Faculty Bibliography

Autophagy is a multistep process in which cytoplasmic components, including invading pathogens, are captured by autophagosomes that subsequently fuse with degradative lysosomes. Negative-strand RNA viruses, including paramyxoviruses, have been shown to alter autophagy, but the molecular mechanisms remain largely unknown. We demonstrate that human parainfluenza virus type 3 (HPIV3) induces incomplete autophagy by blocking autophagosome-lysosome fusion, resulting in increased virus production. The viral phosphoprotein (P) is necessary and sufficient to inhibition autophagosome degradation. P binds to SNAP29 and inhibits its interaction with syntaxin17, thereby preventing these two host SNARE proteins from mediating autophagosome-lysome fusion. Incomplete autophagy and resultant autophagosome accumulation increase extracellular viral production but do not affect viral protein synthesis. These findings highlight how viruses can block autophagosome degradation by disrupting the function of SNARE proteins.

Obesity is associated with infiltration of macrophages into adipose tissue (AT), contributing to insulin resistance and diabetes. However, relatively little is known regarding the origin of AT macrophages (ATMs). We discovered that murine models of obesity have prominent monocytosis and neutrophilia, associated with proliferation and expansion of bone marrow (BM) myeloid progenitors. AT transplantation conferred myeloid progenitor proliferation in lean recipients, while weight loss in both mice and humans (via gastric bypass) was associated with a reversal of monocytosis and neutrophilia. Adipose S100A8/A9 induced ATM TLR4/MyD88 and NLRP3 inflammasome-dependent IL-1beta production. IL-1beta interacted with the IL-1 receptor on BM myeloid progenitors to stimulate the production of monocytes and neutrophils. These studies uncover a positive feedback loop between ATMs and BM myeloid progenitors and suggest that inhibition of TLR4 ligands or the NLRP3-IL-1beta signaling axis could reduce AT inflammation and insulin resistance in obesity.

The contributions of TGF-beta signaling to cancer are complex but involve the inflammatory microenvironment as well as cancer cells themselves. In mice encoding a TGF-beta mutant that precludes its binding to the latent TGF-beta binding protein (Tgfb1-/C33S), we observed multiorgan inflammation and an elevated incidence of various types of gastrointestinal solid tumors due to impaired conversion of latent to active TGF-beta1. By genetically eliminating activators of latent TGF-beta, we further lowered the amount of TGF-beta, which enhanced tumor frequency and multiorgan inflammation. This model system was used to further investigate the relative contribution of TGF-beta1 to lymphocyte-mediated inflammation in gastrointestinal tumorigenesis. Toward this end, we generated Tgfb1-/C33S;Rag2-/- mice that lacked adaptive immune function, which eliminated tumor production. Analysis of tissue from Tgfb1-/C33S mice indicated decreased levels of P-Smad3 compared to wild type animals, whereas tissue from Tgfb1-/C33S;Rag2-/- mice had normal P-Smad3 levels. Inhibiting the inflammatory response normalized levels of IL-1beta and IL-6 and reduced tumor cell proliferation. Additionally, Tgfb1-/C33S;Rag2-/- mice exhibited reduced paracrine signaling in the epithelia, mediated by hepatocyte growth factor produced by gastric stroma. Together, our results indicate that many of the responses of the gastric tissue associated with decreased TGF-beta1 may be directly or indirectly affected by inflammatory processes, which accompany loss of TGF-beta1, rather than a direct effect of loss of the cytokine.

The large intestine is the site most commonly affected in inflammatory bowel diseases. However, the mechanism of T cell homing to the large intestine, which contributes to inflammation, had remained unclear. We show here that an orphan G-protein coupled receptor GPR15 controls the specific homing of T cells, particularly FOXP3+ regulatory T cells (Tregs), to the large intestine lamina propria (LILP). GPR15 expression is promoted by gut microbiota and TGF-beta1, but not by retinoic acid. GPR15-deficient mice had fewer Tregs in LILP and were prone to develop more severe inflammation in the large intestine, which was rescued by the transfer of GPR15-sufficient Tregs. Our findings thus indicate that GPR15 is a T cell homing receptor for LILP and that GPR15 plays a key role in maintaining gut immune homeostasis, largely by regulating the influx of Tregs. Our study also demonstrates that adaptive immune responses in the gut are functionally compartmentalized through the differential requirements for T cell homing to the small and large bowel

Significance: Poor wound healing remains a significant health issue for a large number of patients in the United States. The physiologic response to local wound hypoxia plays a critical role in determining the success of the normal healing process. Hypoxia-inducible factor-1 (HIF-1), as the master regulator of oxygen homeostasis, is an important determinant of healing outcomes. HIF-1 contributes to all stages of wound healing through its role in cell migration, cell survival under hypoxic conditions, cell division, growth factor release, and matrix synthesis throughout the healing process. Recent Advances: Positive regulators of HIF-1, such as prolyl-4-hydroxylase inhibitors, have been shown to be beneficial in enhancing diabetic ischemic wound closure and are currently undergoing clinical trials for treatment of several human-ischemia-based conditions. Critical Issues: HIF-1 deficiency and subsequent failure to respond to hypoxic stimuli leads to chronic hypoxia, which has been shown to contribute to the formation of nonhealing ulcers. In contrast, overexpression of HIF-1 has been implicated in fibrotic disease through its role in increasing myofibroblast differentiation leading to excessive matrix production and deposition. Both positive and negative regulators of HIF-1 therefore provide important therapeutic targets that can be used to manipulate HIF-1 expression where an excess or deficiency in HIF-1 is known to correlate with pathogenesis. Future Directions: Targeting HIF-1 during wound healing has many important clinical implications for tissue repair. Counteracting the detrimental effects of excessive or deficient HIF-1 signaling by modulating HIF-1 expression may improve future management of poorly healing wounds.

Voluntary medical male circumcision (VMMC) is capable of reducing the risk of sexual transmission of HIV from females to males by approximately 60%. In 2007, the WHO and the Joint United Nations Programme on HIV/AIDS (UNAIDS) recommended making VMMC part of a comprehensive HIV prevention package in countries with a generalized HIV epidemic and low rates of male circumcision. Modeling studies undertaken in 2009-2011 estimated that circumcising 80% of adult males in 14 priority countries in Eastern and Southern Africa within five years, and sustaining coverage levels thereafter, could avert 3.4 million HIV infections within 15 years and save US$16.5 billion in treatment costs. In response, WHO/UNAIDS launched the Joint Strategic Action Framework for accelerating the scale-up of VMMC for HIV prevention in Southern and Eastern Africa, calling for 80% coverage of adult male circumcision by 2016. While VMMC programs have grown dramatically since inception, they appear unlikely to reach this goal. This review provides an overview of findings from the PLOS Collection "Voluntary Medical Male Circumcision for HIV Prevention: Improving Quality, Efficiency, Cost Effectiveness, and Demand for Services during an Accelerated Scale-up." The use of devices for VMMC is also explored. We propose emphasizing management solutions to help VMMC programs in the priority countries achieve the desired impact of averting the greatest possible number of HIV infections. Our recommendations include advocating for prioritization and funding of VMMC, increasing strategic targeting to achieve the goal of reducing HIV incidence, focusing on programmatic efficiency, exploring the role of new technologies, rethinking demand creation, strengthening data use for decision-making, improving governments' program management capacity, strategizing for sustainability, and maintaining a flexible scale-up strategy informed by a strong monitoring, learning, and evaluation platform.

The phosphoinositide-3 kinase (PI3K) pathway is deregulated in a significant proportion of melanomas, and PI3K pathway activation in combination with constitutively active mitogen-activated protein kinase signaling shows synergistic effects in the process of melanoma tumorigenesis. Recently, a tumor suppressor function for the lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) has been described in breast and prostate cancers, with impact on PI3K signaling output. Given the importance of PI3K pathway activity for melanoma formation and growth, we aimed to assess the role of INPP4B in melanocytic tumors. Our studies in native tumors suggest that decreased INPP4B expression is an event correlating with tumor progression in melanocytic neoplasms. We further demonstrate that INPP4B regulates PI3K/Akt signaling and exerts a tumor suppressor effect, impacting the proliferative, invasive, and tumorigenic capacity of melanoma cells. INPP4B expression in melanocytic neoplasms may therefore have potential as a biomarker for disease progression and as a modulator for the prediction of treatment outcome.

Noncoding RNAs (ncRNAs) represent a class of RNA molecules that typically do not code for proteins. Emerging data suggest that ncRNAs play an important role in several physiological and pathological conditions such as cancer and cardiovascular diseases, including atherosclerosis. The best-characterized ncRNAs are the microRNAs which are small, approximately 22-nucleotide sequences of RNA that regulate gene expression at the posttranscriptional level through transcript degradation or translational repression. MicroRNAs control several aspects of atherosclerosis, including endothelial cell, vascular smooth cell, and macrophage functions as well as lipoprotein metabolism. Apart from microRNAs, recently ncRNAs, especially long ncRNAs, have emerged as important potential regulators of the progression of atherosclerosis. However, the molecular mechanism of their regulation and function as well as the significance of other ncRNAs such as small nucleolar RNAs during atherogenesis is largely unknown. In this review, we summarize the recent findings in the field, highlighting the importance of ncRNAs in atherosclerosis and discuss their potential use as therapeutic targets in cardiovascular diseases.

The major risks of pacemaker and implantable cardioverter defibrillator extraction are attributable to the fibrotic tissue that encases them in situ, yet little is known about the cellular and functional properties of this response. In the present research, we performed a histological and mechanical analysis of human tissue collected from the lead-tissue interface to better understand this process and provide insights for the improvement of lead design and extraction. The lead-tissue interface consisted of a thin cellular layer underlying a smooth, acellular surface, followed by a circumferentially organized collagen-rich matrix. 51.8+/-4.9% of cells were myofibroblasts via immunohistochemistry, with these cells displaying a similar circumferential organization. Upon mechanical testing, samples exhibited a triphasic force-displacement response consisting of a toe region during initial tensioning, a linear elastic region and a yield and failure region. Mean fracture load was 5.6+/-2.1N, and mean circumferential stress at failure was 9.5+/-4.1MPa. While the low cellularity and fibrotic composition of tissue observed herein is consistent with a foreign body reaction to an implanted material, the significant myofibroblast response provides a mechanical explanation for the contractile forces complicating extractions. Moreover, the tensile properties of this tissue suggest the feasibility of circumferential mechanical tissue disruption, similar to balloon angioplasty devices, as a novel approach to assist with lead extraction.