An Official American Thoracic Society Workshop Report: Obesity and Metabolism. An Emerging Frontier in Lung Health and Disease.

The world is in the midst of an unprecedented epidemic of obesity. This epidemic has changed the presentation and etiology of common diseases. For example, steatohepatitis, directly attributable to obesity, is now the most common cause of cirrhosis in the United States. Type 2 diabetes is increasingly being diagnosed in children. Pulmonary researchers and clinicians are just beginning to appreciate the impact of obesity and altered metabolism on common pulmonary diseases. Obesity has recently been identified as a major risk factor for the development of asthma and for acute respiratory distress syndrome. Obesity is associated with profound changes in pulmonary physiology, the development of pulmonary hypertension, sleep-disordered breathing, and altered susceptibility to pulmonary infection. In short, obesity is leading to dramatic changes in lung health and disease. Simultaneously, the rapidly developing field of metabolism, including mitochondrial function, is shifting the paradigms by which the pathophysiology of many pulmonary diseases is understood. Altered metabolism can lead to profound changes in both innate and adaptive immunity, as well as the function of structural cells. To address this emerging field, a 3-day meeting on obesity, metabolism, and lung disease was convened in October 2015 to discuss recent findings, foster research initiatives, and ultimately guide clinical care. The major findings arising from this meeting are reported in this document.

Effect of NF-kappa B inhibition on TNF-alpha-induced apoptosis in human RPE cells.

PURPOSE: In many cell types, tumor necrosis factor (TNF)-alpha-induced apoptosis is prevented by production of TNF-alpha-induced antiapoptotic protein, a process mediated by nuclear transcription factor (NF)-kappa B. TNF-alpha is widely expressed in proliferative vitreoretinopathy (PVR) membranes and is present in the vitreous of eyes with PVR. To understand mechanisms responsible for RPE cell survival and death in this disease, this study was conducted to determine whether specific NF-kappa B blockade by mutant inhibitory (I)-kappa B (I kappa B) affects TNF-alpha-induced cell death. METHODS: Cultured human RPE cells and T-98G cells were infected with adenovirus encoding either beta-galactosidase or mutant I kappa B and then treated with TNF-alpha or interleukin (IL)-1 beta. I kappa B, inhibitor of apoptosis protein (IAP)-1, and cellular Fas-associated death domain-like interleukin-1 beta-converting enzyme-like inhibitory protein (c-FLIP) expression was determined by Western blot. Functional NF-kappa B activation was examined by luciferase reporter assay. Cell viability was evaluated by trypan blue exclusion assay. Caspase-3 activity and DNA fragmentation was measured with an enzyme-linked immunosorbent assay. RESULTS: Mutant I kappa B expression blocked cytokine-induced I kappa B degradation and NF-kappa B transcriptional activity in RPE cells and T-98G cells. RPE cells were resistant to TNF-alpha-induced apoptosis, even after NF-kappa B activation was specifically blocked. In contrast, TNF-alpha dramatically induced apoptosis in T-98G cells after NF-kappa B inhibition. c-IAP1 expression was not affected by TNF-alpha or mutant I kappa B, and mutant I kappa B abolished TNF-alpha-induced c-FLIP induction in RPE cells. CONCLUSIONS: RPE cells are resistant to TNF-alpha-induced cell death, even after NF-kappa B activation is specifically blocked. RPE cell resistance to apoptotic signals present in eyes with PVR, mediated by survival factors such as c-FLIP and c-IAP1, may help to explain unwanted and unchecked cell proliferation in this disease.

Effect of mutant IkappaB on cytokine-induced activation of NF-kappaB in cultured human RPE cells.

PURPOSE: The nuclear transcription factor (NF)-kappaB is a central regulator of multiple inflammatory cytokines. The current study was conducted to determine whether infection of human retinal pigment epithelial (RPE) cells by adenovirus carrying a mutant inhibitory (I)-kappaB (IkappaB) transgene inhibits cytokine-induced activity of NF-kappaB and expression of NF-kappaB-dependent cytokines by preventing degradation of IkappaB. The persistence of recombinant protein expression and function after the viral infection was also examined. METHODS: Cultured human RPE cells were infected with adenovirus encoding either beta-galactosidase (LacZ) or mutant IkappaB and were treated with interleukin (IL)-1beta or tumor necrosis factor (TNF)-alpha. IkappaB protein expression was determined by Western blot. NF-kappaB nuclear translocation was evaluated by immunofluorescence, and functional NF-kappaB activation was determined by luciferase reporter assay. NF-kappaB-dependent cytokine gene expression was determined by reverse transcription-polymerase chain reaction. IL-1beta-induced monocyte chemoattractant protein (MCP)-1 protein secretion was measured by enzyme-linked immunosorbent assay. RESULTS: Stimulation of RPE cells with IL-1beta or TNF-alpha caused rapid degradation of the endogenous, but not mutant, IkappaB protein. Expression of the mutant IkappaB isoform inhibited cytokine-stimulated NF-kappaB nuclear translocation, NF-kappaB transcriptional activity, NF-kappaB-dependent gene expression, and secretion of MCP-1. Significant levels of mutant IkappaB protein were expressed for at least 7 weeks after infection. CONCLUSIONS: Infection of human RPE by an adenoviral vector carrying a mutant IkappaB transgene blocks NF-kappaB activation and expression of multiple NF-kappaB-dependent cytokine genes over an extended period. This technique will be useful to determine the role of NF-kappaB in experimental proliferative vitreoretinopathy (PVR), and may offer a novel approach to treatment of PVR with a gene therapy approach.

Expression of a chemokine by ciliary body epithelium in horses with naturally occurring recurrent uveitis and in cultured ciliary body epithelial cells.

OBJECTIVE: To determine whether a chemokine (RANTES)-like protein expressed by ciliary epithelium plays a role in uveitis. SAMPLE POPULATION: 3 clinically normal horses intradermal, 5 eyes from 5 horses with recurrent uveitis, and 10 normal eyes from 5 age- and sex-matched horses. PROCEDURE: Cross-reactivity and sensitivity of recombinant human (rh)-regulated upon activation, normal T-cell expressed and secreted (RANTES) protein were evaluated in horses by use of intradermal hypersensitivity reactions and a chemotaxis assay. Aqueous humor and ciliary body of eyes from clinically normal horses and horses with uveitis were examined for RANTES expression by use of an ELISA and reverse transcription-polymerase chain reaction (RT-PCR). Expression of RANTES mRNA and protein content of primary cultures of equine ciliary pigmented epithelial cells (RT-PCR) and culture supernatant (ELISA) were measured 6 or 24 hours, respectively, after cultures were stimulated with interleukin-1beta and tumor necrosis factor-alpha. RESULTS: Strong reactions to intradermal hypersensitivity testing and significant chemotaxis of equine leukocytes to rh-RANTES wereas observed. Aqueous humor of eyes from horses with uveitis contained increased concentrations of rh-RANTES-like protein (mean +/- SD, 45.9+/-31.7 pg/ml), compared with aqueous humor from clinically normal horses (0 pg/ml). Ciliary body from horses with uveitis expressed RANTES mRNA, whereas ciliary body from clinically normal horses had low mRNA expression. Stimulated ciliary pigmented epithelial cells expressed increased amounts of rh-RANTES-like protein (506.1+/-298.3 pg/ml) and mRNA, compared with unstimulated samples. CONCLUSIONS AND CLINICAL RELEVANCE: Ciliary epithelium may play a role in recruitment and activation of leukocytes through expression of RANTES.