The activity of pathway-selective estrogen receptor ligands in experimental septic shock.

Estrogen receptors (ER) are widely expressed in multiple genital and nongenital tissues. Upon engagement of these receptors, multiple genes are affected in target tissues via estrogen response elements. Nonsteroidal pathway-selective ER ligands have recently been identified that inhibit NF-kappaB transcriptional activity and are devoid of conventional estrogenic activities on genital tissues. These pathway-selective ligands are potent anti-inflammatory agents in vivo and may prove to be of therapeutic utility in systemic inflammatory states. These pathway-selective ER ligands were tested in the murine listeriosis model, the neutropenic rat model, and the mouse cecal ligation and puncture model. WAY-204688 did not have any significant activity after systemic infection by Listeria monocytogenes. In the neutropenic rat model, WAY-204688 provided a significant survival benefit against an otherwise lethal challenge of Pseudomonas aeruginosa 12.4.4 compared with the control group (88% versus 25% survival; P < 0.05). Preservation of mucosal weight and prevention of histopathologic changes were observed with the administration of WAY-204688. Similar findings were observed in a cecal ligation and puncture model with WAY-204688 and a related compound WAY-169916. These results indicate that oral administration of these pathway-selective ER ligands preserved gastrointestinal barrier function and improve outcome in experimental models of systemic infection and inflammation. These agents may prove to be useful clinically as a novel treatment strategy for severe sepsis.

Inhibition of the Src and Jak kinases protects against lipopolysaccharide-induced acute lung injury.

The cascade of cellular and molecular pathways mediating acute lung injury is complex and incompletely defined. Although the Src and Jak family of kinases is upregulated in LPS-induced murine lung injury, their role in the development of lung injury is unknown. Here we report that systemic inhibition of these kinases using specific small molecule inhibitors (PP2, SU6656, tyrphostin A1) significantly attenuated LPS-induced lung injury, as determined by histologic and capillary permeability assays. These inhibitors blocked LPS-dependent cytokine and chemokine production in the lung and in the serum. In contrast, lung-targeted inhibition of these kinases in the airway epithelium via adenoviral-mediated gene transfer of dominant negative Src or of suppressor of cytokine signaling (SOCS-1) disrupted lung cytokine production but had no effect on systemic cytokine production or lung vascular permeability. Mice were significantly protected from lethal LPS challenge by the small molecule inhibitors of Jak and Src kinase. Importantly, this protection was still evident even when the inhibitors were administered 6 hours after LPS challenge. Taken together, these observations suggest that Jak and Src kinases participate in acute lung injury and verify the potential of this class of selective tyrosine kinase inhibitors to serve as novel therapeutic agents for this disease.

Inter-alpha-inhibitor proteins are endogenous furin inhibitors and provide protection against experimental anthrax intoxication.

Inter-alpha-inhibitor protein (IalphaIp) functions as an endogenous serine protease inhibitor in human plasma, and IalphaIp levels diminish rapidly during acute inflammatory states. One potential target for IalphaIp is furin, a cell-associated serine endopeptidase essential for the activation of protective antigen and the formation of anthrax lethal toxin (LT). IalphaIp blocks furin activity in vitro and provides significant protection against cytotoxicity for murine peritoneal macrophages exposed to up to 500 ng/ml LT. A monoclonal antibody (MAb), 69.31, that specifically blocks the enzymatic activity of IalphaIp eliminates its protective effect against LT-induced cytotoxicity. IalphaIp (30 mg/kg of body weight) administered to BALB/c mice 1 hour prior to an intravenous LT challenge resulted in 71% survival after 7 days compared with no survivors among the control animals (P < 0.001). We conclude that human IalphaIp may be an effective preventative or therapeutic agent against anthrax intoxication.

Chloroquine enhances survival in Bacillus anthracis intoxication.

The intentional release of anthrax in the United States in 2001 resulted in 11 cases of inhalational disease, with an attendant mortality rate of 45%. Current therapeutic options for anthrax are limited; antimicrobials target only replicating organisms, thus allowing bacterial toxins to cause unchecked, devastating physiological derangements in the host. Novel approaches that target the cytotoxic effects of anthrax exotoxins are needed. Chloroquine (CQ), a commonly used antimalarial agent, endows anthrax-intoxicated murine peritoneal macrophages with a 50% and 35% marginal survival advantage at 2 and 4 h, respectively, over that of untreated control cells. The cell rescue is dose dependent and, at lower concentrations, results in delayed cell death. We subsequently studied the effect of CQ in BALB/c mice challenged with anthrax lethal toxin. CQ-treated mice demonstrated reduced tissue injury, as assessed by histopathological examination of the spleen and by peripheral blood differential cell count ratios. CQ significantly enhanced survival and may augment current treatment and prophylaxis options for this otherwise lethal infection.

Activation of the STAT pathway in acute lung injury.

Acute lung injury (ALI) is a devastating clinical problem with a mortality as high as 60%. It is now appreciated that ALI represents a cytokine excess state that involves the microvasculature of multiple organs. The signal transducers and activators of transcription (STAT) family of transcription factors activate critical mediators of cytokine responses, but there is limited knowledge about their role in mediating ALI. In the present study, we demonstrate that the STAT transcription factors are activated rapidly in the lungs after intraperitoneal and intranasal LPS administration in mice. We also demonstrated that LPS activates both the STAT kinases, Src and JAK, in the lung with kinetics that are consistent with STAT activation. LPS treatment resulted in STAT3 activation throughout the resident lung cells, as well as in the recruited inflammatory cells. Whereas direct LPS treatment did not lead to STAT activation in cultured epithelial or endothelial cells, IL-6 activated STAT3 in both of these cell types. Furthermore, IL-6 was induced by LPS in serum and in the lung with kinetics consistent with STAT3 activation, suggesting that IL-6 may be one mechanism of STAT activation by LPS. In addition, STAT activation required reactive oxygen species, as the overexpression of catalase in mice prevented LPS-mediated STAT activation in the lung. STATs may be a common pathway for mediating ALI, regardless of the inciting factor, as STAT activation also occurred in both a gastric acid aspiration and acute pancreatitis model of ALI. Finally, STATs are activated in the lung long before signs of ALI are present, suggesting that the STAT transcription factors may play a role in initiating the inflammatory response seen in the lung.