Mtfp1 ablation enhances mitochondrial respiration and protects against hepatic steatosis

Hepatic steatosis is the result of imbalanced nutrient delivery and metabolism in the liver and is the first hallmark of Metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD is the most common chronic liver disease and involves the accumulation of excess lipids in hepatocytes, inflammation, and cancer. Mitochondria play central roles in liver metabolism yet the specific mitochondrial functions causally linked to MASLD remain unclear. Here, we identify Mitochondrial Fission Process 1 protein (MTFP1) as a key regulator of mitochondrial and metabolic activity in the liver. Deletion of Mtfp1 in hepatocytes is physiologically benign in mice yet leads to the upregulation of oxidative phosphorylation (OXPHOS) activity and mitochondrial respiration, independently of mitochondrial biogenesis. Consequently, liver-specific knockout mice are protected against high fat diet-induced steatosis and metabolic dysregulation. Additionally, Mtfp1 deletion inhibits mitochondrial permeability transition pore opening in hepatocytes, conferring protection against apoptotic liver damage in vivo and ex vivo. Our work uncovers additional functions of MTFP1 in the liver, positioning this gene as an unexpected regulator of OXPHOS and a therapeutic candidate for MASLD.

H2S Prodrug, SG-1002, Protects against Myocardial Oxidative Damage and Hypertrophy In Vitro via Induction of Cystathionine β-Synthase and Antioxidant Proteins

Endogenously produced hydrogen sulfide (H₂S) is critical for cardiovascular homeostasis. Therapeutic strategies aimed at increasing H₂S levels have proven cardioprotective in models of acute myocardial infarction (MI) and heart failure (HF). The present study was undertaken to investigate the effects of a novel H₂S prodrug, SG-1002, on stress induced hypertrophic signaling in murine HL-1 cardiac muscle cells. Treatment of HL-1 cells with SG-1002 under serum starvation without or with H₂O₂ increased the levels of H₂S, H₂S producing enzyme, and cystathionine β-synthase (CBS), as well as antioxidant protein levels, such as super oxide dismutase1 (SOD1) and catalase, and additionally decreased oxidative stress. SG-1002 also decreased the expression of hypertrophic/HF protein markers such as atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), galectin-3, TIMP1, collagen type III, and TGF-β1 in stressed HL-1 cells. Treatment with SG-1002 caused a significant induction of cell viability and a marked reduction of cellular cytotoxicity in HL-1 cells under serum starvation incubated without or with H₂O₂. Experimental results of this study suggest that SG-1002 attenuates myocardial cellular oxidative damage and/or hypertrophic signaling via increasing H₂S levels or H₂S producing enzymes, CBS, and antioxidant proteins.

CHCHD10 and SLP2 control the stability of the PHB complex: a key factor for motor neuron viability

CHCHD10 is an amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) gene that encodes a mitochondrial protein whose precise function is unclear. Here we show that CHCHD10 interacts with the Stomatin-Like Protein 2 (SLP2) and participates to the stability of the Prohibitin (PHB) complex in the inner mitochondrial membrane. By using patient fibroblasts and mouse models expressing the same CHCHD10 variant (p.Ser59Leu), we show that SLP2 forms aggregates with prohibitins, found in vivo in the hippocampus and as aggresome-like inclusions in spinal motor neurons of Chchd10S59L/+ mice. Affected cells and tissues display instability of the PHB complex which participates at least in part to the activation of the OMA1 cascade with OPA1 processing leading to mitochondrial fragmentation, abnormal mitochondrial cristae morphogenesis and neuronal death found in spinal cord and the hippocampus of Chchd10S59L/+ animals. Destabilization of the PHB complex leads to the instability of the mitochondrial contact site and cristae organizing system (MICOS) complex, likely via the disruption of OPA1/Mitofilin interaction. Thus, SLP2/PHB aggregates and destabilization of the PHB complex are critical in the sequence of events leading to motor neuron death in CHCHD10S59L-related disease.

Effects of a novel hydrogen sulfide prodrug in a porcine model of acute limb ischemia

OBJECTIVE

Previous studies have shown that hydrogen sulfide (H₂S) exerts potent proangiogenic properties under in vitro conditions and in rodent models. We sought to determine whether a novel H₂S prodrug promotes peripheral revascularization in a swine model of acute limb ischemia (ALI).

METHODS

ALI was induced in 17 female miniswine via intravascular occlusion of the external iliac. At day 7 after ALI induction, miniswine (n = 17) were randomized to received placebo or the H₂S prodrug, SG-1002 (800 mg per os twice a day), for 35 days. At day 35 SG-1002 increased circulating levels of H₂S (5.0 ± 1.2 μmol/L vs 1.8 ± 0.50 μmol/L; P < .05), sulfane sulfur (10.6 ± 2.3 μmol/L vs 2.6 ± 0.8 μmol/L; P < .05), and nitrite (0.5 ± 0.05 μmol/L vs 0.3 ± 0.03 μmol/L; P < .005) compared with placebo. SG-1002 therapy increased angiographic scoring in ischemic limb vessel number (27.6 ± 1.6 vs 22.2 ± 1.8; P < .05) compared with placebo. Treatment with SG-1002 preserved existing capillaries in ischemic limbs (128.3 ± 18.7 capillaries/mm² vs 79.0 ± 9.8 capillaries/mm²; P < .05) compared with placebo. Interestingly, treatment with SG-1002 also improved coronary vasorelaxation responses to bradykinin and substance P in miniswine with ALI.

CONCLUSIONS

Our results suggest that daily administration of the H₂S prodrug, SG-1002, leads to an increase in circulating H₂S and nitric oxide signaling and preserves vessel number and density in ischemic limbs. Furthermore, SG-1002 therapy improved endothelial-dependent coronary artery vasorelaxation in the setting of ALI. Our data demonstrate that SG-1002 preserves the vascular architecture in ischemic limbs and exerts vascular protective effects in the coronary vasculature in a model of peripheral vascular disease.

Protective Actions of H2S in Acute Myocardial Infarction and Heart Failure

Hydrogen sulfide (H2S) was identified as the third gasotransmitter in 1996 following the discoveries of the biological importance of nitric oxide and carbon monoxide. Although H2S has long been considered a highly toxic gas, the discovery of its presence and enzymatic production in mammalian tissues supports a critical role for this physiological signaling molecule. H2S is synthesized endogenously by three enzymes: cystathionine β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. H2S plays a pivotal role in the regulation of cardiovascular function as H2S has been shown to modulate: vasodilation, angiogenesis, inflammation, oxidative stress, and apoptosis. Perturbation of endogenous production of H2S has been associated with many pathological conditions of the cardiovascular system such as diabetes, heart failure, and hypertension. As such, modulation of the endogenous H2S signaling pathway or administration of exogenous H2S has been shown to be cytoprotective. This review article will provide a summary of the current body of evidence on the role of H2S signaling in the setting of myocardial ischemia and heart failure. © 2017 American Physiological Society. Compr Physiol 7:583-602, 2017.

Nitrite Therapy Ameliorates Myocardial Dysfunction via H2S and Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2)-Dependent Signaling in Chronic Heart Failure

BACKGROUND

Bioavailability of nitric oxide (NO) and hydrogen sulfide (H2S) is reduced in heart failure (HF). Recent studies suggest cross-talk between NO and H2S signaling. We previously reported that sodium nitrite (NaNO2) ameliorates myocardial ischemia-reperfusion injury and HF. Nuclear factor-erythroid-2-related factor 2 (Nrf2) regulates the antioxidant proteins expression and is upregulated by H2S. We examined the NaNO2 effects on endogenous H2S bioavailability and Nrf2 activation in mice subjected to ischemia-induced chronic heart failure (CHF).

METHODS AND RESULTS

Mice underwent 60 minutes of left coronary artery occlusion and 4 weeks of reperfusion. NaNO2 (165 μg/kgic) or vehicle was administered at reperfusion and then in drinking water (100 mg/L) for 4 weeks. Left ventricular (LV), ejection fraction (EF), LV end diastolic (LVEDD) and systolic dimensions (LVESD) were determined at baseline and at 4 weeks of reperfusion. Myocardial tissue was analyzed for oxidative stress and respective gene/protein-related assays. We found that NaNO2 therapy preserved LVEF, LVEDD and LVSD at 4 weeks during ischemia-induced HF. Myocardial malondialdehyde and protein carbonyl content were significantly reduced in NaNO2-treated mice as compared to vehicle, suggesting a reduction in oxidative stress. NaNO2 therapy markedly increased expression of Cu,Zn-superoxide dismutase, catalase, and glutathione peroxidase during 4 weeks of reperfusion. Furthermore, NaNO2 upregulated the activity of Nrf2, as well as H2S-producing enzymes, and ultimately increased H2S bioavailability in ischemia-induced CHF in mice as compared with vehicle.

CONCLUSIONS

Our results demonstrate that NaNO2 therapy significantly improves LV function via increasing H2S bioavailability, Nrf2 activation, and antioxidant defenses.

Abstract 132: A Novel Hydrogen Sulfide (H 2 S) Prodrug, SG1002, Protects Against Myocardial Oxidative Damage and Hypertrophic Signaling via Induction of Cystathionine &#914;-Synthase (CBS) and Antioxidant Proteins

Background: Endogenously produced H 2 S is critical for cardiovascular homeostasis. Therapeutic strategies aimed at increasing H 2 S levels have proven cardioprotective in models of acute myocardial infarction and heart failure (HF). The present study was under taken to investigate the effects of a novel H 2 S prodrug, SG1002, on stress induced hypertrophic signaling in murine HL1 cardiomyocytes.

Methods: HL1 cells were maintained either in serum starvation (1%) or serum containing (10%) media followed by treatment either with SG1002 or H 2 O 2 , or endothelin-1 (ET-1)/phenylephrine (Phe) or in combination. Treated cells were analyzed for specific experimental needs.

Results: SG1002 significantly increased cellular levels of the H 2 S producing enzyme, CBS, as well as production of H 2 S and nitrosothiol in HL1 cells cultured both in serum starvation or serum containing media. SG1002 significantly inhibited H 2 O 2 and ET-1/Phe induced oxidative stress in both culture media as measured by advanced protein oxidation products and MDA levels. Expression of ANP and BNP were markedly attenuated by SG1002 treatment. Cells cultured in media supplemented with serum containing H 2 O 2 /(ET-1 or Phe) or in 1% serum exhibited decreased levels of CBS, SOD1, and catalase. When the HL1 cells were coincubated with SG1002 cellular damage from oxidative stress was significantly attenuated accompanied by an increase in CBS expression.

Conclusion: Our data clearly demonstrate that SG1002 attenuates myocardial cellular damage via increasing antioxidant proteins. SG1002 directly increases H 2 S levels and upregulates CBS. Studies are currently underway to evaluate the clinical utility of SG1002 in HF.

Zofenopril Protects Against Myocardial Ischemia-Reperfusion Injury by Increasing Nitric Oxide and Hydrogen Sulfide Bioavailability

Background

Zofenopril, a sulfhydrylated angiotensin‐converting enzyme inhibitor (ACEI), reduces mortality and morbidity in infarcted patients to a greater extent than do other ACEIs. Zofenopril is a unique ACEI that has been shown to increase hydrogen sulfide (H₂S) bioavailability and nitric oxide (NO) levels via bradykinin‐dependent signaling. Both H₂S and NO exert cytoprotective and antioxidant effects. We examined zofenopril effects on H₂S and NO bioavailability and cardiac damage in murine and swine models of myocardial ischemia/reperfusion (I/R) injury.

Methods and Results

Zofenopril (10 mg/kg PO) was administered for 1, 8, and 24 hours to establish optimal dosing in mice. Myocardial and plasma H₂S and NO levels were measured along with the levels of H₂S and NO enzymes (cystathionine β‐synthase, cystathionine γ‐lyase, 3‐mercaptopyruvate sulfur transferase, and endothelial nitric oxide synthase). Mice received 8 hours of zofenopril or vehicle pretreatment followed by 45 minutes of ischemia and 24 hours of reperfusion. Pigs received placebo or zofenopril (30 mg/daily orally) 7 days before 75 minutes of ischemia and 48 hours of reperfusion. Zofenopril significantly augmented both plasma and myocardial H₂S and NO levels in mice and plasma H₂S (sulfane sulfur) in pigs. Cystathionine β‐synthase, cystathionine γ‐lyase, 3‐mercaptopyruvate sulfur transferase, and total endothelial nitric oxide synthase levels were unaltered, while phospho‐endothelial nitric oxide synthase¹¹⁷⁷ was significantly increased in mice. Pretreatment with zofenopril significantly reduced myocardial infarct size and cardiac troponin I levels after I/R injury in both mice and swine. Zofenopril also significantly preserved ischemic zone endocardial blood flow at reperfusion in pigs after I/R.

Conclusions

Zofenopril‐mediated cardioprotection during I/R is associated with an increase in H₂S and NO signaling.

l-Cys/CSE/H2S pathway modulates mouse uterus motility and sildenafil effect

Sildenafil, a selective phosphodiesterase type 5 (PDE5) inhibitor, commonly used in the oral treatment for erectile dysfunction, relaxes smooth muscle of human bladder through the activation of hydrogen sulfide (H2S) signaling. H2S is an endogenous gaseous transmitter with myorelaxant properties predominantly formed from l-cysteine (l-Cys) by cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). Sildenafil also relaxes rat and human myometrium during preterm labor but the underlying mechanism is still unclear. In the present study we investigated the possible involvement of H2S as a mediator of sildenafil-induced effect in uterine mouse contractility. We firstly demonstrated that both enzymes, CBS and CSE were expressed, and able to convert l-Cys into H2S in mouse uterus. Thereafter, sildenafil significantly increased H2S production in mouse uterus and this effect was abrogated by CBS or CSE inhibition. In parallel, l-Cys, sodium hydrogen sulfide or sildenafil but not d-Cys reduced spontaneous uterus contractility in a functional study. The blockage of CBS and CSE reduced this latter effect even if a major role for CSE than CBS was observed. This data was strongly confirmed by using CSE(-/-) mice. Indeed, the increase in H2S production mediated by l-Cys or by sildenafil was not found in CSE(-/-) mice. Besides, the effect of H2S or sildenafil on spontaneous contractility was reduced in CSE(-/-) mice. A decisive proof for the involvement of H2S signaling in sildenafil effect in mice uterus was given by the measurement of cGMP. Sildenafil increased cGMP level that was significantly reduced by CSE inhibition. In conclusion, l-Cys/CSE/H2S signaling modulates the mouse uterus motility and the sildenafil effect. Therefore the study may open different therapeutical approaches for the management of the uterus abnormal contractility disorders.

Abstract 264: Nitrite Therapy Ameliorates Myocardial Injury via H2S and Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2)-Dependent Signaling in Chronic Heart Failure

Background: Nitric oxide (NO) and hydrogen sulfide (H 2 S) are reduced in congestive heart failure. Recent studies suggest cross-talk between NO and H 2 S signaling. We previously reported that sodium nitrite (NaNO 2 ) significantly ameliorates myocardial ischemia-reperfusion injury and heart failure. Nrf2 regulates the expression of antioxidant protein genes and is upregulated by H 2 S. We examined the effects of NaNO 2 therapy on endogenous H 2 S bioavailability and Nrf2 activation in mice subjected to ischemia-induced heart failure.

Materials and Methods: Mice underwent 60 min. of left coronary artery occlusion and 4 weeks (WKS) of reperfusion. NaNO 2 (165 μg/kg) or saline vehicle (VEH) was administered at reperfusion and then in drinking water (100 mg/L) for 4 wks. Left ventricular ejection fraction (LVEF) was determined at baseline and 4 wks of reperfusion. Myocardial tissue was collected and analyzed for oxidative stress status and respective gene/protein levels.

Results: NaNO 2 therapy preserved LVEF (47 ± 4% vs. 32 ± 4%, p < 0.01) and LV diastolic and systolic dimensions (LVEDD/LVESD; 4.0/3.1 mm vs. 4.5/3.9 mm, p < 0.05) at 4 wks. MDA and protein carbonyl contents were significantly reduced in NaNO 2 treated mice as compared to VEH. NaNO 2 markedly increased expression of CuZn-superoxide dismutase and catalase at 4 wks. Furthermore, NaNO 2 increased mRNA levels of H 2 S producing enzymes and H 2 S bioavailabilty. Cardiac Nrf2 activation was also observed with NaNO 2 therapy.

Conclusions: Our results demonstrate that NaNO 2 therapy significantly improves left ventricular function via by increasing H 2 S bioavailability, activation of Nrf2, and increased antioxidant defenses.1

Hydrogen Sulfide Levels and Nuclear Factor-Erythroid 2-Related Factor 2 (NRF2) Activity Are Attenuated in the Setting of Critical Limb Ischemia (CLI)

Background

Cystathionine γ-lyase, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase are endogenous enzymatic sources of hydrogen sulfide (H₂S). Functions of H₂S are mediated by several targets including ion channels and signaling proteins. Nuclear factor-erythroid 2-related factor 2 is responsible for the expression of antioxidant response element–regulated genes and is known to be upregulated by H₂S. We examined the levels of H₂S, H₂S-producing enzymes, and nuclear factor-erythroid 2-related factor 2 activation status in skeletal muscle obtained from critical limb ischemia (CLI) patients.

Methods and Results

Gastrocnemius tissues were attained postamputation from human CLI and healthy control patients. We found mRNA and protein levels of cystathionine γ-lyase, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase were significantly decreased in skeletal muscle of CLI patients as compared to control. H₂S and sulfane sulfur levels were significantly decreased in skeletal muscle of CLI patients. We also observed significant reductions in nuclear factor-erythroid 2-related factor 2 activation as well as antioxidant proteins, such as Cu, Zn-superoxide dismutase, catalase, and glutathione peroxidase in skeletal muscle of CLI patients. Biomarkers of oxidative stress, such as malondialdehyde and protein carbonyl formation, were significantly increased in skeletal muscle of CLI patients as compared to healthy controls.

Conclusions

The data demonstrate that H₂S bioavailability and nuclear factor-erythroid 2-related factor 2 activation are both attenuated in CLI tissues concomitant with significantly increased oxidative stress. Reductions in the activity of H₂S-producing enzymes may contribute to the pathogenesis of CLI.

Sustained release nitrite therapy results in myocardial protection in a porcine model of metabolic syndrome with peripheral vascular disease

Metabolic syndrome (MetS) reduces endothelial nitric oxide (NO) bioavailability and exacerbates vascular dysfunction in patients with preexisting vascular diseases. Nitrite, a storage form of NO, can mediate vascular function during pathological conditions when endogenous NO is reduced. The aims of the present study were to characterize the effects of severe MetS and obesity on dyslipidemia, myocardial oxidative stress, and endothelial NO synthase (eNOS) regulation in the obese Ossabaw swine (OS) model and to examine the effects of a novel, sustained-release formulation of sodium nitrite (SR-nitrite) on coronary vascular reactivity and myocardial redox status in obese OS subjected to critical limb ischemia (CLI). After 6 mo of an atherogenic diet, obese OS displayed a MetS phenotype. Obese OS had decreased eNOS functionality and NO bioavailability. In addition, obese OS exhibited increased oxidative stress and a significant reduction in antioxidant enzymes. The efficacy of SR-nitrite therapy was examined in obese OS subjected to CLI. After 3 wk of treatment, SR-nitrite (80 mg · kg(-1) · day(-1) bid po) increased myocardial nitrite levels and eNOS function. Treatment with SR-nitrite reduced myocardial oxidative stress while increasing myocardial antioxidant capacity. Ex vivo assessment of vascular reactivity of left anterior descending coronary artery segments demonstrated marked improvement in vasoreactivity to sodium nitroprusside but not to substance P and bradykinin in SR-nitrite-treated animals compared with placebo-treated animals. In conclusion, in a clinically relevant, large-animal model of MetS and CLI, treatment with SR-nitrite enhanced myocardial NO bioavailability, attenuated oxidative stress, and improved ex vivo coronary artery vasorelaxation.

A new therapeutic approach to erectile dysfunction: urotensin-II receptor high affinity agonist ligands

Urotensin-II (U-II) is a cyclic peptide that acts through a G protein-coupled receptor (urotensin-II receptor [UTR]) mainly involved in cardiovascular function in humans. The urotensinergic system is also implicated in the urogenital tract. Indeed, U-II relaxes human corpus cavernosum strips and causes an increase in intracavernous pressure (ICP) in rats. In light of this, the U-II/UTR pathway can be considered a new target for the treatment of erectile dysfunction. On this hypothesis, herein we report on two new UTR high affinity-agonists, P5U (H-Asp-c[Pen-Phe-Trp-Lys-Tyr-Cys]-Val-OH) and UPG84(H-Asp-c[Pen-Phe-DTrp-Orn-(pNH₂) Phe-Cys]-Val-OH). The effects of P5U and UPG84 were each compared separately with U-II by monitoring the ICP in anesthetized rats. Intracavernous injection of U-II (0.03–1 nmol), P5U (0.03–1 nmol) or UPG84 (0.03–1 nmol) caused an increase in ICP. P5U, in particular, elicited a significant increase in ICP as compared to U-II. The observed effect by using P5U at a dose of 0.1 nmol per rat was comparable to the effect elicited by U-II at a dose of 0.3 nmol. Moreover, UPG84 at the lowest dose (0.03 nmol) showed an effect similar to the highest dose of U-II (1 nmol). Furthermore, UPG84 was found to be more effective than P5U. Indeed, while the lowest dose of P5U (0.03 nmol) did not affect the ICP, UPG84, at the same dose, induced a prominent penile erection in rat. These compounds did not modify the blood pressure, which indicates a good safety profile. In conclusion, UPG84 and P5U may open new perspectives for the management of erectile dysfunction.

Effect of miR-21 and miR-30b/c on TRAIL-induced apoptosis in glioma cells

Glioblastoma is the most frequent brain tumor in adults and is the most lethal form of human cancer. Despite the improvements in treatments, survival of patients remains poor. To define novel pathways that regulate susceptibility to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in glioma, we have performed genome-wide expression profiling of microRNAs (miRs). We show that in TRAIL-resistant glioma cells, levels of different miRs are increased, and in particular, miR-30b/c and -21. We demonstrate that these miRs impair TRAIL-dependent apoptosis by inhibiting the expression of key functional proteins. T98G-sensitive cells treated with miR-21 or -30b/c become resistant to TRAIL. Furthermore, we demonstrate that miR-30b/c and miR-21 target respectively the 3' untranslated region of caspase-3 and TAp63 mRNAs, and that those proteins mediate some of the effects of miR-30 and -21 on TRAIL resistance, even in human glioblastoma primary cells and in lung cancer cells. In conclusion, we show that high expression levels of miR-21 and -30b/c are needed to maintain the TRAIL-resistant phenotype, thus making these miRs as promising therapeutic targets for TRAIL resistance in glioma.