Helicobacter pylori infection delays healing of ischaemia-reperfusion induced gastric ulcerations: new animal model for studying pathogenesis and therapy of H-pylori infection

Objective Helicobacter pylori (Hp) infection is a major risk factor of pept ic ulcerations but studies on its pathogenicity are limited due to the lack of an adequate animal model. In this study we developed the new model of g astric Hp infection in rat gastric mucosa, with acute gastric erosions prog ressing into ulcers in animals subjected initially to ischaemia-reperfusion (I/R). Design I/R lesions were produced in rats by clamping the coeliac artery for 0.5 h followed by 1 h reperfusion and gastric inoculation with type I Hp s train (CagA and VacA positive) or type II Hp strain (CagA and VacA negative ), obtained from fresh clinical isolates, or with vehicle (saline). Gastric secretion during recovery from I/R lesions was determined in a separate gr oup of rats equipped with chronic gastric fistula to inoculate the animals with Hp and then to collect gastric juice for determination of gastric acid ity and pepsin outputs as well as luminal content of somatostatin. Methods The animals were killed at 0, 3, 12 or 24 h and 3, 5, 10 or 15 days after Hp inoculation and the area of gastric lesions was determined planim etrically and gastric blood flow (GBF) was measured by the H-2-gas clearanc e technique. The venous blood was withdrawn for measurement of plasma inter leukin (IL)-1 beta and tumour necrosis factor alpha (TNF alpha) by ELISA an d plasma gastrin, luminal somatostatin by RIA and the mucosal expression of transforming growth factor (TGF alpha) was analysed using RT-PCR with spec ific primers. Gastric Hp infection was assessed by histology, rapid urease test and Hp culture. The effect of triple therapy with omeprazole, amoxycil lin and tinidazole on Hp infection and ulcer healing was also determined. Results Ischaemia alone resulted in an immediate fall in GBF and almost com plete suppression of gastric secretion but without any gastric lesions. Whe n ischaemia was followed by 1 h of reperfusion, acute gastric erosive lesio ns immediately occurred, reaching a maximum at 12 h after I/R and progressi ng after 3 days to deeper gastric ulcers that disappeared after 15 days. In Hp-inoculated rats, the number of viable Hp colonies gradually increased, reaching maximum at day 10 with infection with type I and at day 15 with in fection with type II Hp. At day 15 the difference in Hp colonization was no t significantly different between the stomachs infected by type I and type II Hp. Inoculation, especially with the type I Hp strain, significantly del ayed healing of I/R-induced acute lesions and accelerated their progression into deeper chronic ulcers. This effect was accompanied by a significant f all in GBF and a higher increment in plasma IL-1 beta and TNF alpha levels. Gastric acid secretion, which was completely inhibited up to 12 h after I/ R, returned to the control value 24 h upon completion of the I/R procedure. This return was delayed in Hp-infected rats and accompanied by a significa nt elevation of plasma gastrin and a decrease in luminal somatostatin. The immunoreactivity of TGF alpha and expression of TGF alpha mRNA determined b y RT-PCR were well defined in intact gastric mucosa but were significantly decreased, especially in mucosa infected with type I Hp strain, at day 15 a fter I/R. The triple therapy which cured Hp infection completely abolished the delay in ulcer healing caused by Hp. Conclusions (1) Gastric infection with the Hp strain expressing cagA and va cA encoded cytotoxins delays healing of I/R-induced acute gastric lesions d ue to an impairment of gastric microcirculation, and excessive proinflammat ory cytokine release and suppression of antiulcer TGFa expression. (2) The I/R induced suppression of gastric acid secretion may contribute to the hyp ergastrinaemia as a secondary phenomenon and may account for the spread of Hp infection observed during the progression of acute erosions into chronic ulcers. (3) I/R induced gastric ulcers may be a useful model for studying the action of Hp infection on gastric ulcerogenesis in ischaemic stomach an d for testing anti-Hp therapy. Eur J Gastroenterol Hepatol 12:1299-1313 (C) 2000 Lippincott Williams & Wilkins.