Faculty Bibliography

Macrophages play a central role in the pathogenesis of atherosclerosis. The inflammatory properties of these cells are dictated by their metabolism, of which the mechanistic target of rapamycin (mTOR) signaling pathway is a key regulator. Using myeloid cell-specific nanobiologics in apolipoprotein E-deficient (Apoe^-/-) mice, we found that targeting the mTOR and ribosomal protein S6 kinase-1 (S6K1) signaling pathways rapidly diminished plaque macrophages' inflammatory activity. By investigating transcriptome modifications, we identified Psap, a gene encoding the lysosomal protein prosaposin, as closely related with mTOR signaling. Subsequent in vitro experiments revealed that Psap inhibition suppressed both glycolysis and oxidative phosphorylation. Transplantation of Psap^-/- bone marrow to low-density lipoprotein receptor knockout (Ldlr^-/-) mice led to a reduction in atherosclerosis development and plaque inflammation. Last, we confirmed the relationship between PSAP expression and inflammation in human carotid atherosclerotic plaques. Our findings provide mechanistic insights into the development of atherosclerosis and identify prosaposin as a potential therapeutic target.

Lumen extension in intracellular tubes can occur when vesicles fuse with an invading apical membrane. Within the Caenorhabditis elegans excretory cell, which forms an intracellular tube, the exocyst vesicle-tethering complex is enriched at the lumenal membrane and is required for its outgrowth, suggesting that exocyst-targeted vesicles extend the lumen. Here, we identify a pathway that promotes intracellular tube extension by enriching the exocyst at the lumenal membrane. We show that PAR-6 and PKC-3/aPKC concentrate at the lumenal membrane and promote lumen extension. Using acute protein depletion, we find that PAR-6 is required for exocyst membrane recruitment, whereas PAR-3, which can recruit the exocyst in mammals, appears dispensable for exocyst localization and lumen extension. Finally, we show that CDC-42 and RhoGEF EXC-5/FGD regulate lumen extension by recruiting PAR-6 and PKC-3 to the lumenal membrane. Our findings reveal a pathway that connects CDC-42, PAR proteins, and the exocyst to extend intracellular tubes.

OBJECTIVE:in vitro and in vivo. Treatment of mice with inhibitors of miR-33 increased expression of these miR-33 target genes in brown and subcutaneous white adipose tissue, upregulating expression of UCP1, and rendering mice resistant to cold challenge. CONCLUSIONS:Collectively, our findings demonstrate that miR-33 targets key genes involved in BAT activation and white adipose beiging and expand our understanding of how miR-33 coordinately regulates pathways involved in metabolic homeostasis.

Military veterans who experience blast-related traumatic brain injuries often suffer from chronic cognitive and neurobehavioral syndromes. Reports of abnormal tau processing following blast injury have raised concerns that some cases may have a neurodegenerative basis. Rats exposed to repetitive low-level blast exhibit chronic neurobehavioral traits and accumulate tau phosphorylated at threonine 181 (Thr181). Using data previously reported in separate studies we tested the hypothesis that region-specific patterns of Thr181 phosphorylation correlate with behavioral measures also previously determined and reported in the same animals. Elevated p-tau Thr181 in anterior neocortical regions and right hippocampus correlated with anxiety as well as fear learning and novel object localization. There were no correlations with levels in amygdala or posterior neocortical regions. Particularly striking were asymmetrical effects on the right and left hippocampus. No systematic variation in head orientation toward the blast wave seems to explain the laterality. Levels did not correlate with behavioral measures of hyperarousal. Results were specific to Thr181 in that no correlations were observed for three other phospho-acceptor sites (threonine 231, serine 396, and serine 404). No consistent correlations were linked with total tau. These correlations are significant in suggesting that p-tau accumulation in anterior neocortical regions and the hippocampus may lead to disinhibited amygdala function without p-tau elevation in the amygdala itself. They also suggest an association linking blast injury with tauopathy, which has implications for understanding the relationship of chronic blast-related neurobehavioral syndromes in humans to neurodegenerative diseases.

INTRODUCTION/BACKGROUND:Dalbavancin is a lipoglycopeptide antibiotic approved as a single- and two-dose regimen for adults with acute bacterial skin and skin structure infections (ABSSSI) caused by susceptible gram-positive organisms. We present nephrotoxicity rates for patients with ABSSSI who received dalbavancin in three pivotal clinical trials and compare the rates with vancomycin. METHODS:In a phase 3b clinical trial (DUR001-303), patients were randomized to dalbavancin single-dose (1500 mg intravenous [IV]) or two-dose regimen (1000 mg IV on day 1, 500 mg IV on day 8). In two phase 3 clinical trials (DISCOVER 1 and DISCOVER 2), patients were randomized to dalbavancin (two-dose regimen) or vancomycin 1 g (or 15 mg/kg) IV every 12 h for at least 3 days with an option to switch to orally administered linezolid 600 mg every 12 h for 10-14 days. Patients on dalbavancin with a creatinine clearance below 30 mL/min not on regular dialysis received a reduced dose of 1000 mg (single-dose arm) or 750 mg IV on day 1, 375 mg IV on day 8 (two-dose arm). Nephrotoxicity was defined as a 50% increase from baseline serum creatinine (SCr) or an absolute increase in SCr of 0.5 mg/dL at any time point. P values were obtained using the Cochran-Mantel-Haenszel test. RESULTS:In dalbavancin-treated patients, rates of nephrotoxicity were low. The safety population with available creatinine values included 1325/1347 patients on any regimen of dalbavancin, and 54/651 patients who received vancomycin intravenously for at least 10 days and were not switched to orally administered linezolid. Patients on any regimen of dalbavancin had a lower rate of nephrotoxicity compared with patients receiving vancomycin intravenously for at least 10 days (3.7% vs 9.3%, respectively; P = 0.039). CONCLUSIONS:Nephrotoxicity rates were lower in patients on dalbavancin relative to vancomycin for at least 10 days. On the basis of this experience, dalbavancin may be less nephrotoxic than intravenously administered vancomycin.

Melanoma, the most lethal form of skin cancer, is rarely curable at its advanced stages. The early events of this disease, during which treatment would be beneficial, remain poorly elucidated. Melanocyte stem cells (McSCs) residing in the hair follicle niche have been proposed to be a cell-of-origin for melanoma. To understand the cellular and molecular mechanisms regulating the initiation and progression of McSC derived melanoma, we have established a novel c-Kit- CreER-driven melanoma mouse model that enabled us to \target McSCs and trace their oncogenic behaviors. Using this model, we showed that oncogenic McSCs first expand in the niche and then migrate to the epidermis to form epidermal melanoma that later invade into the underlying dermis and undergo metastasis. Furthermore, Wnt and Endothelin signals, secreted by epithelial niche cells during hair anagen onset promoted the malignant transformation of McSCs to melanoma. Finally, transcriptional profiling revealed a strong resemblance between murine McSC-derived melanoma and human melanoma in heterogeneity and gene signatures. These results suggest that follicular McSCs can be an origin of melanoma and that follicular niche can control McSC oncogenic transformation. The similarities of McSC derived melanoma with human melanoma in epidermal to dermal progression, heterogeneity and gene expression suggest the potential utilization of this mouse model as a pre-clinical model for human melanoma

Liquid-phase deposition of exfoliated 2D nanosheets is the basis for emerging technologies that include writable electronic inks, molecular barriers, selective membranes, and protective coatings against fouling or corrosion. These nanosheet thin films have complex internal structures that are discontinuous assemblies of irregularly tiled micron-scale sheets held together by van der Waals (vdW) forces. On stiff substrates, nanosheet vdW films are stable to many common stresses, but can fail by internal delamination under shear stress associated with handling or abrasion. This "re-exfoliation" pathway is an intrinsic feature of stacked vdW films and can limit nanosheet-based technologies. Here we investigate the shear stability of graphene oxide and MoSe₂ nanosheet vdW films through lap shear experiments on polymer-nanosheet-polymer laminates. These sandwich laminate structures fail in mixed cohesive and interfacial mode with critical shear forces from 40 - 140 kPa and fracture energies ranging from 0.2 - 6 J/m². Surprisingly these energies are higher than delamination energies reported for smooth peeling of ordered stacks of continuous 2D sheets, which we propose is due to energy dissipation and chaotic crack motion during nanosheet film disassembly at the crack tip. Experiment results also show that film thickness plays a key role in determining critical shear force (maximum load before failure) and dissipated energy for different nanosheet vdW films. Using a mechanical model with an edge crack in the thin nanosheet film, we propose a shear-to-tensile failure mode transition to explain a maximum in critical shear force for graphene oxide films but not MoSe₂ films. This transition reflects a weakening of the substrate confinement effect and increasing rotational deformation near the film edge as the film thickness increases. For graphene oxide, the critical shear force can be increased by electrostatic cross-linking achieved through interlayer incorporation of metal cations. These results have important implications for the stability of functional devices that employ 2D nanosheet coatings.

Epidermal melanocytes are constantly exposed to environmental stressors such as ultraviolet light (UV) and chemotoxins. Several evolutionarily conversed survival mechanisms are deployed to ensure melanocyte recovery after damage including the unfolded protein response (UPR) and integrated stress response (ISR). The UPR/ISR promote restoration of homeostasis, by modulating transcription and translation as well as activating Nuclear factor erythroid 2-related factor 2 (NRF2)-mediated antioxidant activity. If repair fails, the UPR/ISR either stimulate cell death, or adaptation that can lead to survival of damaged cells and promote disease. For example, the UPR/ISR may support melanomagenesis by allowing UV-damaged, mutated cells to survive and adapt to a hostile tumor microenvironment that subjects cells to hypoxia, nutrient deprivation and sub-optimal pH. The UPR and ISR can also promote transcriptional changes that support tumor growth and/or metastasis. Furthermore, these pathways may also underlie acquisition of chemoresistance and modulation of protein expression that alters the efficacy of immunotherapies. UPR activation has also been implicated in the pathogenesis of vitiligo and may promote increased expression of chemokines such as interleukin 6 and interleukin 8 that trigger an autoimmune response against melanocytes. We herein review the potential roles of the UPR/ISR in the etiology of melanoma and vitiligo.