Protein S-nitrosylation preserves mitochondrial integrity and function during bovine muscle aging

This study is the first to reveal the regulatory role of protein S-nitrosylation in mitochondrial structure and function during bovine muscle aging. To manipulate S-nitrosylation levels, semimembranosus (SM) muscle samples were treated for 24 h with a nitric oxide (NO) donor (high S-nitrosylation, HSL), a nitric oxide synthase (NOS) inhibitor (low S-nitrosylation, LSL), or 0.9% saline (control, CON), followed by 168 h of aging. Results demonstrated that NO content, NOS activity, and S-nitrosothiol (SNO) content were elevated in the HSL group while reduced in the LSL group (P < 0.05). Besides, the HSL group exhibited markedly reduced mitochondrial Ca²⁺ load and reactive oxygen species (ROS) accumulation compared to the LSL group (P < 0.05). Furthermore, enhanced S-nitrosylation restrained mitochondrial permeability transition pore (MPTP) opening and attenuated the decline in mitochondrial membrane potential (MMP), consequently reducing cytochrome c release (P < 0.05). Meanwhile, HSL treatment preserved mitochondrial structural integrity, as evidenced by transmission electron microscope (TEM) observations. Correlation analysis further revealed significant associations between S-nitrosylation levels and mitochondrial functional indicators. Collectively, these findings provide the first evidence that protein S-nitrosylation maintains mitochondrial functional stability and structural integrity during beef SM aging. This work offers novel insights into meat quality regulation by targeting S-nitrosylation-mediated mitochondrial homeostasis.