| Background: Vasoactive intestinal peptide (VIP) is one of the most important sensory neuropeptides, which comes mainly from non-adrenergic and non-cholinergic nerve fibers. The positive immunoreactivity fibers and receptors of VIP widely distribute in pulmonary. VIP has played a vital role in organism's physiological processes such as relaxing airway smooth muscle, inhibiting phagocytosis of alveolar macrophage and cell proliferation of T lympholeukocyte, reducing the release of inflammation media, enhancing the wound repairing of airway epithelium, eliminating oxygen-derived free radicals and antagonizing cell apoptosis in lung and evidences have being accumulated that its mechanisms are involved in various biological effects.Macrophage played important role in acute lung injury (ALI). It can secrete inflammation mediators such as tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) etc. TNF-αtook part in the genesis and development of ALI as initiating agent. It can aggravate inflammatory reaction, promote the proliferation of the lung fibroblast and facilitate the deposition of collagen and activate the macrophage to release oxygen free radical. TGF-βparticipated in pulmonary remodeling through inducing the proliferation and phenotypic alternation of fibroblast, encouraging the synthesis of collagen fibers and extracellular matrix (ECM). As an important neuropeptide in lung, there were no reports published about the effects of VIP on lung injury after stimulus by lipopolysaccharide (LPS). Therefore, it is significant to adjust the network of neuropeptide- inflammatory reaction back to physiology condition.Objective: The present study was designed to investigate the effects and mechanisms of VIP on wound repair in ALI.Methods: (1) The influence of VIP on wound repair of macrophage: the oxidative damage of macrophage was observed by xanthine oxidase and thio-barbituric acid methods; the mRNA and protein expression of TNF-αand TGF-βwere measured by RT-PCR and Western-blot. (2) The influence of VIP on wound repair of lung fibroblast: the proliferation of lung fibroblast was determined by MTT; a-SMA expression of lung fibroblast was observed by immunohistochemistry; the protein and mRNA expression of III collagen were determined by hydroxyproline content and RT-PCR.Results:1. The influence of VIP on wound repair of macrophage(1) The activity of SOD was decreased while the generation of MDA was increased by SOD and MDA kits, which indicating that LPS could aggravate the oxidative damage. VIP can protect RAW264.7 from oxidative damage (P<0.01) while the VIP receptor antagonist blocked the protective effects of VIP.(2) The protein and mRNA expression of TNF-αwere up-regulated by RT-PCR and Western-blot. VIP pretreated could reverse the effects (P<0.01). There was no significant difference compared with LPS group by using VIP receptor antagonist. There was no change about the expression of TGF-β.2. The influence of VIP on wound repair of lung fibroblast(1) When compared with control group, the proliferation of lung fibroblast treated with LPS was strengthened obviously by using MTT. Pretreated with VIP could repress the proliferation activity while VIP receptor antagonist could block the effects evoked by VIP.(2) The lung fibroblast will have a-SMA for its phenotypic alternation treated with LPS. The immunocytochemistry detected that there was buffy fine grain in the intracytoplasm of lung fibroblast which indicating that fibroblast transformed to myofibroblast. Pretreated with VIP could inhibit obviously the phenotypic alternation (P<0.05). VIP receptor antagonist could eliminate the effects.(3) The hydroxyproline kit and RT-PCR showed that the protein and mRNA expression of III collagen protein in lung fibroblast enhanced with LPS stimulus compared with control group. VIP could attenuate the expression above while VIP receptor antagonist had the opposite effects.Conclusions: (1) After stimulated with LPS, the oxidative damage of RAW264.7 was aggravated and the production of inflammatory factors was increase.(2) After stimulated with LPS, the proliferation activity and collagen synthesis of lung fibroblast were augmented, the phenotype of the lung fibroblast was changed to myofibroblast.(3) Pretreated with VIP could reverse the changes above, indicating that it may participate in cutting down the priming of ALI and enhance the lung wound repair.
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