Histone deacetylase and microtubules as targets for the synthesis of releasable conjugate compounds

Design and synthesis of an HDAC inhibitor and its merger with three tubulin binders to create releasable conjugate compounds is described. The biological evaluation includes: (a) in vitro reactivity with glutathione, (b) antiproliferative activity, (c) cell cycle analysis and (d) quantification of protein acetylation. The cellular pharmacology study indicated that the HDAC-inhibitor-drug conjugates retained antimitotic and proapoptotic activity with a reduced potency.     

Oncocalyxone A Functions As an Anti-Glycation Agent In Vitro

Advanced glycation endproducts (AGE) are the result of post-translational changes to proteins, which ultimately compromise their structure and/or function. The identification of methods to prevent the formation of these compounds holds great promise in the development of alternative therapies for diseases such as diabetes. Plants used in traditional medicine are often rich sources of anti-glycation agents. Therefore, in this study, we investigated the anti-glycation activity of one such compound, Oncocalyxone A (Onco A). Using spectrofluorimetric techniques, we determined that Onco A inhibits AGE formation in a concentration-dependent manner. Its IC₅₀ value (87.88 ± 3.08 μM) was almost two times lower than the standard anti-glycation compound aminoguanidine (184.68 ± 4.85 μM). The excellent anti-glycation activity of Onco A makes it an exciting candidate for the treatment of diseases associated with excessive accumulation of AGE. However, additional studies are necessary to identify its mechanism of action, as well as the in vivo response in suitable model organisms.     

Oxidative Stress and DNA Lesions: The Role of 8-Oxoguanine Lesions in Trypanosoma cruzi Cell Viability

The main consequence of oxidative stress is the formation of DNA lesions, which can result in genomic instability and lead to cell death. Guanine is the base that is most susceptible to oxidation, due to its low redox potential, and 8-oxoguanine (8-oxoG) is the most common lesion. These characteristics make 8-oxoG a good cellular biomarker to indicate the extent of oxidative stress. If not repaired, 8-oxoG can pair with adenine and cause a G:C to T:A transversion. When 8-oxoG is inserted during DNA replication, it could generate double-strand breaks, which makes this lesion particularly deleterious. Trypanosoma cruzi needs to address various oxidative stress situations, such as the mammalian intracellular environment and the triatomine insect gut where it replicates. We focused on the MutT enzyme, which is responsible for removing 8-oxoG from the nucleotide pool. To investigate the importance of 8-oxoG during parasite infection of mammalian cells, we characterized the MutT gene in T. cruzi (TcMTH) and generated T. cruzi parasites heterologously expressing Escherichia coli MutT or overexpressing the TcMTH enzyme. In the epimastigote form, the recombinant and wild-type parasites displayed similar growth in normal conditions, but the MutT-expressing cells were more resistant to hydrogen peroxide treatment. The recombinant parasite also displayed significantly increased growth after 48 hours of infection in fibroblasts and macrophages when compared to wild-type cells, as well as increased parasitemia in Swiss mice. In addition, we demonstrated, using western blotting experiments, that MutT heterologous expression can influence the parasite antioxidant enzyme protein levels. These results indicate the importance of the 8-oxoG repair system for cell viability.     

HIV Drug Resistance Surveillance in Honduras after a Decade of Widespread Antiretroviral Therapy

Introduction

We assessed HIV drug resistance (DR) in individuals failing ART (acquired DR, ADR) and in ART-naïve individuals (pre-ART DR, PDR) in Honduras, after 10 years of widespread availability of ART.

Methods

365 HIV-infected, ART-naïve, and 381 ART-experienced Honduran individuals were enrolled in 5 reference centres in Tegucigalpa, San Pedro Sula, La Ceiba, and Choluteca between April 2013 and April 2015. Plasma HIV protease-RT sequences were obtained. HIVDR was assessed using the WHO HIVDR mutation list and the Stanford algorithm. Recently infected (RI) individuals were identified using a multi-assay algorithm.

Results

PDR to any ARV drug was 11.5% (95% CI 8.4–15.2%). NNRTI PDR prevalence (8.2%) was higher than NRTI (2.2%) and PI (1.9%, p<0.0001). No significant trends in time were observed when comparing 2013 and 2014, when using a moving average approach along the study period or when comparing individuals with >500 vs. <350 CD4+ T cells/μL. PDR in recently infected individuals was 13.6%, showing no significant difference with PDR in individuals with longstanding infection (10.7%). The most prevalent PDR mutations were M46IL (1.4%), T215 revertants (0.5%), and K103NS (5.5%). The overall ADR prevalence in individuals with <48 months on ART was 87.8% and for the ≥48 months on ART group 81.3%. ADR to three drug families increased in individuals with longer time on ART (p = 0.0343). M184V and K103N were the most frequent ADR mutations. PDR mutation frequency correlated with ADR mutation frequency for PI and NNRTI (p<0.01), but not for NRTI. Clusters of viruses were observed suggesting transmission of HIVDR both from ART-experienced to ART-naïve individuals and between ART-naïve individuals.

Conclusions

The global PDR prevalence in Honduras remains at the intermediate level, after 10 years of widespread availability of ART. Evidence of ADR influencing the presence of PDR was observed by phylogenetic analyses and ADR/PDR mutation frequency correlations.     

Development of a Bacillus sphaericus tablet formulation and its evaluation as a larvicide in the biological control of Culex quinquefasciatus

This study aimed to analyze the final fermentation culture of Bacillus sphaericus 2362, standardize it and develop an active tablet formulation for use in urban mosquito breeding sites. It was performed in three phases: analysis and standardization of a B. sphaericus fermented culture; physical, chemical, and biological analysis of the active powder (solubility, residual humidity, particle size, resting angle, flowing off time, compacted density, and biological activity against Culex quinquefasciatus larvae); and the development of fast-disintegrating tablets. Five formulations with differing compositions were developed and a UV protector was added to the selected formulation. The formulation products with or without UV protector, as well as the active powder caused 100% larval mortality from 1 day to 2 months after a single treatment under simulated field conditions. These results show that the UV protector does not affect the initial larvicide activity of B. sphaericus, nor its persistence over a period of two months.     

The role of environmental factors and tree injuries in soil carbon respiration response to fire and fuels treatments in pine plantations

The need to understand how forest management practices affect soil CO₂ exchange with the atmosphere (soil respiration) has increased with the recognition of a likely feedback effect of climate warming on soil respiration rates. Previous research addressing the mechanisms driving soil respiration has yielded inconsistent and/or conflicting results. This study looked to alternative above-ground forest characteristics to help explain spatial variability in soil respiration in a 30-year-old Sierra Nevada pine plantation. Fire hazard mitigation is one of the predominant management goals in these and other western US forests. Therefore, this analysis examined how fuels treatments, including shredding of understory vegetation (mastication), prescribed fire, and a combination thereof, affected soil respiration and its relationship to environmental factors and post-fire tree injuries. Multiple regression models indicated that mastication had no significant impact on soil respiration, but the roles of soil temperature and forest floor depth (O horizons) in the models increased after the treatment. Burning reduced soil respiration by ∼14%, and increased its sensitivity to tree proximity and the exposure of bare mineral soil. Scorch height in burned stands was negatively correlated with soil respiration. Models incorporating only tree injury or tree proximity parameters explained between 63% and 91% of the variability in burned plantations. This work suggests that measures of above-ground forest features can increase understanding of management impacts on soil respiration, and the mechanisms by which these impacts occur. These results are especially applicable in Mediterranean climates, where moisture stress reduces the effectiveness of soil microclimate in explaining soil respiration.