Oxidative stress plays an important role in alcohol-induced inflammation and liver injury. Relatively less is known about how Kupffer cells respond to oxidative stress-induced expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO1) to blunt inflammation and liver injury. We showed that Kupffer cells from ethanol-fed rats and ethanol-treated rat Kupffer cells and THP-1 cells displayed increased mRNA expression of HO-1, NQO1, and hypoxia-inducible factor-1α (HIF-1α). Our studies showed that silencing with HIF-1α and JNK-1 siRNAs attenuated ethanol-mediated mRNA expression of HO-1, but not NQO1, whereas Nrf2 siRNA attenuated the mRNA expression of both HO-1 and NQO1. Additionally, JunD but not JunB formed an activator protein-1 (AP-1) oligomeric complex to augment HO-1 promoter activity. Ethanol-induced HO-1 transcription involved antioxidant response elements, hypoxia-response elements, and an AP-1 binding motif in its promoter, as demonstrated by mutation analysis of the promoter, EMSA, and ChIP. Furthermore, livers of ethanol-fed c-Jun^fl/fl mice showed reduced levels of mRNA for HO-1 but not of NQO1 compared with ethanol-fed control rats, supporting the role of c-Jun or the AP-1 transcriptional complex in ethanol-induced HO-1 expression. Additionally, attenuation of HO-1 levels in ethanol-fed c-Jun^fl/fl mice led to increased proinflammatory cytokine expression in the liver. These results for the first time show that ethanol regulates HO-1 and NQO1 transcription by different signaling pathways. Additionally, up-regulation of HO-1 protects the liver from excessive formation of inflammatory cytokines. These studies provide novel therapeutic targets to ameliorate alcohol induced inflammation and liver injury.

Pulmonary hypertension (PH) is a progressive disorder that causes significant morbidity and mortality despite existing therapies. PH pathogenesis is characterized by metabolic derangements that increase pulmonary artery smooth muscle cell (PASMC) proliferation and vascular remodeling. PH-associated decreases in peroxisome proliferator-activated receptor γ (PPARγ) stimulate PASMC proliferation, and PPARγ in coordination with PPARγ coactivator 1α (PGC1α) regulates mitochondrial gene expression and biogenesis. To further examine the impact of decreases in PPARγ expression on human PASMC (HPASMC) mitochondrial function, we hypothesized that depletion of either PPARγ or PGC1α perturbs mitochondrial structure and function to stimulate PASMC proliferation. To test this hypothesis, HPASMCs were exposed to hypoxia and treated pharmacologically with the PPARγ antagonist GW9662 or with siRNA against PPARγ or PGC1α for 72 hours. HPASMC proliferation (cell counting), target mRNA levels (qRT-PCR), target protein levels (Western blotting), mitochondria-derived H2O2 (confocal immunofluorescence), mitochondrial mass and fragmentation, and mitochondrial bioenergetic profiling were determined. Hypoxia or knockdown of either PPARγ or PGC1α increased HPASMC proliferation, enhanced mitochondria-derived H2O2, decreased mitochondrial mass, stimulated mitochondrial fragmentation, and impaired mitochondrial bioenergetics. Taken together, these findings provide novel evidence that loss of PPARγ diminishes PGC1α and stimulates derangements in mitochondrial structure and function that cause PASMC proliferation. Overexpression of PGC1α reversed hypoxia-induced HPASMC derangements. This study identifies additional mechanistic underpinnings of PH, and provides support for the notion of activating PPARγ as a novel therapeutic strategy in PH.

Significance: The present work establishes that the addition of the prosthetic group lipoic acid to catabolic enzymes is a dynamically regulated posttranslational modification that increases metabolic plasticity under hypoxia and in cancer cells. We show that that the polymerase-δ interacting protein 2 (Poldip2) is an oxygen-sensitive protein that regulates the lipoylation and activation of the pyruvate and α-ketoglutarate dehydrogenase complexes. Additionally, our work reveals that mitochondrial peptidases participate in an integrated response needed for metabolic adaptation. This study positions Poldip2 as a key regulator of mitochondrial function and cell metabolism.

TGF-β1 is a pleiotropic cytokine with an established role in fibrosis; however, the immunosuppressive effects of TGF-β1 are less characterized. Elevated levels of TGF-β1 are found in patients with acute and chronic lung diseases, and the underlying disease processes are exacerbated by respiratory viral infections. The alveolar macrophage is the first line of cellular defense against respiratory viral infections, and its response to infections is dependent on environmental cues. Using the mouse alveolar macrophage line, MH-S, and human CD14⁺ monocyte-derived macrophages, we examined the effects of TGF-β1 on the type I IFN antiviral response, macrophage polarization, and mitochondrial bioenergetics following a challenge with human respiratory syncytial virus (RSV). Our results showed that TGF-β1 treatment of macrophages decreased the antiviral and proinflammatory response, and suppressed basal, maximal, spare mitochondrial respiration, and mitochondrial ATP production. Challenge with RSV following TGF-β1 treatment further exacerbated mitochondrial dysfunction. The TGF-β1 and TGF-β1+RSV–treated macrophages had a higher frequency of apoptosis and diminished phagocytic capacity, potentially through mitochondrial stress. Disruption of TGF-β1 signaling or rescue of mitochondrial respiration may be novel therapeutically targetable pathways to improve macrophage function and prevent secondary bacterial infections that complicate viral respiratory infections.

Pneumonia causes a significant burden of disease worldwide. Although all populations are at risk of pneumonia, those at extremes of age and those with immunosuppressive disorders, underlying respiratory disease, and critical illness are particularly vulnerable. Although clinical practice guidelines addressing the management and treatment of pneumonia exist, few of the supporting studies focus on the crucial contributions of the host in pneumonia pathogenesis and recovery. Such essential considerations include the host risk factors that lead to susceptibility to lung infections; biomarkers reflecting the host response and the means to pursue host-directed pneumonia therapy; systemic effects of pneumonia on the host; and long-term health outcomes after pneumonia. To address these gaps, the Pneumonia Working Group of the Assembly on Pulmonary Infection and Tuberculosis led a workshop held at the American Thoracic Society meeting in May 2018 with overarching objectives to foster attention, stimulate research, and promote funding for short-term and long-term investigations into the host contributions to pneumonia. The workshop involved participants from various disciplines with expertise in lung infection, pneumonia, sepsis, immunocompromised patients, translational biology, data science, genomics, systems biology, and clinical trials. This workshop report summarizes the presentations and discussions and important recommendations for future clinical pneumonia studies. These recommendations include establishing consensus disease and outcome definitions, improved phenotyping, development of clinical study networks, standardized data and biospecimen collection and protocols, and development of innovative trial designs.