Brzozowski Tomasz, Konturek Peter C, Moran Anthony P, Kwiecien Slawomir, Pajdo Robert, Konturek Stanislaw J, Drozdowicz Danuta, Ptak Agata, Pawlik Wieslaw, Hahn Eckhart G
Department of Physiology, Jagiellonian University School of Medicine, Cracow, Poland.
Digestion. 2003;67(4):195-208. doi: 10.1159/000072058.
Lipopolysaccharide (LPS) has been proposed to act as one of numerous virulence factors in the Helicobacter pylori (HP)-infected stomach. However, little is known as to whether the gastric mucosa can withstand the repeated LPS insult, and how the possible adaptation to this endotoxin influences the damage induced by strong irritants. We determined the effect of a single or repeated parenteral administration of LPS obtained from HP on acute gastric lesions induced by intragastric application of 100% ethanol (1.5 ml) and by water immersion and restraint stress (WRS).
The area of the gastric lesions was measured by planimetry, mucosal gastric blood flow (GBF) was determined by H(2) gas clearance, and gastric luminal content was collected for the determination of luminal NO(2)(-)/NO(3)(-) levels by the Griess reaction. Biopsy samples were taken for the measurement of prostaglandin (PG) E(2) by radioimmunoassay and mucosal expression of constitutive and inducible nitric oxide synthase (cNOS and iNOS), constitutive (COX-1) and inducible cyclooxygenase (COX-2), heat shock protein 70 (HSP 70) mRNA and protein were analyzed by RT-PCR and Western blot.
HP LPS (1 mg/kg i.p.) injected once or 5 times produced negligible macroscopic injury and failed to influence GBF significantly compared to the injuries recorded in vehicle-controlled rats. Single and repeated (5 times) administration of HP LPS significantly reduced ethanol- and WRS-induced lesions, these protective effects were accompanied by a rise in GBF and excessive luminal release of NO. The suppression of NOS activity by L-NAME (20 mg/kg i.p.), a nonspecific NOS inhibitor, or L-NIL (30 mg/kg i.g.), a specific iNOS inhibitor, and of COX-2 activity by NS-398 reversed the protective and hyperemic effects of single or repeated LPS administrations against ethanol and WRS damage and the accompanying rise in NO and PGE(2) production. These effects of L-NAME were significantly antagonized by the addition of L-arginine, a substrate for NO synthesis. The signals for cNOS, COX-1 and HSP 70 mRNA were detected by RT-PCR in the vehicle-treated gastric mucosa, whereas gene and protein expression of iNOS, COX-2 and HSP 70 mRNA were significantly increased only in rats treated with 1 or 5 applications of HP LPS.
Repeated injections of HP LPS enhance gastric mucosal resistance to the mucosal damage induced by ethanol and WRS via a mechanism involving mucosal overexpression of iNOS, COX-2 and HSP 70 with subsequent excessive production of NO and PGE(2).
脂多糖（LPS）被认为是幽门螺杆菌（HP）感染胃部众多毒力因子之一。然而，关于胃黏膜能否耐受反复的LPS刺激，以及对这种内毒素的可能适应性如何影响强刺激物所致损伤，目前知之甚少。我们测定了单次或重复经肠外给予HP来源的LPS对胃内灌注100%乙醇（1.5 ml）及水浸束缚应激（WRS）所致急性胃损伤的影响。
通过面积测量法测定胃损伤面积，用氢气清除法测定胃黏膜血流量（GBF），收集胃腔内容物，采用格里斯反应测定腔内容物中NO2(-)/NO3(-)水平。取活检样本，通过放射免疫分析法测定前列腺素（PG）E2，并用逆转录聚合酶链反应（RT-PCR）和蛋白质印迹法分析组成型和诱导型一氧化氮合酶（cNOS和iNOS）、组成型（COX-1）和诱导型环氧化酶（COX-2）、热休克蛋白70（HSP 70）mRNA和蛋白质的黏膜表达。
与溶剂对照大鼠的损伤相比，单次或5次腹腔注射HP LPS（1 mg/kg）产生的肉眼可见损伤可忽略不计，且对GBF无显著影响。单次和重复（5次）给予HP LPS可显著减轻乙醇和WRS诱导的损伤，这些保护作用伴随着GBF增加和胃腔内NO过度释放。非特异性NOS抑制剂L-NAME（20 mg/kg腹腔注射）或特异性iNOS抑制剂L-NIL（30 mg/kg灌胃）抑制NOS活性，以及NS-398抑制COX-2活性，均可逆转单次或重复给予LPS对乙醇和WRS损伤的保护和充血作用，以及随之而来的NO和PGE2生成增加。添加L-精氨酸（一种NO合成底物）可显著拮抗L-NAME的这些作用。在溶剂处理的胃黏膜中，通过RT-PCR检测到cNOS、COX-1和HSP 70 mRNA信号，而仅在接受1次或5次HP LPS处理的大鼠中，iNOS、COX-2和HSP 70 mRNA的基因和蛋白质表达显著增加。
反复注射HP LPS可通过一种机制增强胃黏膜对乙醇和WRS诱导的黏膜损伤的抵抗力，该机制涉及iNOS、COX-2和HSP 70在黏膜中的过度表达，随后导致NO和PGE2过度生成。
