Circulating IL-6 mediates lung injury via CXCL1 production after acute kidney injury in mice

Serum IL-6 is increased in patients with acute kidney injury (AKI) and is associated with prolonged mechanical ventilation and increased mortality. Inhibition of IL-6 in mice with AKI reduces lung injury associated with a reduction in the chemokine CXCL1 and lung neutrophils. Whether circulating IL-6 or locally produced lung IL-6 mediates lung injury after AKI is unknown. We hypothesized that circulating IL-6 mediates lung injury after AKI by increasing lung endothelial CXCL1 production and subsequent neutrophil infiltration. To test the role of circulating IL-6 in AKI-mediated lung injury, recombinant murine IL-6 was administered to IL-6-deficient mice. To test the role of CXCL1 in AKI-mediated lung injury, CXCL1 was inhibited by use of CXCR2-deficient mice and anti-CXCL1 antibodies in mice with ischemic AKI or bilateral nephrectomy. Injection of recombinant IL-6 to IL-6-deficient mice with AKI increased lung CXCL1 and lung neutrophils. Lung endothelial CXCL1 was increased after AKI. CXCR2-deficient and CXCL1 antibody-treated mice with ischemic AKI or bilateral nephrectomy had reduced lung neutrophil content. In summary, we demonstrate for the first time that circulating IL-6 is a mediator of lung inflammation and injury after AKI. Since serum IL-6 is increased in patients with either AKI or acute lung injury and predicts prolonged mechanical ventilation and increased mortality in both conditions, our data suggest that serum IL-6 is not simply a biomarker of poor outcomes but a pathogenic mediator of lung injury.     

Macrophages mediate lung inflammation in a mouse model of ischemic acute kidney injury

Serum IL-6 is increased in acute kidney injury (AKI) and inhibition of IL-6 reduces AKI-mediated lung inflammation. We hypothesized that circulating monocytes produce IL-6 and that alveolar macrophages mediate lung inflammation after AKI via chemokine (CXCL1) production. To investigate systemic and alveolar macrophages in lung injury after AKI, sham operation or 22 min of renal pedicle clamping (AKI) was performed in three experimental settings: 1) systemic macrophage depletion via diphtheria toxin (DT) injection to CD11b-DTR transgenic mice, 2) DT injection to wild-type mice, and 3) alveolar macrophage depletion via intratracheal (IT) liposome-encapsulated clodronate (LEC) administration to wild-type mice. In mice with AKI and systemic macrophage depletion (CD11b-DTR transgenic administered DT) vs. vehicle-treated AKI, blood monocytes and lung interstitial macrophages were reduced, renal function was similar, serum IL-6 was increased, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In wild-type mice with AKI administered DT vs. vehicle, serum IL-6 was increased. In mice with AKI and alveolar macrophage depletion (IT-LEC) vs. AKI with normal alveolar macrophage content, blood monocytes and lung interstitial macrophages were similar, alveolar macrophages were reduced, renal function was similar, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In conclusion, administration of DT in AKI is proinflammatory, limiting the use of the DTR-transgenic model to study systemic effects of AKI. Mice with AKI and either systemic mononuclear phagocyte depletion or alveolar macrophage depletion had reduced lung inflammation and lung CXCL1, but increased lung capillary leak; thus, mononuclear phagocytes mediate lung inflammation, but they protect against lung capillary leak after ischemic AKI. Since macrophage activation and chemokine production are key events in the development of acute lung injury (ALI), these data provide further evidence that AKI may cause ALI.     

HO-1 mitigates acute kidney injury and subsequent kidney-lung cross-talk

Abstract

Ischemia-reperfusion injury (IRI) is a leading cause of acute kidney injury (AKI), which contributes to the development of chronic kidney disease (CKD). IRI-induced AKI releases proinflammatory cytokines (e.g. IL-1β, TNF-α, IL-6) that induce a systemic inflammatory response, resulting in proinflammatory cells recruitment and remote organ damage. AKI is associated with poor outcomes, particularly when extrarenal complications or distant organ injuries occur. Acute lung injury (ALI) is a major remote organ dysfunction associated with AKI. Hence, kidney-lung cross-talk remains a clinical challenge, especially in critically ill population. The stress-responsive enzyme, heme oxygenase-1 (HO-1) is largely known to protect against renal IRI and may be preventively induced using hemin prior to renal insult. However, the use of hemin-induced HO-1 to prevent AKI-induced ALI remains poorly investigated. Mice received an intraperitoneal injection of hemin or sterile saline 1?day prior to surgery. Twenty-four hours later, mice underwent bilateral renal IRI for 26?min or sham surgery. After 4 or 24?h of reperfusion, mice were sacrificed. Hemin-induced HO-1 improved renal outcomes after IRI (i.e. fewer renal damage, renal inflammation, and oxidative stress). This protective effect was associated with a dampened systemic inflammation (i.e. IL-6 and KC). Subsequently, mitigated lung inflammation was found in hemin-treated mice (i.e. neutrophils influx and lung KC). The present study demonstrates that hemin-induced HO-1 controls the magnitude of renal IRI and the subsequent AKI-induced ALI. Therefore, targeting HO-1 represents a promising approach to prevent the impact of renal IRI on distant organs, such as lung.     

Interleukin-19 Mediates Tissue Damage in Murine Ischemic Acute Kidney Injury

Inflammation and renal tubular injury are major features of acute kidney injury (AKI). Many cytokines and chemokines are released from injured tubular cells and acts as proinflammatory mediators. However, the role of IL-19 in the pathogenesis of AKI is not defined yet. In bilateral renal ischemia/reperfusion injury (IRI)-induced and HgCl₂-induced AKI animal models, real-time quantitative (RTQ)-PCR showed that the kidneys, livers, and lungs of AKI mice expressed significantly higher IL-19 and its receptors than did sham control mice. Immunohistochemical staining showed that IL-19 and its receptors were strongly stained in the kidney, liver, and lung tissue of AKI mice. In vitro, IL-19 upregulated MCP-1, TGF-β1, and IL-19, and induced mitochondria-dependent apoptosis in murine renal tubular epithelial M-1 cells. IL-19 upregulated TNF-α and IL-10 in cultured HepG2 cells, and it increased IL-1β and TNF-α expression in cultured A549 cells. In vivo, after renal IRI or a nephrotoxic dose of HgCl₂ treatment, IL-20R1-deficient mice (the deficiency blocks IL-19 signaling) showed lower levels of blood urea nitrogen (BUN) in serum and less tubular damage than did wild-type mice. Therefore, we conclude that IL-19 mediates kidney, liver, and lung tissue damage in murine AKI and that blocking IL-19 signaling may provide a potent therapeutic strategy for treating AKI.     

Antecedent acute kidney injury worsens subsequent endotoxin-induced lung inflammation in a two-hit mouse model

Acute kidney injury (AKI) contributes greatly to morbidity and mortality in critically ill adults and children. Patients with AKI who subsequently develop lung injury are known to suffer worse outcomes compared with patients with lung injury alone. Isolated experimental kidney ischemia alters distal lung water balance and capillary permeability, but the effects of such an aberration on subsequent lung injury are unknown. We present a clinically relevant two-hit murine model wherein a proximal AKI through bilateral renal ischemia (30 min) is followed by a subsequent acute lung injury (ALI) via intratracheal LPS endotoxin (50 μg at 24 h after surgery). Mice demonstrated AKI by elevation of serum creatinine and renal histopathological damage. Mice with ALI and preexisting AKI had increased lung neutrophilia in bronchoalveolar lavage fluid and by myeloperoxidase activity over Sham-ALI mice. Additionally, lung histopathological damage was greater in ALI mice with preexisting AKI than Sham-ALI mice. There was uniform elevation of monocyte chemoattractant protein-1 in kidney, serum, and lung tissue in animals with both AKI and ALI over those with either injury alone. The additive lung inflammation after ALI with antecedent AKI was abrogated in MCP-1-deficient mice. Taken together, our two-hit model demonstrates that kidney injury may prime the lung for a heightened inflammatory response to subsequent injury and MCP-1 may be involved in this model of kidney-lung cross talk. The model holds clinical relevance for patients at risk of lung injury after ischemic injury to the kidney.     

Acute Lung Injury and Acute Kidney Injury Are Established by Four Hours in Experimental Sepsis and Are Improved with Pre,but Not Post,Sepsis Administration of TNF-α Antibodies

Introduction

Acute kidney injury (AKI) and acute lung injury (ALI) are serious complications of sepsis. AKI is often viewed as a late complication of sepsis. Notably, the onset of AKI relative to ALI is unclear as routine measures of kidney function (BUN and creatinine) are insensitive and increase late. In this study, we hypothesized that AKI and ALI would occur simultaneously due to a shared pathophysiology (i.e., TNF-α mediated systemic inflammatory response syndrome [SIRS]), but that sensitive markers of kidney function would be required to identify AKI.

Methods

Sepsis was induced in adult male C57B/6 mice with 5 different one time doses of intraperitoneal (IP) endotoxin (LPS) (0.00001, 0.0001, 0.001, 0.01, or 0.25 mg) or cecal ligation and puncture (CLP). SIRS was assessed by serum proinflammatory cytokines (TNF-α, IL-1β, CXCL1, IL-6), ALI was assessed by lung inflammation (lung myeloperoxidase [MPO] activity), and AKI was assessed by serum creatinine, BUN, and glomerular filtration rate (GFR) (by FITC-labeled inulin clearance) at 4 hours. 20 µgs of TNF-α antibody (Ab) or vehicle were injected IP 2 hours before or 2 hours after IP LPS.

Results

Serum cytokines increased with all 5 doses of LPS; AKI and ALI were detected within 4 hours of IP LPS or CLP, using sensitive markers of GFR and lung inflammation, respectively. Notably, creatinine did not increase with any dose; BUN increased with 0.01 and 0.25 mg. Remarkably, GFR was reduced 50% in the 0.001 mg LPS dose, demonstrating that dramatic loss of kidney function can occur in sepsis without a change in BUN or creatinine. Prophylactic TNF-α Ab reduced serum cytokines, lung MPO activity, and BUN; however, post-sepsis administration had no effect.

Conclusions

ALI and AKI occur together early in the course of sepsis and TNF-α plays a role in the early pathogenesis of both.     

Macrophage migration inhibitory factor promotes renal injury induced by ischemic reperfusion

Macrophage migration inhibitory factor (MIF) is pleiotropic cytokine that has multiple effects in many inflammatory and immune diseases. This study reveals a potential role of MIF in acute kidney injury (AKI) in patients and in kidney ischemic reperfusion injury (IRI) mouse model in MIF wild‐type (WT) and MIF knockout (KO) mice. Clinically, plasma and urinary MIF levels were largely elevated at the onset of AKI, declined to normal levels when AKI was resolved and correlated tightly with serum creatinine independent of disease causes. Experimentally, MIF levels in plasma and urine were rapidly elevated after IRI‐AKI and associated with the elevation of serum creatinine and the severity of tubular necrosis, which were suppressed in MIF KO mice. It was possible that MIF may mediate AKI via CD74/TLR4‐NF‐κB signalling as mice lacking MIF were protected from AKI by largely suppressing CD74/TLR‐4‐NF‐κB associated renal inflammation, including the expression of MCP‐1, TNF‐α, IL‐1β, IL‐6, iNOS, CXCL15(IL‐8 in human) and infiltration of macrophages, neutrophil, and T cells. In conclusion, our study suggests that MIF may be pathogenic in AKI and levels of plasma and urinary MIF may correlate with the progression and regression of AKI.     

Downregulation of TIMP2 attenuates sepsis-induced AKI through the NF-κb pathway

Acute kidney injury (AKI) is a frequent complication of sepsis and contributes to increased morbidity and mortality. Urinary tissue inhibitor of metalloproteinases-2 (TIMP2) has been recently recognized as an early biomarker to predict AKI in critically ill patients. However, the biological functions of TIMP2 remain largely unknown. In this study, we investigated the role of TIMP2 in mediating inflammation and tubular cell apoptosis in AKI. In kidney tissue taken from mice exposed to cecal ligation and puncture (CLP) and in human kidney 2 (HK-2) cells exposed to lipopolysaccharide (LPS) in culture, TIMP2 expression was significantly upregulated. The expression of TIMP2 in the kidney tissue correlated with the severity of AKI in vivo. In cultured HK-2 cells, LPS challenge markedly induced cytokine release, and recombinant cytokines promoted TIMP2 expression and apoptosis. However, TIMP2 silencing ameliorated LPS-induced cytokine release, apoptosis, and cell injury. We further found that the effects of downregulation of TIMP2 on a suppression of release of inflammatory cytokines were mediated by p-P65. Stable, kidney-specific TIMP2 knockdown mice were transduced by injecting the TIMP2 knockdown lentiviral vector into kidney parenchyma. TIMP2 silencing ameliorated CLP-induced proinflammatory cytokines, kidney dysfunction as measured by serum creatinine level, and histopathological changes. Downregulation of TIMP2 showed renoprotective effects on endotoxin-induced AKI, which was associated with the anti-inflammatory activity through inhibition of the nuclear factor (NF)-κB pathway. Collectively, our results indicate that TIMP2 plays an important role in mediating sepsis-induced AKI through regulation of NF-κB. These findings reveal the pathogenic role of TIMP2 in AKI and suggest a novel target for the treatment of AKI.     

Acute unilateral ischemic renal injury induces progressive renal inflammation, lipid accumulation, histone modification, and "end-stage" kidney disease

There is an emerging concept in clinical nephrology that acute kidney injury (AKI) can initiate chronic kidney disease (CKD). However, potential mechanisms by which this may occur remain elusive. Hence, this study tested the hypotheses that 1) AKI triggers progressive activation of selected proinflammatory genes, 2) there is a relative failure of compensatory anti-inflammatory gene expression, 3) proinflammatory lipid accumulation occurs, 4) these changes correspond with "gene-activating" histone acetylation, and 5) in concert, progressive renal disease results. CD-1 mice were subjected to 30 min of unilateral renal ischemia. Assessments were made 1 day, 1 wk, or 3 wk later. Results were contrasted to those observed in uninjured contralateral kidneys or in kidneys from normal mice. Progressive renal injury occurred throughout the 3-wk postischemic period, as denoted by stepwise increases in neutrophil gelatinase-associated lipocalin gene induction and ongoing histologic damage. By 3 wk postischemia, progressive renal disease was observed (massive tubular dropout; 2/3rds reduction in renal weight). These changes corresponded with progressive increases in proinflammatory cytokine/chemokine gene expression (MCP-1, TNF-α, TGF-β1), a relative failure of anti-inflammatory enzyme/cytokine (heme oxygenase-1; IL-10) upregulation, and progressive renal lipid (cholesterol/triglyceride) loading. Stepwise increases in collagen III mRNA and collagen deposition (Sirius red staining) indicated a progressive profibrotic response. Postischemic dexamethasone treatment significantly preserved renal mass, indicating functional significance of the observed proinflammatory state. Progressive gene-activating H3 acetylation was observed by ELISA, rising from 5% at baseline to 75% at 3 wk. This was confirmed by chromatin immunoprecipitation assay of target genes. In sum, these results provide experimental support for the clinical concept that AKI can trigger CKD, this is partially mediated by progressive postischemic inflammation, ongoing lipid accumulation results (potentially evoking "lipotoxicity"), and increasing histone acetylation at proinflammatory/profibrotic genes may contribute to this self-sustaining injury-promoting state.     

TNFR1-dependent pulmonary apoptosis during ischemic acute kidney injury

Despite advancements in renal replacement therapy, the mortality rate for acute kidney injury (AKI) remains unacceptably high, likely due to remote organ injury. Kidney ischemia-reperfusion injury (IRI) activates cellular and soluble mediators that incite a distinct pulmonary proinflammatory and proapoptotic response. Tumor necrosis factor receptor 1 (TNFR1) has been identified as a prominent death receptor activated in the lungs during ischemic AKI. We hypothesized that circulating TNF-α released from the postischemic kidney induces TNFR1-mediated pulmonary apoptosis, and we aimed to elucidate molecular pathways to programmed cell death. Using an established murine model of kidney IRI, we characterized the time course for increased circulatory and pulmonary TNF-α levels and measured concurrent upregulation of pulmonary TNFR1 expression. We then identified TNFR1-dependent pulmonary apoptosis after ischemic AKI using TNFR1-/- mice. Subsequent TNF-α signaling disruption with Etanercept implicated circulatory TNF-α as a key soluble mediator of pulmonary apoptosis and lung microvascular barrier dysfunction during ischemic AKI. We further elucidated pathways of TNFR1-mediated apoptosis with NF-κB (Complex I) and caspase-8 (Complex II) expression and discovered that TNFR1 proapoptotic signaling induces NF-κB activation. Additionally, inhibition of NF-κB (Complex I) resulted in a proapoptotic phenotype, lung barrier leak, and altered cellular flice inhibitory protein signaling independent of caspase-8 (Complex II) activation. Ischemic AKI activates soluble TNF-α and induces TNFR1-dependent pulmonary apoptosis through augmentation of the prosurvival and proapoptotic TNFR1 signaling pathway. Kidney-lung crosstalk after ischemic AKI represents a complex pathological process, yet focusing on specific biological pathways may yield potential future therapeutic targets.     

An inflammasome-independent role for epithelial-expressed Nlrp3 in renal ischemia-reperfusion injury

Cytoplasmic innate immune receptors are important therapeutic targets for diseases associated with overproduction of proinflammatory cytokines. One cytoplasmic receptor complex, the Nlrp3 inflammasome, responds to an extensive array of molecules associated with cellular stress. Under normal conditions, Nlrp3 is autorepressed, but in the presence of its ligands, it oligomerizes, recruits apoptosis-associated speck-like protein containing a caspase recruitment domain (Asc), and triggers caspase 1 activation and the maturation of proinflammatory cytokines such as IL-1β and IL-18. Because ischemic tissue injury provides a potential source for Nlrp3 ligands, our study compared and contrasted the effects of renal ischemia in wild-type mice and mice deficient in components of the Nlrp3 inflammasome (Nlrp3(-/-) and Asc(-/-) mice). To examine the role of the inflammasome in renal ischemia-reperfusion injury (IRI) we also tested its downstream targets caspase 1, IL-1β, and IL-18. Both Nlrp3 and Asc were highly expressed in renal tubular epithelium of humans and mice, and the absence of Nlrp3, but not Asc or the downstream inflammasome targets, dramatically protected from kidney IRI. We conclude that Nlrp3 contributes to renal IRI by a direct effect on renal tubular epithelium and that this effect is independent of inflammasome-induced proinflammatory cytokine production.     

Involvement of vitronectin in lipopolysaccaride-induced acute lung injury

Vitronectin is present in large concentrations in serum and participates in regulation of humoral responses, including coagulation, fibrinolysis, and complement activation. Because alterations in coagulation and fibrinolysis are common in acute lung injury, we examined the role of vitronectin in LPS-induced pulmonary inflammation. Vitronectin concentrations were significantly increased in the lungs after LPS administration. Neutrophil numbers and proinflammatory cytokine levels, including IL-1beta, MIP-2, KC, and IL-6, were significantly reduced in bronchoalveolar lavage fluid from vitronectin-deficient (vitronectin(-/-)) mice, as compared with vitronectin(+/+) mice, after LPS exposure. Similarly, LPS induced increases in lung edema, myeloperoxidase-concentrations, and pulmonary proinflammatory cytokine concentrations were significantly lower in vitronectin(-/-) mice. Vitronectin(-/-) neutrophils demonstrated decreased KC-induced chemotaxis as compared with neutrophils from vitronectin(+/+) mice, and incubation of vitronectin(+/+) neutrophils with vitronectin was associated with increased chemotaxis. Vitronectin(-/-) neutrophils consistently produced more TNF-alpha, MIP-2, and IL-1beta after LPS exposure than did vitronectin(+/+) neutrophils and also showed greater degradation of IkappaB-alpha and increased LPS-induced nuclear accumulation of NF-kappaB compared with vitronectin(+/+) neutrophils. These findings provide a novel vitronectin-dependent mechanism contributing to the development of acute lung injury.     

Genetic deficiency of Smad3 protects against murine ischemic acute kidney injury

TGF-β1 contributes to chronic kidney disease, at least in part, via Smad3. TGF-β1 is induced in the kidney following acute ischemia, and there is increasing evidence that TGF-β1 may protect against acute kidney injury. As there is a paucity of information regarding the functional significance of Smad3 in acute kidney injury, the present study explored this issue in a murine model of ischemic acute kidney injury in Smad3(+/+) and Smad3(-/-) mice. We demonstrate that, at 24 h after ischemia, Smad3 is significantly induced in Smad3(+/+) mice, whereas Smad3(-/-) mice fail to express this protein in the kidney in either the sham or postischemic groups. Compared with Smad3(+/+) mice, and 24 h following ischemia, Smad3(-/-) mice exhibited greater preservation of renal function as measured by blood urea nitrogen (BUN) and serum creatinine; less histological injury assessed by both semiquantitative and qualitative analyses; markedly suppressed renal expression of IL-6 and endothelin-1 mRNA (but comparable expression of MCP-1, TNF-α, and heme oxygenase-1 mRNA); and no increase in plasma IL-6 levels, the latter increasing approximately sixfold in postischemic Smad3(+/+) mice. We conclude that genetic deficiency of Smad3 confers structural and functional protection against acute ischemic injury to the kidney. We speculate that these effects may be mediated through suppression of IL-6 production. Finally, we suggest that upregulation of Smad3 after an ischemic insult may contribute to the increased risk for chronic kidney disease that occurs after acute renal ischemia.     

Cutting edge: TLR2-mediated proinflammatory cytokine and chemokine production by microglial cells in response to herpes simplex virus

Recent studies indicate that TLRs are critical in generating innate immune responses during infection with HSV-1. In this study, we investigated the role of TLR2 signaling in regulating the production of neuroimmune mediators by examining cytokine and chemokine expression using primary microglial cells obtained from TLR2-/- as well as wild-type mice. Data presented here demonstrate that TLR2 signaling is required for the production of proinflammatory cytokines and chemokines: TNF-alpha, IL-1beta, IL-6, IL-12, CCL7, CCL8, CCL9, CXCL1, CXCL2, CXCL4, and CXCL5. CXCL9 and CXCL10 were also induced by HSV, but their production was not dependent upon TLR2 signaling. Because TLR2-/- mice display significantly reduced mortality and diminished neuroinflammation in response to brain infection with HSV, the TLR2-dependent cytokines identified here might function as key players influencing viral neuropathogenesis.     

Absence of endogenous interleukin-10 enhances the evolution of acute lung injury

Interleukin-10 (IL-10) exerts a wide spectrum of regulatory activities in the immune and inflammatory response. The aim of this study was to investigate the role of endogenous IL-10 on the modulation of the inflammatory response in mice subjected to carrageenan-induced lung injury. When compared to carrageenan-treated IL-10 wild-type (WT) mice, carrageenan-treated IL-10 knock-out mice (IL-10KO) mice experienced a higher rate of pleural exudation, and polymorphonuclear cell migration. Exudate levels of the pro-inflammatory cytokines tumour necrosis factor, interleukin-1beta and interleukin-6 were also greatly enhanced in IL-10KO mice in comparison to wild-type mice. Lung myeloperoxidase (MPO) activity was significantly reduced in IL-10WT mice when compared to IL-10KO mice-treated with carrageenan. The degree of oxidative and nitrosative damage was significantly higher in IL-10KO mice than in wild-type littermates, as indicated by elevated malondialdehyde levels and formation of nitrotyrosine and poly (ADP-ribose) synthetase (PARS). Staining of lung tissue sections obtained from carrageenan-treated IL-10WT with an anti-COX-2 antibody showed a positive staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase (iNOS) was found mainly in the macrophages of the inflamed lungs from carrageenan-treated IL-10WT mice. The intensity and degree of the staining for COX-2 and iNOS were markedly enhanced in tissue sections obtained from carrageenan-treated IL-10KO mice. Most notably, the degree of lung injury caused by carrageenan was also enhanced in IL-10KO mice. Taken together, our results clearly demonstrate that endogenous IL-10 exerts an anti-inflammatory role during acute inflammation and tissue damage associated with carrageenan-induced pleurisy, possibly by regulating neutrophil recruitment, and the subsequent cytokine and oxidant generation.     

Pulmonary overexpression of IL-10 augments lung fibrosis and Th2 responses induced by silica particles

Chronic inflammation and proinflammatory cytokines as well as T helper type 2 (Th2) cytokines have been involved in the pathogenesis of pulmonary injury and lung fibrosis. The actual role of IL-10 in lung fibrosis is still unclear because this cytokine has been identified as Th2 but possesses strong anti-inflammatory properties. To better dissect the potential role of IL-10 in silica-induced lung fibrosis, IL-10 was overexpressed in the lung of mice by adenoviral gene transfer during the inflammatory (administered at day -1) or the fibrotic (administered at day +30) stages of the disease. Pulmonary overexpression of IL-10 during both silica-induced lung inflammation and fibrosis exacerbated the fibrotic lesions as estimated by the measurement of hydroxyproline and other biochemical and histological markers. Increased expression of IL-10 significantly enhanced the number of lung lymphocytes and bronchoalveolar lavage fluid IgG1 but not IgG2a levels, indicating the induction of a Th2-like immune response. In addition, the production of the profibrotic Th2 cytokines IL-4 and IL-13 was also significantly increased upon IL-10 overexpression. No difference in transforming growth factor-beta or PGE(2) production was noted after adenoviral IL-10 treatment of silica-treated mice. Together, these data indicate that the increased expression of IL-10 significantly contributed to silica-induced lung fibrosis by exacerbating the Th2 response and the production of the profibrotic cytokines IL-4 and IL-13.     

Maternal LPS induces cytokines in the amniotic fluid and corticotropin releasing hormone in the fetal rat brain

Perinatal infections are a risk factor for fetal neurological pathologies, including cerebral palsy and schizophrenia. Cytokines that are produced as part of the inflammatory response are proposed to partially mediate the neurological injury. This study investigated the effects of intraperitoneal injections of lipopolysaccharide (LPS) to pregnant rats on the production of cytokines and stress markers in the fetal environment. Gestation day 18 pregnant rats were treated with LPS (100 microg/kg body wt i.p.), and maternal serum, amniotic fluid, placenta, chorioamnion, and fetal brain were harvested at 1, 6, 12, and 24 h posttreatment to assay for LPS-induced changes in cytokine protein (ELISA) and mRNA (real-time RT-PCR) levels. We observed induction of proinflammatory cytokines interleukin (IL)-1 beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) as well as the anti-inflammatory cytokine IL-10 in the maternal serum within 6 h of LPS exposure. Similarly, proinflammatory cytokines were induced in the amniotic fluid in response to LPS; however, no significant induction of IL-10 was observed in the amniotic fluid. LPS-induced mRNA changes included upregulation of the stress-related peptide corticotropin-releasing factor in the fetal whole brain, TNF-alpha, IL-6, and IL-10 in the chorioamnion, and TNF-alpha, IL-1 beta, and IL-6 in the placenta. These findings suggest that maternal infections may lead to an unbalanced inflammatory reaction in the fetal environment that activates the fetal stress axis.     

IL-10 Mediated Regulation of Liver Inflammation during Acute Murine Cytomegalovirus Infection

Various cell types in both lymphoid and non-lymphoid tissues produce the anti-inflammatory cytokine interleukin (IL)-10 during murine cytomegalovirus (MCMV) infection. The functions of IL-10 in the liver during acute infection and the cells that generate this cytokine at this site have not been extensively investigated. In this study, we demonstrate that the production of IL-10 in the liver is elevated in C57BL/6 mice during late acute MCMV infection. Using IL-10 green fluorescence protein (GFP) reporter knock-in mice, designated IL-10-internal ribosomal entry site (IRES)-GFP-enhanced reporter (tiger), NK cells are identified as major IL-10 expressing cells in the liver after infection, along with T cells and other leukocytes. In the absence of IL-10, mice exhibit marked elevations in proinflammatory cytokines and in the numbers of mononuclear cells and lymphocytes infiltrating the liver during this infection. IL-10-deficiency also enhances liver injury without improving viral clearance from this site. Collectively, the results indicate that IL-10-producing cells in the liver provide protection from collateral injury by modulating the inflammatory response associated with MCMV infection.