Spatiotemporal regulation of hydrogen sulfide signaling in the kidney

Hydrogen sulfide (H2S) has long been recognized as a putrid, toxic gas. However, as a result of intensive biochemical research in the past two decades, H2S is now considered to be the third gasotransmitter alongside nitric oxide (NO) and carbon monoxide (CO) in mammalian systems. H2S-producing enzymes are expressed in all organs, playing an important role in their physiology. In the kidney, H2S is a critical regulator of vascular and cellular function, although the mechanisms that affect (sub)cellular levels of H2S are not precisely understood. H2S modulates systemic and renal blood flow, glomerular filtration rate and the renin-angiotensin axis through direct inhibition of nitric oxide synthesis. Further, H2S affects cellular function by modulating protein activity via post-translational protein modification: a process termed persulfidation. Persulfidation modulates protein activity, protein localization and protein-protein interactions. Additionally, acute kidney injury (AKI) due to mitochondrial dysfunction, which occurs during hypoxia or ischemia-reperfusion (IR), is attenuated by H2S. H2S enhances ATP production, prevents damage due to free radicals and regulates endoplasmic reticulum stress during IR. In this review, we discuss current insights in the (sub)cellular regulation of H2S anabolism, retention and catabolism, with relevance to spatiotemporal regulation of renal H2S levels. Together, H2S is a versatile gasotransmitter with pleiotropic effects on renal function and offers protection against AKI. Unraveling the mechanisms that modulate (sub)cellular signaling of H2S not only expands fundamental insight in the regulation of functional effects mediated by H2S, but can also provide novel therapeutic targets to prevent kidney injury due to hypoxic or ischemic injury

Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.

The Tricarboxylic Acid (TCA) Cycle is arguably the most critical metabolic cycle in physiology and exists as an essential interface coordinating cellular metabolism, bioenergetics, and redox homeostasis. Despite decades of research, a comprehensive investigation into the consequences of TCA cycle dysfunction remains elusive. Here, we targeted two TCA cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), and combined metabolomics, transcriptomics, and proteomics analyses to fully appraise the consequences of TCA cycle inhibition (TCAi) in murine kidney epithelial cells. Our comparative approach shows that TCAi elicits a convergent rewiring of redox and amino acid metabolism dependent on the activation of ATF4 and the integrated stress response (ISR). Furthermore, we also uncover a divergent metabolic response, whereby acute FHi, but not SDHi, can maintain asparagine levels via reductive carboxylation and maintenance of cytosolic aspartate synthesis. Our work highlights an important interplay between the TCA cycle, redox biology, and amino acid homeostasis

Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.

The Tricarboxylic Acid (TCA) Cycle is arguably the most critical metabolic cycle in physiology and exists as an essential interface coordinating cellular metabolism, bioenergetics, and redox homeostasis. Despite decades of research, a comprehensive investigation into the consequences of TCA cycle dysfunction remains elusive. Here, we targeted two TCA cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), and combined metabolomics, transcriptomics, and proteomics analyses to fully appraise the consequences of TCA cycle inhibition (TCAi) in murine kidney epithelial cells. Our comparative approach shows that TCAi elicits a convergent rewiring of redox and amino acid metabolism dependent on the activation of ATF4 and the integrated stress response (ISR). Furthermore, we also uncover a divergent metabolic response, whereby acute FHi, but not SDHi, can maintain asparagine levels via reductive carboxylation and maintenance of cytosolic aspartate synthesis. Our work highlights an important interplay between the TCA cycle, redox biology, and amino acid homeostasis

Overexpression of Cystathionine gamma-Lyase Suppresses Detrimental Effects of Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3) is a polyglutamine (polyQ) disorder caused by a CAG repeat expansion in the ataxin-3 (ATXN3) gene resulting in toxic protein aggregation. Inflammation and oxidative stress are considered secondary factors contributing to the progression of this neurodegenerative disease. There is no cure that halts or reverses the progressive neurodegeneration of SCA3. Here we show that overexpression of cystathionine.-lyase, a central enzyme in cysteine metabolism, is protective in a Drosophila model for SCA3. SCA3 flies show eye degeneration, increased oxidative stress, insoluble protein aggregates, reduced levels of protein persulfidation and increased activation of the innate immune response. Overexpression of Drosophila cystathionine.-lyase restores protein persulfidation, decreases oxidative stress, dampens the immune response and improves SCA3-associated tissue degeneration. Levels of insoluble protein aggregates are not altered; therefore, the data implicate a modifying role of cystathionine.-lyase in ameliorating the downstream consequence of protein aggregation leading to protection against SCA3-induced tissue degeneration. The cystathionine.-lyase expression is decreased in affected brain tissue of SCA3 patients, suggesting that enhancers of cystathionine.-lyase expression or activity are attractive candidates for future therapies

Nitric oxide is reduced to HNO (azanone) by ascorbic acid, tyrosine, and other alcohols. A new route for azanone formation in biological media.

The role of NO in biology is well established. However, an increasing body of evidence suggests that azanone (HNO), could also be involved in biological processes, some of which are attributed to NO. In this context, one of the most important and yet unanswered questions is whether and how HNO is produced in vivo. A possible route concerns the chemical or enzymatic reduction of NO. In the present work, we have taken advantage of a selective HNO sensing method, to show that NO is reduced to HNO by biologically relevant alcohols with moderate reducing capacity, such as ascorbate or tyrosine. The proposed mechanism involves a nucleophilic attack to NO by the alcohol, coupled to a proton transfer (PCNA: proton-coupled nucleophilic attack) and a subsequent decomposition of the so-produced radical to yield HNO and an alkoxyl radical. (Graph Presented).Fil: Suarez, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; ArgentinaFil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Álvarez, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Bikiel, Damian Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Brondino, Carlos Dante. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ivanovic Burmazovic, Ivana. Universitat Erlangen-Nuremberg; AlemaniaFil: Miljkovic, Jan Lj.. Universitat Erlangen-Nuremberg; AlemaniaFil: Filipovic, Milos R.. Universitat Erlangen-Nuremberg; AlemaniaFil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Doctorovich, Fabio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Naked mole-rats have distinctive cardiometabolic and genetic adaptations to their underground low-oxygen lifestyles.

Funder: School Of Biological and Behavioural Sciences, QMULThe naked mole-rat Heterocephalus glaber is a eusocial mammal exhibiting extreme longevity (37-year lifespan), extraordinary resistance to hypoxia and absence of cardiovascular disease. To identify the mechanisms behind these exceptional traits, metabolomics and RNAseq of cardiac tissue from naked mole-rats was compared to other African mole-rat genera (Cape, Cape dune, Common, Natal, Mahali, Highveld and Damaraland mole-rats) and evolutionarily divergent mammals (Hottentot golden mole and C57/BL6 mouse). We identify metabolic and genetic adaptations unique to naked mole-rats including elevated glycogen, thus enabling glycolytic ATP generation during cardiac ischemia. Elevated normoxic expression of HIF-1α is observed while downstream hypoxia responsive-genes are down-regulated, suggesting adaptation to low oxygen environments. Naked mole-rat hearts show reduced succinate levels during ischemia compared to C57/BL6 mouse and negligible tissue damage following ischemia-reperfusion injury. These evolutionary traits reflect adaptation to a unique hypoxic and eusocial lifestyle that collectively may contribute to their longevity and health span

Chemical Characterization of the Smallest <i>S</i>-Nitrosothiol, HSNO; Cellular Cross-talk of H₂S and <i>S</i>-Nitrosothiols

Dihydrogen sulfide recently emerged as a biological signaling molecule with important physiological roles and significant pharmacological potential. Chemically plausible explanations for its mechanisms of action have remained elusive, however. Here, we report that H₂S reacts with <i>S</i>-nitrosothiols to form thionitrous acid (HSNO), the smallest <i>S</i>-nitrosothiol. These results demonstrate that, at the cellular level, HSNO can be metabolized to afford NO⁺, NO, and NO^– species, all of which have distinct physiological consequences of their own. We further show that HSNO can freely diffuse through membranes, facilitating transnitrosation of proteins such as hemoglobin. The data presented in this study explain some of the physiological effects ascribed to H₂S, but, more broadly, introduce a new signaling molecule, HSNO, and suggest that it may play a key role in cellular redox regulation

Cytochrome <i>c</i> Reduction by H₂S Potentiates Sulfide Signaling

Hydrogen sulfide (H₂S) is an endogenously produced gas that is toxic at high concentrations. It is eliminated by a dedicated mitochondrial sulfide oxidation pathway, which connects to the electron transfer chain at the level of complex III. Direct reduction of cytochrome <i>c</i> (Cyt C) by H₂S has been reported previously but not characterized. In this study, we demonstrate that reduction of ferric Cyt C by H₂S exhibits hysteretic behavior, which suggests the involvement of reactive sulfur species in the reduction process and is consistent with a reaction stoichiometry of 1.5 mol of Cyt C reduced/mol of H₂S oxidized. H₂S increases O₂ consumption by human cells (HT29 and HepG2) treated with the complex III inhibitor antimycin A, which is consistent with the entry of sulfide-derived electrons at the level of complex IV. Cyt C-dependent H₂S oxidation stimulated protein persulfidation in vitro, while silencing of Cyt C expression decreased mitochondrial protein persulfidation in a cell culture. Cyt C released during apoptosis was correlated with persulfidation of procaspase 9 and with loss of its activity. These results reveal a potential role for the electron transfer chain in general, and Cyt C in particular, for potentiating sulfide-based signaling

Nitric Oxide Is Reduced to HNO by Proton-Coupled Nucleophilic Attack by Ascorbate, Tyrosine, and Other Alcohols. A New Route to HNO in Biological Media?

The role of NO in biology is well established. However, an increasing body of evidence suggests that azanone (HNO), could also be involved in biological processes, some of which are attributed to NO. In this context, one of the most important and yet unanswered questions is whether and how HNO is produced in vivo. A possible route concerns the chemical or enzymatic reduction of NO. In the present work, we have taken advantage of a selective HNO sensing method, to show that NO is reduced to HNO by biologically relevant alcohols with moderate reducing capacity, such as ascorbate or tyrosine. The proposed mechanism involves a nucleophilic attack to NO by the alcohol, coupled to a proton transfer (PCNA: proton-coupled nucleophilic attack) and a subsequent decomposition of the so-produced radical to yield HNO and an alkoxyl radical