Elamipretide (SS-31) and Nicotinamide Mononucleotide (NMN) Combination Therapy Targets TREM2 to Mitigate Post-ischemic Brain Injury in Mice.

Ischemic stroke is a severe cerebrovascular disorder characterized by a cascade of pathological processes, including neuroinflammation and apoptosis. These processes lead to high mortality rates and long-term disabilities, imposing substantial socioeconomic burdens. Although reperfusion therapies have improved patient outcomes, many remain ineligible due to narrow therapeutic windows or clinical contraindications. Consequently, developing novel neuroprotective strategies is of significant clinical importance. Elamipretide (SS-31) and nicotinamide mononucleotide (NMN) are well-documented neuroprotective agents operating through distinct mechanisms; however, their combined efficacy and underlying mechanisms in ischemic stroke remain elusive. This study investigated the neuroprotective efficacy of SS-31 and NMN, alone or in combination, in a mouse model of ischemic stroke, with a specific focus on their modulation of triggering receptor expressed on myeloid cells 2 (TREM2)-mediated neuroinflammatory and apoptotic pathways. A middle cerebral artery occlusion/reperfusion (MCAO/R) model was established in male mice, followed by treatment with SS-31, NMN, or their combination. Therapeutic outcomes were evaluated using neurobehavioral scoring, histopathological staining, transcriptomic sequencing, and protein expression analyses. TREM2 overexpression experiments and specific pharmacological inhibition of the NF-κB pathway were conducted to elucidate the specific molecular mechanisms. Co-administration of SS-31 and NMN significantly attenuated post-ischemic brain damage and ameliorated neurological deficits (P < 0.0001), demonstrating effects markedly superior to either monotherapy. Transcriptomic profiling revealed that the combination therapy specifically modulated innate immune and apoptotic pathways, concomitant with a significant downregulation of TREM2. Mechanistically, the combination therapy effectively inhibited NF-κB (p65) activation, thereby downregulating TREM2 expression. This suppression attenuated microglial activation, reduced the expression of canonical pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6), and rebalanced the Bcl-2/Bax apoptotic axis. Overexpression of TREM2 entirely reversed these neuroprotective benefits. Combination therapy with SS-31 and NMN provides robust neuroprotection against ischemic stroke by suppressing the NF-κB/TREM2 signaling axis, thereby combinatorially modulating post-stroke neuroinflammation and apoptosis. These findings highlight a novel, multi-targeted strategy for precision stroke interventions.