Rat gastric injury after lipopolysaccharide: Role of inducible nitric oxide synthase

Calcium trafficking and gastrointestinal physiology following an acute lipopolysaccharide challenge in pigs

The influence of systemic immune activation on whole-body calcium (Ca) trafficking and gastrointestinal tract (GIT) physiology is not clear. Thus, the study objectives were to characterize the effects of lipopolysaccharide (LPS) on Ca pools and GIT dynamics to increase understanding of immune-induced hypocalcemia, ileus, and stomach hemorrhaging. Twelve crossbred pigs [44 ± 3 kg body weight (BW)] were randomly assigned to 1 of 2 intramuscular treatments: (1) control (CON; 2 mL saline; n = 6) or (2) LPS (40 µg LPS/kg BW; n = 6). Pigs were housed in metabolism stalls to collect total urine and feces for 6 h after treatment administration, at which point they were euthanized, and various tissues, organs, fluids, and digesta were weighed, and analyzed for Ca content. Data were analyzed with the MIXED procedure in SAS 9.4. Rectal temperature and respiration rate increased in LPS relative to CON pigs (1.4 °C and 32%, respectively; P ≤ 0.05). Inflammatory biomarkers such as circulating alkaline phosphatase, aspartate aminotransferase, and total bilirubin increased in LPS compared with CON pigs whereas albumin decreased (P ≤ 0.02). Plasma glucose and urea nitrogen decreased and increased, respectively, after LPS (43% and 80%, respectively; P < 0.01). Pigs administered LPS had reduced circulating ionized calcium (iCa) compared to CON (15%; P < 0.01). Considering estimations of total blood volume, LPS caused an iCa deficit of 23 mg relative to CON (P < 0.01). Adipose tissue and urine from LPS pigs had reduced Ca compared to CON (39% and 77%, respectively; P ≤ 0.05). There did not appear to be increased Ca efflux into GIT contents and no detectable increases in other organ or tissue Ca concentrations were identified. Thus, while LPS caused hypocalcemia, we were unable to determine where circulating Ca was trafficked. LPS administration markedly altered GIT dynamics including stomach hemorrhaging, diarrhea (increased fecal output and moisture), and reduced small intestine and fecal pH (P ≤ 0.06). Taken together, changes in GIT physiology suggested dyshomeostasis and alimentary pathology. Future research is required to fully elucidate the etiology of immune activation-induced hypocalcemia and GIT pathophysiology.

The role of nitric oxide and oxidative stress in intestinal damage induced by selenium deficiency in chickens

Nitric oxide (NO) is an essential messenger molecule and is associated with inflammation and oxidative stress. Although NO has important biological functions in mammals, its role in the mechanism that occurs after intestinal injuries in chickens remains unknown. The objective of the present study was to investigate the real role of NO and oxidative stress in the intestinal injuries of chickens induced by selenium (Se) deficiency. A total 150 chickens were randomly divided into the following two groups: a low-Se group (L group, fed a Se-deficient diet containing 0.020 mg/kg Se) and a control group (C group, fed a commercial diet containing 0.2 mg/kg Se). The activities and mRNA levels of glutathione peroxidase (GSH-Px), the production of glutathione (GSH) and NO, and the protein and mRNA levels of inducible nitric oxide synthase (iNOS) were examined in the intestinal tissues (duodenum, jejunum, and rectum) at 15, 25, 35, 45, and 55 days. Methane dicarboxylic aldehyde (MDA) levels were also detected by assay kits. Then, the morphologies of the tissues were observed under the microscope after hematoxylin and eosin staining (H&E staining). The results showed that Se deficiency induced higher inflammatory damage and MDA levels (P < 0.05), which were accompanied by higher levels of iNOS and NO but lower levels of GSH and GSH-Px (P < 0.05). Our results indicated that Se deficiency induced oxidative damage in the intestinal tracts of chickens and that low levels of GSH-Px and high contents of NO may exert a major role in the injury of the intestinal tract induced by Se deficiency.

Creation of a female rabbit model for intrauterine adhesions using mechanical and infectious injury

BACKGROUND

Intrauterine adhesions (IUA) are associated with secondary amenorrhea, infertility, and recurrent pregnancy loss. An IUA animal model would contribute to research on the pathogenesis and pathologic changes of IUA and the exploration of new treatments.

MATERIALS AND METHODS

Eighty female rabbits were randomly divided into five groups: mechanical injury (16), infectious injury (16), dual injury (16), experimental control (16), and normal (16). Three methods were applied to establish the model: uterine curettage, uterine cavity left alone, lipopolysaccharide surgical suture in place for 48 h, and suture retention for 48 h after curettage. A sterile surgical suture was left in the uterine cavity for 48 h in the experimental control group. Histologic changes were monitored at 0, 24, 48, and 72 h and 7, 14, and 28 d after operation.

RESULTS

The experiments revealed that endometrium injured by simple curettage or infection could be repaired. Although endometrial regeneration was severely impaired by dual injury, the ratio of the area with endometrial stromal fibrosis to total endometrial area significantly increased (P < 0.01), and the number of endometrial glands was significantly reduced (P < 0.01).

CONCLUSIONS

The method of dual injury can establish a stable rabbit IUA model.

Laparotomy attenuates lipopolysaccharide-induced gastric bleeding in the rat

Lipopolysaccharide (LPS) increases systemic inflammation and causes duodenogastric reflux of bile and gastric bleeding. Laparotomy prevents gastric injury from the luminal irritant bile, but its effects on LPS-induced gastric injury are unknown. We hypothesized that laparotomy would diminish inflammation and attenuate gastric bleeding caused by LPS. In the rat, laparotomy, done either before or after administration of LPS, attenuated LPS-induced bile reflux, gastric bleeding, and cyclooxygenase-2, but not inducible nitric oxide synthase, expression when compared to controls given LPS. Laparotomy also blunted LPS-induced changes in serum cytokine production. These data suggest that laparotomy has gastroprotective effects by preventing LPS-induced bile reflux and gastric bleeding and by a mechanism mediated, at least in part by cyclooxygenase-2.

Ketamine suppresses LPS-induced bile reflux and gastric bleeding in the rat

BACKGROUND

Although ketamine has many beneficial effects in a rat model of noninfectious inflammation with lipopolysaccharide (LPS), its effects on gut ileus are unknown. We hypothesized that ketamine would improve LPS-induced ileus and therefore examined its effects on gastric emptying and intestinal transit as well as duodenogastric bile reflux and associated gastric bleeding.

METHODS

Male rats received saline or ketamine (7 mg/kg ip) 1 hour before saline or LPS (20 mg/kg ip) for 5 hours. Thirty minutes before killing, rats received orogastric rhodamine B isothiocyanate-labeled dextran and 5 minutes later fluorescein isothiocyanate-labeled dextran via a duodenal catheter. GI contents were collected for dye, bile acid, and hemoglobin (index of bleeding) determinations.

RESULTS

LPS significantly impaired intestinal transit and increased duodenogastric bile reflux and gastric luminal hemoglobin content. Ketamine improved intestinal transit, prevented LPS-induced bile reflux, and diminished gastric bleeding. In mechanistic studies, ketamine also attenuated LPS-induced upregulation of the proinflammatory genes inducible nitric oxide synthase and cyclo-oxygenase-2 in the stomach but preserved expression of the anti-inflammatory gene heme-oxygenase-1 (Western blot).

CONCLUSIONS

These data suggest that ketamine may prevent LPS-induced gastric bleeding by decreasing bile reflux through improved intestinal transit or by local changes in nitric oxide, prostaglandin, and carbon monoxide metabolism.

Fasting exacerbates and feeding diminishes LPS-induced liver injury in the rat

INTRODUCTION

Enteral nutrition improves clinical outcomes. The effects of feeding on LPS induced liver injury are unknown. We hypothesized that feeding would attenuate liver injury from LPS.

METHODS

Fasted or fed rats were given LPS (20 mg/kg i.p.) or saline for 5 h and sacrificed. Serum aminotransferases and cytokines (immunoassay) were measured. Oxidative stress protein (iNOS, COX2, and HO1) assessments (Western immunoblot) were also obtained.

RESULTS

In fasted rats, LPS significantly increased serum aminotransferase levels, enhanced hepatic COX2, iNOS, and HO1 immunoreactivity, and increased serum cytokine levels when compared to controls. While feeding diminished liver enzymes, attenuated expression of COX2 and iNOS, and blunted production of pro-inflammatory cytokines, it did not modulate LPS-induced expression of the anti-inflammatory markers HO1 and IL-10.

CONCLUSION

These data suggest that feeding decreases liver injury by attenuating expression of pro-inflammatory mediators while maintaining expression of anti-inflammatory mediators, both systemically and locally.

iNOS expression in oral and gastrointestinal tract mucosa

It is known that the overproduction of nitric oxide (NO) by nitric oxide synthase (NOS) occurs during the progression of various inflammatory diseases in intestinal tract. NOS inhibitors or inducible nitric oxide synthase (iNOS) gene expression inhibitors should be considered as potential anti-inflammatory agents, as NO synthesized by iNOS is related to various pathophysiological processes including inflammation. In order to understand the relationship between iNOS and pathological reactions such as the inflammatory process and malign transformation clearly, the existence and amount of constitutive expression should be determined. It is crucial to comprehend the harmful and protective amounts of iNOS expressions in order to clarify the relationship between iNOS and pathological processes. Evidently, only after this inspection is it possible to utilize iNOS as a marker and treatment instrument during the diagnosis and treatment of malign transformation and the inflammatory process.

Selective iNOS inhibition reduces renal damage induced by cisplatin

Cisplatin is a chemotherapeutic agent used in the treatment of several cancer tumors; however, nephrotoxicity has restricted its use. Reactive oxygen species and peroxynitrite, which is formed by the reaction between superoxide anion and nitric oxide (NO*), are implicated in cisplatin-induced nephrotoxicity. In contrast, both toxic and beneficial effects of NO* have been suggested in cisplatin-induced nephrotoxicity. Therefore, nowadays the role of NO* in this experimental model remains controversial. The aim of the present work was to elucidate the role of NO* in cisplatin-induced renal damage using N-[3-(aminomethyl)benzyl]acetamidine (1400W), a selective and irreversible inhibitor of iNOS. The mRNA levels of iNOS were increased in cisplatin-treated rats. The administration of 1400W reduced the cisplatin induced histological damage, renal dysfunction (increase in proteinuria and kidney injury molecule expression and decrease in creatinine clearance), tubulointerstitial infiltration, oxidative stress (increase in renal malondialdehyde and inmmunostaining for 4-hydroxy-2-nonenal) and nitrosative stress (immunostaining for 3-nitrotyrosine). In addition, the administration of 1400W was unable to modify systolic blood pressure in control rats. Our data demonstrate that selective iNOS inhibition reduces the cisplatin-induced nephrotoxicity and nitrosative stress which strongly suggest that in this experimental model (1) the NO* production is toxic and (2) iNOS is the main source of NO*.