Cooling and Sterile Inflammation in an Oxygen-Glucose-Deprivation/Reperfusion Injury Model in BV-2 Microglia

Abstract

Objective. Cold-inducible RNA-binding protein (CIRBP) has been shown to be involved not only in cooling-induced cellular protection but also as a mediator of sterile inflammation, a critical mechanism of the innate immune response in ischemia/reperfusion (I/R) injury. The role of microglia and its activation in cerebral I/R injury warrants further investigation as both detrimental and regenerative properties have been described. Therefore, we investigated the effects of cooling, specifically viability, activation, and release of damage associated molecular patterns (DAMPs) on oxygen glucose deprivation/reperfusion- (OGD/R-) induced injury in murine BV-2 microglial cells. Methods. Murine BV-2 microglial cells were exposed to 2 to 6 h OGD (0.2% O2 in glucose- and serum-free medium) followed by up to 19 h of reperfusion, simulated by restoration of oxygen (21% O2) and nutrients. Cells were maintained at either normothermia (37°C) or cooled to 33.5°C, 1 h after experimental start. Cultured supernatants were harvested after exposure to OGD for analysis of DAMP secretions, including high-mobility group box 1 (HMGB1), heat shock protein 70 (HSP70), and CIRBP, and cytotoxicity was assessed by lactate dehydrogenase releases after exposure to OGD and reperfusion. Intracellular cold-shock proteins CIRBP and RNA-binding motif 3 (RBM3) as well as caspases 9, 8, and 3 were also analyzed via Western blot analysis. Furthermore, inducible nitric oxide synthase (iNOS), ionized calcium-binding adaptor molecule 1 (Iba1), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), interleukin-1α (IL-1α), monocyte chemotactic protein 1 (MCP-1), transforming growth factor β (TGFβ), CIRBP, and RBM3 gene expressions were assessed via reverse transcription polymerase chain reaction, and TNF-α, IL-6, and IL-1β releases into the cultured supernatants were assessed via enzyme-linked immunosorbent assays (ELISA). Results. Prolonged exposure to OGD resulted in increased BV-2 necrotic cell death, which was attenuated by cooling. Cooling also significantly induced cold-shock proteins CIRBP and RBM3 gene expressions, with CIRBP expression more rapidly regulated than RBM3 and translatable to significantly increased protein expression. DAMPs including HMGB-1, HSP70, and CIRBP could be detected in cultured supernatants after 6 h of OGD with CIRBP release being significantly attenuated by cooling. Exposure to OGD suppressed cytokine gene expressions of IL-1β, TNF-α, MCP-1, and TGFβ independently of temperature management, whereas cooling led to a significant increase in IL-1α gene expression after 6 h of OGD. In the reperfusion phase, TNF-α and MCP-1 gene expressions were increased, and cooling was associated with significantly lower TGFβ gene expression. Interestingly, cooled Normoxia groups had significant upregulations of microglial activation marker, Iba1, IL-1β, and TNF-α gene expressions. Conclusion. BV-2 microglial cells undergo necrotic cell death resulting in DAMP release due to OGD/R-induced injury. Cooling conveyed neuroprotection in OGD/R-injury as observable in increased cell viability as well as induced gene expressions of cold shock proteins. As cooling alone resulted in both upregulation of microglial activation, expression of proinflammatory cytokines, and cold shock protein transcript and protein expression, temperature management might have ambiguous effects in sterile inflammation. However, cooling resulted in a significant decrease of extracellular CIRBP, which has recently been characterized as a novel DAMP and a potent initiator and mediator of inflammation.

Photobiomodulation Inhibits Ischemia-Induced Brain Endothelial Senescence via Endothelial Nitric Oxide Synthase

“…In fact, L-NAME has been widely employed to inhibit eNOS activity in various cellular studies [ 52 , 53 , 54 ]. Although it has been reported that iNOS expression and cellular death can be observed in endothelial cells (ECs) 4 h after OGD [ 55 ], iNOS levels return to normal levels 25 h after OGD [ 51 , 56 ]. We discovered in the present study that endostatin levels were increased by L-NAME at 48 h following OGD, suggesting that L-NAME modulates endostatin in an iNOS-independent manner.…”

Ferroptosis mediated by TNFSF9 interferes in acute ischaemic stroke reperfusion injury with the progression of acute ischaemic stroke

“…The cells with proper density should suck up the original culture medium, pre‐cool the PBS cells twice, then add 2 mL of glycose‐free culture medium (without serum) and put them into a mix gas incubator (37°C, 1% O 2 + 94% N 2 + 5% CO 2 ) for oxygen–glucose deprivation (OGD). After 6 h of OGD operation, discard the original culture medium and PBS cells twice, add 2 mL of high glucose culture medium (without serum) and put them into a normal incubator (37°C, 5% CO 2 ) for reoxygenation treatment to simulate reperfusion (Lücht et al., 2021; Xian et al., 2021). BV2 cells were infected with lentiviral particles, contained short hairpin (sh)RNA and exogenous over‐expression (OE) RNA according to the manufacturer's protocol.…”

Mechanisms of action behind the protective effects of proactive esophageal cooling during radiofrequency catheter ablation in the left atrium

“… 97 A large number of inflammatory markers have been shown to be inhibited by cooling. 80 , 86 , 93 , 117 , 118 , 119 , 123 , 124 , 125 , 126 , 127 , 128 , 129 Downregulatory effects are seen on the expression of MMP-9 mRNA and upregulating effects on the expression of chemokine (C-X-C motif) ligand 13 (CXCL13), lipopolysaccharide binding protein, and chemokine (C-C motif) ligand 6 (CCL6) and chemokine (C-C motif) ligand 24 (CCL24). These molecules have important functions in B-cell maturation, reduction in endotoxin load and improved bacterial opsonization, keratinocyte proliferation, and collagen synthesis and deposition by fibroblasts.…”