Effects of endotoxin on endothelin receptor in hepatic and intestinal tissues after endotoxemia in rats

Effects of transmitters and interleukin-10 on rat hepatic fibrosis induced by CCl4

AIM: To study the effects of transmitters ET, AgII, PGI₂, CGRP and GG on experimental rat hepatic fibrosis and the antifibrogenic effects of IL-10.

METHODS: One hundred SD rats were randomly divided into 3 groups: control group (N): intraperitoneal injection with saline 2 mL·kg^-1 twice a week; the fibrogenesis group (C): intraperitoneal injection with 50% CCl₄ 2 mL·kg^-1 twice a week; IL-10 treated group (E): besides same dosage of CCl₄ given, intraperitoneal injection with IL-10 4 μg·kg^-1 from the third week. In the fifth, the seventh and the ninth week, rats in three groups were selected randomly to collect plasma and liver tissues. The levels of ET, AgII, PGI₂, CGRP and GG were assayed by radioimmunoassay (RIA). The liver fibrosis was observed with silver staining.

RESULTS: The hepatic fibrosis was developed with the increase of the injection frequency of CCl₄. The ET, AgII, PGI₂, CGRP and GG levels in serum of group N were 71.84 ± 60.2 ng·L^-1, 76.21 ± 33.3 ng·L^-1, 313.03 ± 101.71 ng·L^-1, 61.97 ± 21.4 ng·L^-1 and 33.62 ± 14.37 ng·L^-1, respectively; the levels of them in serum of group C were 523.30 ± 129.3 ng·L^-1, 127.24 ± 50.0 ng·L^-1, 648.91 ± 357.29 ng·L^{- 1}, 127.15 ± 62.0 ng·L^-1 and 85.26 ± 51.83 ng·L^{- 1}, respectively; the levels of them in serum of group E were 452.52 ± 99.5 ng·L^-1, 90.60 ± 44.7 ng·L^-1, 475.57 ± 179.70 ng·L^-1, 102.2 ± 29.7 ng·L^-1 and 38.05 ± 19.94 ng·L^-1, respectively. The histological examination showed that the degrees of the rats liver fibrosis in group E were lower than those in group C.

CONCLUSION: The transmitters ET, AgII, PGI₂, CGRP and GG play a significant role in the rat hepatic fibrosis induced by CCl₄. IL-10 has the antagonistic action on these transmitters and can relieve the degree of the liver fibrosis.

Intestinal damage mediated by Kupffer cells in rats with endotoxemia

AIM

To determine the in vivo effects of phagocytic blockade of Kupffer cell (KC) on the release of proinflammatory cytokines in small intestinal lesion and on the integrity of intestinal tract by using gadolinium chloride (GdCl(3)) during early endotoxemia.

METHODS

Wistar rats were divided into three groups: Group A, rats were injected with endotoxin (E. coli O111:B(4), a dose of 12 mg x kg(-1)) only; Group B, rats were pretreated intravenously with 25 mg of GdCl(3) per kg 24 h are given endotoxin; and Group C, sham operation only. All animals were sacrificed 4 h after endotoxin injection. In portion of the rats of three groups, bile duct was cannulated, which the bile was collected externally. Morphological changes of ileum were observed under light microscopy and electronic microscopy. The KC were isolated from rats by collagenase perfusion and in KC, expression of TNF-alpha and IL-6 mRNA were determined by RT-PCR analysis. Plasma and bile TNF-alpha and IL-6 Levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In group A, there were neutrophil infiltration and superficial epithelial necrosis of the ileal villi, sloughing of mucosal epithelium, and disappearance of some villi. In group B, the ileal mucosal damage was much reduced. which in group C, no significant morphological changes were seen. GdCl(3) pretreatment decreased significantly the expression of TNF-alpha and IL-6 mRNA in group B (4.32+/-0.47 and 4.05+/-0.43) when compared to group A (9.46+/-1.21 and 9.04+/-1.09) (P<0.05). There was no significant expression of TNF-alpha and IL-6 mRNA in group C (1.03+/-0.14 and 10.4+/-0.13). In rats of group A, the levels of TNF-alpha and IL-6 in bile and plasma were 207+/-29 ng x L(-1), 1032+/-107 ng x L(-1), 213+/-33 ng x L(-1), and 1185+/-127 ng x L(-1), respectively. In group B, they were 113+/-18 ng x L(-1), 521+/-76 ng x L(-1), 147+/-22 ng x L(-1), and 572+/-54 ng x L(-1), respectively. In group C, they were 67+/-10 ng x L(-1), 72+/-13 ng x L(-1), 109+/-18 ng x L(-1), and 118+/-22 ng x L(-1) respectively. There were significant difference between the three group (P<0.05).

CONCLUSION

KC release cytokines TNF-alpha and IL-6 causing damage to the integrity of intestinal epithelium and play a crucial role in the initiation and progression of intestinal mucosal damage during early endotoxemia.

Hepatoprotective role of ganoderma lucidum polysaccharide against BCG-induced immune liver injury in mice

AIM: To examine the effect of ganoderma lucidum polysaccharide (GLP) on the immune liver injury induced by BCG infection, and investigate the relationship between degrees of hepatic damage and NO production in mice.

METHODS: Immune hepatic injury was markedly induced by BCG-pretreatment (125 mg·kg^-1, 2-week, iv) or by BCG-pretreatment plus lipopolysaccharide (LPS, 125 μg·kg^-1, 12-hour, iv) in mice in vivo. Hepatocellular damage induced by BCG-pretreated plus inflammatory cytokines mixture (CM), which was included TNF-α, IL-1β, IFN-γ and LPS in culture medium in vitro. Administration of GLP was performed by oral or incubating with culture medium at immune stimuli simultaneity. Liver damage was determined by activity of alanine aminotransferase (ALT) in serum and in hepatocytes cultured supernatant, by liver weight changes and histopathological examination. NO production in the cultured supernatant was determined by the Griess reaction. Moreover, inducible nitric oxide synthase (iNOS) protein expression was also examinated by immunohistochemical method.

RESULTS: Immune hepatic injury was markedly induced by BCG or BCG plus inflammatory cytokines in BALB/c mice in vivo and in vitro. Under BCG-stimulated condition, augment of the liver weight and increase of the serum/supernatant ALT level were observed, as well as granuloma forming and inflammatory cells soakage were observed by microscopic analysis within liver tissues. Moreover, NO production was also increased by BCG or/and CM stimuli in the culture supernatant, and a lot of iNOS positive staining was observed in BCG-prestimulated hepatic sections. Application of GLP significantly mitigated hepatic tumefaction, decreased ALT enzyme release and NO production in serum/supernatant, improved the pathological changes of chronic and acute inflammation induced by BCG-stimuli in mice. Moreover, the immunohistochemical result showed that GLP inhibited iNOS protein expression in BCG-immune hepatic damage model.

CONCLUSION: The present study indicates that NO participates in immune liver injury induced by Mycobacterium bovis BCG infection. The mechanisms of protective roles by GLP for BCG-induced immune liver injury may be due to influence NO production in mice.

Effect of endotoxin on portal hemodynamic in rats

AIM: To study the effects of endotoxin on portal hemodynamic of normal and noncirrhotic portal hypertensive rats.

METHODS: Normal rats were intraperitonealy injected with 0.1, 0.25, 0.5, 1.0, 2.0, 4.0 mg·kg^-1 of lipopolysaccharide (LPS) respectively, portal vein ligation (PVL) and intrahepatic portal occlusion (IPO) rats as well as sham-operated rats were treated with an intraperitoneal injection of 1.0 mg·kg^-1 of LPS, the portal vein pressure (PVP), portal venous flow (PVF), inferior vena cava pressure (IVCP) and portal vein resistance (PVR) were detected 4 hours after injection.

RESULTS: PVF of the 5 groups of rats accepting intraperitoneal injection of LPS were increased from 14.0 to 18.0, 22.2, 26.2, 34.8, 39.6, 38.8 mL·min^-1 4 hours after injection of LPS (P < 0.01). PVP of the 4 groups of rats accepting more than 0.1 mg/kg·b.w of LPS was increased from 1.04 to1.25, 1.50, 1.80, 1.95, 2.05 kPa (P < 0.01). The increments of PVF and PVP were in a dose-dependent manner of LPS. PVR of the 5 groups of rats was decreased from 51 to 42, 44, 48, 45, 44, 47 kPa·min·L^-1 (P < 0.05) and no dose-dependent manner was observed. PVF of PVL, IPO and sham-operated rats increased from 22.6 to 32.8, 22.0 to 28.0, 14.0 to 34.8 mL·min^-1 (P < 0.01), and PVP increased from 1.86 to 2.24, 1.74 to 1.95, 1.04 to 1.80 kPa (P < 0.01), PVR decreased from 71 to 61, 67 to 61, 52 to 44 kPa·min·L^-1 after intraperitoneal injection of 1 mg·kg^-1 of LPS. The increments of PVF and PVP of PVL and IPO rats were significantly less than the sham-operated rats (P < 0.01), There was no significant difference between the amounts of PVR decreased in the two groups of PHT model rats and sham-operated rats (P > 0.05) after intraperitoneal injection 1 mg·kg^-1 of LPS.

CONCLUSION: Endotoxin could prompt portal hypertension of the normal and noncirrhotic portal hypertensive rats by increasing portal blood flow mainly.

Relationship between lymphocyte apoptosis and endotoxin translocation after thermal injury in rats

AIM: To investigate the relationship between lymphocyte apoptosis in peripheral blood, spleen and mesenteric lymph nodes (MLN) and endotoxin translocation after thermal injury in rats.

METHODS: In a Wistar rat model inflicted with 30% TBSA III degree scalding, serum LPS levels in portal vein and vena cava were quantified by tachypleus amebocyte lysate (TAL) technique. The analysis of peripheral blood lymphocyte was employed in in situ Cell Death Detection Kit and evaluated by flow cytometry. Apoptotic lymphocytes in paraffin-embedded spleen and MLN sections were examined by histologic analysis, in situ deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) and peroxidase (POD) staining. The imagines were taken by Cooldccd camera system, and the count and optical density value (transmission light) of apoptotic lymphocytes were analyzed with software Spot and Imagine proplus 4.10a (IPP4.10a).

RESULTS: In the period of 3 to 48 postburn hours (PBHs) serum LPS level (× 10³ EU·L^-1) in portal vein (2.11 ± 0.02, 5.66 ± 0.20, 3.70 ± 0.22, 2.56 ± 0.28, 0.90 ± 0.11) was higher than that in vena cava (0.63 ± 0.01, 1.53 ± 0.18, 0.83 ± 0.32, 0.52 ± 0.12, 0.23 ± 0.02, P < 0.01), but both increased sharply in postburn rats (P < 0.01) and reached a peak at 6 PBH. Analysis of apoptotic lymphocytes showed that the proportion (%) of postburn apoptotic cells was much higher than that in healthy rats (8.34 ± 1.53, 8.13 ± 1.81, 20.77 ± 3.94, 23.90 ± 3.92, 11.23 ± 1.35 and 13.26 ± 2.09 at 3, 6, 12, 24, 48 and 72 PBH, respectively, vs 3.99 ± 1.72, P < 0.01), especially after 6 PBH. The concentrations of lymphocytic apoptosis at 12 and 24 PBH were markedly higher than that at other time points. Meantime, few apoptotic lymphocytes were found in normal MLN, but increased postburn obviously (3 ± 1 vs 546 ± 83, 285 ± 39, 149 ± 30, 58 ± 10, 36 ± 11 and 33 ± 9 in turn, P < 0.01), especially at 3 PBH, whereas apoptotic lymphocytes were concentrated in splenic cortex before the burn and decreased obviously during 72 PBHs (499 ± 186 vs 12 ± 8, 19 ± 15, 12 ± 7, 100 ± 15, 123 ± 25 and 226 ± 26 in turn, P < 0.01) though a slight rise was found in the medulla after 24 PBH. Optical density of apoptotic lymphocytes was significantly reduced in spleen in the 24 PBHs and raised in MLN during 48 PBHs than that prior to the burn, respectively.

CONCLUSION: Gut-origin LPS is a major cause of endotoxemia taken place early in rats following severe thermal injury and could induce extensive lymphocyte apoptosis in blood and MLN, which suggests an immunosuppression state could follow the initial injury and favores a septic state based on apoptotic mechanism.

Liver sinusoidal endothelial cell injury by neutrophils in rats with acute obstructive cholangitis

AIM: The objective of this study is to elucidate the potential role of poly-morphonuclear neutrophils (PMN) in the development of such a sinusoidal endothelial cell (SEC) injury during early acute obstructive cholangitis (AOC) in rats.

METHODS: Twenty one Wistar rats were divided into three groups: the AOC group, the bile duct ligated group (BDL group), and the sham operation group (SO group). The common bile duct (CBD) of rats in AOC group was dually ligated and 0.2 mL of the E. coli O₁₁₁ B₄ (5 × 10⁹ cfu/mL) suspension was injected into the upper segment, in BDL group, only the CBD was ligated and in SO group, neither injection of E. coli suspension nor CBD ligation was done, but the same operative procedure. Such group consisted of seven rats, all animals were killed 6 h after the operation. Morphological changes of the liver were observed under light and electron microscope. Expression of intercellular adhesion molecule-1 (ICAM-1) mRNA in hepatic tissue was determined with reverse transcription polymerase chain reaction (RT-PCR). The serum levels of alanine aminotransferase (ALT) were determined with anutoanalyger and cytokine-induced neutrophil chemoattractant (CINC) was determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: Neutrophils was accumulated in the hepatic sinusoids and sinusoidal endothelial cell injury existed in AOC group. In contrast, in rats of BDL group, all the features of SEC damage were greatly reduced. Expression of ICAM-1 mRNA in hepatic tissue in three groups were 7.54 ± 0.82, 2.87 ± 0.34, and 1.01 ± 0.12, respectively. There were significant differences among three groups (P < 0.05). The serum CINC levels in the three groups were 188 ± 21 ng•L⁻¹, 94 ± 11 ng•L⁻¹, and 57 ± 8 ng•L⁻¹, respectively. There were also significant differences among the three groups (P < 0.05). Activity of the serum ALT was 917 ± 167 nkat•L⁻¹, 901 ± 171 nkat•L⁻¹, and 908 ± 164 nkat•L⁻¹, respectively, (P > 0.05).

CONCLUSION: Hepatic SEC injury occurs earlier than hepatic parenchymal cells during AOC. Recruitments of circulating neutrophils in the hepatic sinusoidal space might mediate the SEC injury, and ICAM-1 in the liver may modulate the PMN of accumulation.

Expression of lipopolysaccharide binding protein and its receptor CD14 in experimental alcoholic liver disease

AIM: To evaluate the relationship between the expression of lipopolysaccharides (LPS) binding protein (LBP) and CD14 mRNA and the severity of liver injury in alcohol-fed rats.

METHODS: Twenty Wistar rats were divided into two groups: ethanol-fed group (group E) and control group (group C). Group E was fed with ethanol (5-12 g·kg¯¹·d¯¹) and group C received dextrose instead of ethanol. Rats of the two groups were sacrificed at 4 wk and 8 wk. Levels of endotoxin and alanine transaminase (ALT) in blood were measured, and liver pathology was observed under light and electronic microscopy. Expressions of LBP and CD14 mRNA in liver tissues were determined by RT-PCR analysis.

RESULTS: Plasma endotoxin levels were increased more significantly in group E (129 ± 21) ng·L¯¹ and (187 ± 35) ng·L¯¹ at 4 and 8 wk than in control rats (48 ± 9) ng·L¯¹ and (53 ± 11) ng·L¯¹, respectively (P < 0.05). Mean values of plasma ALT levels were (1867 ± 250) nkat·L¯¹ and (2450 ± 367) nkat·L¯¹ in Group E. The values were increased more dramatically in ethanol-fed rats than in Group C after 4 and 8 wk. In liver section from ethanol-fed rats, there were marked pathological changes (steatosis, cell infiltration and necrosis). In ethanol-fed rats, ethanol administration led to a significant increase in LBP and CD14 mRNA levels compared with the control group (P < 0.05).

CONCLUSION: Ethanol administration led to a significant increase in endotoxin levels in serum and LBP and CD14 mRNA expressions in liver tissues. The increase of LBP and CD14 mRNA expression might wake the liver more sensitive to endotoxin and liver injury.

Effects of aminoguanidine on nitric oxide production induced by inflammatory cytokines and endotoxin in cultured rat hepatocytes

AIM: To study the effects of aminoguanidine (AG) and two L-arginine analogues N^ω-nitro-L-arginine methyl ester (L-NAME) and N^ω-nitro-L-arginine (L-NNA) on nitric oxide (NO) production induced by cytokines (TNF-α, IL-1β, and IFN-γ) and bacterial lipopolysaccharide (LPS) mixture (CM) in the cultured rat hepatocytes, and examine their mechanisms action.

METHODS: Rat hepatocytes were incubated with AG, L-NAME, L-NNA, Actinomycin D (ActD) and dexamethasone in a medium containing CM (LPS plus TNF-α, IL-1β, and IFN-γ) for 24 h. NO production in the cultured supernatant was measured with the Griess reaction. Intracellular cGMP level was detected with radioimmunoassy.

RESULTS: NO production was markedly blocked by AG and L-NAME in a dose-dependent manner under inflammatory stimuli condition triggered by CM in vitro. The rate of the maximum inhibitory effects of L-NAME (38.9%) was less potent than that obtained with AG (53.7%, P < 0.05). There was no significant difference between the inhibitory effects of AG and two L-arginine analogues on intracellular cGMP accumulation in rat cultured hepatocytes. Non-specific NOS expression inhibitor dexamethasone(DEX) and iNOS mRNA transcriptional inhibitor ActD also significantly inhibited CM-induced NO production. AG (0.1 mmol·L^-1) and ActD (0.2 ng·L^-1) were equipotent in decreasing NO production induced by inflammatory stimuli in vitro, and both effects were more potent than that induced by non-selectivity NOS activity inhibitor L-NAME (0.1 mmol·L^-1) under similar stimuli conditions (P < 0.01).

CONCLUSION: AG is a potent selective inhibitor of inducible isoform of NOS, and the mechanism of action may be not only competitive inhibition in the substrate level, but also the gene expression level in rat hepatocytes.