The aim of the present study was to investigate the antioxidant mechanisms of dexmedetomidine against lung injury during intestinal ischemia reperfusion (iir) in rats. The model of iir-induced acute lung injury was established by occluding the superior mesenteric artery (SMa) for 1 h and reperfusing for 2 h using Sprague-dawley rats. Pathological examination was used to assess the extent of the lung injury. oxidative stress was evaluated by measuring malondialdehyde, myeloperoxidase and superoxide dismutase in the lung and plasma. The proinflammatory cytokines tumor necrosis factor-α and interleukin-6 were determined via an enzyme-linked immunosorbent assay. The mrna and protein expression of nuclear factor-erythroid 2 related factor 2 (nrf2) and heme oxygenase 1 (Ho-1) were determined using a reverse transcription-quantitative polymerase chain reaction and western blotting. Pretreatment with dexmedetomidine significantly inhibited the oxidative stress response and proinflammatory factor release caused by IIR compared with the normal saline group (Mda and Sod in lung and plasma, P<0.05; MPo, il-1β and TnF-α in lung and plasma, P<0.05). dexmedetomidine improved pulmonary pathological changes in iir rats compared with the normal saline group. investigations into the molecular mechanism revealed that dexmedetomidine increased the expression levels of nrf2 and Ho-1 via activating α2 adrenergic receptors compared with the normal saline group. The antagonism of α2 adrenergic receptors may reverse the protective effect of dexmedetomidine on lung injury during iir, including decreasing the expression levels of nrf2 and Ho-1, elevating the oxidative stress response and increasing the proinflammatory factor release. in conclusion, pretreatment with dexmedetomidine demonstrated protective effects against lung injury during iir via α2 adrenergic receptors. The nrf2/Ho-1 signaling pathway may serve a function in the protective effect of dexmedetomidine.
MK-801, also known as dizocilpine, is a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist that induces schizophrenia-like symptoms. Our previous study showed that brain-derived neurotrophic factor (BDNF) signaling was upregulated in cultured hippocampal astrocytes in response to MK-801. However, dysfunctional NMDA receptors are mainly expressed in neurons. The effects of MK-801 on neuron-derived BDNF expression and of risperidone on MK-801-induced cognitive impairment and changes in BDNF expression are unclear. To address this issue, we examined BDNF expression in the hippocampus of rats that received repeated injections of MK-801 (0.5 mg/kg body weight for 6 days) and in primary cultured hippocampal neurons incubated with 20 μM MK-801 for 24 h. BDNF expression and cognitive function were also evaluated in rats receiving intraperitoneal injections of risperidone (1 mg/kg body weight) once daily for 7 days and in hippocampal neurons incubated with 10 μM risperidone following MK801 treatment. MK-801 treatment decreased BDNF expression in the rat hippocampus as well as the expression and secretion of BDNF in hippocampal neurons in vitro . However, risperidone reversed the effects of MK801 on BDNF level and improved cognitive function in rats treated with MK801. These findings suggest that risperidone may alleviate cognitive impairment caused by MK801 via upregulation of BNDF signaling in the hippocampus.
Background Propofol improves rodent pulmonary injury after intestinal ischemia-reperfusion (IIR). However, its effect and underlying mechanisms in large animals remain unclear. Here, we examined whether pretreatment with propofol could relieve lung injury during IIR in pigs, then investigated the underlying mechanism. Material/Methods A porcine model of IIR-induced lung injury was built by clamping the super mesenteric artery for 2 h and loosening the clamp for 4 h. Randomized grouping was used, and pigs were assigned to a sham-operated group, an IIR with saline pretreatment group, and an IIR with propofol pretreatment group. Pulmonary histopathologic changes, permeability, and oxygenation were assessed to evaluate the effect of propofol. We assessed levels of methane dicarboxylic aldehyde (MDA), superoxide dismutase (SOD), myeloperoxidase (MPO), high-mobility group box 1 protein (HMGB1), Toll-like receptor 4 (TLR4), and double-stranded RNA activated protein kinase R (PKR) to investigate the underlying mechanism. Results IIR caused severe lung damage, including morphological changes, high permeability, airway resistance, low static compliance, hypoxemia, and acidemia. Pulmonary and plasma MDA content and MPO activity increased, whereas SOD activity decreased. The HMGB1/TLR4/PKR signaling pathway was activated following IIR. Pretreatment with propofol markedly attenuated lung injury (such as reducing the lung edema and permeability), increased MDA content and MPO activity, and restored SOD activity induced by IIR, accompanied by inhibiting the effect of the HMGB1/TLR4/PKR signaling pathway. Conclusions IIR caused acute lung injury in pigs. Pretreatment with propofol alleviated the lung injury, which was related to its suppression of the HMGB1/TLR4/PKR signaling pathway.
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