CSE/H 2S/SESN2 Signalling Mediates the Protective Effect of Exercise Against Immobilization-Induced Muscle Atrophy in Mice.

Hydrogen sulphide (H 2S), a gasotransmitter synthesized by cystathionine-γ-lyase (CSE), exhibits antioxidant properties and may mimic exercise-induced muscle protection. However, its mechanistic role in muscle atrophy and exercise intervention remains unclear.

Six-month-old male wild-type (WT) and SESN2 knockout (SESN2 -/-) C57BL/6J mice were subjected to a 2-week hindlimb immobilization, followed by combined resistance and aerobic exercise or pharmacological intervention using the H 2S donor NaHS (30 μmol/kg) or the CSE inhibitor DL-propargylglycine (PAG, 50 mg/kg). In vitro, C 2C 12 myotubes were treated with H 2O 2 and NaHS to assess oxidative stress injury.

Muscle mass, cross-sectional area (CSA), collagen deposition and oxidative stress markers were evaluated via histology, Western blot and immunofluorescence. Compared with the immobilization (IM) group, mice receiving a 2-week combined exercise intervention (IM + EX) exhibited significantly increased gastrocnemius muscle mass/body weight (10.86 ± 0.62 vs. 8.56 ± 1.61, p < 0.01), enlarged muscle fibre CSA (1628 ± 265 μm 2 vs. 905.5 ± 88.52 μm 2, p < 0.01) and reduced collagen deposition as indicated by Sirius red staining (collagen-positive area: 2.86% ± 1.12% vs. 7.06 ± 1.18%, p < 0.001).

Pharmacological inhibition of CSE with PAG significantly attenuated these exercise-induced improvements (muscle mass/body weight: 10.22 ± 0.59, CSA: 1139 ± 96.21 μm 2, collagen area: 5.04 ± 0.66%, all p < 0.05 vs. IM + EX).

Conversely, administration of the H 2S donor NaHS mimicked the protective effects of exercise, increasing muscle mass/body weight (8.94 ± 0.51), CSA (1474 ± 176.1 μm 2) and reducing collagen accumulation (collagen area: 3.04 ± 0.74%, all p < 0.05 vs. IM).

In vitro, NaHS treatment (30 μM) significantly reversed H 2O 2-induced reductions in myotube diameter (19.16 ± 0.91 μm vs. 15.61 ± 0.72 μm, p < 0.01) and improved fusion index (46.47 ± 1.51% vs. 35.28 ± 2.87%, p < 0.05). Western blot analysis showed that NaHS upregulated SESN2 and Nrf2 expression, as well as downstream antioxidant proteins HO-1 and NQO1 (p < 0.05), whereas SESN2 knockdown blocked these effects and abolished NaHS-mediated protection in myotubes.

In SESN2 -/- mice, NaHS failed to increase muscle mass/body weight (7.24 ± 1.3 vs. WT + NaHS 10.12 ± 0.38, p < 0.001), CSA (699.2 ± 21.51 μm 2 vs.

WT + NaHS 1189 ± 93.27 μm 2, p < 0.001) or antioxidant capacity, confirming the essential role of SESN2 in mediating H 2S-dependent muscle protection. H 2S protects against disuse-induced muscle atrophy by enhancing antioxidant defences via the SESN2/Nrf2 signalling pathway.

These findings identify H 2S as a potential exercise-mimetic therapeutic strategy for preserving muscle mass and function.