Hydrogen sulfide donor protects against mechanical ventilation-induced atrophy and contractile dysfunction in the rat diaphragm

Abstract

Mechanical ventilation (MV) is a clinical tool providing adequate alveolar ventilation in patients that require respiratory support. Although a life-saving intervention for critically ill patients, prolonged MV results in the rapid development of inspiratory muscle weakness due to both diaphragmatic atrophy and contractile dysfunction; collectively known as "ventilator-induced diaphragm dysfunction" (VIDD). VIDD is a severe clinical problem because diaphragmatic weakness is a risk factor for difficulties in weaning patients from MV. Currently, no standard treatment to prevent VIDD exists. Nonetheless, growing evidence reveals that hydrogen sulfide (H₂ S) possesses cytoprotective properties capable of protecting skeletal muscles against several hallmarks of VIDD, including oxidative damage, accelerated proteolysis, and mitochondrial damage. Therefore, we used an established animal model of MV to test the hypothesis that treatment with sodium sulfide (H₂ S donor) will defend against VIDD. Our results confirm that sodium sulfide was sufficient to protect the diaphragm against both MV-induced fiber atrophy and contractile dysfunction. H₂ S prevents MV-induced damage to diaphragmatic mitochondria as evidenced by protection against mitochondrial uncoupling. Moreover, treatment with sodium sulfide prevented the MV-induced activation of the proteases, calpain, and caspase-3 in the diaphragm. Taken together, these results support the hypothesis that treatment with a H₂ S donor protects the diaphragm against VIDD. These outcomes provide the first evidence that H₂ S has therapeutic potential to protect against MV-induced diaphragm weakness and to reduce difficulties in weaning patients from the ventilator. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Mechanical ventilation (MV) results in diaphragm atrophy and contractile dysfunction, known as ventilator-induced diaphragm dysfunction (VIDD). VIDD is important because diaphragm weakness is a risk factor for problems in weaning patients from MV. Currently, no accepted treatment exists to protect against VIDD. Growing evidence reveals that hydrogen sulfide (H₂ S) donors protect skeletal muscle against ischemia-reperfusion-induced injury. Nonetheless, it is unknown if treatment with a H₂ S donor can protect against VIDD. WHAT QUESTION DID THIS STUDY ADDRESS? Can treatment with an H₂ S donor protect against VIDD? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? This study provides the first evidence that treatment with a H₂ S donor protects against VIDD. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? These new findings provide the basis for further exploration of H₂ S donors as a therapy to prevent VIDD and reduce the risk of problems in weaning patients from MV.

FIGURE 1

Hydrogen sulfide (H₂S) donor prevents diaphragm contractile dysfunction and fiber atrophy induced by mechanical ventilation. (a) Diaphragm specific force production as a function of the stimulation frequency (i.e., force‐frequency curve) measured in vitro in costal diaphragm strips following 12 h of mechanical ventilation (MV) or spontaneous breathing (SB). (b) Diaphragm muscle fiber cross‐sectional area in type I, type IIa, and type IIx/b fibers. Values are means ± SD. ^Significantly different versus SB‐Sham and MV‐Sham. *Significantly different versus all groups (p < 0.05)

FIGURE 2

Hydrogen sulfide (H₂S) donor prevents mechanical ventilation‐induced oxidative stress, mitochondrial dysfunction, and protease activation in diaphragm. (a) The relative abundance of 4‐hydroxynonenal (4‐HNE)‐modified proteins (index of lipid peroxidation). (b) Mitochondrial respiratory control ratio (state 3/state 4; RCR). (c) Calpain‐mediated cleavage of αII‐spectrin releases a specific breakdown product at 145 kDa; abundance of this product is a surrogate biomarker of calpain activity. (d) Caspase‐3 mediated cleavage of αII‐spectrin releases a specific breakdown product at 120 kDa; abundance of this product is a surrogate biomarker of caspase‐3 activity. Note that the lane labeled as “x” in the gel scan of αII‐spectrin was excluded from the analysis. Values are means ± SD. *Significantly different versus all groups (p < 0.05)