Effect of Sema4D on microglial function in middle cerebral artery occlusion mice

Glia. 2015 Dec;63(12):2249-59. doi: 10.1002/glia.22890. Epub 2015 Jul 22.

Abstract

Cerebral ischemia evokes neuroinflammatory response. Inflammatory stimulation induces microglial activation, such as changes of their morphology from ramified to ameboid, expression of iNOS and cytokines, and the elevation of proliferative activity. Activated microglia play important roles in pathogenesis of cerebral ischemia. A previous study indicated that Sema4D promoted iNOS expression in cultured microglia; however, roles of Sema4D on microglial activation in ischemic injury remains unclear. We investigated the effect of Sema4D-deficiency on microglial activation by using permanent middle cerebral artery occlusion (MCAO) in mice. In this study, ischemia-induced activated microglia were classified into activated-ramified microglia and ameboid microglia based on their morphology. We demonstrated that the rate of iNOS expression in activated-ramified microglia was lower than that in ameboid microglia, while the most proliferating microglia were activated-ramified microglia but not ameboid microglia after cerebral ischemia. Sema4D-deficiency decreased the number of ameboid microglia and iNOS-expressing activated-ramified microglia in the peri-ischemic cortex. These changes by Sema4D-deficiency contributed to the reduction of NO production that was estimated by nitrite concentration in ischemic cortex. On the other hand, Sema4D-deficiency promoted proliferation of microglia in the peri-ischemic cortex. Importantly, ischemia-induced apoptosis and postischemic behavioral abnormality were moderated in Sema4D(-/-) mice. These findings suggest that Sema4D promotes cytotoxic activation of microglia and inhibits functional recovery after cerebral ischemia.

Keywords: MCAO; activation; iNOS expression; microglia; morphology; proliferation.

MeSH terms

  • Animals
  • Apoptosis / physiology
  • Calcium-Binding Proteins / metabolism
  • Cell Proliferation / physiology
  • Cerebral Cortex / metabolism*
  • Cerebral Cortex / pathology
  • Disease Models, Animal
  • Infarction, Middle Cerebral Artery / metabolism*
  • Infarction, Middle Cerebral Artery / pathology
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microfilament Proteins / metabolism
  • Microglia / metabolism*
  • Microglia / pathology
  • Motor Activity / physiology
  • Nitric Oxide Synthase Type II / metabolism
  • Recovery of Function / physiology
  • Semaphorins / metabolism*

Substances

  • Aif1 protein, mouse
  • Calcium-Binding Proteins
  • Microfilament Proteins
  • Sema4d protein, mouse
  • Semaphorins
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse