Transport Dynamics of MtrD: An RND Multidrug Efflux Pump from Neisseria gonorrhoeae.

The MtrCDE system confers multidrug resistance to Neisseria gonorrhoeae, the causative agent of gonorrhea. Using free and directed molecular dynamics (MD) simulations, we analyzed the interactions between MtrD and azithromycin, a transport substrate of MtrD, and a last-resort clinical treatment for multidrug-resistant gonorrhea. We then simulated the interactions between MtrD and streptomycin, an apparent nonsubstrate of MtrD. Using known conformations of MtrD homologues, we simulated a potential dynamic transport cycle of MtrD using targeted MD techniques (TMD), and we noted that forces were not applied to ligands of interest. In these TMD simulations, we observed the transport of azithromycin and the rejection of streptomycin. In an unbiased, long-time scale simulation of AZY-bound MtrD, we observed the spontaneous diffusion of azithromycin through the periplasmic cleft. Our simulations show how the peristaltic motions of the periplasmic cleft facilitate the transport of substrates by MtrD. Our data also suggest that multiple transport pathways for macrolides may exist within the periplasmic cleft of MtrD.

Transport of Alzheimer's associated amyloid-ß catalyzed by P-glycoprotein.

P-glycoprotein (P-gp) is a critical membrane transporter in the blood brain barrier (BBB) and is implicated in Alzheimer's disease (AD). However, previous studies on the ability of P-gp to directly transport the Alzheimer's associated amyloid-ß (Aß) protein have produced contradictory results. Here we use molecular dynamics (MD) simulations, transport substrate accumulation studies in cell culture, and biochemical activity assays to show that P-gp actively transports Aß. We observed transport of Aß40 and Aß42 monomers by P-gp in explicit MD simulations of a putative catalytic cycle. In in vitro assays with P-gp overexpressing cells, we observed enhanced accumulation of fluorescently labeled Aß42 in the presence of Tariquidar, a potent P-gp inhibitor. We also showed that Aß42 stimulated the ATP hydrolysis activity of isolated P-gp in nanodiscs. Our findings expand the substrate profile of P-gp, and suggest that P-gp may contribute to the onset and progression of AD.

Clinical Spectrum of KCNA1 Mutations: New Insights into Episodic Ataxia and Epilepsy Comorbidity.

Mutations in the KCNA1 gene, which encodes voltage-gated Kv1.1 potassium channel α-subunits, cause a variety of human diseases, complicating simple genotype-phenotype correlations in patients. KCNA1 mutations are primarily associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1). However, some patients have EA1 in combination with epilepsy, whereas others have epilepsy alone. KCNA1 mutations can also cause hypomagnesemia and paroxysmal dyskinesia in rare cases. Why KCNA1 variants are associated with such phenotypic heterogeneity in patients is not yet understood. In this review, literature databases (PubMed) and public genetic archives (dbSNP and ClinVar) were mined for known pathogenic or likely pathogenic mutations in KCNA1 to examine whether patterns exist between mutation type and disease manifestation. Analyses of the 47 deleterious KCNA1 mutations that were identified revealed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein. In addition, insights from animal models of KCNA1 channelopathy were considered, as well as the possible influence of genetic modifiers on disease expressivity and severity. Elucidation of the complex relationship between KCNA1 variants and disease will enable better diagnostic risk assessment and more personalized therapeutic strategies for KCNA1 channelopathy.

Optimizing Targeted Inhibitors of P-Glycoprotein Using Computational and Structure-Guided Approaches.

Overexpression of ABC transporters like P-glycoprotein (P-gp) has been correlated with resistances in cancer chemotherapy. Intensive efforts to identify P-gp inhibitors for use in combination therapy have not led to clinically approved inhibitors to date. Here, we describe computational approaches combined with structure-based design to improve the characteristics of a P-gp inhibitor previously identified by us. This hit compound represents a novel class of P-gp inhibitors that specifically targets and inhibits P-gp ATP hydrolysis while not being transported by the pump. We describe here a new program for virtual chemical synthesis and computational assessment, ChemGen, to produce hit compound variants with improved binding characteristics. The chemical syntheses of several variants, efficacy in reversing multidrug resistance in cell culture, and biochemical assessment of the inhibition mechanism are described. The usefulness of the computational predictions of binding characteristics of the inhibitor variants is discussed and compared to more traditional structure-based approaches.

Hepatitis B virus coinfection is associated with high early mortality in HIV-infected Tanzanians on antiretroviral therapy.

OBJECTIVES: There is limited data on the effect of antiviral therapies on clinical outcomes in HIV and hepatitis B virus (HBV)-infected individuals in sub-Saharan Africa. DESIGN: Single center, prospective longitudinal cohort study at Management and Development for Health supported HIV Care and Treatment clinics in Dar es Salaam, Tanzania. METHODS: Between April 2014 and December 2015, HIV-infected, HBV-infected and HIV/HBV-coinfected, treatment naïve, Tanzanian adults more than 18 years of age were eligible for enrollment and followed for 10-18 months after initiating antivirals. All HIV-infected and HIV/HBV-coinfected participants received tenofovir, lamivudine and efavirenz; HBV-infected participants received lamivudine. Multivariate regression models were constructed to identify factors associated with mortality in HIV-infected and HIV/HBV-coinfected participants. RESULTS: A total of 265 HIV-infected, 165 HBV-infected and 64 HIV/HBV-coinfected participants were analyzed. At baseline, HBV-infected participants were younger and had a higher BMI than HIV-infected and HIV/HBV-coinfected participants. After a median of 371 (interquartile range 50) days on treatment, there were 40 deaths. Mortality was significantly higher among HIV/HBV-coinfected participants compared with HIV and HBV-infected participants [HIV/HBV-coinfected 12 of 64 (19%) vs. HIV-infected 26 of 265 (10%) and HBV-infected two of 265 (1%), P < 0.01]. High baseline HIV RNA and low hemoglobin levels, but not HBV coinfection were independently associated with early mortality in multivariate analyses of HIV-infected participants. CONCLUSION: High rates of early mortality were observed after treatment initiation in HIV/HBV-coinfected individuals compared with participants with HIV or HBV alone, despite robust aspartate aminotransferase to platelet ratio index declines and high rates of virologic suppression. HIV rather than HBV-related factors are more important contributors to mortality in these individuals.

Formation of Metal Nanoparticles Directly from Bulk Sources Using Ultrasound and Application to E-Waste Upcycling.

A method for creating nanoparticles directly from bulk metal by applying ultrasound to the surface in the presence of a two-part surfactant system is presented. Implosive collapse of cavitation bubbles near the bulk metal surface generates powerful microjets, leading to material ejection. This liberated material is captured and stabilized by a surfactant bilayer in the form of nanoparticles. The method is characterized in detail using gold, but is also demonstrated on other metals and alloys, and is generally applicable. It is shown that nanoparticles can be produced regardless of the bulk metal form factor, and the method is extended to an environmentally important problem, the reclamation of gold from an electronic waste stream.

Brief Report: HIV/HBV Coinfection is a Significant Risk Factor for Liver Fibrosis in Tanzanian HIV-Infected Adults.

BACKGROUND: In sub-Saharan Africa, the burden of liver disease associated with chronic hepatitis B virus (HBV) and HIV is unknown. We characterized liver disease using aspartate aminotransferase-to-platelet ratio index (APRI) and FIB-4 in patients with HIV, HBV, and HIV/HBV coinfection in Tanzania. METHODS: Using a cross-sectional design, we compared the prevalence of liver fibrosis in treatment-naive HIV monoinfected, HBV monoinfected, and HIV/HBV-coinfected adults enrolled at Management and Development for Health (MDH)-supported HIV treatment clinics in Dar es Salaam, Tanzania. Risk factors associated with significant fibrosis (APRI >0.5 and FIB-4 >1.45) were examined. RESULTS: Two hundred sixty-seven HIV-infected, 165 HBV-infected, and 63 HIV/HBV-coinfected patients were analyzed [44% men, median age 37 (interquartile range 14), body mass index 23 (7)]. APRI and FIB-4 were strongly correlated (r = 0.78, P < 0.001, R = 0.61). Overall median APRI scores were low {HIV/HBV [0.36 (interquartile range 0.4)], HIV [0.23 (0.17)], HBV [0.29 (0.15)] (P < 0.01)}. In multivariate analyses, HIV/HBV coinfection was associated with APRI >0.5 [HIV/HBV vs. HIV: odds ratio (OR) 3.78 (95% confidence interval: 1.91 to 7.50)], [HIV/HBV vs. HBV: OR 2.61 (1.26 to 5.44)]. HIV RNA per 1 log10 copies/mL increase [OR 1.53 (95% confidence interval: 1.04 to 2.26)] and HBV DNA per 1 log10 copies/mL increase [OR 1.36 (1.15, 1.62)] were independently associated with APRI >0.5 in HIV-infected and HBV-infected patients, respectively. CONCLUSIONS: HIV/HBV coinfection is an important risk factor for significant fibrosis. Higher levels of circulating HIV and HBV virus may play a direct role in liver fibrogenesis. Prompt diagnosis and aggressive monitoring of liver disease in HIV/HBV coinfection is warranted.

High rates of hepatitis C virus (HCV) cure using direct-acting antivirals in HIV/HCV-coinfected patients: a real-world perspective.

OBJECTIVES: There are few data on the real-world experience of FDA-approved oral hepatitis C virus (HCV) direct-acting antiviral (DAA) drug combinations in HIV/HCV-coinfected patients. We evaluated the safety and efficacy of DAA therapies in a cohort of HIV/HCV patients in a large urban clinic in Chicago. METHODS: HIV/HCV-coinfected adults (≥18 years) enrolled in the Northwestern University Viral Hepatitis Registry between January 2013 and June 2015 were analysed. Treated patients received one of the following DAA combinations: sofosbuvir/ledipasvir, sofosbuvir/ribavirin, sofosbuvir/simeprevir or paritaprevir/ritonavir/ombitasvir/dasabuvir ±â€Šribavirin. The primary outcome was sustained virological response at 12 weeks after DAA completion (SVR12). RESULTS: Seventy-seven HIV/HCV patients were evaluated for DAA therapy. Most patients were male (62/77, 81%) and infected with HCV genotype 1 (67/77, 87%). Some 32/77 (42%) were cirrhotic and 29/77 (38%) had received prior treatment with an IFN-containing regimen. DAA therapy was more likely to be started in Caucasians than persons of other ethnicities (P = 0.01). The overall SVR12 rate was 92% in 52 patients who completed therapy and had follow-up by the end of the study: sofosbuvir/simeprevir, 32/33 (97%); sofosbuvir/ribavirin, 4/7 (57%); sofosbuvir/ledipasvir, 11/11 (100%); and paritaprevir/ritonavir/ombitasvir/dasabuvir, 1/1 (100%). Four patients relapsed after therapy with sofosbuvir/simeprevir (n = 1) or sofosbuvir/ribavirin (n = 3). Adverse events were uncommon and did not result in DAA treatment interruption or discontinuation. CONCLUSIONS: The HCV DAA combinations of sofosbuvir/ledipasvir and sofosbuvir/simeprevir were highly effective and well tolerated in this diverse population of HIV/HCV-coinfected patients, many of whom had advanced liver disease. HIV coinfection should not be considered a barrier to successful HCV treatment with DAAs.

Size control and quantum confinement in Cu2ZnSnS4 nanocrystals.

Starting with metal dithiocarbamate complexes, we synthesize colloidal Cu(2)ZnSnS(4) (CZTS) nanocrystals with diameters ranging from 2 to 7 nm. Structural and Raman scattering data confirm that CZTS is obtained rather than other possible material phases. The optical absorption spectra of nanocrystals with diameters less than 3 nm show a shift to higher energy due to quantum confinement.