutic approaches for endothelial cell injury, focusing specifically on endothelial damage in cardiac ischemia/reperfusion (I/R) injury, sepsis, and diabetes. It delves into the intricate signaling pathways involved in endothelial cell injury, emphasizing the roles of oxidative stress, mitochondrial dysfunction, inflammatory mediators, and barrier damage. Current treatment strategies-ranging from pharmacological interventions to regenerative approaches and lifestyle modifications-face ongoing challenges and limitations. Overall, this review highlights the importance of understanding endothelial cell injury within the context of various diseases and the necessity for innovative therapeutic methods to improve patient outcomes.

Erhong Jiangzhi Decoction Inhibits Lipid Accumulation and Alleviates Nonalcoholic Fatty Liver Disease with Nrf2 Restoration Under Obesity

Background

Nonalcoholic fatty liver disease (NAFLD) refers to the liver pathological changes caused by excessive fat accumulation in hepatocytes owing to various reasons, which has become an emerging health challenge. Erhong Jiangzhi Decoction (EHJD) is a traditional Chinese medicine decoction. This study aims to investigate the therapeutic effect of EHJD on NAFLD.

Methods

NAFLD model was constructed by high-fat diet (HFD)-induced mice and oleic acid-induced HepG2 cells. Mice were intragastrically administered with EHJD and HepG2 cells were treated with EHJD drug-containing serum. The effects of EHJD on NAFLD were explored in vivo and in vitro. Histological assessment was performed by hematoxylin-eosin and oil red O staining. ELISA was exploited to detect the expression of lipid accumulation, liver function, inflammation, and oxidative stress related indicators. The expression of Nrf2/HO-1 pathway was detected by qRT-PCR and Western blot.

Results

In HFD-induced NAFLD mice, the body weight was increased, and liver/weight, inguinal fat/weight, and epididymal fat/weight were higher, while EHJD reduced them. Staining results exhibited that EHJD decreased inflammatory cell infiltration and oil red lipid droplets in HFD-induced mice. In addition, EHJD treatment suppressed TC, TG, ALT and AST levels; TNF-α, IL-1β, IL-6 and MDA levels were inhibited by EHJD, while GSH-Px, CAT and T-AOC levels were increased in NAFLD through the in vivo and in vitro experiments. The suppression of Nrf2 weakened the inhibitory effect of EHJD on lipid metabolism, liver injury, inflammation and oxidative stress.

Conclusion

EHJD had a protective effect on NAFLD by alleviating lipid accumulation and liver injury, inhibiting inflammation, and oxidative stress, which was achieved by the restoration of Nrf2.

A peptide alleviated oxidative damages in the L02 cells and mice liver

The liver is vitally metabolic for a multitude of biochemical reactions. Consequently, it generates many free radicals and reactive oxygen species, rendering it more susceptible to oxidative stress-induced damage. Oxidative stress represents a pivotal factor in the pathogenesis of liver diseases. We screened some antioxidant peptides previously. Here we investigated whether the peptides could attenuate oxidative damage with APPH in L02 cells. The results showed that one of the peptides, sequence FETLMPLWGNK, could decrease the excessive reactive oxygen species, increase antioxidant enzyme activity and protect mitochondrial function, reduce the ratio of apoptosis and S phase cycle arrest, and improve the survival rate of L02 cells damaged by APPH compared to cells of the control group. Then the peptide was evaluated in mice that CCl4 injured. We found that CCl4-injured mice had significantly increased serum inflammatory factors and liver injury markers, a large number of inflammatory cell infiltration, and local necrosis in the liver. The peptide could reduce inflammation, and improve liver pathological changes. This phenomenon may be associated with the activation of the Nrf2 signaling pathway. Concurrently, the peptide protects the liver by regulating the expression of proteins related to the mitochondrial apoptosis pathway (p53, Bax, Bcl-2, and Caspase3) and mitophagy-related proteins (PINK1, Parkin, and AMPKα). Therefore, the results indicated that the peptide is an active substance with antioxidant activity and anti-inflammatory effects.

Carbon monoxide and mitochondria: Cell energy and fate control

Carbon monoxide (CO) is a ubiquitously produced endogenous gas in mammalian cells and is involved in stress response being considered as a cytoprotective and homeostatic factor. In the present review, the underlying mechanisms of CO are discussed, in particular CO's impact on cellular metabolism affecting cell fate and function. One of the principal signaling molecules of CO is reactive oxygen species (ROS), particularly hydrogen peroxide, which is mainly generated at the mitochondrial level. Likewise, CO acts on mitochondria modulating oxidative phosphorylation and mitochondria quality control, namely mitochondrial biogenesis (mitobiogenesis) and mitophagy. Other metabolic pathways are also involved in CO's mode of action such as glycolysis and pentose phosphate pathway. The review ends with some new perspectives on CO Biology research. Carboxyhemoglobin (COHb) formation can also be implicated in the CO mode of action, as well as its potential biological role. Finally, other organelles such as peroxisomes hold the potential to be targeted and modulated by CO.

Carbon monoxide-loaded red blood cells ameliorate metabolic dysfunction-associated steatohepatitis progression via enhancing AMP-activated protein kinase activity and inhibiting Kupffer cell activation

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive form of nonalcoholic fatty liver disease characterised by fat accumulation, inflammation, oxidative stress, fibrosis, and impaired liver regeneration. In this study, we found that heme oxygenase-1 (HO-1) is induced in both MASH patients and in a MASH mouse model. Further, hepatic carbon monoxide (CO) levels in MASH model mice were >2-fold higher than in healthy mice, suggesting that liver HO-1 is activated as MASH progresses. Based on these findings, we used CO-loaded red blood cells (CO-RBCs) as a CO donor in the liver, and evaluated their therapeutic effect in methionine-choline deficient diet (MCDD)-induced and high-fat-diet (HFD)-induced MASH model mice. Intravenously administered CO-RBCs effectively delivered CO to the MASH liver, where they prevented fat accumulation by promoting fatty acid oxidation via AMP-activated protein kinase (AMPK) activation and peroxisome proliferator-activated receptor induction. They also markedly suppressed Kupffer cell activation and their corresponding anti-inflammatory and antioxidative stress activities in MASH mice. CO-RBCs also helped to restore liver regeneration in mice with HFD-induced MASH by activating AMPK. We confirmed the underlying mechanisms by performing in vitro experiments in RAW264.7 cells and palmitate-stimulated HepG2 cells. Taken together, CO-RBCs show potential as a promising cellular treatment for MASH.

Single-Atom Ce-N-C Nanozyme Ameliorates Type 2 Diabetes Mellitus by Improving Glucose Metabolism Disorders and Reducing Oxidative Stress

Type 2 diabetes mellitus (T2DM) as a chronic metabolic disease has become a global public health problem. Insulin resistance (IR) is the main pathogenesis of T2DM. Oxidative stress refers to an imbalance between free radical production and the antioxidant system, causing insulin resistance and contributing to the development of T2DM via several molecular mechanisms. Besides, the reduction in hepatic glycogen synthesis also leads to a decrease in peripheral insulin sensitivity. Thus, reducing oxidative stress and promoting glycogen synthesis are both targets for improving insulin resistance and treating T2DM. The current study aims to investigate the pharmacological effects of single-atom Ce-N-C nanozyme (SACe-N-C) on the improvement of insulin resistance and to elucidate its underlying mechanisms using HFD/STZ-induced C57BL/6J mice and insulin-resistant HepG2 cells. The results indicate that SACe-N-C significantly improves hepatic glycogen synthesis and reduces oxidative stress, as well as pancreatic and liver injury. Specifically, compared to the T2DM model group, fasting blood glucose decreased by 29%, hepatic glycogen synthesis increased by 17.13%, and insulin secretion increased by 18.87%. The sod and GPx in the liver increased by 17.80% and 25.28%, respectively. In terms of mechanism, SACe-N-C modulated glycogen synthesis through the PI3K/AKT/GSK3β signaling pathway and activated the Keap1/Nrf2 pathway to alleviate oxidative stress. Collectively, this study suggests that SACe-N-C has the potential to treat T2DM.

Carbon monoxide-loaded cell therapy as an exercise mimetic for sarcopenia treatment

Sarcopenia is characterized by loss of muscle strength and muscle mass with aging. The growing number of sarcopenia patients as a result of the aging population has no viable treatment. Exercise maintains muscle strength and mass by increasing peroxisome growth factor activating receptor γ-conjugating factor-1α (PGC-1α) and Akt signaling in skeletal muscle. The present study focused on the carbon monoxide (CO), endogenous activator of PGC-1α and Akt, and investigated the therapeutic potential of CO-loaded red blood cells (CO-RBCs), which is bioinspired from in vivo CO delivery system, as an exercise mimetic for the treatment of sarcopenia. Treatment of C2C12 myoblasts with the CO-donor increased the protein levels of PGC-1α which enhanced mitochondrial biogenesis and energy production. The CO-donor treatment also activated Akt, indicating that CO promotes muscle synthesis. CO levels were significantly elevated in the skeletal muscle of normal mice after intravenous administration of CO-RBCs. Furthermore, CO-RBCs restored the mRNA expression levels of PGC-1α in the skeletal muscle of two experimental sarcopenia mouse models, denervated (Den) and hindlimb unloading (HU) models. CO-RBCs also restored muscle mass in Den mice by activating Akt signaling and suppressing the muscle atrophy factors myostatin and atrogin-1, and oxidative stress. Treadmill tests further showed that the reduced running distance in HU mice was significantly restored by CO-RBC administration. These findings suggest that CO-RBCs have potential as an exercise mimetic for sarcopenia treatment.

Bone Marrow Mesenchymal Stem Cells-derived Exosomes Promote Survival of Random Flaps in Rats through Nrf2-mediated Antioxidative Stress

BACKGROUND

 Random flaps are the most used defect repair method for head and neck tumors and trauma plastic surgery. The distal part of the flap often undergoes oxidative stress (OS), ultimately leading to flap necrosis. Stem cells' exosomes exhibit potential effects related to anti-inflammatory, regenerative, and antioxidant properties. Nuclear factor erythroid-2-related factor 2 (Nrf2) is an important factor in regulating oxidative balance. Exosomes have been reported to monitor its transcription to alleviate OS. This study examined the impacts and underlying mechanisms of antioxidant actions of exosomes derived from bone marrow mesenchymal stem cells (BMSCs-Exo) on random flaps.

METHODS

 BMSCs-Exo were injected into the tail veins of rats on days 0, 1, and 2 after surgery of random flaps. The rats were euthanized on day 3 to calculate the survival rate. Immunohistochemical staining, western blotting, dihydroethidium probe, superoxide dismutase, and malondialdehyde assay kits were used to detect the OS level. Human umbilical vein endothelial cells were cocultured with BMSCs-Exo and ML385 (an inhibitor of Nrf2) in vitro.

RESULTS

 BMSCs-Exo may significantly improve the survival rate of the random flaps by reducing apoptosis, inflammation, and OS while increasing angiogenesis. Besides, BMSCs-Exo can also increase mitochondrial membrane potential and reduce reactive oxygen species levels in vitro. These therapeutic effects might stem from the activation of the Kelch-like enyol-CoA hydratase (ECH)-associated protein 1 (Keap1)/Nrf2 signaling pathway.

CONCLUSION

 BMSCs-Exo improved the tissue antioxidant capacity by regulating the Keap1/Nrf2 signaling pathway. BMSCs-Exo may be a new strategy to solve the problem of random flap necrosis.

Diet/photoperiod mediated changes in cerebellar clock genes causes locomotor shifts and imperative changes in BDNF-TrkB pathway

Neuropsychological studies report anxiety and depression like symptoms in patients suffering from lifestyle disorder but its impact on locomotor function lacks clarity. Our study investigates locomotor deficits resulting due to perturbations in cerebellum of high fat diet (HFD), chronodisruption (CD) or a combination (HCD) model of lifestyle disorder. Significant downregulation in levels of cerebellar clock genes (Bmal-1, Clock, Per 1 and Per 2) and Bdnf-Trkb pathway genes (Bdnf, TrkB and Syn1 levels) were recorded. Further, locomotor deficits were observed in all the three experimental groups as evidenced by actimeter test, pole test and wire hanging test. Nuclear pyknosis of Purkinje cells, their derangement and inflammation were the hallmark of cerebellar tissue of all the three experimental groups. Taken together, this study generates important links between cerebellar clock oscillations, locomotor function and Bdnf-TrkB signaling.

The role and mechanism of hydrogen sulfide in liver fibrosis

Hydrogen sulfide (H2S) is the third new gas signaling molecule in the human body after the discovery of NO and CO. Similar to NO, it has the functions of vasodilation, anti-inflammatory, antioxidant, and regulation of cell formation. Enzymes that can produce endogenous H2S, such as CSE, CSB, and 3-MST, are common in liver tissues and are important regulatory molecules in the liver. In the development of liver fibrosis, H2S concentration and expression of related enzymes change significantly, which makes it possible to use exogenous gases to treat liver diseases. This review summarizes the role of H2S in liver fibrosis and its complications induced by NAFLD and CCl4, and elaborates on the anti-liver fibrosis effect of H2S through the mechanism of reducing oxidative stress, inhibiting inflammation, regulating autophagy, regulating glucose and lipid metabolism, providing theoretical reference for further research on the treatment of liver fibrosis with H2S.

Suppression of A-to-I RNA-editing enzyme ADAR1 sensitizes hepatocellular carcinoma cells to oxidative stress through regulating Keap1/Nrf2 pathway

BACKGROUND

A-to-I RNA editing is an abundant post-transcriptional modification event in hepatocellular carcinoma (HCC). Evidence suggests that adenosine deaminases acting on RNA 1 (ADAR1) correlates to oxidative stress that is a crucial factor of HCC pathogenesis. The present study investigated the effect of ADAR1 on survival and oxidative stress of HCC, and underlying mechanisms.

METHODS

ADAR1 expression was measured in fifty HCC and normal tissues via real-time quantitative PCR, and immunohistochemistry. For stable knockdown or overexpression of ADAR1, adeno-associated virus vectors carrying sh-ADAR1 or ADAR1 overexpression were transfected into HepG2 and SMMC-7721 cells. Transfected cells were exposed to oxidative stress agonist tBHP or sorafenib Bay 43-9006. Cell proliferation, apoptosis, and oxidative stress were measured, and tumor xenograft experiment was implemented.

RESULTS

ADAR1 was up-regulated in HCC and correlated to unfavorable clinical outcomes. ADAR1 deficiency attenuated proliferation of HCC cells and tumor growth and enhanced apoptosis. Moreover, its loss facilitated intracellular ROS accumulation, and elevated Keap1 and lowered Nrf2 expression. Intracellular GSH content and SOD activity were decreased and MDA content was increased in the absence of ADAR1. The opposite results were observed when ADAR1 was overexpressed. The effects of tBHP and Bay 43-9006 on survival, apoptosis, intracellular ROS accumulation, and Keap1/Nrf2 pathway were further exacerbated by simultaneous inhibition of ADAR1.

CONCLUSIONS

The current study unveils that ADAR1 is required for survival and oxidative stress of HCC cells, and targeting ADAR1 may sensitize HCC cells to oxidative stress via modulating Keap1/Nrf2 pathway.

Baicalin and N-acetylcysteine regulate choline metabolism via TFAM to attenuate cadmium-induced liver fibrosis

(Background): Cadmium is an environmental pollutant associated with several liver diseases. Baicalin and N-Acetylcysteine have antioxidant and hepatoprotective effects. (Purpose): However, it is unclear whether baicalin and N-Acetylcysteine can alleviate Cadmium -induced liver fibrosis by regulating metabolism, or whether they exert a synergistic effect. (Study design): We treated Cadmium-poisoned mice with baicalin, N-Acetylcysteine, or baicalin+ N-Acetylcysteine. We studied the effects of baicalin and N-Acetylcysteine on Cadmium-induced liver fibers and their specific mechanisms. (Methods): We used C57BL/6 J mice, and AML12, and HSC-6T cells to establish in vitro assays and in vivo models. (Results): Metabolomics was used to detect the effect of baicalin and N-Acetylcysteine on liver metabolism, which showed that compared with the control group, the Cadmium group had increased fatty acid and amino acid levels, with significantly reduced choline and acetylcholine contents. Baicalin and N-Acetylcysteine alleviated these Cadmium-induced metabolic changes. We further showed that choline alleviated Cadmium -induced liver inflammation and fibrosis. In addition, cadmium significantly promoted extracellular leakage of lactic acid, while choline alleviated the cadmium -induced destruction of the cell membrane structure and lactic acid leakage. Western blotting showed that cadmium significantly reduced mitochondrial transcription factor A (TFAM) and Choline Kinase α(CHKα2) levels, and baicalin and N-Acetylcysteine reversed this effect. Overexpression of Tfam in mouse liver and AML12 cells increased the expression of CHKα2 and the choline content, alleviating and cadmium-induced lactic acid leakage, liver inflammation, and fibrosis. (Conclusion): Overall, baicalin and N-Acetylcysteine alleviated cadmium-induced liver damage, inflammation, and fibrosis to a greater extent than either drug alone. TFAM represents a target for baicalin and N-Acetylcysteine, and alleviated cadmium-induced liver inflammation and fibrosis by regulating hepatic choline metabolism.

Unveiling global research trends and hotspots on mitochondria in NAFLD from 2000 to 2023: A bibliometric analysis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has garnered significant attention in the past decade as a prevalent chronic liver condition. Despite a growing body of evidence implicating mitochondria in NAFLD development, comprehensive bibliometric analyses within this research domain are scarce. This study aims to provide a thorough overview of the knowledge framework and key research areas related to mitochondria in the context of NAFLD, utilizing bibliometric techniques.

METHODS

A comprehensive search of publications on mitochondria in NAFLD from 2000 to 2023 was conducted using the Web of Science Core Collection database. VOSviewers, CiteSpace, and the R package "bibliometrix" were employed for a precise assessment of the literature.

RESULTS

Examining 2530 articles from 77 countries, primarily led by the United States and China, revealed a consistent increase in publications on mitochondria's role in NAFLD. Leading research institutions include the University of Coimbra, the University of Missouri, the Chinese Academy of Sciences, Fudan University, and Shanghai Jiao Tong University. Notably, the International Journal of Molecular Sciences emerged as the most popular journal, and Hepatology was the most frequently cited. With contributions from 14,543 authors, Michael Roden published the highest number of papers, and A. J. Samyal was the most frequently cocited author. Key focus areas include investigating mitochondrial mechanisms impacting NAFLD and developing therapeutic strategies targeting mitochondria. Emerging research hotspots are associated with keywords such as "inflammation," "mitochondrial dysfunction," "autophagy," "obesity," and "insulin resistance."

CONCLUSION

This study, the first comprehensive bibliometric analysis, synthesizes research trends and advancements in the role of mitochondria in NAFLD. Insights derived from this analysis illuminate current frontiers and emerging areas of interest, providing a valuable reference for scholars dedicated to mitochondrial studies.

Non-thermal plasma promotes boar sperm quality through increasing AMPK methylation

Boar sperm quality, as an important indicator of reproductive efficiency, directly affects the efficiency of livestock production. Here, this study was conducted to improve the boar sperm quality by using a non-thermal dielectric barrier discharge (DBD) plasma. Our results showed that DBD plasma exposure at 2.1 W for 15 s could improve boar sperm quality by increasing exon methylation level of adenosine monophosphate-activated protein kinase (AMPK) and thus improving the glycolytic flux, mitochondrial function, and antioxidant capacity without damaging the integrity of sperm DNA and acrosome. In addition, DBD plasma could rescue DNA methyltransferase inhibitor decitabine-caused low sperm quality through reducing the oxidative stress and mitochondrial damage. Therefore, the application of non-thermal plasma provides a new strategy for reducing sperm oxidative damage and improving sperm quality, which shows a great potential in assisted reproduction to solve the problem of male infertility.

The emerging significance of mitochondrial targeted strategies in NAFLD treatment

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, ranging from liver steatosis to nonalcoholic steatohepatitis, which ultimately progresses to fibrosis, cirrhosis, and hepatocellular carcinoma. Individuals with NAFLD have a higher risk of developing cardiovascular and extrahepatic cancers. Despite the great progress being made in understanding the pathogenesis and the introduction of new pharmacological targets for NAFLD, no drug or intervention has been accepted for its management. Recent evidence suggests that NAFLD may be a mitochondrial disease, as mitochondrial dysfunction is involved in the pathological processes that lead to NAFLD. In this review, we describe the recent advances in our understanding of the mechanisms associated with mitochondrial dysfunction in NAFLD progression. Moreover, we discuss recent advances in the efficacy of mitochondria-targeted compounds (e.g., Mito-Q, MitoVit-E, MitoTEMPO, SS-31, mitochondrial uncouplers, and mitochondrial pyruvate carrier inhibitors) for treating NAFLD. Furthermore, we present some medications currently being tested in clinical trials for NAFLD treatment, such as exercise, mesenchymal stem cells, bile acids and their analogs, and antidiabetic drugs, with a focus on their efficacy in improving mitochondrial function. Based on this evidence, further investigations into the development of mitochondria-based agents may provide new and promising alternatives for NAFLD management.

miR34a-5p impedes CLOCK expression in chronodisruptive C57BL/6J mice and potentiates pro-atherogenic manifestations

INTRODUCTION

Altered circadian rhythms underlie manifestation of several cardiovascular disorders, however a little is known about the mediating biomolecules. Multiple transcriptional-translational feedback loops control circadian-clockwork wherein; micro RNAs (miRNAs) are known to manifest post transcriptional regulation. This study assesses miR34a-5p as a mediating biomolecule.

METHOD

8-10-week-old male C57BL/6J mice (n = 6/group) were subjected to photoperiodic manipulation induced chronodisruption and thoracic aortae were examined for miRNA, gene (qPCR) and protein (Immunoblot) expression studies. Histomorphological changes were assessed for pro-atherogenic manifestations (fibrillar arrangement, collagen/elastin ratio, intima-media thickening). Computational studies for miRNA-mRNA target prediction were done using TargetScan and miRDB. Correlative in vitro studies were done in serum synchronized HUVEC cells. Time point based studies were done at five time points (ZT 0, 6, 12, 18, 24) in 24h.

RESULTS

Chronodisruption induced hypomethylation in the promoter region of miR34a-5p, in the thoracic aortae, culminating in elevated miRNA titers. In a software-based detection of circadian-clock-associated targets of miR34a-5p, Clock and Sirt1 genes were identified. Moreover, miR34a-5p exhibited antagonist circadian oscillations to that of its target genes CLOCK and SIRT1 in endothelial cells. Luciferase reporter gene assay further showed that miR34a-5p interacts with the 3'UTR of the Clock gene to lower its expression, disturbing the operation of positive arm of circadian clock system. Elevated miR34a-5p and impeded SIRT1 expression in a chronodisruptive aortae exhibited pro-atherogenic changes observed in form of gene expression, increased collagen/elastin ratio, fibrillar derangement and intimal-media thickening.

CONCLUSION

The study reports for the first time chronodisruption mediated miR34a-5p elevation, its circadian expression and interaction with the 3'UTR of Clock gene to impede its expression. Moreover, elevated miR34a-5p and lowered SIRT1 expression in the chronodisruptive aortae lead off cause-consequence relationship of chronodisruption mediated proatherogenic changes.

High Heme and Low Heme Oxygenase-1 Are Associated with Mast Cell Activation/Degranulation in HIV-Induced Chronic Widespread Pain

An overwhelming number of people with HIV (PWH) experience chronic widespread pain (CWP) throughout their lifetimes. Previously, we demonstrated that PWH with CWP have increased hemolysis and attenuated heme oxygenase 1 (HO-1) levels. HO-1 degrades reactive, cell-free heme into antioxidants like biliverdin and carbon monoxide (CO). We found that high heme or low HO-1 caused hyperalgesia in animals, likely through multiple mechanisms. In this study, we hypothesized that high heme or low HO-1 caused mast cell activation/degranulation, resulting in the release of pain mediators like histamine and bradykinin. PWH who self-report CWP were recruited from the University of Alabama at Birmingham HIV clinic. Animal models included HO-1-/- mice and hemolytic mice, where C57BL/6 mice were injected intraperitoneally with phenylhydrazine hydrochloride (PHZ). Results demonstrated that plasma histamine and bradykinin were elevated in PWH with CWP. These pain mediators were also high in HO-1-/- mice and in hemolytic mice. Both in vivo and in vitro (RBL-2H3 mast cells), heme-induced mast cell degranulation was inhibited by treatment with CORM-A1, a CO donor. CORM-A1 also attenuated mechanical and thermal (cold) allodynia in hemolytic mice. Together, the data suggest that mast cell activation secondary to high heme or low HO-1 seen in cells and animals correlates with elevated plasma levels of heme, histamine, and bradykinin in PWH with CWP.

CORM-A1 Alleviates Pro-Atherogenic Manifestations via miR-34a-5p Downregulation and an Improved Mitochondrial Function

Atherogenesis involves multiple cell types undergoing robust metabolic processes resulting in mitochondrial dysfunction, elevated reactive oxygen species (ROS), and consequent oxidative stress. Carbon monoxide (CO) has been recently explored for its anti-atherogenic potency; however, the effects of CO on ROS generation and mitochondrial dysfunction in atherosclerosis remain unexplored. Herein, we describe the anti-atherogenic efficacy of CORM-A1, a CO donor, in in vitro (ox-LDL-treated HUVEC and MDMs) and in vivo (atherogenic diet-fed SD rats) experimental models. In agreement with previous data, we observed elevated miR-34a-5p levels in all our atherogenic model systems. Administration of CO via CORM-A1 accounted for positive alterations in the expression of miR-34a-5p and transcription factors/inhibitors (P53, NF-κB, ZEB1, SNAI1, and STAT3) and DNA methylation pattern, thereby lowering its countenance in atherogenic milieu. Inhibition of miR-34a-5p expression resulted in restoration of SIRT-1 levels and of mitochondrial biogenesis. CORM-A1 supplementation further accounted for improvement in cellular and mitochondrial antioxidant capacity and subsequent reduction in ROS. Further and most importantly, CORM-A1 restored cellular energetics by improving overall cellular respiration in HUVECs, as evidenced by restored OCR and ECAR rates, whereas a shift from non-mitochondrial to mitochondrial respiration was observed in atherogenic MDMs, evidenced by unaltered glycolytic respiration and maximizing OCR. In agreement with these results, CORM-A1 treatment also accounted for elevated ATP production in both in vivo and in vitro experimental models. Cumulatively, our studies demonstrate for the first time the mechanism of CORM-A1-mediated amelioration of pro-atherogenic manifestations through inhibition of miR-34a-5p expression in the atherogenic milieu and consequential rescue of SIRT1-mediated mitochondrial biogenesis and respiration.

Erianin alleviated liver steatosis by enhancing Nrf2-mediated VE-cadherin expression in vascular endothelium

Non-alcoholic fatty liver disease (NAFLD) is emerging as the most common chronic liver disease and is closely associated with metabolic syndrome. Endothelial dysfunction was involved in many metabolic diseases, but the concrete participation of hepatic vascular endothelial dysfunction in liver steatosis that is an early stage of NAFLD is still unclear. In this study, the formation of liver steatosis and the elevation of serum insulin content were observed accompanying with the decreased vascular endothelial cadherin (VE-cadherin) expression in hepatic vessels from db/db mice, Goto-Kakizaki (GK) and high-fat diet (HFD)-fed rats. Liver steatosis was obviously enhanced in mice after the application of VE-cadherin neutralizing antibody. In vitro results showed that insulin decreased VE-cadherin expression and caused endothelial barrier breakdown. Furthermore, the alteration of VE-cadherin expression was found to be positively related with the transcriptional activation of nuclear erythroid 2-related factor 2 (Nrf2), and chromatin immunoprecipitation (ChIP) assay displayed that Nrf2 could directly regulate VE-cadherin expression. Insulin reduced Nrf2 activation by decreasing sequestosome-1 (p62/SQSTM1) expression downstream of insulin receptor. Moreover, the p300-mediated Nrf2 acetylation was weakened by enhancing the competitive binding of transcription factor GATA-binding protein 4 (GATA4) to p300. Finally, we found that erianin, a natural compound, could promote VE-cadherin expression by inducing Nrf2 activation, thereby alleviating liver steatosis in GK rats. Our results suggest that hepatic vascular endothelial dysfunction owing to the VE-cadherin deficiency dependent on the reduced Nrf2 activation promoted liver steatosis, and erianin alleviated liver steatosis through enhancing Nrf2-mediated VE-cadherin expression.

Carbon Monoxide Stimulates Both Mitophagy And Mitochondrial Biogenesis to Mediate Protection Against Oxidative Stress in Astrocytes

Astrocytes are key glial cells for the metabolic and functional support of the brain. Mitochondrial quality control (MQC), in particular the balance between mitophagy and mitochondrial biogenesis, is a major event for the maintenance of cellular homeostasis. Carbon monoxide (CO) is an endogenous gasotransmitter that inhibits cell death and inflammation by targeting mitochondria. It is well established that CO promotes cytoprotection by increasing mitochondrial population and metabolism (oxidative phosphorylation). Thus, it is hypothesized that CO-induced cytoprotection may also be mediated by the balance between mitophagy and mitochondrial biogenesis. Herein, the carbon monoxide releasing molecule-A1 (CORM-A1) was used in primary cultures of astrocytes to assess CO role on mitochondrial turnover. PINK1/Parkin-dependent mitophagy was stimulated by CORM-A1 following 1 h of treatment. While at 24 h after treatment, CORM-A1 increased mitochondrial population, which may indicate mitochondrial biogenesis. In fact, mitochondrial biogenesis was confirmed by the enhancement of PGC-1α expression that upregulates several mitochondrial transcription factors. Furthermore, inhibition of mitophagy by knocking down PINK1 expression reverted CO-induced mitochondrial biogenesis, indicating that mitochondrial turnover is dependent on modulation of mitophagy. Finally, CORM-A1 prevented astrocytic cell death induced by oxidative stress in a mitophagy-dependent manner. In fact, whenever PINK1 was knocked down, CORM-A1-induced cytoprotection was lost. In summary, CORM-A1 stimulates mitochondrial turnover, which in turn prevents astrocytic cell death. CO cytoprotection depends on increasing mitochondrial population and on eliminating dysfunctional mitochondria.

An Approach to Evaluate the Effective Cytoplasmic Concentration of Bioactive Agents Interacting with a Selected Intracellular Target Protein

To compare the effectiveness of various bioactive agents reversibly acting within a cell on a target intracellular macromolecule, it is necessary to assess effective cytoplasmic concentrations of the delivered bioactive agents. In this work, based on a simple equilibrium model and the cellular thermal shift assay (CETSA), an approach is proposed to assess effective concentrations of both a delivered bioactive agent and a target protein. This approach was tested by evaluating the average concentrations of nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associated-protein 1 (Keap1) proteins in the cytoplasm for five different cell lines (Hepa1, MEF, RAW264.7, 3LL, and AML12) and comparing the results with known literature data. The proposed approach makes it possible to analyze both binary interactions and ternary competition systems; thus, it can have a wide application for the analysis of protein-protein or molecule-protein interactions in the cell. The concentrations of Nrf2 and Keap1 in the cell can be useful not only in analyzing the conditions for the activation of the Nrf2 system, but also for comparing the effectiveness of various drug delivery systems, where the delivered molecule is able to interact with Keap1.

Network Pharmacology to Reveal the Molecular Mechanisms of Rutaceous Plant-derived Limonin Ameliorating Non-alcoholic Steatohepatitis

BACKGROUND

Limonin shows promise in alleviating non-alcoholic fatty liver disease. We investigated the mechanisms of limonin against non-alcoholic steatohepatitis (NASH) using network pharmacology and molecular docking.

METHODS

Public databases provided NASH- and limonin-associated targets. VennDiagram identified potential limonin targets for NASH. Enrichment analysis explored the limonin-NASH relationship. PPI network analysis, CytoHubba models, and bioinformatics identified hub genes for NASH treatment. Molecular docking assessed limonin's binding ability to hub targets.

RESULTS

We found 37 potential limonin targets in NASH, involved in oxidative stress, inflammation, and signaling pathways. PPI network analysis revealed seven hub genes (STAT3, NFKBIA, MTOR, TLR4, CASP8, PTGS2, NFKB1) as NASH treatment targets. Molecular docking confirmed limonin's binding to STAT3, CASP8, and PTGS2. Animal experiments on high-fat diet mice showed limonin reduced hepatic steatosis, lipid accumulation, and expression of p-STAT3/STAT3, CASP8, and PTGS2.

CONCLUSION

Limonin's therapeutic effects in NASH may stem from its antioxidant and anti-inflammatory properties. STAT3, CASP8, and PTGS2 are potential key targets for NASH treatment, warranting further investigation.

Dendrobium and its active ingredients: Emerging role in liver protection

Dendrobium is a traditional medicinal plant, which has a variety of clinical applications in China. It has been reported that Dendrobium contains various bioactive components, mainly including polysaccharides and alkaloids. Previous studies have shown that Dendrobium has pharmacological activities including antiviral, anti-inflammatory, and antioxidant effects, as well as immune regulation. Particularly, the anti-aging functions and neuroprotective effects of Dendrobium have been well characterized in a wide array of cell and animal models. In recent years, the effect of Dendrobium on the liver has emerged as a new direction to explore its therapeutic benefits and has received more and more attention. This review is focused on the beneficial effects of Dendrobium on liver toxicity and various liver disorders, which presumably are attributed to a consequence of an array of modes of action due to its multiple bioactive components, and largely lack mechanistic and pharmacokinetic characterization. A particular emphasis is placed on the potential action mechanisms related to Dendrobium's liver protection. Research perspectives in regard to the potential therapeutic application for Dendrobium are also discussed in this review.

Nuclear factor erythroid 2-related factor 2-mediated signaling and metabolic associated fatty liver disease

Oxidative stress is a key driver in the development and progression of several diseases, including metabolic associated fatty liver disease (MAFLD). This condition includes a wide spectrum of pathological injuries, extending from simple steatosis to inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Excessive buildup of lipids in the liver is strictly related to oxidative stress in MAFLD, progressing to liver fibrosis and cirrhosis. The nuclear factor erythroid 2-related factor 2 (NRF2) is a master regulator of redox homeostasis. NRF2 plays an important role for cellular protection by inducing the expression of genes related to antioxidant, anti-inflammatory, and cytoprotective response. Consistent evidence demonstrates that NRF2 is involved in every step of MAFLD deve-lopment, from simple steatosis to inflammation, advanced fibrosis, and ini-tiation/progression of hepatocellular carcinoma. NRF2 activators regulate lipid metabolism and oxidative stress alleviating the fatty liver disease by inducing the expression of cytoprotective genes. Thus, modulating NRF2 activation is crucial not only in understanding specific mechanisms underlying MAFLD progression but also to characterize effective therapeutic strategies. This review outlined the current knowledge on the effects of NRF2 pathway, modulators, and mechanisms involved in the therapeutic implications of liver steatosis, inflammation, and fibrosis in MAFLD.

Effect of carbon monoxide administration using haemoglobin-vesicles on the hippocampal tissue

Carbon monoxide (CO) is a toxic gas that causes neuropathy. However, CO is endogenously produced in small amounts showing various beneficial effects. We hypothesized that CO-bound haemoglobin-vesicle (HbV) administration would reduce cerebral ischaemia-reperfusion injury without causing neuropathy. Three experiments were conducted. First, rats were exposed to CO inhalation to create a CO-poisoning group, and they were sacrificed on 0, 7, 14, and 21 days after CO exposure. Histopathologically, hippocampal damage was prominent at 14 days. Second, the rats were administered with CO-HbV equivalent to 50 or 25% of circulating blood volume (CO-HbV50 or CO-HbV25 group). Rats were sacrificed 14 days after administration. Third, rats put into haemorrhagic shock by 50% of circulating blood withdrawal were resuscitated using saline, autologous blood, and CO-HbV. They were sacrificed 14 days after resuscitation. Hippocampal damage assessment clarified that almost no necrotic cells were observed in the CO-HbV50 group. Necrotic cells in the CO-HbV25 group were comparable to those found for the control group. In rats resuscitated from haemorrhagic shock, the hippocampal damage in the group using CO-HbV was the mildest. Administration of CO-HbV did not lead to marked hippocampal damage. Furthermore, CO-HbV was effective at preventing cerebral ischaemia-reperfusion injury after haemorrhagic shock.

Melatonin alleviates the heat stress-induced impairment of Sertoli cells by reprogramming glucose metabolism

Sertoli cells (SCs) provide structural and nutritional support for developing germ cells. Normal glucose metabolism of SCs is necessary for spermatogenesis. Melatonin could alleviate the effects of heat stress on spermatogenesis. However, the influences of heat stress on glucose metabolism in SCs remain unclear, and the potential protective mechanisms of melatonin on SCs need more exploration. In this study, boar SCs were treated at 43°C for 30 min, and different concentrations of melatonin were added to protect SCs from heat stress-induced impairment. These results showed that heat stress-induced oxidative stress caused cell apoptosis, inhibited the pentose phosphate pathway, and decreased the ATP content. Furthermore, heat stress increased the expressions of glucose intake- and glycolytic-related enzymes, which enhanced the glycolysis activity to compensate for the energy deficit. Melatonin relieved heat stress-induced oxidative stress and apoptosis by activating the Kelch-like ECH-associated protein 1 (KEAP1)/NF-E2-related factor 2 signaling pathway to increase the capacity of antioxidants. In addition, melatonin enhanced heat-shock protein 90 (HSP90) expression through melatonin receptor 1B (MTNR1B), thereby stabilizing hypoxia-inducible factor-1α (HIF-1α). Activation of the HIF-1α signaling pathway enhanced glycolysis, promoted the pentose phosphate pathway, and increased cell viability. Our results suggest that melatonin reprograms glucose metabolism in SCs through the MTNR1B-HSP90-HIF-1α axis and provides a theoretical basis for preventing heat stress injury.

Controlled therapeutic delivery of CO from carbon monoxide-releasing molecules (CORMs)

Carbon monoxide (CO) has been regarded as a "silent killer" for its toxicity toward biological systems. However, a low concentration of endogenously produced CO has shown a number of therapeutic benefits such as anti-inflammatory, anti-proliferative, anti-apoptosis, and cytoprotective activities. Carbon monoxide-releasing molecules (CORMs) have been developed as alternatives to direct CO inhalation, which requires a specialized setting for strict dose control. CORMs are efficient CO donors, with central transition metals (such as ruthenium, iron, cobalt, and manganese) surrounded by CO as a ligand. CORMs can stably store and subsequently release their CO payload in the presence of certain triggers including solvent, light, temperature, and ligand substitution. However, CORMs require appropriate delivery strategies to improve short CO release half-life and target specificity. Herein, we highlighted the therapeutic potential of inhalation and CORMs-delivered CO. The applications of conjugate and nanocarrier systems for controlling CO release and improving therapeutic efficacy of CORMs are also described in detail. The review concludes with some of the hurdles that limit clinical translation of CORMs. Keeping in mind the tremendous potential and growing interest in CORMs, this review would be helpful for designing controlled CO release systems for clinical applications.

CORM-3 Attenuates Oxidative Stress-Induced Bone Loss via the Nrf2/HO-1 Pathway

Bone metabolism occurs in the entire life of an individual and is required for maintaining skeletal homeostasis. The imbalance between osteogenesis and osteoclastogenesis eventually leads to osteoporosis. Oxidative stress is considered a major cause of bone homeostasis disorder, and relieving excessive oxidative stress in bone mesenchymal stem cells (BMSCs) is a potential treatment strategy for osteoporosis. Carbon monoxide releasing molecule-3 (CORM-3), the classical donor of carbon monoxide (CO), possesses antioxidation, antiapoptosis, and anti-inflammatory properties. In our study, we found that CORM-3 could reduce reactive oxygen species (ROS) accumulation and prevent mitochondrial dysfunction thereby restoring the osteogenic potential of the BMSCs disrupted by hydrogen peroxide (H₂O₂) exposure. The action of CORM-3 was preliminarily considered the consequence of Nrf2/HO-1 axis activation. In addition, CORM-3 inhibited osteoclast formation in mouse primary bone marrow monocytes (BMMs) by inhibiting H₂O₂-induced polarization of M1 macrophages and endowing macrophages with M2 polarizating ability. Rat models further demonstrated that CORM-3 treatment could restore bone mass and enhance the expression of Nrf2 and osteogenic markers in the distal femurs. In summary, CORM-3 is a potential therapeutic agent for the treatment of osteoporosis.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

P4HB UFMylation regulates mitochondrial function and oxidative stress

UFMylation is a ubiquitin-like modification which attaches the ubiquitin-fold modifier 1 to target proteins. To date, only a few UFMylation targets have been identified. In the current study, we demonstrated that P4HB is a new target protein for UFMylation and it can be UFMylated at three lysine residues in the form of mono-UFMylation. P4HB has oxidoreductase, chaperone and isomerase effects. It presents in the endoplasmic reticulum, mitochondria and cytosol. Next, we generated a stable HepG2 cell line, the hepatocellular cells, with defective P4HB UFMylation. Our data show that P4HB UFMylation defect promotes P4HB protein degradation via the ubiquitin-proteasome pathway. Defective P4HB UFMylation causes mitochondrial function damage, oxidative stress, and endoplasmic reticulum stress in HepG2 cells. These effects are more obvious when treating HepG2 cells with palmitic acid, which is frequently used as one of the cell models of non-alcoholic fatty liver disease (NAFLD). Our results identify UFMylation as a key post-translational modification for the maintenance of P4HB stability and biological functions in HepG2 cells, and point to P4HB UFMylation as a potential direction in the study of NAFLD.

Dimethylglycine Sodium Salt Alleviates Intrauterine Growth Restriction-Induced Low Growth Performance, Redox Status Imbalance, and Hepatic Mitochondrial Dysfunction in Suckling Piglets

This study aimed to investigate the mechanism of redox status imbalance and hepatic mitochondrial dysfunction induced by intrauterine growth restriction (IUGR) and relieve this condition through dimethylglycine sodium salt (DMG-Na) supplementation during the suckling period. Thirty normal birth weight (NBW) and 30 IUGR newborns were selected from 20 sows. Briefly, 1 NBW and 1 IUGR newborn were obtained from each litter of 10 sows, and 10 NBW and 10 IUGR newborns were obtained. Additionally, 2 NBW and 2 IUGR newborns were obtained from each litter of another 10 sows, and 20 NBW newborns were allocated to the N [basic milk diets (BMDs)] and ND (BMDs+0.1% DMG-Na) groups. Furthermore, 20 IUGR newborns were assigned to the I (BMDs) and ID (BMDs+0.1% DMG-Na) groups. The results revealed that the growth performance, serum and hepatic redox status, and hepatic gene and protein expression levels were lower (P < 0.05) in the I group compared to the N group. Additionally, supplementation with DMG-Na (ND and ID groups) improved (P < 0.05) these parameters compared to the non-supplemented groups (N and I groups). In conclusion, the activity of Nrf2/SIRT1/PGC1α was inhibited in IUGR newborns, and this led to their hepatic dysfunctions. Supplementation with DMG-Na activated Nrf2/SIRT1/PGC1α in IUGR newborns, thereby improving their performance.

Dimethylglycine sodium salt activates Nrf2/SIRT1/PGC1α leading to the recovery of muscle stem cell dysfunction in newborns with intrauterine growth restriction

The objectives of this study were focused on the mechanism of mitochondrial dysfunction in skeletal muscle stem cells (MuSCs) from intrauterine growth restriction (IUGR) newborn piglets, and the relief of dimethylglycine sodium salt (DMG-Na) on MuSCs mitochondrial dysfunction by Nrf2/SIRT1/PGC1α network. In this study, six newborn piglets with normal birth weight (NBW) and six IUGR newborn piglets were slaughtered immediately after birth to obtain longissimus dorsi muscle (LM) samples. MuSCs were collected and divided into three groups: MuSCs from NBW newborn piglets (N), MuSCs from IUGR newborn piglets (I), and MuSCs from IUGR newborn piglets with 32 μmol DMG-Na (ID). Compared with the NBW group, the IUGR group showed decreased (P < 0.05) serum and LM antioxidant defense capacity, and increased (P < 0.05) serum and LM damage. Compared with the N group, the I group showed decreased (P < 0.05) MuSCs antioxidant defense capacity, mitochondrial ETC complexes, energy metabolites, and antioxidant defense-related and mitochondrial function-related gene and protein expression levels. The antioxidant defense capacity, mitochondrial ETC complexes, energy metabolites, and antioxidant defense-related and mitochondrial function-related gene and protein expression levels of MuSCs were improved (P < 0.05) in the ID group compared to those in the I group. The MuSCs of IUGR newborns activate the Nrf2/SIRT1/PGC1α network by taking in DMG-Na, thereby neutralizing excessive generated O₂^•- that may help to improve their unfavorable mitochondrial dysfunction in skeletal muscle.

Empagliflozin-Enhanced Antioxidant Defense Attenuates Lipotoxicity and Protects Hepatocytes by Promoting FoxO3a- and Nrf2-Mediated Nuclear Translocation via the CAMKK2/AMPK Pathway

Lipotoxicity is an important factor in the development and progression of nonalcoholic steatohepatitis. Excessive accumulation of saturated fatty acids can increase the substrates of the mitochondrial electron transport chain in hepatocytes and cause the generation of reactive oxygen species, resulting in oxidative stress, mitochondrial dysfunction, loss of mitochondrial membrane potential, impaired triphosphate (ATP) production, and fracture and fragmentation of mitochondria, which ultimately leads to hepatocellular inflammatory injuries, apoptosis, and necrosis. In this study, we systematically investigated the effects and molecular mechanisms of empagliflozin on lipotoxicity in palmitic acid-treated LO2 cell lines. We found that empagliflozin protected hepatocytes and inhibited palmitic acid-induced lipotoxicity by reducing oxidative stress, improving mitochondrial functions, and attenuating apoptosis and inflammation responses. The mechanistic study indicated that empagliflozin significantly activated adenosine 5'-monophosphate (AMP)-activated protein kinase alpha (AMPKα) through Calcium/Calmodulin dependent protein kinase kinase beta (CAMKK2) instead of liver kinase B1 (LKB1) or TGF-beta activated kinase (TAK1). The activation of empagliflozin on AMPKα not only promoted FoxO3a phosphorylation and thus forkhead box O 3a (FoxO3a) nuclear translocation, but also promoted Nrf2 nuclear translocation. Furthermore, empagliflozin significantly upregulated the expressions of antioxidant enzymes superoxide dismutase (SOD) and HO-1. In addition, empagliflozin did not attenuate lipid accumulation at all. These results indicated that empagliflozin mitigated lipotoxicity in saturated fatty acid-induced hepatocytes, likely by promoting antioxidant defense instead of attenuating lipid accumulation through enhanced FoxO3a and Nrf2 nuclear translocation dependent on the CAMKK2/AMPKα pathway. The CAMKK2/AMPKα pathway might serve as a promising target in treatment of lipotoxicity in nonalcoholic steatohepatitis.

Mitochondrial Dysfunction and Acute Fatty Liver of Pregnancy

The liver is one of the richest organs in mitochondria, serving as a hub for key metabolic pathways such as β-oxidation, the tricarboxylic acid (TCA) cycle, ketogenesis, respiratory activity, and adenosine triphosphate (ATP) synthesis, all of which provide metabolic energy for the entire body. Mitochondrial dysfunction has been linked to subcellular organelle dysfunction in liver diseases, particularly fatty liver disease. Acute fatty liver of pregnancy (AFLP) is a life-threatening liver disorder unique to pregnancy, which can result in serious maternal and fetal complications, including death. Pregnant mothers with this disease require early detection, prompt delivery, and supportive maternal care. AFLP was considered a mysterious illness and though its pathogenesis has not been fully elucidated, molecular research over the past two decades has linked AFLP to mitochondrial dysfunction and defects in fetal fatty-acid oxidation (FAO). Due to deficient placental and fetal FAO, harmful 3-hydroxy fatty acid metabolites accumulate in the maternal circulation, causing oxidative stress and microvesicular fatty infiltration of the liver, resulting in AFLP. In this review, we provide an overview of AFLP and mitochondrial FAO followed by discussion of how altered mitochondrial function plays an important role in the pathogenesis of AFLP.

Heme Oxygenase-1: An Anti-Inflammatory Effector in Cardiovascular, Lung, and Related Metabolic Disorders

The heme oxygenase (HO) enzyme system catabolizes heme to carbon monoxide (CO), ferrous iron, and biliverdin-IXα (BV), which is reduced to bilirubin-IXα (BR) by biliverdin reductase (BVR). HO activity is represented by two distinct isozymes, the inducible form, HO-1, and a constitutive form, HO-2, encoded by distinct genes (HMOX1, HMOX2, respectively). HO-1 responds to transcriptional activation in response to a wide variety of chemical and physical stimuli, including its natural substrate heme, oxidants, and phytochemical antioxidants. The expression of HO-1 is regulated by NF-E2-related factor-2 and counter-regulated by Bach-1, in a heme-sensitive manner. Additionally, HMOX1 promoter polymorphisms have been associated with human disease. The induction of HO-1 can confer protection in inflammatory conditions through removal of heme, a pro-oxidant and potential catalyst of lipid peroxidation, whereas iron released from HO activity may trigger ferritin synthesis or ferroptosis. The production of heme-derived reaction products (i.e., BV, BR) may contribute to HO-dependent cytoprotection via antioxidant and immunomodulatory effects. Additionally, BVR and BR have newly recognized roles in lipid regulation. CO may alter mitochondrial function leading to modulation of downstream signaling pathways that culminate in anti-apoptotic, anti-inflammatory, anti-proliferative and immunomodulatory effects. This review will present evidence for beneficial effects of HO-1 and its reaction products in human diseases, including cardiovascular disease (CVD), metabolic conditions, including diabetes and obesity, as well as acute and chronic diseases of the liver, kidney, or lung. Strategies targeting the HO-1 pathway, including genetic or chemical modulation of HO-1 expression, or application of BR, CO gas, or CO donor compounds show therapeutic potential in inflammatory conditions, including organ ischemia/reperfusion injury. Evidence from human studies indicate that HO-1 expression may represent a biomarker of oxidative stress in various clinical conditions, while increases in serum BR levels have been correlated inversely to risk of CVD and metabolic disease. Ongoing human clinical trials investigate the potential of CO as a therapeutic in human disease.

MicroRNA-137-3p Improves Nonalcoholic Fatty Liver Disease through Activating AMPKα

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide and can develop to nonalcoholic steatohepatitis and later hepatic cirrhosis with a high prevalence to hepatocellular carcinoma. Oxidative stress and chronic hepatic inflammation are implicated in the pathogenesis of NAFLD. MicroRNA-137-3p (miR-137-3p) are associated with oxidative stress and inflammation; however, its role and mechanism in NAFLD remain unclear. Mice were fed with a high-fat diet (HFD) for 24 weeks to establish the NAFLD model. To overexpress or suppress hepatic miR-137-3p expression, mice were intraperitoneally injected with the agomir, antagomir, or respective controls of miR-137-3p at a dose of 100 mg/kg weekly for 6 consecutive weeks before the mice were sacrificed. To validate the involvement of AMP-activated protein kinase alpha (AMPKα) or cAMP-specific phosphodiesterase 4D (PDE4D), HFD mice were intraperitoneally injected with 20 mg/kg compound C or 0.5 mg/kg rolipram every other day for 8 consecutive weeks before the mice were sacrificed. Hepatic miR-137-3p expression was significantly decreased in mice upon HFD stimulation. miR-137-3p agomir alleviated, while miR-137-3p antagomir facilitated HFD-induced oxidative stress, inflammation, and hepatic dysfunction in mice. Mechanistically, we revealed that miR-137-3p is directly bound to the 3'-untranslated region of PDE4D and subsequently increased hepatic cAMP level and protein kinase A activity, thereby activating the downstream AMPKα pathway. In summary, miR-137-3p improves NAFLD through activating AMPKα and it is a promising therapeutic candidate to treat NAFLD.

Melatonin-primed ADMSCs elicit an efficacious therapeutic response in improving high-fat diet induced non-alcoholic fatty liver disease in C57BL/6J mice

Background

Stem cells are widely used for therapy including treatment of liver damage. Adipose-derived mesenchymal stem cells (ADMSCs) administered to treat fatty liver are known to improve liver function but their use is restricted due to a poor success rate. This study investigates efficacy of melatonin-primed ADMSCs (Mel. MSCs) in experimentally induced non-alcoholic fatty liver disease (NAFLD).

Results

MSCs treated with LPS showed prominent DCFDA fluorescence as compared to the untreated cells. Also, the JC-1 staining had accounted for higher intensity of green monomer and a weak fluorescence of red dimer indicating weaker mitochondrial membrane potential. But melatonin co-treatment could make necessary corrective changes as evidenced by reverse set of results. The overall cell survival was also found to be improved following melatonin treatment as evidenced by the MTT assay. Also, the antioxidant (Nrf2 and Ho-1) and anti-inflammatory genes (Il-4 and Il-10) showed a decrement in their mRNA levels following LPS treatment whereas the pro-inflammatory genes (Tnf-α, Il-6, Tlr-4, and Lbp) showed a reciprocal increment in the said group. Melatonin co-treatment accounted for an improved status of antioxidant and anti-inflammatory genes as evidenced by their mRNA levels. High-fat high-fructose diet (HFFD) fed C57BL/6J mice recorded higher serum AST and ALT levels and fatty manifestation in histology of liver along with lowered mRNA levels of antioxidant (Nrf2, Catalase, and Gss) genes and Hgf. These set of parameters showed a significant improvement in HFFD + Mel.MSC group.

Conclusion

A significant improvement in viability of MSCs was recorded due to lowered intracellular oxidative stress and improves mitochondrial membrane potential. Further, melatonin-primed MSCs accounted for a significant decrement in fatty manifestations in liver and an improved physiological status of NAFLD in HFFD fed C57BL/6J mice. Taken together, it is hypothesized that melatonin priming to MSCs prior to its use can significantly augment the success of stem cell therapy.

Carbon Monoxide-Neuroglobin Axis Targeting Metabolism Against Inflammation in BV-2 Microglial Cells

Microglia are the immune competent cell of the central nervous system (CNS), promoting brain homeostasis and regulating inflammatory response against infection and injury. Chronic or exacerbated neuroinflammation is a cause of damage in several brain pathologies. Endogenous carbon monoxide (CO), produced from the degradation of heme, is described as anti-apoptotic and anti-inflammatory in several contexts, including in the CNS. Neuroglobin (Ngb) is a haemoglobin-homologous protein, which upregulation triggers antioxidant defence and prevents neuronal apoptosis. Thus, we hypothesised a crosstalk between CO and Ngb, in particular, that the anti-neuroinflammatory role of CO in microglia depends on Ngb. A novel CO-releasing molecule (ALF826) based on molybdenum was used for delivering CO in microglial culture.BV-2 mouse microglial cell line was challenged with lipopolysaccharide (LPS) for triggering inflammation, and after 6 h ALF826 was added. CO exposure limited inflammation by decreasing inducible nitric oxide synthase (iNOS) expression and the production of nitric oxide (NO) and tumour necrosis factor-α (TNF-α), and by increasing interleukine-10 (IL-10) release. CO-induced Ngb upregulation correlated in time with CO's anti-inflammatory effect. Moreover, knocking down Ngb reversed the anti-inflammatory effect of CO, suggesting that dependents on Ngb expression. CO-induced Ngb upregulation was independent on ROS signalling, but partially dependent on the transcriptional factor SP1. Finally, microglial cell metabolism is also involved in the inflammatory response. In fact, LPS treatment decreased oxygen consumption in microglia, indicating a switch to glycolysis, which is associated with a proinflammatory. While CO treatment increased oxygen consumption, reverting LPS effect and indicating a metabolic shift into a more oxidative metabolism. Moreover, in the absence of Ngb, this phenotype was no longer observed, indicating Ngb is needed for CO's modulation of microglial metabolism. Finally, the metabolic shift induced by CO did not depend on alteration of mitochondrial population. In conclusion, neuroglobin emerges for the first time as a key player for CO signalling against exacerbated inflammation in microglia.

Up-regulation of Nrf2/P62/Keap1 involves in the anti-fibrotic effect of combination of monoammonium glycyrrhizinate and cysteine hydrochloride induced by CCl4

Combination of monoammonium glycyrrhizinate and cysteine hydrochloride (MG-CH) has been used in the treatment of chronic liver disease for decades, however, its mechanism is still unclear. Our previous studies showed that MG-CH confers the optimal therapeutic effect at the ratio of 2:1 to against acute liver damage. In this study, it was used to investigate the anti-fibrotic effect induced by CCl₄. The results showed that injection of MG-CH produced anti-fibrotic effect ranged from 30 mg/kg to 60 mg/kg, evidenced by decreased the collagens deposition and inhibited the production of hydroxyproline. Mechanism study found that Nrf2/ARE signaling pathway was activated by MG-CH, whereas loss of hepatocytic Nrf2 abolished its anti-fibrotic effect significantly. Furthermore, it was demonstrated that MG-CH is a non-canonical NRF2 inducer, which promoted the autophagy activity and release the Nrf2 from keap 1 by promoting the phosphorylation of p62 at Ser351. Knockdown of p62 abolished the enhancement of nuclear accumulation of Nrf2 by MG-CH. All of these results suggested that up-regulation of Nrf2/P62/Keap1 involves in the anti-fibrotic effect of MG-CH, which provide a rational explanation for the usage of MG-CH in the treatment of fibrosis.

Ontogeny of Carbon Monoxide-Related Gene Expression in a Deep-Diving Marine Mammal

Marine mammals such as northern elephant seals (NES) routinely experience hypoxemia and ischemia-reperfusion events to many tissues during deep dives with no apparent adverse effects. Adaptations to diving include increased antioxidants and elevated oxygen storage capacity associated with high hemoprotein content in blood and muscle. The natural turnover of heme by heme oxygenase enzymes (encoded by HMOX1 and HMOX2) produces endogenous carbon monoxide (CO), which is present at high levels in NES blood and has been shown to have cytoprotective effects in laboratory systems exposed to hypoxia. To understand how pathways associated with endogenous CO production and signaling change across ontogeny in diving mammals, we measured muscle CO and baseline expression of 17 CO-related genes in skeletal muscle and whole blood of three age classes of NES. Muscle CO levels approached those of animals exposed to high exogenous CO, increased with age, and were significantly correlated with gene expression levels. Muscle expression of genes associated with CO production and antioxidant defenses (HMOX1, BVR, GPX3, PRDX1) increased with age and was highest in adult females, while that of genes associated with protection from lipid peroxidation (GPX4, PRDX6, PRDX1, SIRT1) was highest in adult males. In contrast, muscle expression of mitochondrial biogenesis regulators (PGC1A, ESRRA, ESRRG) was highest in pups, while genes associated with inflammation (HMOX2, NRF2, IL1B) did not vary with age or sex. Blood expression of genes involved in regulation of inflammation (IL1B, NRF2, BVR, IL10) was highest in pups, while HMOX1, HMOX2 and pro-inflammatory markers (TLR4, CCL4, PRDX1, TNFA) did not vary with age. We propose that ontogenetic upregulation of baseline HMOX1 expression in skeletal muscle of NES may, in part, underlie increases in CO levels and expression of genes encoding antioxidant enzymes. HMOX2, in turn, may play a role in regulating inflammation related to ischemia and reperfusion in muscle and circulating immune cells. Our data suggest putative ontogenetic mechanisms that may enable phocid pups to transition to a deep-diving lifestyle, including high baseline expression of genes associated with mitochondrial biogenesis and immune system activation during postnatal development and increased expression of genes associated with protection from lipid peroxidation in adulthood.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.

Dihydromyricetin attenuates palmitic acid-induced oxidative stress by promoting autophagy via SIRT3-ATG4B signaling in hepatocytes

BACKGROUND

Oxidative stress in hepatocytes was important pathogenesis of nonalcoholic steatohepatitis (NASH). Autophagy was a cellular process that can remove damaged organelles under oxidative stress, and thus presented a potential therapeutic target against NASH. This work aimed to investigate whether autophagy was participated in the protective effects of dihydromyricetin (DHM) on palmitic acid (PA)-induced oxidative stress in hepatocytes and the underlying mechanism.

METHODS

HepG2 and HHL-5 cell lines were pretreated with DHM (20 μM) for 2 h, followed by PA (0.2 mM) treatment for 16 h. The oxidative stress was assessed by the quantification of intracellular reactive oxygen species (ROS), mitochondrial ROS (mtROS), mitochondrial membrane potential (MMP) and mitochondrial ultrastructural analyses. The protein expressions of SIRT3, LC3I/II, P62 and ATG4B, as well as the acetylation of AGT4B were determined by western blotting using HepG2 and HepG2/ATG4B^± cells with heterozygous knockout of ATG4B.

RESULTS

Exposure to PA resulted in increased intracellular ROS and mtROS, decreased MMP and aggravated mitochondrial injury in HepG2 cells, which were notably attenuated by DHM treatment. DHM-induced inhibition of oxidative stress was associated with the induction of autophagy, characterized by upregulated ATG4B and LC3 II as well as downregulated P62 levels. Furthermore, the inhibitory effects of DHM on PA-induced autophagy arrest and oxidative stress were eliminated when pretreated with a SIRT3 inhibitor 3-TYP or conducted in HepG2/ATG4B^± cells, suggesting that SIRT3 and ATG4B were involved in DHM-induced benefits. Moreover, DHM treatment increased the protein expression of SIRT3 and SIRT3-dependent deacetylation of ATG4B in HepG2 cells.

CONCLUSION

Our results demonstrated that DHM attenuated PA-induced oxidative stress in hepatocytes through induction of autophagy, which was mediated through the increased expression of SIRT3 and SIRT3-mediated ATG4B deacetylation following DHM treatment.

Melatonin induces Nrf2-HO-1 reprogramming and corrections in hepatic core clock oscillations in Non-alcoholic fatty liver disease

Melatonin pleiotropically regulates physiological events and has a putative regulatory role in the circadian clock desynchrony-mediated Non-alcoholic fatty liver disease (NAFLD). In this study, we investigated perturbations in the hepatic circadian clock gene, and Nrf2-HO-1 oscillations in conditions of high-fat high fructose (HFHF) diet and/or jet lag (JL)-mediated NAFLD. Melatonin treatment (100 µM) to HepG2 cells led to an improvement in oscillatory pattern of clock genes (Clock, Bmal1, and Per) in oleic acid (OA)-induced circadian desynchrony, while Cry, Nrf2, and HO-1 remain oblivious of melatonin treatment that was also validated by circwave analysis. C57BL/6J mice subjected to HFHF and/or JL, and treated with melatonin showed an improvement in the profile of lipid regulatory genes (CPT-1, PPARa, and SREBP-1c), liver function (AST and ALT) and histomorphology of fatty liver. A detailed scrutiny revealed that hepatic mRNA and protein profiles of Bmal1 (at ZT6) and Clock (at ZT12) underwent corrective changes in oscillations, but moderate corrections were recorded in other components of clock genes (Per1, Per2, and Cry2). Melatonin induced changes in oscillations of anti-oxidant genes (Nrf2, HO-1, and Keap1) subtly contributed in the overall improvement in NAFLD recorded herein. Taken together, melatonin induced reprograming of hepatic core clock and Nrf2-HO-1 genes leads to an improvement in HFHF/JL-induced NAFLD.

Carbon Monoxide Therapy Using Hybrid Carbon Monoxide-Releasing/Nrf2-Inducing Molecules through a Neuroprotective Lens

Carbon monoxide (CO) has long been known for its toxicity. However, in recent decades, new applications for CO as a therapeutic compound have been proposed, and multiple forms of CO therapy have since been developed and studied. Previous research has found that CO has a role as a gasotransmitter and promotes anti-inflammatory and antioxidant effects, making it an avenue of interest for medicine. Such effects are possible because of the Nrf2/HO1 pathway, which has become a target for therapy development because its activation also leads to CO release. Currently, different forms of treatment involving CO include inhaled CO (iCO), carbon monoxide-releasing molecules (CORMs), and hybrid carbon monoxide-releasing molecules (HYCOs). In this article, we review the progression of CO studies to develop possible therapies, the possible mechanisms involved in the effects of CO, and the current forms of therapy using CO.

Green Tea and Epigallocatechin Gallate (EGCG) for the Management of Nonalcoholic Fatty Liver Diseases (NAFLD): Insights into the Role of Oxidative Stress and Antioxidant Mechanism

Nonalcoholic fatty liver diseases (NAFLD) represent a set of liver disorders progressing from steatosis to steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma, which induce huge burden to human health. Many pathophysiological factors are considered to influence NAFLD in a parallel pattern, involving insulin resistance, oxidative stress, lipotoxicity, mitochondrial dysfunction, endoplasmic reticulum stress, inflammatory cascades, fibrogenic reaction, etc. However, the underlying mechanisms, including those that induce NAFLD development, have not been fully understood. Specifically, oxidative stress, mainly mediated by excessive accumulation of reactive oxygen species, has participated in the multiple NAFLD-related signaling by serving as an accelerator. Ameliorating oxidative stress and maintaining redox homeostasis may be a promising approach for the management of NAFLD. Green tea is one of the most important dietary resources of natural antioxidants, above which epigallocatechin gallate (EGCG) notably contributes to its antioxidative action. Accumulative evidence from randomized clinical trials, systematic reviews, and meta-analysis has revealed the beneficial functions of green tea and EGCG in preventing and managing NAFLD, with acceptable safety in the patients. Abundant animal and cellular studies have demonstrated that green tea and EGCG may protect against NAFLD initiation and development by alleviating oxidative stress and the related metabolism dysfunction, inflammation, fibrosis, and tumorigenesis. The targeted signaling pathways may include, but are not limited to, NRF2, AMPK, SIRT1, NF-κB, TLR4/MYD88, TGF-β/SMAD, and PI3K/Akt/FoxO1, etc. In this review, we thoroughly discuss the oxidative stress-related mechanisms involved in NAFLD development, as well as summarize the protective effects and underlying mechanisms of green tea and EGCG against NAFLD.

Rosmarinic acid prevents refractory bacterial pneumonia through regulating Keap1/Nrf2-mediated autophagic pathway and mitochondrial oxidative stress

Methicillin-resistant Staphylococcus aureus (MRSA) is the leading cause of bacterial pneumonia, featured with exuberant inflammatory cytokine production, extensive oxidative stress and tissue injury. The Keap1/Nrf2 system is the major apparatus essential for host defense against oxidative and electrophilic stresses of both exogenous and endogenous origins, representing a logical target for host-directed strategy to treat severe inflammatory diseases including MRSA-induced pneumonia. In an effort to search therapeutics for bacterial pneumonia, we identify rosmarinic acid (RA) as a covalent modifier of Keap1 and hence an activator of Nrf2. Specifically, RA forms a covalent bond with the cysteine 151 of Keap1 in BTB domain, and blocks its association with Nrf2 for proteasome-mediated degradation. Consequently, RA treatment caused the increased Nrf2 nuclear translocation to initiate antioxidant and mitochondrial biogenic programs, as well as macrophage bactericidal activity through inducing autophagic pathway, which eventually led to expedited bacterial eradication, inflammation resolution, and disease recovery. Collectively, our findings establish RA as a specific inducer of Nrf2 and show its potential to prevent MRSA pneumonia.

Chemical Reactivities of Two Widely Used Ruthenium-Based CO-Releasing Molecules with a Range of Biologically Important Reagents and Molecules

Ruthenium-based CO-releasing molecules (CO-RMs), CORM-2 and CORM-3, have been widely used as surrogates of CO for studying its biological effects in vitro and in vivo with much success. However, several previous solution-phase and in vitro studies have revealed the ability of such CO-RMs to chemically modify proteins and reduce aromatic nitro groups due to their intrinsic chemical reactivity under certain conditions. In our own work of studying the cytoprotective effects of CO donors, we were in need of assessing chemical factors that could impact the interpretation of results from CO donors including CORM-2,3 in various in vitro assays. For this, we examined the effects of CORM-2,3 toward representative reagents commonly used in various bioassays including resazurin, tetrazolium salts, nitrites, and azide-based H₂S probes. We have also examined the effect of CORM-2,3 on glutathione disulfide (GSSG), which is a very important redox regulator. Our studies show the ability of these CO-RMs to induce a number of chemical and/or spectroscopic changes for several commonly used biological reagents under near-physiological conditions. These reactions/spectroscopic changes cannot be duplicated with CO-deleted CO-RMs (iCORMs), which are often used as negative controls. Furthermore, both CORM-2 and -3 are capable of consuming and reducing GSSG in solution. We hope that the results described will help in the future design of control experiments using Ru-based CO-RMs.

The effects of carbon monoxide releasing molecules on paraquat-induced pulmonary interstitial inflammation and fibrosis

Paraquat, an herbicide used extensively worldwide, can cause severe toxicity in humans and animals, leading to irreversible, lethal lung fibrosis. The potential of CO-releasing molecules (CORMs), substances that release CO (Carbon monoxide) within animal tissues, for treating paraquat-induced ROS generation and inflammation is investigated here. Our results show that the fast CO releaser CORM-3 (4-20 μM) acts as a potential scavenger of free radicals and decreases fibrosis progression by inhibiting paraquat-induced overexpression of connective tissue growth factor and angiotensin II in MRC-5 cells. The slow CO releaser CORM-A1 (5 mg/kg) clearly decreased expression of the lung profibrogenic cytokines COX-2, TNF-α, and α-SMA and serum hydroxyproline, resulting in a lower mortality rate in paraquat-treated mice. Mice treated with higher-dose CORM-A1 (10 mg/kg) had relatively intact lung lobes and fewer fibrotic patches by gross observation, with less collagen deposition, mesangial matrix accumulation, and pulmonary fibrosis resulting from the mitigation of TGF-β overexpression. In conclusion, our data demonstrate for the first time that CORM-A1 alleviated the development of the fibrotic process and improved survival rate in mice exposed to PQ, would be an attractive therapeutic approach to attenuate the progression of pulmonary fibrosis following PQ exposure.

S-allyl cysteine ameliorates heat stress-induced oxidative stress by activating Nrf2/HO-1 signaling pathway in BMECs

Heat stress-induced oxidative stress in bovine mammary epithelial cells (BMECs) threatens the normal growth and development of bovine mammary tissue, resulting in lower milk production of dairy cows. The aim of the present study is to investigate the protective effects of S-allyl cysteine (SAC), an organosulfur component extracted from aged garlic, on heat stress-induced oxidative stress and apoptosis in BMECs and to explore its underlying mechanisms. Our results showed that heat stress treatment considerably decreased cell viability, whereas SAC treatment dose-dependently restored cell viability of BMECs under heat-stress conditions. In addition, SAC protected BMECs from heat stress-induced oxidative damage by inhibiting the excessive accumulation of reactive oxygen species (ROS) and increasing the activity of antioxidant enzymes. It also inhibited heat stress-induced apoptosis by reducing the ratio of Bax/Bcl-2 and blocking proteolytic the cleavage of caspase-3 in BMECs. Interestingly, we found that the protective effect of SAC on heat stress-induced oxidative stress and apoptosis was dependent on the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. SAC promoted the Nrf2 nuclear translocation in heat stress-induced BMECs. The results were also validated by Nrf2 and Keap1 knockdown experiments further demonstrating that Nrf-2 was indeed involved in the protective effect of SAC on heat stress-induced oxidative damage and apoptosis. In summary, our results showed that SAC could protect BMECs from heat stress-induced injury by mediating the Nrf2/HO-1 signaling pathway, suggesting that SAC could be considered as a therapeutic drug for attenuating heat stress-induced mammary gland diseases.