L-Lactate Treatment at 24 h and 48 h after Acute Experimental Stroke Is Neuroprotective via Activation of the L-Lactate Receptor HCA.

Stroke is the main cause for acquired disabilities. Pharmaceutical or mechanical removal of the thrombus is the cornerstone of stroke treatment but can only be administered to a subset of patients and within a narrow time window. Novel treatment options are therefore required. Here we induced stroke by permanent occlusion of the distal medial cerebral artery of wild-type mice and knockout mice for the lactate receptor hydroxycarboxylic acid receptor 1 (HCA). At 24 h and 48 h after stroke induction, we injected L-lactate intraperitoneal. The resulting atrophy was measured in Nissl-stained brain sections, and capillary density and neurogenesis were measured after immunolabeling and confocal imaging. In wild-type mice, L-lactate treatment resulted in an HCA-dependent reduction in the lesion volume accompanied by enhanced angiogenesis. In HCA knockout mice, on the other hand, there was no increase in angiogenesis and no reduction in lesion volume in response to L-lactate treatment. Nevertheless, the lesion volumes in HCA knockout mice-regardless of L-lactate treatment-were smaller than in control mice, indicating a multifactorial role of HCA in stroke. Our findings suggest that L-lactate administered 24 h and 48 h after stroke is protective in stroke. This represents a time window where no effective treatment options are currently available.