Effect of central corticotropin-releasing factor on carbon tetrachloride-induced acute liver injury in rats

Bufothionine induced the mitochondria-mediated apoptosis in H22 liver tumor and acute liver injury

Background

Bufothionine is an alkaloid in Cinobufacini (Huachansu). This study aims to investigate the effects of bufothionine on liver tumors and acute liver injury.

Methods

In the hepatoprotective experiment, fifty rats were randomly divided into five groups (n = 10): normal saline group, model group, compound glycyrrhizin injection (9.14 mL/kg); cinobufacini injection (3.42 mL/kg) (InjA) and bufothionine (9.77 mL/kg) (BufoA) group. Liver weight indices were recorded to judge the degree of liver swelling, hematoxylin and eosin (H&E) staining of liver tissues was carried out to observe liver histological morphology injury and biochemical indicators including aspartate aminotransferase (AST); alanine aminotransferase (ALT); alkaline phosphatase (ALP); and total bilirubin (TBIL) were determined by modular auto-analyzer. In anti-tumor experiment, H₂₂-tumor-bearing mice were randomly divided into five groups (n = 10): normal saline group, model group, cinobufacini injection (InjB) (5.14 mL/kg), bufothionine (8.02 mL/kg) (BufoB) and 5-fluorouracil (5-Fu) (3.42 mL/kg). Tumors were picked out and determined with vernier calipers. Histological morphology of tumors was observed by H&E staining. In SMMC-7721 cells, expressions of proteins related to mitochondria-mediated apoptosis pathway including Bcl-2, Bax, caspase-3, caspase-9, cyto-c, Bid, and p53 were analyzed by western blotting at low, medium, high concentrations of bufothione (3.62 μg/mL, 18.12 μg/mL,90.62 μg/mL).

Results

Butothionine relieved CCl₄-induced liver morphology, decreased the level of ALT (P =2.46 × 10^-2) and expressed tendency to decrease other biochemical markers including AST, ALP and TBIL. Butothionine could also promote necrosis of tumor tissue in H₂₂-tumor-bearing mice and restrained tumor growth with 65.16% inhibition rate. Its mechanism might relate to up-regulation of p53 (at low, mediate and high concentration, corresponding P values were 0.142, 0.0257, 0.0162), caspase-3 (P = 0.246, 0.0267 and 0.0236), cyto-c (P = 0.276, 0.0343 and 0.0429), Bid (P = 0.0125, 0.0395 and 0.0132) and Bax (P = 0.563, 0.0492 and 0.0357) in a dose-dependent manner, down-regulation of Bcl-2 expression (P = 0.0232, 0.0178 and 0.0464), but had no significant effects on caspase-9 (P = 0.253, 0.147 and 0.287).

Conclusion

Bufothionine induced the proteins for the mitochondria-mediated apoptosis that inhibits liver tumors and protects the liver against acute injury.

Gastric Vagal Efferent Inhibition Evoked by Intravenous CRF Is Unrelated to Simultaneously Recorded Vagal Afferent Activity in Urethane-Anesthetized Rats

Corticotropin-releasing factor (CRF) injected peripherally or released in response to stressful challenges to the organism reduces gastric tone and contractility, in part by vagal pathways. However, information on the changes in gastric vagal impulse activity evoked by peripheral CRF administration is entirely lacking. Using a novel “dual recording” method in urethane-anesthetized rats, vagal efferent (VE) and afferent (VA) impulse activities were recorded simultaneously from separate, fine bundles dissected from the ventral gastric vagus nerve branch innervating the glandular stomach. Activity records for 38 VA single units (SUs) and 33 VE SUs were sorted from multiunit records obtained from 13 preparations. Intravenous (iv) administration of saline had no effect on multiunit VE activity, whereas CRF (1 μg/kg, iv) immediately inhibited VE activity, reaching a nadir of 54 ± 8.0% of preinjection levels at 3.0 min postinjection. CRF (1 μg/kg, iv) inhibited 25/33 (75.8%) VE SUs and excited three of 33 (9.1%) VE SUs. In contrast to potent effects on VE activity, iv CRF did not alter multiunit VA activity. Single-unit analysis, however, revealed five of 38 (13.1%) VA SUs excited by iv CRF at widely varying latencies (suggesting an indirect mode of action) and one inhibited VA SU. VA SUs excited after iv CRF did not respond during gastric distention and vice versa. These experiments are the first to use simultaneous recording of gastric VA and VE units. The data demonstrate a predominantly inhibitory influence of iv CRF on VE outflow to the hindstomach, not driven by gastric vagovagal reflex activity.

Sympathetic vesicovascular reflex induced by acute urinary retention evokes proinflammatory and proapoptotic injury in rat liver

Increased hepatic sympathetic activity affects hepatic metabolism and hemodynamics and subsequently causes acute hepatic injury. We examined whether the vesicovascular reflex evoked by bladder overdistension could affect hepatic function, specifically reactive oxygen species (ROS)-induced inflammation and apoptosis, through activation of the hepatic sympathetic nerve. We evaluated the hepatic hemodynamics, hepatic sympathetic nervous activities, and cystometrograms in anesthetized rats subjected to acute urinary retention. We used a chemiluminescence method, an in situ nitro blue tetrazolium perfusion technique, and a DNA fragmentation/apoptosis-related protein assay to demonstrate de novo and colocalize superoxide production and apoptosis formation in rat liver. Acute urinary retention increased the hepatic sympathetic-dependent vesicovascular reflex, which caused hepatic vasoconstriction/hypoxia and increased superoxide anion production from the periportal Kupffer cells and hepatocytes, which were aggravated by the increase in volume and duration of urinary retention. The ROS-enhanced proinflammatory NF-κB, activator protein-1, and ICAM-1 expression also promoted proapoptotic mechanisms, including increases in the Bax/Bcl-2 ratio, CPP32 expression, poly-(ADP-ribose)-polymerase cleavages, and DNA fragmentation and apoptotic cells in the liver. The proinflammatory and proapoptotic mechanisms were significantly attenuated in rats treated with hepatic sympathetic nerve denervation or catechin (antioxidant) supplement. In conclusion, our results suggest that acute urine retention enhances hepatic sympathetic activity, which causes hepatic vasoconstriction and evokes proinflammatory and proapoptotic oxidative injury in the rat liver. Reduction of the hepatic sympathetic tone or antioxidant supplement significantly attenuates these injuries.

Restraint stress delays solid gastric emptying via a central CRF and peripheral sympathetic neuron in rats

Central corticotropin-releasing factor (CRF) delays gastric emptying through the autonomic nervous system. CRF plays an important role in mediating delayed gastric emptying induced by stress. However, it is not clear whether a sympathetic or parasympathetic pathway is involved in the mechanism of central CRF-induced inhibition of solid gastric emptying. The purpose of this study was to investigate whether 1) CRF inhibits solid gastric emptying via a peripheral sympathetic pathway and 2) stress-induced inhibition of solid gastric emptying is mediated via a central CRF and peripheral sympathetic pathways. Using male Sprague-Dawley rats, CRF was injected intracisternally with or without various adrenergic-blocking agents. To investigate whether central CRF-induced inhibition of solid gastric emptying is mediated via a peripheral sympathetic pathway, rats underwent celiac ganglionectomy 1 wk before the gastric emptying study. After solid meal ingestion (90 min), gastric emptying was calculated. To investigate the role of endogenous CRF in stress-induced delayed gastric emptying, a CRF type2 receptor antagonist, astressin2-B, was intracisternally administered. Rats were subjected to a restraint stress immediately after the feeding. Intracisternal injection of CRF (0.1-1.0 microg) dose-dependently inhibited solid gastric emptying. The inhibitory effect of CRF on solid gastric emptying was significantly blocked by guanethidine, propranolol, and celiac ganglionectomy but not by phentolamine. Restraint stress significantly delayed solid gastric emptying, which was improved by astressin2-B, guanethidine, and celiac ganglionectomy. Our research suggests that restraint stress inhibits solid gastric emptying via a central CRF type2 receptor and peripheral sympathetic neural pathway in rats.

Involvement of endogenous CRF in carbon tetrachloride-induced acute liver injury in rats

Central neuropeptides play important roles in many physiological and pathophysiological regulation mediated through the autonomic nervous system. In regard to the hepatobiliary system, several neuropeptides act in the brain to regulate bile secretion, hepatic blood flow, and hepatic proliferation. Central injection of corticotropin-releasing factor (CRF) aggravates carbon tetrachloride (CCl4)-induced acute liver injury through the sympathetic nervous pathway in rats. However, still nothing is known about a role of endogenous neuropeptides in the brain in hepatic pathophysiological regulations. Involvement of endogenous CRF in the brain in CCl4-induced acute liver injury was investigated by centrally injecting a CRF receptor antagonist in rats. Male fasted Wistar rats were injected with CRF receptor antagonist alpha-helical CRF-(9-41) (0.125-5 microg) intracisternally just before and 6 h after CCl4 (2 ml/kg) administration, and blood samples were obtained before and 24 h after CCl4 injection for measurement of hepatic enzymes. The liver sample was removed 24 h after CCl4 injection, and histological changes were examined. Intracisternal alpha-helical CRF-(9-41) dose dependently (0.25-2 microg) reduced the elevation of alanine aminotransferase and aspartate aminotransferase levels induced by CCl4. Intracisternal alpha-helical CRF-(9-41) reduced CCl4-induced liver histological changes, such as centrilobular necrosis. The effect of central CRF receptor antagonist on CCl4-induced liver injury was abolished by sympathectomy and 6-hydroxydopamine pretreatment but not by hepatic branch vagotomy or atropine pretreatment. These findings suggest the regulatory role of endogenous CRF in the brain in experimental liver injury in rats.