Roles of sphincter of Oddi motility and serum vasoactive intestinal peptide,gastrin and cholecystokinin octapeptide

AIM: To investigate roles of sphincter of Oddi (SO) motility played in pigment gallbladder stone formation in model of guinea pigs.

Cholecystokinin octapeptide improves cardiac function by activating Cholecystokinin octapeptide receptor in endotoxic shock rats

AIM: To explore the effect of sulfated cholecystokinin octapeptide (sCCK-8) on cardiac functions and its receptor mechanism in endotoxic shock (ES) rats. METHODS: The changes of the mean arterial pressure (MAP), heart rate (HR), the left ventricular pressure (LVP) and the maximal/minimum rate of LVP (±LVdp/dt max) were measured by using physiological record instrument in eight groups of rats. The expression of cholecystokinin-A receptor (CCK-AR) and cholecystokinin-B receptor (CCK-BR) mRNA of myocardium in ES rats was examined by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: (1) Low doses of sCCK-8 (0.4 μg/kg) caused tachycardia (441±27, normal control 391±22 s/min) and slight increase in MAP, LVP and ±LVdp/dtmax (16.96±1.79, 18.21±1.69 and +768.85±31.28/-565.04±27.71 kPa, respectively, all P<0.01), while medium doses (4.0 μg/kg) and high doses of sCCK-8 (40 μg/kg) elicited bradycardia and marked increase in MAP, LVP and ±LVdp/dtmax (17.29±1.63, 19.46±2.57 and +831.46±22.57/-606.08 ±31.32; 17.46±1.08, 19.83±2.91 and +914.52±35.95/ -639.15±30.23 kPa, respectively, all P<0.01). Proglumide (1.0 mg/kg), a nonselective antagonist of CCK-receptor (CCK-R), significantly inhibited the pressor effects of sCCK-8 (15.96±1.38, 17.36±0.66 and +748.18±19.29/-512.12±14.39 kPa, respectively, all P<0.01), whilst reversing the bradycardiac responses. (2) High doses of LPS (8 mg/kg) elicited marked decrease in MAP, LVP and ±LVdp/dtmax. (7.16±0.59, 7.6±0.68 and +298.01±25.52/ -166.96±19.25 kPa, respectively, all P<0.01). Pretreatment with sCCK-8 (40 μg/kg) could reverse the decline of cardiac functions (10.71±0.45, 11.7±1.26 and +446.04±67.18/ -347.90±36.98 kPa, respectively, all P<0.01), while proglumide could cause further decline of cardiac function in ES rats (4.71±0.67, 5.58±1.25 and +226.48±15.84/ -142.83±20.23 kPa, respectively, all P<0.01). (3) CCK-A/BR mRNAs were expressed in myocardium of control rats. Gene expression of CCK-AR and CCK-BR significantly increased in myocardium of ES rats. The increase of CCK-AR mRNA induced by LPS began at 0.5 h, peaked at 2 h, kept a high level at 6 h and declined at 12 h, respectively. Similar to CCK-AR mRNA, the expression of CCK-BR mRNA peaked at 2 h and kept a high level at 6 h, but it did not change at the first 0.5 h and was stable at a high level at 12 h. CONCLUSION: The above results indicate that endogenous and exogenous sCCK-8 may significantly improve cardiac function and intractable hypotension of ES rats, which was likely related to high expression of CCK-A/BR in myocardium induced by LPS.

Effects of cholecystokinin octapeptide receptor on lung injury in endotoxemia rats

Objective:To investigate the effects of CCK-8 receptor on lung injury in endotoxemia rats. Methods: Male SD rats were randomized into four groups (n=6): control group (LPS+CCK-8 group), CCK-1R antagonist group, CCK-2R antagonist group, DFSO+PF group. The rats were injected by LPS (5 mg.kg-1). CCK-8 (20 μg.kg-1) was administered 30 min after LPS injection. Either a specific CCK-1R antagonist or CCK-2R antagonist (0.5.kg-1) was injected before CCK-8 treatment (after LPS 20min). The tidal volume (TV) was collected by a multi-channel data physiological recorder. The lung injury was observed by light and electron microscopy. The concentrations of TNF-α、IL-1 and IL-6 in lung homogenates were measured by ELISA kits.Rresults: Compared with control group, the TV were significantly lower and the lung injuries were more serious in CCK-2R antagonist group. As well as the concentrations of TNF-α、IL-1 and IL-6 in lung homogenates were higher.Conclusion: CCK-2 receptor plays a major role in the effect of CCK-8 on lung injury in ETM rats.

Selective cyclooxygenase-2 inhibitor ameliorates cholecystokinin-octapeptide-induced acute pancreatitis in rats

AIM： To investigate the effect of selective Cyclooxygenase-2 （COX-2） inhibitor 4-[5-（4-Chloro-phenyl）-3- （trifluoromethyl）- 1H-pyrazol- 1-yl] benzenesulfonamide （SC-236）, on the cholecystokinin （CCK）-octapeptideinduced acute pancreatitis （AP） in rats. METHODS： Wistar rat weighing 240 g to 260 g were divided into three groups. （1） Normal DMSO treated group, （2） SC-236 at 4 mg/kg treated group; SC-236 systemically administered via the intravenous （i.v.） catheter, followed by 75 μg/kg CCK octapeptide subcutaneously three times, after 1, 3 and 5 h. This whole procedure was repeated for 5 d. （3） Dimethyl sulfoxide （DMSO） treated group： an identical protocol was used in this group as in the SC-236 cohort （see 2. above）. Repeated CCK octapeptide treatment resulted in a typical experimentally induced pancreatitis in the Wistar rats. RESULTS： SC-236 improved the severity of CCK- octapeptide-induced AP as measured by laboratory criteria [the pancreatic weight/body weight （p.w/ b.w） ratio, the level of serum amylase and lipase]. The SC-236 treated group showed minimal histologic evidence of pancreatitis and a significant reduction in myeloperoxidase activity. SC-236 also increased heat shock protein （HSP）-60 and HSP72 compared with the DMSO-treated group in the CCK-octapeptide-induced AP and also reduced the pancreatic levels of COX-2. Furthermore, SC-236 reduced proinflammatory cytokine synthesis and inhibited NF-KB activation compared with the DMSO-treated group in the CCK-octapeptide-induced AP. CONCLUSION： Our results suggested that COX-2 plays pivotal role in the development of AP and COX-2 inhibitors may play a beneficial role in preventing AP.

Mechanisms of cholecystokinin-induced calcium mobilization in gastric antral interstitial cells of Cajal

AIM:To investigate the effect of sulfated cholecystokinin-8(CCK-8S) on calcium mobilization in cultured murine gastric antral interstitial cells of Cajal(ICC) and its possible mechanisms.METHODS:ICC were isolated from the gastric antrum of mice and cultured.Immunofluorescence staining with a monoclonal antibody for c-Kit was used to identify ICC.The responsiveness of ICC to CCK-8S was measured using Fluo-3/AM based digital microfluorimetric measurement of intracellular Ca2+ concentration([Ca2+]i).A confocal laser scanning microscope was used to monitor [Ca2+]i changes.The selective CCK1 receptor antagonist lorglumide,the intracellular Ca2+-ATPase inhibitor thapsigargin,the type Ⅲ inositol 1,4,5-triphosphate(InsP3) receptor blocker xestospongin C and the L-type voltage-operated Ca2+ channel inhibitor nifedipine were used to examine the mecha-nisms of [Ca2+]i elevation caused by CCK-8S.Immunoprecipitation and Western blotting were used to determine the regulatory effect of PKC on phosphorylation of type Ⅲ InsP3 receptor(InsP3R3) in ICC.Protein kinase C(PKC) activator phorbol 12-myristate 13-acetate(PMA) and inhibitor chelerythrine were used to assess the role of PKC in the CCK-8S-evoked [Ca2+]i increment of ICC.RESULTS:ICC were successfully isolated from the gastric antrum of mice and cultured.Cultured ICC were identified by immunofluorescence staining.When given 80 nmol/L or more than 80 nmol/L CCK-8S,the [Ca2+]i in ICC increased and 100 nmol/L CCK-8S significantly increased the mean [Ca2+]i by 59.30% ± 4.85%(P < 0.01).Pretreatment of ICC with 5 μmol/L lorglumide inhibited 100 nmol/L CCK-8S-induced [Ca2+]i increment from 59.30% ± 4.85% to 14.97% ± 9.05%(P < 0.01),suggesting a CCK1R-mediated event.Emptying of intracellular calcium stores by thapsigargin(5 μmol/L) prevented CCK-8S(100 nmol/L) from inducing a [Ca2+]i increase.Moreover,pretreatment with xestospongin C(1 μmol/L) could also abolish the CCK-8S-induced effect,indicating that Ca2+ release from InsP3R-operated stores appeared to be a major mechanism responsible for CCK-8S-induced calcium mobilization in ICC.On the other hand,by removing extracellular calcium or blocking the L-type voltage-operated calcium channel with nifedipine,a smaller but significant rise in the [Ca2+]i could be still elicited by CCK-8S.These data suggest that the [Ca2+]i release is not stimulated or activated by the influx of extracellular Ca2+ in ICC,but the influx of extracellular Ca2+ can facilitate the [Ca2+]i increase evoked by CCK-8S.CCK-8S increased the phosphorylation of InsP3R3,which could be prevented by chelerythrine.Pretreatment with lorglumide(5 μmol/L) could significantly reduce the CCK-8S intensified phosphorylation of InsP3R3.In the positive control group,treatment of cells with PMA also resulted in an enhanced phosphorylation of InsP3R3.Pretreatment with various concentrations of PMA(10 nmol/L-10 μmol/L) apparently inhibited the effect of CCK-8S and the effect of100 nmol/L PMA was most obvious.Likewise,the effect of CCK-8S was augmented by the pretreatment with chelerythrine(10 nmol/L-10 μmol/L) and 100 nmol/L chelerythrine exhibited the maximum effect.CONCLUSION:CCK-8S increases [Ca2+]i in ICC via the CCK1 receptor.This effect depends on the release of InsP3R-operated Ca2+ stores,which is negatively regulated by PKC-mediated phosphorylation of InsP3R3.

Therapeutic proteasome inhibition in experimental acute pancreatitis

AIM： To establish the therapeutic potential of proteasome inhibition, we examined the therapeutic effects of MG132 （Z-Leu-Leu-Leu-aldehyde） in an experimental model of acute pancreatitis. METHODS： Pancreatitis was induced in rats by two hourly intraperitoneal （ip） injections of cholecystokinin octapeptide （CCK; 2×100μg/kg） and the proteasome inhibitor MG132 （10 mg/kg ip） was administered 30 min after the second CCK injection. Animals were sacrificed 4 h after the first injection of CCK. RESULTS： Administering the proteasome inhibitor MG132 （at a dose of 10 mg/kg, ip） 90 min after the onset of pancreatic inflammation induced the expression of cell-protective 72 kDa heat shock protein （HSP72） and decreased DNA-binding of nuclear factor-κB （NF-κB）. Furthermore MG132 treatment resulted in milder inflammatory response and cellular damage, as revealed by improved laboratory and histological parameters of pancreatitis and associated oxidative stress. CONCLUSION： Our findings suggest that proteasome inhibition might be beneficial not only for the prevention, but also for the therapy of acute pancreatitis.