Regulatory effect and mechanism of gastrin and its antagonists on colorectal carcinoma

AIM To explore the effect and mechanism ofgastrin and its antagonists proglumide and somatostatin on coIorectal carcinoma and their clinical significance.METHODS A model of transplanted human colonic carcinoma was established from SW480cell line in gymnomouse body. The volume andweight of transplanted carcinoma was observedunder the effect of pentagatrin (PG), proglumide (PGL) and octapeptide somotostatin (SMS201-995, SMS). The cAMP content ot carcinoma cell was determined by redioimmunoassay and the DNA, protein content and cell cycle were determined by flow-cytometry. The amount of viabIe cells was determined by MTT colorimetric analysis, lP3 content was determined by radioimmunoassay, Ca2+ concentration in cell by fluorometry and PKC activity by isotopic enzymolysis. The expression of gastrin, c-myc,C-fos and rasP21 in 48 cases of colorectal carcinoma tissue was detected by the immunocytochemistry SP method. Argyrophilianucleolar organizer regions was determined withargyrophilia stain.RESULTS The volume, weight, cAMP, DNAand protein content in carcinoma cell, cellamount and proliferation index of S and G2Mphase in PG group were all significantly higher than those of control group. When PG was at theconcentration of 25 mg/ L, the amount of viablecells, lP3 content and Ca2+ concentration in celland membrane PKC activity in PG group weresigniticantly higher than those in control group;when PGL was at a concentration ot 32 mg/L,they dropped to the lowest level in PG (25 mg/L)+ PGL group, but without significant differencefrom the control group. The positive expression rate of gastrin, c-myc, c-fos and rasp21 in carcinoma tissue was 39 .6%, 54 .2%, 47. 9% and54 .2% resPectively and significantly higher than that in mucosa 3 cm and 6 cm adjacent tocarcinoma tissue and normal colorectal mucosa.The positive expression rate of gastrin of highlydifferentiated adenocarcinoma group was significantly higher than that of poorly differentiated and mucinous adenocarcinoma groups. The AgNORs count of carcinoma tissue was significantly higher than that in mucosa 3 cm and 6 cm adjacent to carcinoma tissue and normal colorectal mucosa; and the positive expression of c-myc and c-fos and the AgNORs count in gastrin-positive group was significantly higher than those in gastrin-negative group.CONCLUSION Pentagastrin has a promoting effect on the growth of transplanted human colonic carcinoma from SW480 cell line. PGL hasno obvious effect on the growth of human colonic carcinoma SW480 cell line, but couldinhibit the growth-promoting effect of PG on transplanted carcinoma. Somatostatin can not only inhibit the growth of transplanted human colonic carcinoma from SW480 cell line directlybut also depress the growth-promoting effect ofgastrin on the transplanted carcinoma. Somecolorectal carcinoma cells can produce and secrete gastrin through autocrine, highly-differentiated adenocarcinoma express the highest level gastrin. Endogenous gastrin can stimulate the cell division and proliferation of carcinoma cell and promote the growth of colorectal carcinoma regulating the expression of oncogene omyc, c-fos. Our study has provided experimental basis for the adjuvant treatment using gastrin antagonist such as PGL,somatostatin of patients with colorectalcarcinoma.

Role of p38 Signaling Pathway in Pentagastrin-Regulated Cell Proliferation of Colorectal Carcinoma Cell Line HT-29

Objective: To investigate the effects and mechanisms of p38 signaling pathway in pentagastrin-regulated cell proliferation of colorectal carcinoma cell line HT-29. Methods: HT-29 cell line of colorectal carcinoma was in vitro incubated and divided into the control group, pentagastrin group, proglumide group, and pentagastrin + proglumide group. MTT reduction assay was performed to detect the proliferation status of HT-29 cell line and determine the optimal dosage of pentagastrin and proglumide. Annexin V-fluorescein isothiocyanate flow cytometry was used to detect the proliferation index (PI) and apoptosis rate (AR) of HT-29 cells. Reverse transcriptase polymerase chain reaction was performed to detect the mRNA expression of the pentagastrin receptor/cholecystokinin-B receptor (CCK-BR) and p38. The protein and phosphorylation levels of p38 were estimated by western blotting. Results: RT-PCR detection showed that CCK-BR mRNA was expressed in the HT-29 cell line. Pentagatrin improved HT-29 cell proliferation in dosage of 6.25 - 100 mg/L, and the optimal dosage of pentagastrin was 25.0 mg/L. Proglumide had no significant effect on the proliferation of HT-29 cells, but significantly inhibited the proliferation of HT-29 cells stimulated by pentagastrin when the dosage of proglumide was 8.0 - 128.0 mg/L, and the optimal dosage was 32.0 mg/L. The AR in the pentagastrin group was significantly lower than that in the control group and in the pentagastrin + proglumide group. The PI in the pentagastrin group was significantly higher than that in the control group and in the pentagastrin + proglumide group. P38 phosphorylation level in the pentagastrin group was significantly lower than that in the control group, and in the pentagastrin + proglumide group. There were no significant differences in the mRNA and protein expression of p38 in the control, pentagastrin, proglumide and pentagastrin + proglumide groups. Conclusion: Pentagastrin can improve proliferation of the CRC cell line HT-29 and inhibit apoptosis via the p38 signal transduction pathway. This mechanism may be associated with suppressed p38 protein phosphorylation level due to inhibition of proglumide, a gastrin receptor antagonist.

CENTRAL CHOLECYSTOKININ OCTAPEPTIDE ACCELERATING THE RECOVERY OF THE RAT FROM HEMORRHAGIC SHOCK

There have been data showing that central cholecystokinin oetapeptide (CCK-8) could antagonize the analgesia induced by exogenous and endogenoust opioid peptides. Recently, we found that the hypotension produced by opioid peptides could also be reversed by central administration of CCK-8 (Mei Lin et al., unpublished result). The above-mentioned results either in physiology or in pharmacology suggested that CCK-8 appeared to have a potent antagonistic effect against opioid peptides and may be the endogenous anti-opioid substance.

The Antagonistic Effect of Cholecystokinin Octapeptide (CCK-8) on Opioid Effects in Cardiovascular Activities Was Mediated by CCK-B Receptor

Previous studies have shown that CCK-8 has distinct antiopioid effect in the central sites related with pain control and blood pressure control. The aim of this study was to explore the receptor mechanism by which CCK-8 antagonized the depressor effect of u- and k-opioid(?) agonists, and to observe whether CCK-8 could antagonize the depressor effect induced by muscimol, a nonopioid substance. The results showed that (i) The antagonistic effect of CCK-8 on opioid-induced hypotension could be blocked by intrathecal (i.t.) administration of CCK-B antagonist L-365, 260 at nanogram doses, or by CCK-A antagonist devazepide at doses 20—40 times higher than L-365, 260, indicating that it was the CCK-B receptor which mediates the antiopioid effect. (ⅱ) The depressor effect induced by intrathecal muscimol, a GABA agonist, was blocked neither by naloxone nor by CCK-8, supporting the notion that CCK-8 is an endogenous opioid antagonist rather than a universal anti-hypotension agent.