Mitochondrial Cardiolipin-Targeted Tetrapeptide, SS-31, Exerts Neuroprotective Effects Within In Vitro and In Vivo Models of Spinal Cord Injury

Abstract

Spinal cord injury (SCI) affects millions globally, leading to severe motor and sensory deficits with no effective clinical treatment. Cardiolipin (CL), a mitochondria-specific phospholipid, plays a critical role in bioenergetics and apoptosis. Emerging evidence suggests that CL alterations contribute to secondary SCI pathology, but their precise role and underlying mechanisms remain fully understudied. In this study, we investigated the protective effects of SS-31 on CL alteration, neuronal death, tissue damage, and behavioral recovery after SCI using both in vitro and in vivo models, lipidomics analysis, histological evaluation, and behavioral assessments. In vitro investigations used primary spinal cord neuron cultures, challenged with either rotenone or glutamatergic excitotoxicity, with protective capabilities measured via cell death assays and neurite morphological analysis. In vivo investigations used female adult C57Bl/6 mice, challenged with a contusive SCI. The results showed that SS-31 reduced rotenone- and glutamate-induced mitochondrial dysfunction and neuronal death in a dose-dependent manner in vitro. Additionally, SS-31 attenuated rotenone- and glutamate-induced neurite degeneration in vitro. Lipidomics analysis revealed a reduction in CL at 24 h post-SCI in adult mice, which was attenuated by SS-31 in a dose-dependent manner. Consistent with this effect, SS-31 improved behavioral recovery after SCI in adult mice, although it had no significant effect on tissue damage. These findings suggest that CL alteration may play a key role in the pathogenesis of SCI, at least in the C57BL/6 mouse, and as such could be an attractive therapeutic target for ameliorating secondary SCI.