In the present study, therefore, we hypothesized that serum IL-6 produced by circulating monocytes would stimulate alveolar macrophage production of CXCL1, leading to neutrophil recruitment and lung injury after AKI

In the present study, therefore, we hypothesized that serum IL-6 produced by circulating monocytes would stimulate alveolar macrophage production of CXCL1, leading to neutrophil recruitment and lung injury after AKI. was comparable, 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 comparable, alveolar macrophages were reduced, renal function was comparable, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In conclusion, administration of DT in AKI is usually 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 CPI 4203 may cause ALI. Keywords:IL-6, CXCL1, macrophage depletion, acute lung injury acute kidney injury(AKI) is usually a common complication in hospitalized patients that is associated with increased mortality (3,9,24,25,35). The increased mortality of AKI may be explained, in part, by the development of pulmonary complications such as respiratory failure and acute lung injury (ALI) (8,29). For example, patients with AKI are twice as likely to need mechanical ventilation as patients without AKI (30,44) and patients with AKI have an impaired ability to CPI 4203 wean from mechanical ventilation (43). We recently demonstrated that this proinflammatory cytokines IL-6 and IL-8 are increased in the serum of patients with AKI and predict prolonged mechanical ventilation (26). In mice, we exhibited that IL-6 and CXCL1 (also known as KC and a murine analog of IL-8) are increased in the serum after AKI (18). Furthermore, inhibition of IL-6 utilizing IL-6-deficient mice and IL-6 antibodies improved lung injury Rabbit polyclonal to ZC3H12D after ischemic AKI and bilateral nephrectomy; improvement in lung CPI 4203 injury was associated with a reduction in lung CXCL1, neutrophil infiltration, and pulmonary capillary leak (22). Together, these data suggest that IL-6 contributes to AKI-mediated lung injury via upregulation of lung CXCL1. The cellular source of serum IL-6 in AKI is usually unknown. Mononuclear phagocytes, known as monocytes in circulation and macrophages in tissues, are sources of cytokines in inflammatory conditions. With regard to lung injury, alveolar macrophage production of IL-8 may mediate ALI (5,28,45). In the present study, therefore, we hypothesized that serum IL-6 produced by circulating monocytes would stimulate alveolar macrophage production of CXCL1, leading to neutrophil recruitment and lung injury after AKI. To determine whether mononuclear phagocytes are a source of serum IL-6 in AKI, systemic mononuclear phagocytes were depleted by diphtheria toxin (DT) injection to CD11b-DTR transgenic mice. To specifically determine the role of alveolar macrophages in AKI-mediated lung injury, liposome-encapsulated clodronate (LEC) was administered intratracheally to deplete alveolar, but not systemic, mononuclear phagocytes (42). == METHODS == == == == Animals. == Eight- to 12-wk-old CD11b-DTR transgenic mice on a BALB/c background, BALB/c wild-type mice, and wild-type C57BL6 mice that weighed 2025 g were used. Mice were maintained on a standard diet, and water was freely available. All experiments were conducted with adherence to the National Institutes of HealthGuide for the Care and Use of Laboratory Animals. The animal protocol was approved by the Animal Care and Use Committee of the University of Colorado at Denver. == Surgical protocol. == Mice were anesthetized with intraperitoneal avertin (2,2,2-tribromoethanol; Aldrich, Milwaukee, WI) and exposed to either sham operation or ischemic AKI. In each group, a midline incision was made, and both renal pedicles were uncovered. In the AKI group, both renal pedicles were clamped for 22 min. After clamp removal, kidneys were observed for blood reperfusion, as noted by a return to their original color. The abdomen was closed in one layer. Sham surgery consisted of the same procedure, except no clamps were applied. CD11b-DTR mice received either 25 ng/g body wt DT or vehicle (sterile saline) via tail vein injection 18 h before sham operation or ischemic AKI. To deplete alveolar macrophages specifically, C57BL6 mice received either 10 g CPI 4203 LEC (Encapsula NanoSciences, Nashville, TN) or empty liposomes via intratracheal (IT) injection 24 h before sham operation or ischemic AKI. == Tissue collection. == Animals were euthanized by anesthetic overdose using intraperitoneal pentobarbital sodium, after which blood, bronchoalveolar lavage (BAL) fluid, and organs were collected. == Serum. ==.