Cavin1; a regulator of lung function and macrophage phenotype.

Caveolae are cell membrane invaginations that are highly abundant in adipose tissue, endothelial cells and the lung. The formation of caveolae is dependent on the expression of various structural proteins that serve as scaffolding for these membrane invaginations. Cavin1 is a newly identified structural protein whose deficiency in mice leads to loss of caveolae formation and to development of a lipodystrophic phenotype. In this study, we sought to investigate the functional role of Cavin1 in the lung. Cavin1 deficient mice possessed dramatically altered distal lung morphology and exhibited significant physiological alterations, notably, increased lung elastance. The changes in distal lung architecture were associated with hypercellularity and the accumulation of lung macrophages. The increases in lung macrophages occurred without changes to circulating numbers of mononuclear cells and without evidence for increased proliferation. However, the increases in lung macrophages were associated with higher levels of macrophage chemotactic factors CXCL2 and CCL2 in BAL fluid from Cavin1-/- mice suggesting a possible mechanism by which these cells accumulate. In addition, lung macrophages from Cavin1-/- mice were larger and displayed measurable differences in gene expression when compared to macrophages from wild-type mice. Interestingly, macrophages were also increased in adipose tissue but not in liver, kidney or skeletal muscle from Cavin1-/- mice, and similar tissue specificity for macrophage accumulation was observed in lungs and adipose tissue from Caveolin1-/- mice. In conclusion, this study demonstrates an important role for Cavin1 in lung homeostasis and suggests that caveolae structural proteins are necessary for regulating macrophage number and phenotype in the lung.

Obesity: "priming" the lung for injury.

Acute lung injury (ALI) is a severe inflammatory condition that develops in response to local and systemic lung challenges. To date, specific risk factors for development of ALI remain poorly defined. Recent epidemiological studies have reported obesity as an important predisposing factor in the development of this condition. Although the pathogenic mechanisms linking obesity and ALI have not been well-elucidated, emerging scientific evidence has described factors secreted by adipose tissue that have important biological activities in lung and has suggested that altered secretion of these factors during obesity contributes to increased ALI susceptibility. The objective of this manuscript is to highlight recent clinical evidence supporting the association between obesity and ALI and to discuss the posited role for adipose tissue-derived factors in the pathogenesis of this condition.

Adiponectin attenuates lipopolysaccharide-induced acute lung injury through suppression of endothelial cell activation.

Adiponectin (APN) is an adipose tissue-derived factor with anti-inflammatory and vascular protective properties whose levels paradoxically decrease with increasing body fat. In this study, APN's role in the early development of ALI to LPS was investigated. Intratracheal LPS elicited an exaggerated systemic inflammatory response in APN-deficient (APN(-/-)) mice compared with wild-type (wt) littermates. Increased lung injury and inflammation were observed in APN(-/-) mice as early as 4 h after delivery of LPS. Targeted gene expression profiling performed on immune and endothelial cells isolated from lung digests 4 h after LPS administration showed increased proinflammatory gene expression (e.g., IL-6) only in endothelial cells of APN(-/-) mice when compared with wt mice. Direct effects on lung endothelium were demonstrated by APN's ability to inhibit LPS-induced IL-6 production in primary human endothelial cells in culture. Furthermore, T-cadherin-deficient mice that have significantly reduced lung airspace APN but high serum APN levels had pulmonary inflammatory responses after intratracheal LPS that were similar to those of wt mice. These findings indicate the importance of serum APN in modulating LPS-induced ALI and suggest that conditions leading to hypoadiponectinemia (e.g., obesity) predispose to development of ALI through exaggerated inflammatory response in pulmonary vascular endothelium.