Systemic inflammation exacerbates developmental neurotoxicity induced by sevoflurane in neonatal rats.

BACKGROUND: General anaesthesia in the neonatal period has detrimental effects on the developing mammalian brain. The impact of underlying inflammation on anaesthesia-induced developmental neurotoxicity remains largely unknown. METHODS: Postnatal day 7 (PND7) rats were randomly assigned to receive sevoflurane (3 vol% for 3 h) or carrier gas 12 h after bacterial lipopolysaccharide (LPS; 1 µg g-1) or vehicle injection. Pharmacological inhibition of caspase-1 by Vx-765 (two doses of 50 µg g-1 body weight) was used to investigate mechanistic pathways of neuronal injury. Histomorphological injury and molecular changes were quantified 2 h after the end of anaesthesia. Long-term functional deficits were tested at 5-8 weeks of age using a battery of behavioural tests in the memory and anxiety domains. RESULTS: Sevoflurane or LPS treatment increased activated caspase-3 and caspase-9 expression in the hippocampal subiculum and CA1, which was greater when sevoflurane was administered in the setting of LPS-induced inflammation. Neuronal injury induced by LPS+sevoflurane treatment resulted in sex-specific behavioural outcomes when rats were tested at 5-8 weeks of age, including learning and memory deficits in males and heightened anxiety-related behaviour in females. Hippocampal caspase-1 and NLRP1 (NLR family pyrin domain containing 1), but not NLRP3, were upregulated by LPS or LPS+sevoflurane treatment, along with related proinflammatory cytokines, interleukin (IL)-1ß, and IL-18. Pretreatment with Vx-765, a selective caspase-1 inhibitor, led to reduced IL-1ß in LPS and LPS+sevoflurane groups. Caspase-1 inhibition by Vx-765 significantly decreased activated caspase-3 and caspase-9 immunoreactivity in the subiculum. CONCLUSIONS: Systemic inflammation promotes developmental neurotoxicity by worsening anaesthesia-induced neuronal damage with sex-specific behavioural outcomes. This highlights the importance of studying anaesthesia-induced neurotoxicity in more clinically relevant settings.

Role of microRNA-21 and Its Underlying Mechanisms in Inflammatory Responses in Diabetic Wounds.

A central feature of diabetic wounds is the persistence of chronic inflammation, which is partly due to the prolonged presence of pro-inflammatory (M1) macrophages in diabetic wounds. Persistence of the M1 macrophage phenotype and failure to transition to the regenerative or pro-remodeling (M2) macrophage phenotype plays an indispensable role in diabetic wound impairment; however, the mechanism underlying this relationship remains unclear. Recently, microRNAs have been shown to provide an additional layer of regulation of gene expression. In particular, microRNA-21 (miR-21) is essential for an inflammatory immune response. We hypothesize that miR-21 plays a role in regulating inflammation by promoting M1 macrophage polarization and the production of reactive oxygen species (ROS). To test our hypothesis, we employed an in vivo mouse skin wound model in conjunction with an in vitro mouse model to assess miR-21 expression and macrophage polarization. First, we found that miR-21 exhibits a distinct expression pattern in each phase of healing in diabetic wounds. MiR-21 abundance was higher during early and late phases of wound repair in diabetic wounds, while it was significantly lower in the middle phase of wounding (at days 3 and 7 following wounding). In macrophage cells, M1 polarized macrophages exhibited an upregulation of miR-21, as well as the M1 and pro-inflammatory markers IL-1b, TNFa, iNos, IL-6, and IL-8. Overexpression of miR-21 in macrophage cells resulted in an upregulation of miR-21 and also increased expression of the M1 markers IL-1b, TNFa, iNos, and IL-6. Furthermore, hyperglycemia induced NOX2 expression and ROS production through the HG/miR-21/PI3K/NOX2/ROS signaling cascade. These findings provide evidence that miR-21 is involved in the regulation of inflammation. Dysregulation of miR-21 may explain the abnormal inflammation and persistent M1 macrophage polarization seen in diabetic wounds.

Long Noncoding RNA GAS5 Regulates Macrophage Polarization and Diabetic Wound Healing.

A central feature of diabetic (Db) wounds is the persistence of chronic inflammation, which is partly due to the prolonged presence of proinflammatory (M1) macrophages. Using in vivo and in vitro analyses, we have tested the hypothesis that long noncoding RNA GAS5 is dysregulated in Db wounds. We have assessed the contribution of GAS5 to the M1 macrophage phenotype, as well as the functional consequences of knocking down its expression. We found that expression of GAS5 is increased significantly in Db wounds and in cells isolated from Db wounds. Hyperglycemia induced GAS5 expression in macrophages in vitro. Overexpression of GAS5 in vitro promoted macrophage polarization toward an M1 phenotype by upregulating signal transducer and activator of transcription 1. Of most significance in our judgment, GAS5 loss-of-function enhanced Db wound healing. These data indicate that the relative level of long noncoding RNA GAS5 in wounds plays a key role in the wound healing response. Reductions in the levels of GAS5 in wounds appeared to enhance healing by promoting transition of M1 macrophages to M2 macrophages. Thus, our results suggest that targeting long noncoding RNA GAS5 may provide a therapeutic intervention for correcting impaired Db wound healing.