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At least 343 records · Page 19Linked to original sources
PubMed2003

Pancreatic enzymes sustain systemic inflammation after an initial endotoxin challenge.

BACKGROUND: Sepsis is accompanied by severe inflammation whose mechanism remains uncertain. We recently demonstrated that pancreatic proteases in the ischemic intestine have the ability to generate powerful inflammatory mediators that can be detected in the portal vein and in the general circulation. This study was designed to examine several circulatory and inflammatory indices during experimental endotoxemia and intraintestinal pancreatic protease inhibition. METHODS: Immediately after intravenous endotoxin administration, the small intestine was subjected to intraluminal lavage with and without gabexate mesilate, an inhibitor of pancreatic proteases. Shams and rats without lavage served as controls. Hemodynamics, leukocyte (neutrophil and monocyte), and endothelial cell activation, as well as organ injury in the intestine and the cremaster muscle, were examined. RESULTS: After endotoxin administration, control rats developed hypotension, tachycardia, hyperventilation, and leukopenia. The intestine and plasma contained mediators that activated leukocytes. The leukocyte-endothelial interaction within the cremaster muscle microcirculation was enhanced. Endotoxin administration resulted in elevated interleukin-6 plasma levels. Histologic evidence indicated liver and intestinal injury. In contrast, blockade of pancreatic proteases in the intestinal lumen significantly improved hemodynamic parameters and reduced all indices of inflammation in plasma and cell injury in skeletal muscle microcirculation. CONCLUSIONS: Inflammatory mediators derived from the intestine by pancreatic proteases may be involved in the prolonged inflammatory response and sustain symptoms of sepsis after endotoxin challenge.

Animals↗
PubMed1997

Multivariate regression modeling for the prediction of inflammation, systemic pressure, and end-organ function in severe sepsis.

The purpose of this study was to evaluate the feasibility of developing multivariate equations that predicted blood pressure and measured levels of end-organ function indicators quantitatively up to 72 h in advance in critically ill patients with severe sepsis. Data collected prospectively from 59 patients entered into two sequential placebo-controlled clinical trials of recombinant interleukin-1 receptor antagonist in severe sepsis and septic shock was analyzed retrospectively. A series of multivariate equations were developed to predict systemic pressure, coagulation, and vital organ function indicators quantitatively at 24, 48, and 72 h after the onset of severe sepsis. These equations used physiologic and clinical laboratory measurements, plus circulating levels of eicosanoids and cytokines obtained when severe sepsis criteria first were met, and end-organ function indicators measured 24, 48, and 72 h later. Multivariate predictive equations were developed for temperature, white blood cell count, mean arterial pressure (MAP), Pao2/FiO2 ratio, the Murray acute lung injury score, alanine and aspartate aminotransferases, prothrombin time, partial thromboplastin time, platelet count, serum creatinine, and Glasgow Coma Scale. The percentage of data variation explained by the equations ranged from 11.4% (MAP at 48 h) to 85.1% (platelet count at 24 h). Linear regression analysis of predicted values, obtained by entering baseline data from individual patients into the multivariate equations, versus observed results at 24, 48, and 72 h yielded regression coefficients ranging from .371 (MAP at 48 h) to .924 (platelet count at 24 h). Among patients without end-organ dysfunction at baseline, sensitivities for predicting values consistent with the onset of organ failure were > or = 88% in 21/27 (78%) of the predictive equations. Resolution of organ failure indicators present at baseline was predicted successfully in individual patients, with 20/27 (74%) specificities > or = 76%. In critically ill patients with severe sepsis, multivariate analysis of interactions among clinical observations, standard laboratory tests, and inflammatory response mediators produced equations that predicted systemic blood pressure and inflammatory and end-organ function indicators quantitatively up to 72 h in advance. Whether or not this methodology might be developed further to predict subclinically the onset and resolution of acute organ failure and shock in critically ill patients, and if it can be validated in a prospective trial will require further studies.

Adolescent↗
PubMed2005

Dramatic elevations of interleukin-6 and acute-phase reactants in athletes participating in the ultradistance foot race spartathlon: severe systemic inflammation and lipid and lipoprotein changes in protracted exercise.

CONTEXT AND OBJECTIVE: Plasma IL-6, the serum inflammatory markers C-reactive protein (CRP) and serum amyloid A (SAA), and the tissue destruction marker-free plasma DNA, as well as the circulating lipid profile, were examined in athletes participating in the ultradistance foot race of the 246-km Spartathlon. SETTING, DESIGN, AND PARTICIPANTS: This race consists of continuous, prolonged, brisk exercise. Blood samples were obtained from 15 male athletes, who finished the race in less than 36 h, taken before, at the end of, and 48 h after the end of the race. RESULTS: IL-6, CRP, SAA, and free plasma DNA levels markedly increased (by 8000-, 152- 108-, and 10-fold, respectively) over the baseline at the end of the race. However, IL-6 levels returned to normal by 48 h, whereas CRP, SAA, and free plasma DNA remained elevated. The mean values of cholesterol, triglycerides, low-density lipoprotein, and apolipoprotein B decreased to a minimum value at the end of the race and remained low 48 h after the race. High-density lipoprotein levels, on the other hand, were mildly increased at the end of the race (P < 0.015) and decreased to normal 48 h after the race. Apolipoprotein AI levels decreased significantly during the time course of the exercise and remained low 48 h after the race (P < 0.001). CONCLUSIONS: These observations suggest that continuous, prolonged, moderate-intensity exercise is associated with markedly elevated IL-6 and acute-phase reactant concentrations, peripheral tissue damage, and significant changes in serum lipid levels. The biochemical changes observed during the Spartathlon amount to a potent systemic inflammatory response, which might explain severe cardiovascular events that occur during prolonged exercise in compromised individuals.

Acute-Phase Proteins↗
PubMed2006

Ventilation-induced lung injury in rats is associated with organ injury and systemic inflammation that is attenuated by dexamethasone.

OBJECTIVE: To determine whether mechanical ventilation using high tidal volume is associated with nonpulmonary organ dysfunction that can be attenuated by dexamethasone. DESIGN: Prospective randomized animal intervention study. SETTING: Animal care facility in a university hospital. SUBJECTS: Sedated and tracheostomized male Sprague-Dawley rats. INTERVENTIONS: Three groups of rats were ventilated with different strategies: tidal volume = 9 mL/kg, positive end-expiratory pressure = 8 cm H(2)O, control group (C); tidal volume = 35 mL/kg, positive end-expiratory pressure = 0 cm H(2)O, overventilated group (OV); and tidal volume = 35 mL/kg, positive end-expiratory pressure = 0 cm H(2)O, plus administration of 6 mg/kg dexamethasone intraperitoneally (OV + dexamethasone). All rats were ventilated for 75 mins with respiratory rate = 70 breaths/min, FIO(2) = 0.35, and plateau time = 0. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure and peak airway pressure were monitored. We measured arterial blood gases, aspartate aminotransferase, alanine aminotransferase, lactate, nitrates and nitrites, tumor necrosis factor-alpha, and interleukin-6 serum concentration. Lung slices were prepared for blind histologic examination. Heart tissue was analyzed for cyclooxygenase-1 and -2 expression (reverse transcription-polymerase chain reaction). Compared with the C group, the OV group showed hypotension; worsened gas exchange; increased aspartate aminotransferase, lactate, nitrates and nitrites, and interleukin-6 serum concentrations; and hyaline membrane formation in the lungs, as well as increased cyclooxygenase-1 and cyclooxygenase-2 expression in the heart. Dexamethasone prevented the pulmonary and cardiovascular injury and attenuated the increase in aspartate aminotransferase, nitrates and nitrites, interleukin-6, and cyclooxygenase-1 and cyclooxygenase-2 expression. CONCLUSIONS: High tidal volume ventilation induces cardiovascular, pulmonary, and liver injury as well as a systemic proinflammatory response. These changes are attenuated by dexamethasone, suggesting that inflammatory rather than purely hemodynamic mechanisms are involved in the changes induced by high tidal volume ventilation.

Animals↗
PubMed2004

Fever in systemic inflammation: roles of purines.

Extracellular purine nucleotide and nucleoside signalling molecules, such as ATP and adenosine, acting through specific receptors (P2 and P1, respectively) play significant roles in the mechanisms underlying the febrile response. A variety of P2 and P1 receptor subunits have been identified in the hypothalamus, the area of the brain that orchestrates the febrile response. Importantly, both ATP and adenosine have been shown to modulate release and/or action of cytokines that are implicated in fever, as well as to be involved in the central mechanisms of cardiovascular and respiratory control. Our data indicate that at the level of the anterior hypothalamus extracellular ATP is involved in the control of the development of fever. A population of warm-sensitive neurones in the anterior hypothalamus is likely to be the site of action of ATP on body temperature. ATP-induced cytokine release does not appear to play a significant role in the hypothalamic mechanisms leading to the development of the febrile response. However, the blockade of fever by P2 receptor antagonists given systemically suggests that ATP-mediated signalling may play a role in the release of pyrogenic cytokines in the periphery. At the level of the anterior hypothalamus adenosine appears to be released tonically, and acts to maintain body temperature under afebrile conditions. There is also evidence that adenosine-mediated signalling may play a role in the hypothalamic mechanisms controlling the degree of body temperature increase during fever. Our investigations have identified possible mechanisms by which purines modulate the febrile response. The actions of purines on body temperature during fever are most likely "site specific" (brain vs. periphery), may or may not involve their effect on cytokine release and/or action, and are likely to involve P2 and P1 receptors of different subtypes. Further extensive studies are needed to elucidate these mechanisms in greater detail and may lead to the development of new approaches for modifying febrile, cytokine and acute-phase responses to infection.

Adenosine↗
PubMed2003

Role of cytokines in photodynamic therapy-induced local and systemic inflammation.

Photodynamic therapy (PDT) of tumour results in the rapid induction of an inflammatory response that is considered important for the activation of antitumour immunity, but may be detrimental if excessive. The response is characterised by the infiltration of leucocytes, predominantly neutrophils, into the treated tumour. Several preclinical studies have suggested that suppression of long-term tumour growth following PDT using Photofrin((R)) is dependent upon the presence of neutrophils. The inflammatory pathways leading to the PDT-induced neutrophil migration into the treated tumour are unknown. In the following study, we examined, in mice, the ability of PDT using the second-generation photosensitiser 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) to induce proinflammatory cytokines and chemokines, as well as adhesion molecules, known to be involved in neutrophil migration. We also examined the role that these mediators play in PDT-induced neutrophil migration. Our studies show that HPPH-PDT induced neutrophil migration into the treated tumour, which was associated with a transient, local increase in the expression of the chemokines macrophage inflammatory protein (MIP)-2 and KC. A similar increase was detected in functional expression of adhesion molecules, that is, E-selectin and intracellular adhesion molecule (ICAM)-1, and both local and systemic expression of interleukin (IL)-6 was detected. The kinetics of neutrophil immigration mirrored those observed for the enhanced production of chemokines, IL-6 and adhesion molecules. Subsequent studies showed that PDT-induced neutrophil recruitment is dependent upon the presence of MIP-2 and E-selectin, but not on IL-6 or KC. These results demonstrate a PDT-induced inflammatory response similar to, but less severe than obtained with Photofrin((R)) PDT. They also lay the mechanistic groundwork for further ongoing studies that attempt to optimise PDT through the modulation of the critical inflammatory mediators.

Animals↗
PubMed2005

Systemic inflammation induces apoptosis with variable vulnerability of different brain regions.

During severe sepsis several immunological defence mechanisms initiate a cascade of inflammatory events leading to multi-organ failure including septic encephalopathy and ultimately death. To assess the reaction and participation of parenchymal brain cells during endotoxaemia, the present study evaluates micro- and astroglial activation, expression of the inducible nitric oxide synthase (iNOS) pro- and antiapoptotic protein levels Bax and Bcl-2, and apoptosis. Male Wistar rats received 10 mg/kg lipopolysaccharide (LPS) or vehicle intraperitoneally and were sacrificed for brain collection at 4, 8 or 24 h after induction of experimental sepsis. One group of animals received 10 mg/kg of the NOS inhibitor N-monomethyl-L-arginine (L-NMMA) intraperitoneally 1 day before and during the experiment. Immunohistochemical evaluation revealed a sepsis-induced, time-dependent increase in the immunoreactivity of iNOS, glial fibrillary acidic protein (GFAP) and activated microglia (ED-1), paralleled by a time-dependent increase of apoptotic brain cells marked by terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL), an increase of Bax-positive cells and a decrease of Bcl-2-positive cells. Evaluation of different brain regions revealed that the hippocampus is the most vulnerable region during experimental sepsis. iNOS-inhibition with L-NMMA significantly reduced the number of apoptotic cells in hippocampus, midbrain and cerebellum. In addition, it reduced the increase of the proapoptotic protein Bax in all examined brain regions and reduced the decrease of Bcl-2-positive cells in the hippocampus. We therefore conclude, that peripheral inflammation leads to a profound glial activation, the generation of nitric oxide and changes of Bax and Bcl-2 protein regulation critical for apoptosis.

Animals↗
PubMed2005

Long-term changes in blood-brain barrier permeability and white matter following prolonged systemic inflammation in early development in the rat.

Epidemiological evidence in human fetuses links inflammation during development with white matter damage. Breakdown of the blood-brain barrier has been proposed as a possible mechanism. This was investigated in the present study by inducing a prolonged inflammatory response in newborn rats, with intraperitoneal injections of lipopolysaccharide (LPS; 0.2 mg/kg) given at postnatal (P) day 0, P2, P4, P6 and P8. An acute phase response was present over the whole period of injections. Changes in blood-brain barrier permeability were determined for small (sucrose and inulin) and large (protein) molecules. During and immediately after the inflammatory response, plasma proteins were detected in the brain only within white matter tracts, indicating an increased permeability of the blood-brain barrier to protein during this period. The alteration in permeability to protein was transient. In contrast, the permeability of the blood-brain barrier to 14C-sucrose and 14C-inulin was significantly higher in adult animals that had received serial LPS injections during development. Adult animals receiving a single 1 mg/kg LPS injection at P0 showed no alteration in blood-brain barrier permeability to either small or larger molecules. A significant decrease in the volume of CNPase immunoreactive presumptive white matter tracts occurred in the external capsule and corpus callosum at P9. These results demonstrate that a prolonged systemic inflammatory response in the early postnatal period in rats causes size selective increases in blood-brain barrier permeability at different stages of brain development and results in changes in white matter volume.

Animals↗
PubMed2004

Expression of rat I-TAC/CXCL11/SCYA11 during central nervous system inflammation: comparison with other CXCR3 ligands.

The chemokines are a large gene superfamily with critical roles in development and immunity. The chemokine receptor CXCR3 appears to play a major role in the trafficking of activated Th1 lymphocytes. There are at least three major ligands for CXCR3: mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11, and of these three ligands, CXCL11 is the least well-characterized. In this study, we have cloned a rat ortholog of CXCL11, evaluated its function, and examined its expression in the Th-1-mediated disease, experimental autoimmune encephalomyelitis (EAE) in the rat. Based on its predicted primary amino-acid sequence, rat I-TAC/CXCL11 was synthesized and shown to induce chemotaxis of activated rat T lymphocytes in vitro and the in vivo migration of T lymphocytes when injected into the skin. I-TAC/CXCL11 expression, as determined by RT-PCR, increased in lymph node and spinal cord tissue collected from rats in which EAE had been actively induced, and in spinal cord tissue from rats in which EAE had been passively induced. The kinetics of expression were similar to that of CXCR3 and IP-10/CXCL10, although expression of both CXCR3 and IP-10/CXCL10 was more intense than that of I-TAC/CXCL11 and increased more rapidly in both lymph nodes and the spinal cord. Only minor levels of expression of the related chemokine mig/CXCL9 were observed. Immunohistochemistry revealed that the major cellular source of I-TAC/CXCL11 in the central nervous system (CNS) during EAE is likely to be the astrocyte. Together, these data indicate that I-TAC/CXCL11 is expressed in the CNS during the clinical phase of EAE. However, the observation that I-TAC/CXCL11 is expressed after receptor expression is detected suggests that it is not essential for the initial migration of CXCR3-bearing cells into the CNS.

Amino Acid Sequence↗
PubMedDate not supplied

Multiorgan failure is an adaptive, endocrine-mediated, metabolic response to overwhelming systemic inflammation.

Sepsis and other critical illnesses produce a biphasic inflammatory, immune, hormonal, and metabolic response. The acute phase is marked by an abrupt rise in the secretion of so-called stress hormones with an associated increase in mitochondrial and metabolic activity. The combination of severe inflammation and secondary changes in endocrine profile diminish energy production, metabolic rate, and normal cellular processes, leading to multiple organ dysfunction. This perceived failure of organs might instead be a potentially protective mechanism, because reduced cellular metabolism could increase the chances of survival of cells, and thus organs, in the face of an overwhelming insult. We propose that, first, multiple organ failure induced by critical illness is primarily a functional, rather than structural, abnormality. Indeed, it may not be failure as such, but a potentially protective, reactive mechanism. Second, the decline in organ function is triggered by a decrease in mitochondrial activity and oxidative phosphorylation, leading to reduced cellular metabolism. Third, this effect on mitochondria might be the consequence of acute-phase changes in hormones and inflammatory mediators.

Acute-Phase Reaction↗
PubMed2002

Central nervous system inflammation and neurological disease in transgenic mice expressing the CC chemokine CCL21 in oligodendrocytes.

To study the biological role of the chemokine ligands CCL19 and CCL21, we generated transgenic mice expressing either gene in oligodendrocytes of the CNS. While all transgenic mice expressing CCL19 in the CNS developed normally, most (18 of 26) of the CCL21 founder mice developed a neurological disease that was characterized by loss of landing reflex, tremor, and ataxia. These neurological signs were observed as early as postnatal day 9 and were associated with weight loss and death during the first 4 wk of life. Microscopic examination of the brain and spinal cord of CCL21 transgenic mice revealed scattered leukocytic infiltrates that consisted primarily of neutrophils and eosinophils. Additional findings included hypomyelination, spongiform myelinopathy with evidence of myelin breakdown, and reactive gliosis. Thus, ectopic expression of the CC chemokine CCL21, but not CCL19, induced a significant inflammatory response in the CNS. However, neither chemokine was sufficient to recruit lymphocytes into the CNS. These observations are in striking contrast to the reported activities of these molecules in vitro and may indicate specific requirements for their biological activity in vivo.

Animals↗
PubMed2006

beta-Adrenergic blockade during systemic inflammation: impact on cellular immune functions and survival in a murine model of sepsis.

AIM OF THE STUDY: Adrenergic immuno-modulation mediated by beta-adrenergic receptors has been demonstrated. Pharmacological blockade of beta-adrenergic receptors is a therapeutic intervention frequently used in critically ill patients. The effect of beta-adrenergic blockade on cellular immune functions in a critical illness, such as polymicrobial sepsis, has not been investigated. METHODS: Male NMRI-mice were subjected to sham operation or to sepsis (caecal ligation and puncture, CLP) following administration of either the non-selective beta-adrenergic antagonist propranolol (0.5 mg/kg s.c. every 12 h in 1 ml vehicle) or saline 0.9% (1 ml s.c. every 12 h). Mice were kept in metabolic cages and were sacrificed 48 h after induction of sepsis. Survival rate, clinical situation (body weight and temperature, fluid and food intake, urine output), and immunological variables (splenocyte proliferation, apoptosis, and IFN-gamma and IL-6 release) were determined. RESULTS: Administration of propranolol in septic mice increased the splenocyte apoptosis rate, reduced the proliferative capacity of splenocytes, and modulated cellular cytokine release (IL-6, IFN-gamma). This was paralleled by a higher loss of body weight and temperature, and a decreased urine output. Furthermore, treatment with propranolol increased the sepsis-induced lethality from 47% up to 68%, respectively. CONCLUSION: beta-Adrenergic blockade was accompanied by alterations of cellular immune functions, a deterioration in the clinical situation and a reduced survival in a murine model of sepsis. These data demonstrate the potential immuno-modulatory effects of beta-adrenergic antagonists.

Adrenergic beta-Antagonists↗
PubMed2005

Metallothionein reduces central nervous system inflammation, neurodegeneration, and cell death following kainic acid-induced epileptic seizures.

We examined metallothionein (MT)-induced neuroprotection during kainic acid (KA)-induced excitotoxicity by studying transgenic mice with MT-I overexpression (TgMT mice). KA induces epileptic seizures and hippocampal excitotoxicity, followed by inflammation and delayed brain damage. We show for the first time that even though TgMT mice were more susceptible to KA, the cerebral MT-I overexpression decreases the hippocampal inflammation and delayed neuronal degeneration and cell death as measured 3 days after KA administration. Hence, the proinflammatory responses of microglia/macrophages and lymphocytes and their expression of interleukin (IL)-1, IL-6, IL-12, tumor necrosis factor-alpha and matrix metalloproteinases (MMP-3, MMP-9) were significantly reduced in hippocampi of TgMT mice relative to wild-type mice. Also by 3 days after KA, the TgMT mice showed significantly less delayed damage, such as oxidative stress (formation of nitrotyrosine, malondialdehyde, and 8-oxoguanine), neurodegeneration (neuronal accumulation of abnormal proteins), and apoptotic cell death (judged by TUNEL and activated caspase-3). This reduced bystander damage in TgMT mice could be due to antiinflammatory and antioxidant actions of MT-I but also to direct MT-I effects on the neurons, in that significant extracellular MT presence was detected. Furthermore, MT-I overexpression stimulated astroglia and increased immunostaining of antiinflammatory IL-10, growth factors, and neurotrophins (basic fibroblastic growth factor, transforming growth factor-beta, nerve growth factor, brain-derived neurotrophic factor, glial-derived neurotrophic factor) in hippocampus. Accordingly, MT-I has different functions that likely contribute to the increased neuron survival and improved CNS condition of TgMT mice. The data presented here add new insight into MT-induced neuroprotection and indicate that MT-I therapy could be used against neurological disorders.

Amyloid beta-Peptides↗
PubMed2004

Signaling the brain in systemic inflammation: the role of complement.

The complement (C) cascade is activated in almost immediate reaction to the appearance in the body of pathogenic microorganims and their products, e.g., bacterial endotoxic lipopolysaccharide (LPS), resulting in the generation of a series of potent bioactive fragments that have critical roles in the innate immune response of the afflicted host, including, potentially, the production of the fever that so characteristically marks bacterial infections. For instance, its derivatives C3a, C3b, iC3b, C5a, and C5b-9 independently induce the production by myeloid and non-myeloid cells of the cytokines interleukin (IL)-1(, IL-6 and tumor necrosis factor-(, and of prostaglandin (PG)E2, all putative mediators of fever. Therefore, any one of these C components could be involved, centrally or peripherally, in the induction of the febrile response to LPS. Indeed, we have shown that hypocomplementation by cobra venom factor (CVF) dose-dependently attenuates LPS-induced fever in guinea pigs and wild-type (WT) mice, and that C5 gene-ablated mice are unable to develop fever after LPS. In further studies, we found that a specific antagonist to the C5a receptor, C5aR1a, prevents the LPS-induced febrile rise of WT and C3 null mutant mice, implicating C5a as the responsible factor. Various lines of evidence from our laboratory suggest that the macrophages of the liver (Kupffer cells [Kc]) may be the specific target cells of C5a and that the product they release may be PGE2. PGE2, in turn, may be the substance that binds to vagal afferents in the liver that convey the pyrogenic message to the brain. Other studies by our group (not included in this review) have separately traced the neural pathway by which this message may be transmitted from the liver to the brain and processed there for action. The purpose of this article is to review the studies that have led us to conclude that C5a, Kc and Kc-generated PGE2 may be integrally involved in the pathogenesis of LPS fever. If further verified, these results will be important for better understanding how infectious stimuli may trigger the multivariate acute-phase responses generally, and fever particularly, that promptly spring into action to defend the continued well-being of the afflicted host.

Animals↗
PubMed1998

Kupffer cell depletion partially prevents hepatic heme oxygenase 1 messenger RNA accumulation in systemic inflammation in mice: role of interleukin 1beta.

The heme oxygenase 1 (HO-1) gene is rapidly activated in the liver after lipopolysaccharide (LPS) treatment. Ninety minutes after LPS treatment (0.1 mg/kg, intraperitoneally) hepatic HO-1 messenger RNA (mRNA) of mice was 40 times the control value. To investigate the hepatic cellular source of the increased HO-1 transcript, we treated mice with LPS and galactosamine (700 mg/kg, intraperitoneally), a selective transcriptional inhibitor of hepatocytes. Galactosamine prevented the LPS-mediated increase of HO-1 mRNA in the liver, indicating that hepatocytes are the main cell type in which HO-1 mRNA accumulates after LPS treatment. We then tested in vitro and in vivo the hypothesis that LPS-mediated hepatic accumulation of HO-1 mRNA is caused by intercellular communication between Kupffer cells and hepatocytes. Isolated rat hepatocytes showed an increase in HO-1 mRNA compared with controls after 90 minutes of exposure to a LPS stimulated Kupffer cell-conditioned medium. This suggests that soluble mediators from Kupffer cells were responsible for this effect. To study the role of Kupffer cells in vivo, we treated mice with Kupffer cell-inactivating or -depleting agents and LPS. Gadolinium chloride and liposome-encapsulated dichloromethylene diphosphonate lowered LPS-mediated HO-1 mRNA accumulation (by about 50%); in these groups hepatic levels of interleukin (IL)-1beta were decreased, by more than 75%. Methylpalmitate hardly affected hepatic HO-1 mRNA accumulation or IL-1beta content after LPS treatment. There was no relationship between HO-1 mRNA and serum TNF or IL-6 levels. These results suggest that LPS-mediated hepatic HO-1 mRNA accumulation is a hepatocyte response partly caused by soluble mediators, particularly IL-1beta, released from Kupffer cells.

Animals↗