Caveolin‐1 (Cav‐1), the principal structural protein of caveolae, is implicated in normal endothelial barrier function, buts its role in lung inflammation is not well understood. Using caveolin‐1 knockout (Cav‐1 −/−) mice, we addressed the role of Cav‐1 in sepsis‐induced lung injury. We assessed lung inflammation in Cav‐1 −/− mice following i.p. injection of LPS. Neutrophil (PMN) binding was measured by an adhesion assay performed on primary cultured mouse endothelial cells. PMN sequestration was assessed by myeloperoxidase activity in the whole lung. Lung microvascular permeability was determined using iodine‐125 radio‐labeled albumin. When compared to wild type (WT) mice, Cav‐1 −/− mice exhibited significantly impaired PMN binding and sequestration after LPS challenge. LPS‐induced increases in lung microvascular permeability and edema formation were also markedly reduced in Cav‐1 −/− mice relative to WT. To address the basis of the reduced lung inflammation, we examined the specific role of nitric oxide (NO). As Cav‐1 is known to sequester eNOS rendering it inactive, we postulated that in Cav‐1 −/− mice there should be increased eNOS activity and eNOS‐derived NO levels in response to LPS challenge. We observed a marked increase in eNOS activity and NO production in Cav‐1 −/− lung relative to WT. Corresponding to the known role of NO in modulating NF‐κB activity, we also noted a time‐dependent suppression of NF‐κB activity in Cav‐1 −/− mice. Thus, Cav‐1 expression and its ability to regulate eNOS‐derived NO production is a crucial determinant of the lung inflammatory response to sepsis. This abstract is funded by: NIH(T32HL007829, HL60678, HL77806)

The E3 ubiquitin ligase Cblb has a crucial role in the prevention of chronic inflammation and autoimmunity. Here we show that Cblb also has an unexpected function in acute lung inflammation. Cblb attenuates the sequestration of inflammatory cells in the lungs after administration of lipopolysaccharide (LPS). In a model of polymicrobial sepsis in which acute lung inflammation depends on the LPS receptor (Toll-like receptor 4, TLR-4), the loss of Cblb expression accentuates acute lung inflammation and reduces survival. Loss of Cblb significantly increases sepsis-induced release of inflammatory cytokines and chemokines. Cblb controls the association between TLR4 and the intracellular adaptor MyD88. Expression of wild-type Cblb, but not expression of a Cblb mutant that lacks E3 ubiquitin ligase function, prevents the activity of a reporter gene for the transcription factor nuclear factor-kappaB (NF-kappaB) in monocytes that have been challenged with LPS. The downregulation of TLR4 expression on the cell surface of neutrophils is impaired in the absence of Cblb. Our data reveal that Cblb regulates the TLR4-mediated acute inflammatory response that is induced by sepsis.

Caveolin-1 (Cav1), the scaffolding protein of caveolae, has been shown to play an important role in host defense and inflammation. However , the underlying molecular basis for these actions remains elusive. Here , using double mutant mice with genetic deletions of Cav1 and NOS3 , we show that chronic endothelial nitric oxide synthase (eNOS) activation secondary to loss of Cav1 serves a crucial immunomodulatory function through tyrosine nitration-mediated impairment of interleukin-1 receptor associated kinase (IRAK)4, a signaling component required for nuclear factor-B activation and innate immunity. We observed an eNOS-dependent decrease in the plasma concentration of pro-inflammatory cytokines and marked improvement of survival in Cav1 ؊/؊ mice following lipopolysaccharide challenge. Activation of eNOS secondary to loss of Cav1 resulted in decreased activation of nuclear factor-B in response to lipopolysaccharide challenge, and thereby protected the animals from lipopolysaccharide-induced lung injury. IRAK4 was prominently nitrated in Cav1-deficient endothelial cells, whereas eNOS deletion in Cav1-deficient endothelial cells resulted in marked decrease of IRAK4 nitration and restored the inflammatory response after lipopolysaccharide challenge. Furthermore, in vitro nitration of IRAK4 resulted in impairment of the kinase activity. Thus , eNOS activation secondary to loss of Cav1 signals dampening of the innate immune response to lipopolysaccharide through IRAK4 nitration and the resultant impairment of kinase activity , and consequently mitigates inflammatory lung injury.

Sirolimus is a potent immunosuppressive agent used with increasing frequency in solid organ transplantation (SOT). However, it has been associated with rare but devastating pulmonary toxicity. We describe a case of pulmonary toxicity associated with the use of sirolimus in a 64-yr-old heart transplant recipient. We also review all reported cases of sirolimus-associated lung toxicity among SOT recipients in an effort to better understand the pathophysiology, risk factors, and outcomes of this rare but serious complication. A total of 64 cases have been reported since January 2000 including the present case. These consisted of 52 kidney, four lung, three liver, three heart, one heart-lung and one islet cell transplants. In most cases, patients presented with a constellation of symptoms consisting of fever, dyspnea, fatigue, cough, and occasionally hemoptysis. Although the risk factors for this association have not been clearly established, high dose, late exposure to the drug and male gender have been noticed among most. In almost all of the reported cases, sirolimus was added later in the course of immunosuppressive therapy, usually in an effort to attenuate the nephrotoxic effects of a previous regimen containing a calcineurin inhibitor. There were three deaths (4.8%) among 62 patients with known status at follow up; all deaths were among heart transplant recipients. Most patients (95%) resolved their clinical and radiographic findings with discontinuation or dose-reduction of the drug. Sirolimus-induced pulmonary toxicity is a rare but serious entity that should be considered in the differential diagnosis of a transplant recipient presenting with respiratory compromise. Dose-reduction or discontinuation of the drug can be life saving.