Nimodipine exerts a protective effect against spreading depolarization and neuroinflammation

Abstract

Hypothesis, objective: Voltage gated Ca2+ channels (VGCCs) are widely expressed in the central nervous system and implicated in neuronal injury and microglial activation. Nimodipine, a potent cerebrovascular dilator and VGCC antagonist is found to be effective against the vasoconstriction caused by spreading depolarization (SD) in preclinical studies of ischemia. However, it is still unclear whether the beneficial effect of nimodipine is achieved by the improvement of perfusion or a direct action on neuronal or glial cells. Our aim was to explore the direct action of nimodipine on the nervous tissue and microglia. Methods: Brain slices prepared from C57BL/6 mice (n=16) were perfused with artificial cerebrospinal fluid (aCSF). After 30 min nimodipine (nimo; 10 μM) incubation, low glucose aCSF (5 mM) and transient anoxia (1 min) were applied to mimic ischemia and to elicit SD. Intrinsic optical signal imaging was used to analyze SD features, TTC staining was applied to assess tissue injury. Primary mixed and pure microglia cultures prepared from the cortex of neonatal SPRD rats were treated with lipopolysaccharide (LPS;20 ng/ml) and nimodipine (5,10,20 μM), alone or in combination for 24 h. Microglial activation was evaluated by Iba1 immunolabeling (degree of arborization expressed by a transformation index (TI)), Western blot analysis and the visualization of phagocytosis with fluorescent microbeads. Results: In brain slices, nimodipine reduced the focal area of SD (2.37±0.94 vs 3.38±0.88%, nimo vs control), the total cortical area affected by SD (17.12±8.63 vs 39.88±22.42%, nimo vs control) and the propagation velocity of SD (0.19±0.79 vs 1.59±2.29mm/min, nimo vs control). Nimodipine decreased tissue injury, viability expressed as the number of TTC-stained particles (4.48±1.45 vs 3.52±1.52 particle/1000 μm2, nimo vs control). Nimodipine reduced microglial activation in LPS-treated cultures reflected by more ramified cell morphology (3.1±0.91 vs 1.89±0.41 TI, LPS+nimo vs LPS), decreased Iba1 intensity in Western blot analysis (108.3±20.1 and 77.2±8.49 vs 213.4±29.7 integrated optical density, LPS+nimo 10 and 20 μM vs LPS) and attenuated phagocytic activity (6±10 vs 22±20 bead/cell LPS+nimo vs LPS). Conclusion: Nimodipine was protective against SD and successfully reduced neuroinflammation by decreasing microglial activation. Neuroprotection was achieved independent of nimodipine’s vascular action. Our data suggest that nimodipine may be applicable against neuroinflammation and ischemia, in which neurodegeneration is believed to be linked to neurotoxic microglial activation. NKFIH K134377 and K134334, H2020 No. 739593, NAP3.0, TKP2021-EGA-28 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.