Protective effects of a PAF receptor antagonist and a neutrophil elastase inhibitor on multiple organ failure induced by cerulein plus lipopolysaccharide in rats

Liver Necrosis and Lethal Systemic Inflammation in a Murine Model of Rickettsia typhi Infection: Role of Neutrophils, Macrophages and NK Cells

Rickettsia (R.) typhi is the causative agent of endemic typhus, an emerging febrile disease that is associated with complications such as pneumonia, encephalitis and liver dysfunction. To elucidate how innate immune mechanisms contribute to defense and pathology we here analyzed R. typhi infection of CB17 SCID mice that are congenic to BALB/c mice but lack adaptive immunity. CB17 SCID mice succumbed to R. typhi infection within 21 days and showed high bacterial load in spleen, brain, lung, and liver. Most evident pathological changes in R. typhi-infected CB17 SCID mice were massive liver necrosis and splenomegaly due to the disproportionate accumulation of neutrophils and macrophages (MΦ). Both neutrophils and MΦ infiltrated the liver and harbored R. typhi. Both cell populations expressed iNOS and produced reactive oxygen species (ROS) and, thus, exhibited an inflammatory and bactericidal phenotype. Surprisingly, depletion of neutrophils completely prevented liver necrosis but neither altered bacterial load nor protected CB17 SCID mice from death. Furthermore, the absence of neutrophils had no impact on the overwhelming systemic inflammatory response in these mice. This response was predominantly driven by activated MΦ and NK cells both of which expressed IFNγ and is considered as the reason of death. Finally, we observed that iNOS expression by MΦ and neutrophils did not correlate with R. typhi uptake in vivo. Moreover, we demonstrate that MΦ hardly respond to R. typhi in vitro. These findings indicate that R. typhi enters MΦ and also neutrophils unrecognized and that activation of these cells is mediated by other mechanisms in the context of tissue damage in vivo.

Development of a rat model of severe acute pancreatitis-associated lung injury

AIM: To establish a rat model of severe acute pancreatitis (SAP)-associated lung injury (LI) by occluding the head of the pancreas.

METHODS: Two hundred and ten rats were randomly and equally divided into a control group, a sham-operated group, and a SAP-LI model group. Rats in each group was further divided into seven subgroups for testing at 0, 6, 12, 18, 24, 36, and 48 h (n = 10 for each). The SAP-LI model group underwent occlusion of the head of the pancreas with vessel forceps. The sham-operated group underwent a surgical procedure similar to the SAP-LI model group but the head of the pancreas was not occluded. The control group only underwent anesthetization for 3 h. Blood, pulmonary alveolar lavage fluid, lung tissue and pancreatic tissue samples were collected at various time points. The level of serum amylase, content of serum proteins, percentage of polymorphonuclear neutrophils, wet/dry weight ratio of lung tissue, and content of proteins in pulmonary alveolar lavage fluid were determined. Pathological changes in lung and pancreatic tissues were observed under a light microscope.

RESULTS: All rats were live in the experiment. The level of serum amylase (5052.1 U/L ± 114.9 U/L, P < 0.01) and the percentage of polymorphonuclear neutrophils (75.2% ± 5.8%, P < 0.05) reached the peak at 12 h, and the ratio of the content of proteins in pulmonary alveolar lavage fluid to the content of serum proteins reached the peak at 36 h in the SAP-LI model group (0.009021 ± 0.000107, P < 0.01). The wet/dry weight ratio of lung tissue, reaching the minimum at 36 h in the SAP-LI mold group (1.2001 ± 0.0443, P < 0.01), differed significantly between the SAP-LI group and the other two groups (both P < 0.05). Pancreatic tissue injury became worse with the prolongation of time. LI was most serious at 36 h. Serum amylase showed a correlation with the percentage of polymorphonuclear neutrophils and wet/dry weight ratio of lung tissue (r = 0.788,P < 0.01; r = 0.365, P = 0.002). The percentage of polymorphonuclear neutrophils showed a correlation with the wet/dry weight ratio of lung tissue (r = 0.348, P = 0.003). The wet/dry weight ratio of lung tissue showed a correlation with the ratio of the content of proteins in pulmonary alveolar lavage fluid to the content of serum proteins (r = -0.717, P < 0.01). The score of pancreatic tissue pathology showed a correlation with that of lung tissue pathology (r = 0.934, P < 0.01).

CONCLUSION: A new rat model of SAP-associated LI has been successfully developed by occluding the head of the pancreas, providing an ideal model for studying the pathogenesis and treatment of this condition. LI was most serious at 36 h, which is the optimal time point for inducing SAP-associated LI.

TLR2, TLR4 and the MYD88 signaling pathway are crucial for neutrophil migration in acute kidney injury induced by sepsis

The aim of this study was to investigate the role of TLR2, TLR4 and MyD88 in sepsis-induced AKI. C57BL/6 TLR2^−/−, TLR4^−/− and MyD88^−/− male mice were subjected to sepsis by cecal ligation and puncture (CLP). Twenty four hours later, kidney tissue and blood samples were collected for analysis. The TLR2^−/−, TLR4^−/− and MyD88^−/− mice that were subjected to CLP had preserved renal morphology, and fewer areas of hypoxia and apoptosis compared with the wild-type C57BL/6 mice (WT). MyD88^−/− mice were completely protected compared with the WT mice. We also observed reduced expression of proinflammatory cytokines in the kidneys of the knockout mice compared with those of the WT mice and subsequent inhibition of increased vascular permeability in the kidneys of the knockout mice. The WT mice had increased GR1^+low cells migration compared with the knockout mice and decreased in GR1^+high cells migration into the peritoneal cavity. The TLR2^−/−, TLR4^−/−, and MyD88^−/− mice had lower neutrophil infiltration in the kidneys. Depletion of neutrophils in the WT mice led to protection of renal function and less inflammation in the kidneys of these mice. Innate immunity participates in polymicrobial sepsis-induced AKI, mainly through the MyD88 pathway, by leading to an increased migration of neutrophils to the kidney, increased production of proinflammatory cytokines, vascular permeability, hypoxia and apoptosis of tubular cells.

Neutrophils in development of multiple organ failure in sepsis

Multiple organ failure is a major threat to the survival of patients with sepsis and systemic inflammation. In the UK and in the USA, mortality rates are currently comparable with and projected to exceed those from myocardial infarction. The immune system combats microbial infections but, in severe sepsis, its untoward activity seems to contribute to organ dysfunction. In this Review we propose that an inappropriate activation and positioning of neutrophils within the microvasculature contributes to the pathological manifestations of multiple organ failure. We further suggest that targeting neutrophils and their interactions with blood vessel walls could be a worthwhile therapeutic strategy for sepsis.

Neutrophil engagement and septic challenge in acute experimental pancreatitis in rats

AIM: To investigate the influence of neutrophil adhesion molecule blockade with monoclonal antibody (MoAb CD11b) and E. coli lipopolysaccharide (LPS) administration on experimental acute pancreatitis (AP).

METHODS: AP was induced by four ip injections of cerulein (Cn) at 1-h intervals. MoAb CD 11b and LPS were administered at the beginning of the experiment.

RESULTS: The neutrophil count and chemiluminescence were diminished at the beginning of AP. The oxidative stress parameters were found within the pancreatic gland. MoAb CD 11b used for AP resulted in a significant reduction of pancreatic infiltration and pancreatitis oxidative stress parameters. Serum interleukin-6 (IL-6) was not detected in AP animals, whereas high serum IL-6 concentration was noted only in animals receiving LPS.

CONCLUSION: Neutrophils are involved in pancreatic damage in the early stage of AP. Neutrophil infiltration reduction protects the pancreatic gland from destruction during AP. LPS does not change the early course of Cn pancreatitis in rats.

Calcium/calmodulin-dependent kinase II is required for platelet-activating factor priming

Platelet-activating factor (PAF) primes the macrophage proinflammatory response to inflammatory stimuli, such as lipopolysaccharide (LPS). The cellular events responsible for this priming or reprogramming remain unresolved, but may occur through an increase in cytosolic calcium, inducing calcium/calmodulin-dependent kinase (CaMK) activation. To study this, differentiated THP-1 cells were used to study the effect of CaMK II and IV inhibition on PAF-induced reprogramming of TLR4-mediated events. LPS induced p38, ERK 1/2, and JNK/SAPK phosphorylation, NF-kappaB and AP-1 activation, and TNF-alpha and IL-10 production. PAF pretreatment selectively increased LPS-induced ERK 1/2, JNK/SAPK, NF-kappaB and AP-1 activation, and TNF-alpha production. Inhibition of CaMK II prevented PAF-induced priming of these events. Inhibition of CaMK IV prevented LPS-induced ERK 1/2, JNK/SAPK, NF-kappaB and AP-1 activation, and TNF-alpha production, but increased IL-10 production with or without PAF pretreatment. Neither CaMK II nor IV inhibition had any affect on p38 activity. These data suggest that the function of CaMK II is essential for PAF-induced macrophage priming. This priming event is mediated in part by modulation of ERK 1/2, JNK/SAPK, NF-kappaB, and AP-1 activation. CaMK IV, on the other hand, is not specific for priming by PAF and appears to have a direct link in TLR4-mediated events.

Dextromethorphan prevents circulatory failure in rats with endotoxemia

Dextromethorphan (DM), an antitussive agent, has been claimed to have anti-inflammatory and immunomodulatory effects in vitro. Thus, the aim of this study was to evaluate the effects of DM on sepsis induced by intravenous (i.v.) administration of lipopolysaccharide (LPS) in anesthetized Wistar rats and by intraperitoneal administration in conscious ICR mice. Results demonstrated that pretreatment with DM (1, 5 and 10 mg/kg, i.v.) significantly attenuated the deleterious hemodynamic changes (e.g., hypotension and tachycardia) in rats treated with LPS. Meanwhile, DM (5 mg/kg) significantly inhibited the elevation of plasma tumor necrosis factor-alpha and interleukin-10 levels, as well as values of GOT and GPT (as an index of liver function), and BUN and creatinine (as an index of renal function) caused by LPS. The induction of inducible NO synthase and the overproduction of NO and superoxide anions by LPS were also reduced by DM. Moreover, infiltration of neutrophils into the lungs and liver of rats 6 h after treatment with LPS was also reduced by DM. In conclusion, the beneficial effects of DM on LPS-induced sepsis result from its anti-inflammatory and antioxidant effects. Thus, DM can possibly be used as a prophylactic agent for sepsis in the future.

Influence of molecule CD 11b blockade on the course of acute ceruleine pancreatitis in rats

Polymorphonuclear cells (PMN) activation is an essential step in acute pancreatitis (AP). We investigated the activation status of PMN, oxidative stress and pancreatic damage in early stage of experimental ceruleine pancreatitis in rats. The PMN action was modulated by monoclonal antibody CD 11b administration. The circulating WBC and polymorphonuclear cells count was reduced after AP induction. Chemiluminescence of whole blood PMN was remarkably reduced in AP group and increased after MoAb CD 11b administration. The CD 11b blockade significantly reduced the WBC infiltration and malondialdehyde (MDA) concentration within pancreatic gland. These data suggest that activated PMN are an important factor in early AP pathogenesis. Neutrophil aggregation within pancreatic gland modulated by monoclonal antibody CD11b contribute to the extent of injury during the early stage of ceruleine experimental pancreatitis in rats.

Testosterone acts as a coronary vasodilator by a calcium antagonistic action

T acts as a vasodilator in vitro and in vivo. Supplemental T therapy in humans with angina improves symptoms and reduces objective measures of ischemia. In left anterior descending coronary arteries taken from adult male Wistar rats, T abolishes 100+/-4.2% of calcium-dependent contraction induced by potassium chloride, 82.3+/-6.1% of the mostly calcium-dependent contraction induced by prostaglandin-F-2-alpha, but only 45.3+/-3.4% of the contraction induced by phorbol-12,13-dibutyrate (PDBu) in the presence of extracellular calcium, and 54.5+/-4.5% of the contraction induced by PDBu in the absence of extracellular calcium. These findings suggest that T is primarily inhibiting the calcium-dependent elements of vascular contraction.

Concurrent inflammation as a determinant of susceptibility to toxicity from xenobiotic agents

Sensitivity to the toxic effects of xenobiotic agents is influenced by a number of factors. Recent evidence derived from studies using experimental animals suggests that inflammation is one of these factors. For example, induction of inflammation by coexposure to bacterial endotoxin, vitamin A or Corynebacterium parvum increases injury in response to a number of xenobiotic agents that target liver. These agents are diverse in chemical nature and in mechanism of hepatotoxic action. Factors critical to the augmentation of liver injury by inflammation include Kupffer cells, neutrophils, cytokines such as tumor necrosis factor-alpha (TNF-alpha) and lipid mediators such as prostaglandins, but these may vary depending on the xenobiotic agent and the mechanisms by which it alters hepatocellular homeostasis. In addition, the timing of inflammagen exposure can qualitatively alter the toxic response to chemicals. Inflammation-induced increases in susceptibility to toxicity are not limited to liver. Concurrent inflammation also sensitizes animals to the toxic effects of agents that damage the respiratory tract, kidney and lymphoid tissue. It is concluded that inflammation should be considered as a determinant of susceptibility to intoxication by xenobiotic exposure.