Improvement of functional recovery by chronic metformin treatment is associated with enhanced alternative activation of microglia/macrophages and increased angiogenesis and neurogenesis following experimental stroke.

Acute AMPK activation exacerbates ischemic brain damage experimentally. Paradoxically, the clinical use of an AMPK activator metformin reduces the incidence of stroke. We investigated whether post-stroke chronic metformin treatment promotes functional recovery and tissue repair via an M2-polarization mechanism following experimental stroke. Mice were randomly divided to receive metformin or vehicle daily beginning at 24h after middle cerebral artery occlusion (MCAO). Neurological deficits were monitored for 30days following MCAO. To characterize the polarization of the microglia and infiltrating macrophages, the expression of the M1 and M2 signature genes was analyzed with qPCR, ELISA and immunohistochemistry. Post-MCAO angiogenesis and neurogenesis were examined immunohistochemically. An in vitro angiogenesis model was employed to examine whether metformin promoted angiogenesis in a M2 polarization-dependent manner. Post-stroke chronic metformin treatment had no impact on acute infarction but enhanced cerebral AMPK activation, promoted functional recovery and skewed the microglia/macrophages toward an M2 phenotype following MCAO. Metformin also significantly increased angiogenesis and neurogenesis in the ischemic brain. Consistently, metformin-induced M2 polarization of BV2 microglial cells depended on AMPK activation in vitro. Furthermore, treatment of brain endothelial cells with conditioned media collected from metformin-polarized BV2 cells promoted angiogenesis in vitro. In conclusion, post-stroke chronic metformin treatment improved functional recovery following MCAO via AMPK-dependent M2 polarization. Modulation of microglia/macrophage polarization represents a novel therapeutic strategy for stroke.

Jin Q ，Cheng J ，Liu Y ，Wu J ，Wang X ，Wei S ，Zhou X ，Qin Z ，Jia J ，Zhen X ... -  《-》

Berberine Facilitates Angiogenesis Against Ischemic Stroke Through Modulating Microglial Polarization via AMPK Signaling.

Zhu J ，Cao D ，Guo C ，Liu M ，Tao Y ，Zhou J ，Wang F ，Zhao Y ，Wei J ，Zhang Y ，Fang W ，Li Y ... -  《-》

Noggin improves ischemic brain tissue repair and promotes alternative activation of microglia in mice.

We previously reported that bone morphogenetic proteins (BMPs) and their endogenous antagonist noggin are expressed in the brain weeks after an ischemic insult. Here, to define their roles in ischemic brain tissue repair and remodeling, we infused recombinant BMP7 or noggin into the ipsilateral ventricle of mice for 2weeks starting 2weeks after transient middle cerebral artery occlusion (MCAO). Four weeks after MCAO, we measured ischemic brain volume, functional recovery, and molecules related to neurogenesis and angiogenesis such as synaptophysin, GAP-43, and VEGF. Noggin-treated mice but not BMP7-treated mice showed preserved ipsilateral brain volume and reduced neurological deficits compared with artificial cerebrospinal fluids (aCSF)-treated mice. Noggin treatment also decreased glial scar thickness, increased levels of GAP-43 and VEGF protein, and increased the number of Iba1-positive activated microglia in the ipsilateral brain. Furthermore, noggin treatment decreased M1 markers (IL-1β, TNF-α, IL-12, CCL2 and CD86) and increased M2 markers (IL-1ra, IL-10, arginase 1, CD206 and Ym1) of activated microglia, suggesting a shift from M1 to M2 phenotypes. These results suggest that noggin improves functional recovery from ischemic stroke and enhances alternatively activated microglia, thereby promoting tissue repair and remodeling.

Shin JA ，Lim SM ，Jeong SI ，Kang JL ，Park EM ... -  《-》

Astragaloside IV promotes microglia/macrophages M2 polarization and enhances neurogenesis and angiogenesis through PPARγ pathway after cerebral ischemia/reperfusion injury in rats.

Microglia/macrophages play a dual role in brain injury and repair following cerebral ischemia/reperfusion. Promoting microglia/macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotype has been considered as a potential treatment for ischemic stroke. Astragaloside IV (AS-IV) is a primary active ingredient of Chinese herb Radix Astragali, which protects against acute cerebral ischemic/reperfusion injury through its antioxidant, anti-inflammatory, and anti-apoptotic properties. However, it remains unknown whether AS-IV improves ischemic brain tissue repair and its underlying mechanism. A transient middle cerebral artery occlusion (tMCAO) rat model was used in this study. The results showed that AS-IV significantly improved long-term brain injury, reduced the expression of M1 microglia/macrophage markers and increased the expression of M2 microglia/macrophage markers 14 days after cerebral ischemia/reperfusion. AS-IV also increased peroxisome proliferator-activated receptor γ (PPARγ) mRNA and protein expression. Moreover, AS-IV promoted neurogenesis and angiogenesis, and increased the protein expression of brain-derived growth factor (BDNF), insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF). However, these beneficial effects were greatly blocked by PPARγ antagonist T0070907. These results together suggest that AS-IV could enhance neurogenesis, angiogenesis and neurological functional recovery, which may be partially through transforming microglia/macrophage from M1 to M2 phenotype in a PPARγ-dependent manner after cerebral ischemia/reperfusion injury. Therefore, AS-IV can be considered as a promising therapeutic agent for ischemic stroke.

Li L ，Gan H ，Jin H ，Fang Y ，Yang Y ，Zhang J ，Hu X ，Chu L ... -  《-》

Phthalide derivative CD21 alleviates cerebral ischemia-induced neuroinflammation: Involvement of microglial M2 polarization via AMPK activation.

Microglia can be activated to become the classic phenotype (M1) or alternative phenotype (M2), which play an important role in regulating neuroinflammatory response and tissue repair after ischemic stroke. CD21, a novel phthalide derivative, is a potential neuroprotectant against ischemic brain injury. The present study further investigated the effects of CD21 on post-ischemic microglial polarization and the underlying mechanisms. Transient middle cerebral artery occlusion (tMCAO) was used as a mouse model of ischemic stroke, while BV2 cells stimulated with conditioned medium collected from oxygen-glucose deprivation-treated HT22 cells were used in in vitro ischemic studies. The current results showed that CD21 dose-dependently and significantly improved neurological outcomes in tMCAO mice. Biochemical analyses revealed that CD21 decreased the expression of M1 phenotype markers (CD86, interleukin-1β and inducible nitric oxide synthase) and increased the expression of M2 phenotype markers (CD206, interleukin-10 and YM1/2) in both ischemic brain tissues and BV2 cells. Meanwhile, CD21 decreased the production of proinflammatory cytokines (interleukin-1β, interleukin-6 and tumor necrosis factor-α), promoted the release of the antiinflammatory cytokine (interleukin-10), and enhanced the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) in ischemic brain tissue and BV2 cells. Furthermore, the AMPK inhibitor (compound C) reversed these effects of CD21 in BV2 cells. These findings indicate that CD21 alleviates post-ischemic neuroinflammation through induction of microglial M2 polarization that is at least in part medicated by AMPK activation, suggesting that CD21 may be a promising candidate for protecting against ischemic brain injury.

Gan YM ，Liu DL ，Chen C ，Duan W ，Yang YX ，Du JR ... -  《-》