Abstract
A study was conducted to investigate the effect of interleukin-1β (IL-1β) on hypoxia ischemia (HI) of cultured astrocyte and neonatal rat models and to explore the underlying molecular regulation mechanism. Primary rat astrocyte was exposed to hypoxia (2 % O2, 98 % N2) and cultured in serum-free medium for 6, 12, and 18 h to establish cell model of HI. Morphologic changes of astrocyte were monitored and gene expression change of IL-1β evaluated by real-time polymerase chain reaction (PCR). To establish the HI animal model, 3 days old postnatal Sprague–Dawley (SD) rats were treated with the right carotid artery ligation and were exposed to 8 % oxygen for 8, 16 and 24 h, respectively. Longa score scale, hematoxylin and eosin (HE) staining and water content were examined to assess neurologic function and morphology changes. IL-1β siRNA lentivirus (IL-1β-RNAi-LV) was injected into cerebral cortex motor area 2 days before HI and the interference efficiency examined by real-time PCR and Western blotting, respectively. Immunofluorescence staining of GFAP and IL-1β was performed to identify the location and interference effect of IL-1β, respectively. To further explore the potential mechanisms, the expression of inflammatory factors, including IL-6, IL-10 and tumor necrosis factor-alpha (TNF-α), was examined following IL-1β down-regulation. The size of soma astrocyte was increased greatly after 12 and 18 h of HI with IL-1β up-regulation. IL-1β knockdown by siRNA in vitro or by lentivirus in vivo can reverse cell swelling, brain edema and neurologic function deficiencies induced by HI. Lastly, interference of IL-1β remarkably increased IL-6 expression but not IL-10 and TNF-α. Therefore, down-regulation of IL-1β improves the deficiencies of neurologic function and morphology induced by HI, maybe closely associating with IL-6 regulation.
Highlights
Hypoxia–ischemia (HI) insult of neonatal is a vital cause of perinatal brain injury, which may cause cerebral palsy, seizures, learning limitations and epilepsy [1,2,3,4]
Three IL-1β-specific siRNA fragments (F1, F2, F3) were transfected into astrocyte for 2 days, and the silencing effect was examined by real-time polymerase chain reaction (PCR)
To explore the optimal siRNA-dependent silencing effect of IL-1β at 2, 4 and 7 days after transfection of F3, the mRNA levels were determined by real-time PCR, as described in Methods
Summary
Hypoxia–ischemia (HI) insult of neonatal is a vital cause of perinatal brain injury, which may cause cerebral palsy, seizures, learning limitations and epilepsy [1,2,3,4]. Inflammation, as a complex intrinsic network of multiple subsets of immune cells, plays a pivotal role in HI pathogenesis. The phenomenon of apoptotic, swelling, necrotic cell deaths and excitotoxicity is prominent in the developing brain edema after HI [7,8,9,10]. Interleukin-1β (IL-1β), a member of the interleukin 1 cytokine family that was produced by activated macrophages as a proprotein, is known to play a major role in the development of osteoarthritis, hypoxic ischemic encephalopathy and hepatic damage [11,12,13]
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