Enhanced anti-apoptosis and gut epithelium protection function of acidic fibroblast growth factor after cancelling of its mitogenic activity

AIM: Mitogenic and non-mitogenic activities of fibroblast growth factor (FGF) are coupled to a range of biological functions, from cell proliferation and differentiation to the onset of many diseases. Recent reports have shown that acidic fibroblast growth factor (aFGF) has a powerful antiapoptosis function, which may have potentially therapeutical effect on gut ischemia and reperfusion injuries. However,whether this function depends on its mitogenic or nonmitogenic activity remains unclear. In this study, we identified the source of its anti-apoptosis function with a mutant,aFGF28-154 and observed its effect on reducing gut ischemia and reperfusion injury.METHODS: aFGF28-154 was generated by amplification of appropriate DNA fragments followed by subcloning the products into pET-3c vectors, then they were expressed in BL21 (DE3) cells and purified on an M2 agarose affinity column.This mutant aFGF28-154 maintained its non-mitogenic activity and lost its mitogenic activity. With a dexamethasone (DEX)-induced mouse thymocyte apoptosis model in vitro and in vivo, we studied the anti-apoptotic function of aFGF28-154. Also, in vivo study was performed to further confirm whether aFGF28-154 could significantly reduce apoptosis in gut epithelium after gut ischemia-reperfusion injury in rats. Based on these studies, the possible signal transduction pathways involved were studied.RESULTS: With a dexamethasone (DEX)-induced mouse thymocyte apoptosis model in vitro and in vivo, we found that the anti-apoptotic function of aFGF28-154 was significantly enhanced when compared with the wild type aFGF. In vivo study further confirmed that aFGF28-154 significantly reduced apoptosis in gut epithelium after gut ischemiareperfusion injury in rats. The mechanisms of anti-apoptosis function of aFGF28-154 did not depend on its mitogenic activity and were mainly associated with its non-mitogenic activities, including the intracellular calcium ion balance protection, ERK1/2 activation sustaining and cell o/de balance.CONCLUSION: These findings emphasize the importance of non-mitogenic effects of aFGF, and have implications for its therapeutic use in preventing apoptosis and other injuries in tissues and internal organs triggered by ischemia-reperfusion injury.

Inhibition of p38 mitogen-activated protein kinase may decrease intestinal epithelial cell apoptosis and improve intestinal epithelial barrier function after ischemia- reperf usion injury

AIM: To investigate the role of p38 mitogen-activated protein kinase in rat small intestine after ischemia-reperfusion (I/R)insult and the relationship between activation of p38 MAPK and apoptotic cell death of intestine.METHODS: Ninety Wistar rats were divided randomly into three groups, namely sham-operated group (C), I/R vehicle group (R) and SB203580 pre-treated group(S).In groups R and S, the superior mesenteric artery(SMA)was separated and occluded for 45 min, then released for reperfusion for0.25, 0.5, 1, 2, 6, 12 and 24 h. In group C, SMA was separated without occlusion. Plasma D-lactate levels were examined and histological changes were observed under a light microscope. The activity of p38 MAPK was determined by Western immunoblotting and apoptotic cells were detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUDP-biotin nick end labeling (TUNEL).RESULTS: Intestinal ischemia followed by reperfusion activated p38 MAPK, and the maximal level of activation (7.3-fold vs sham-operated group) was reached 30 min after I/R. Treatment with SB 203580, a p38 MAPK inhibitor,reduced intestinal apoptosis (26.72±3.39% vs62.50±3.08%in I/R vehicle, P＜0.01) and decreased plasma D-lactate level (0.78±0.15 mmol/L in I/R vehicle vs0.42±0.17 mmol/L in SB-treated group) and improved post-ischemic intestinal histological damage.CONCLUSION: p38 MAPK plays a crucial role in the signal transduction pathway mediating post-ischemic intestinal apoptosis, and inhibition of p38 MAPK may attenuate ischemia-reperfusion injury.

Intravenous acid fibroblast growth factor protects intestinal mucosal cells against ischemia-reperfusion injury via regulating Bcl-2/Bax expression

AIM: To detect the effect of acid fibroblast growth factor (aFGF) on apoptosis and gene expression of bax and bcl-2 gene in rat intestine after ischemia/reperfusion (I/R) injury, and to explore the protective mechanisms of aFGF.METHODS: One hundred and eight Wistar rats were randomly divided into sham-operated control group (C)(n = 6), intestinal ischemia group (I) (n = 6), aFGF treatment group (A) (n = 48) and intestinal ischemia reperfusion group (R) (n = 48). In group I, the animals were killed after 45 min of superior mesenteric artery (SMA) occlusion, while in groups R and A, the rats sustained 45 min of SMA occlusion and were then treated with normal saline and aFGF, respectively, sustained 15 min, 30 min, 1, 2, 6, 12, 24, or 48 h of reperfusion, respectively. In group C, SMA was separated, but without occlusion. Apoptosis in intestinal villus was determined with terminal deoxynucleotidyl transferase mediated dUTP-biotin nickend labeling technique (TUNEL). Intestinal tissue samples were taken not only for detection of bax and bcl-2 gene expression by RT-PCR, but also for detection of bax and bcl 2 protein expression and distribution by immunohistochemical analysis.RESULTS: The rat survival rates in aFGF treated group were higher than group R (P＜0.05) and the improvement of intestinal histological structures was observed at 2, 6, and 12 h after the reperfusion in group A compared with group R. The apoptotic rates were (41.17±3.49)%, (42.83±5.23)% and (53.33±6.92)% at 2, 6 and 12 h after reperfusion, respectively in group A, apparently less than those of group R at matched time points (50.67±6.95, 54.17±7.86, 64.33±6.47, respectively) (P＜0.05). The bax gene transcription and translation were significantly decreased in group A vs group R, while mRNA and protein contents of Bcl-2 in group A were obviously higher than those in groupR during 2-12 h period after reperfusion.CONCLUSION: The changes in histological structure and the increment of apoptotic rate indicated that the intestinal barrier was damaged after intestinal I/R injury, whilst intravenous aFGF could alleviate apoptosis induced by ischemia and reperfusion in rat intestinal tissues, in which genes of bax and bcl-2 might play important roles.