A nuclear import inhibitory peptide ameliorates the severity of cholecystokinin-induced acute pancreatitis

AIM: To assess the effect of our novel cell-permeable nuclear factor-kappaB (NF-κB) inhibitor peptide PN50 in an experimental model of acute pancreatitis. PN50 was produced by conjugating the cell-penetrating penetratin peptide with the nuclear localization signal of the NF-κB p50 subunit.METHODS: Pancreatitis was induced in male Wistar rats by administering 2×100 μg/kg body weight of cholecystokininoctapeptide (CCK) intraperitoneally (IP) at an interval of 1 h. PN50-treated animals received 1 mg/kg of PN50 IP 30 min before or after the CCK injections. The animals were sacrificed 4 h after the first injection of CCK.RESULTS: All the examined laboratory (the pancreatic weight/body weight ratio, serum amylase activity,pancreatic levels of TNF-α and IL-6, degree of lipid peroxidation, reduced glutathione levels, NF-κB binding activity, pancreatic and lung myeloperoxidase activity) and morphological parameters of the disease were improved before and after treatment with the PN50 peptide.According to the histological findings, PN50 protected the animals against acute pancreatitis by favoring the induction of apoptotic, as opposed to necrotic acinar cell death associated with severe acute pancreatitis.CONCLUSION: Our study implies that reversible inhibitors of stress-responsive transcription factors like NF-κB might be clinically useful for the suppression of the severity of acute pancreatitis.

Interplay between nitric oxide and VIP in CCK-8-induced phasic contractile activity in the rabbit sphincter of Oddi

AIM: The sphincter of Oddi (SO) plays an important role in delivery of bile into the duodenum. To establish whether vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) were involved in phasic contractile activity of the rabbit SO stimulated by cholecystokinin-octapeptide (CCK-8). METHODS: Isolated SO muscle rings were cleaned of fat and mounted horizontally on two small L-shaped hooks one of which was connected to a force transducer for the measurement of isometric tension.The experiments were carried out in a thermostatically controlled (37±0.2℃) organ bath (5 mL) containing Krebs solution.The organ fluid was gassed with 95% O2 and 50 mL/L CO2 to keep the pH at 7.40±0.05. Contractile responses to CCK-8 (1 μmol/L) were evaluated in the presence and absence of NG-nitro-L-arginine (LNNA), an inhibitor of NO synthase (100 μmol/L), and (p-chloro-D-Phe6-Leu17)-VIP (VlPa, 30 μmol/L), a VIP receptor antagonist. RESULTS: CCK-8 stimulated the phasic activity of the SO. NO synthase inhibition increased the frequency and amplitude of contractions with a slight increase in developed tension. Pre-incubation with VlPa also attenuated this CCK-8 effect. The combined application of LNNA and VlPa abolished the phasic activity of the muscle rings with a marked increase in tension in response to CCK-8. CONCLUSION: VIP and NO together contribute to an increase in phasic activity of SO.

Effect of herpesvirus infection on pancreatic duct cell secretion

AIM： To examine the effect of acute infection caused by herpesvirus （pseudorabies virus, PRV） on pancreatic ductal secretion. METHODS： The virulent Ba-DupGreen （BDG） and non- virulent Ka-RREp01acgfp （KEG） genetically modified strains of PRV were used in this study and both of them contain the gene for green fluorescent protein （GFP）. Small intra/ interlobular ducts were infected with BDG virus （10^7 PFU/mL for 6 h） or with KEG virus （10^10 PFU/mL for 6 h）, while non-infected ducts were incubated only with the culture media. The ducts were then cultured for a further 18 h. The rate of HCO3 secretion [base efflux -λ（B）] was determined from the buffering capacity of the cells and the initial rate of intracellular acidification （1） after sudden blockage of basolateral base loaders with dihydro-4,4,- diisothiocyanatostilbene-2,2,-disulfonic acid （500 μmol/L） and amiloride （200 μmol/L）, and （2） after alkali loading the ducts by exposure to NH4Cl. All the experiments were performed in HCO3-buffered Ringer solution at 37 ℃ （n = 5 ducts for each experimental condition）. Viral structural proteins were visualized by immunohistochemistry. Virallyencoded GFP and immunofluorescence signals were recorded by a confocal laser scanning microscope.RESULTS： The BDG virus infected the majority of accessible cells of the duct as judged by the appearance of GFP and viral anUgens in the ductal cells. KEG virus caused a similarly high efficiency of infection. After blockage of basolateral base loaders, BDG infection significantly elevated -λB-） 24 h after the infection, compared to the non-infected group. However, KEG infection did not modify -λB-）. After alkali loading the ducts, -λB-） was significantly elevated in the BDG group compared to the control group 24 h after the infection. As we found with the inhibitor stop method, no change was observed in the group KEG compared to the non-infected group. CONCLUSION： Incubation with the BDG or KEG strains of PRV results in an effective infection of ductal epithelial cells. The BDG strain of PRV, which is able to initiate a lytic viral cycle, stimulates HCO3 secretion in guinea pig pancreatic duct by about fourto fivefold, 24 h after the infection. However, the KEG strain of PRV, which can infect, but fails to replicate, has no effect on HCO3 secretion. We suggest that this response of pancreatic ducts to virulent PRV infection may represent a defense mechanism against invasive pathogens to avoid pancreatic injury.