Penetration of didanosine in semen of HIV-1-infected men

Histomorphometric changes in testis following administration of tenofovir nanoparticles in an animal model

BACKGROUND

Nanoparticle-based drugs are new inventions in the management of the Human immunodeficiency virus (HIV) pandemic, especially resistant forms of the virus in anatomical sanctuary sites and organs such as the testis. However, safety issues must be resolved to attain the optimal potential of newer nano-drug formulations.

AIM

The study investigated the toxicological potential of synthesized Tenofovir Nanoparticles (TDF-N) on testicular indices when used for the prevention and treatment of HIV.

METHODOLOGY

Fifteen male Sprague-Dawley (SD) rats with weight ranging from 230 g to 250 g were randomly assigned into groups A (control, saline), B (TDF), and C (TDF-N). The testes were removed for sperm analysis and processed for H/E and PAS stains. Cell counts and cellular measurements; the diameter and the area of the testicular seminiferous tubules were measured using ImageJ and Leica software 2.0.

RESULTS

A significant reduction (p < 0.05) in sperm count was noticed in the TDF-N group. Also observed in the TDF and TDF-N groups was a significant reduction (p < 0.05) in sperm motility and in the number of dead sperms compared with the control. Sperm abnormalities such as distorted basement membranes, loss of germ cells, hypocellular interstitium, and loss of spermatogenic series were increased in the TDF and TDF-N groups. There was also a significant reduction (p < 0.05) in the cell count, diameter, and area of seminiferous tubules observed in these groups.

CONCLUSION

TDF and TDF-N may be detrimental to the testis and testicular tissue, leading to significantly reduced sperm counts, motility, and ultimately-male fertility.

Nucleoside Analogues Are Potent Inducers of Pol V-mediated Mutagenesis

Drugs targeting DNA and RNA in mammalian cells or viruses can also affect bacteria present in the host and thereby induce the bacterial SOS system. This has the potential to increase mutagenesis and the development of antimicrobial resistance (AMR). Here, we have examined nucleoside analogues (NAs) commonly used in anti-viral and anti-cancer therapies for potential effects on mutagenesis in Escherichia coli, using the rifampicin mutagenicity assay. To further explore the mode of action of the NAs, we applied E. coli deletion mutants, a peptide inhibiting Pol V (APIM-peptide) and metabolome and proteome analyses. Five out of the thirteen NAs examined, including three nucleoside reverse transcriptase inhibitors (NRTIs) and two anti-cancer drugs, increased the mutation frequency in E. coli by more than 25-fold at doses that were within reported plasma concentration range (Pl.CR), but that did not affect bacterial growth. We show that the SOS response is induced and that the increase in mutation frequency is mediated by the TLS polymerase Pol V. Quantitative mass spectrometry-based metabolite profiling did not reveal large changes in nucleoside phosphate or other central carbon metabolite pools, which suggests that the SOS induction is an effect of increased replicative stress. Our results suggest that NAs/NRTIs can contribute to the development of AMR and that drugs inhibiting Pol V can reverse this mutagenesis.

Pharmacokinetics of antiretrovirals in genital secretions and anatomic sites of HIV transmission: implications for HIV prevention

The incidence of HIV remains alarmingly high in many parts of the world. Prophylactic use of antiretrovirals, capable of concentrating in the anatomical sites of transmission, may reduce the risk of infection after an unprotected sexual exposure. To date, orally and topically administered antiretrovirals have exhibited variable success in preventing HIV transmission in large-scale clinical trials. Antiretroviral mucosal pharmacokinetics may help explain the outcomes of these investigations. Penetration and accumulation of antiretrovirals into sites of transmission can influence dosing strategies and pre-exposure prophylaxis clinical trial design. Antiretroviral tissue distribution varies widely within and between drug classes, attributed in part to their physicochemical properties and tissue-specific drug transporter expression. Nucleoside(-tide) reverse transcriptase inhibitors, the CCR5 antagonist maraviroc, and the integrase inhibitor raltegravir demonstrate the highest penetration into the male and female reproductive tracts and colorectal tissue relative to blood. This review describes antiretroviral exposure in anatomic sites of transmission, and places these findings in context with the prevention of HIV and the efficacy of pre-exposure prophylactic strategies.

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Expression of ATP-binding cassette membrane transporters in rodent and human sertoli cells: relevance to the permeability of antiretroviral therapy at the blood-testis barrier

The blood-testis barrier (BTB), composed primarily of Sertoli cells, is responsible for protecting developing germ cells from xenobiotic exposure. ATP-binding cassette (ABC) membrane-associated drug efflux transporters, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and the multidrug resistance-associated proteins (Mrps), have been shown to restrict antiretroviral drug permeability at blood-tissue barriers such as the blood-brain barrier. However, it remains unclear whether these transporters are functional at the level of Sertoli cells and can regulate anti-HIV drug permeability at the BTB. This study investigated the functional expression of ABC transporters in a mouse Sertoli cell line system (TM4) and in primary cultures of human Sertoli cells (HSECs). Expression of multidrug resistance Mdr1a/1b/MDR1/P-gp, Mrp1/MRP1, and Mrp4/MRP4 is confirmed by quantitative polymerase chain reaction and immunoblotting analysis in TM4 cells and HSECs. Immunofluorescence studies revealed plasma membrane localization of P-gp, Mrp1/MRP1, and Mrp4/MRP4 in both cell systems. However, Bcrp expression and localization was only detected in rodent cells. Accumulation of 1) rhodamine-6G (R-6G), a fluorescent P-gp substrate, 2) [³H]atazanavir, a HIV protease inhibitor and known P-gp substrate, 3) 2'7'-bis-(2-carboxyethyl)-5-(and-6)carboxyfluorescein (BCECF), a fluorescent Mrp substrate, and 4) [³H]mitoxantrone, a BCRP substrate, by TM4 monolayer cells in the presence of established inhibitors demonstrates that these transporters are functional. In addition, several anti-HIV drugs significantly enhance the accumulation of R-6G, [³H]atazanavir, BCECF, and [³H]mitoxantrone by TM4 cells. This study provides the first evidence of ABC transporter expression and activity in Sertoli cells and suggests that these transporters could play an important role in restricting antiretroviral drug permeability at the BTB.

HIV dynamics in seminal plasma during primary HIV infection

HIV dynamics in seminal plasma during primary HIV infection was evaluated through an observational study of individuals with primary HIV infection at the University of Washington Primary Infection Clinic. Seminal plasma HIV RNA was quantified using a real-time reverse transcription PCR assay. Blood plasma RNA was quantified by bDNA or PCR-based assays. Longitudinal analyses of HIV RNA levels over time used random effects regression analysis. From 1993 to 2005, 110 men collected 327 semen specimens. Initial blood and seminal plasma RNA levels in untreated men were only moderately correlated (Spearman r = 0.38, p = 0.0002). Estimated peak and set point levels were lower in semen than blood by 0.8 (p = 0.001) and 0.7 (p < 0.001) log(10) copies/ml, respectively. RNA decay rates were similar in the two compartments (p = 0.4). For 2 months after infection, mean HIV RNA levels in seminal plasma remained above a threshold level (3.8 log(10) copies/ml) that has been associated with recovery of infectious virus in vitro. HIV-positive men are likely to be most infectious in the first months following HIV acquisition. However, the modest relationship between HIV RNA levels in blood and seminal plasma suggests that the relative risk of HIV transmission during primary infection may vary from current estimates that are solely based on blood levels. Incorporating seminal plasma HIV levels into future mathematical models may increase the accuracy of these models.

A mechanistic latent variable model for estimating drug concentrations in the male genital tract: a case study in drug kinetics

The purpose of this study is to develop statistical methodology to facilitate indirect estimation of the concentration of antiretroviral drugs and viral loads in the prostate gland and the seminal vesicle. The differences in antiretroviral drug concentrations in these organs may lead to suboptimal concentrations in one gland. Suboptimal levels of the antiretroviral drugs may not be able to fully suppress the virus in that gland, leading to a source of sexually transmissible virus and increasing the chance of selecting for a drug-resistant virus. This information may be useful for selecting an antiretroviral drug regimen that will achieve optimal concentrations in the genital tract glands. Using fractionally collected semen ejaculates, Lundquist (Acta Physiol. Scand. 1949; 19:1-95) measured levels of surrogate markers in each fraction that are uniquely produced by specific male accessory glands. To determine the original glandular concentrations of the surrogate markers, Lundquist solved a simultaneous series of linear equations. This method has several limitations. In particular, it does not yield a unique solution, it does not address measurement error, and it does not provide population-averaged estimates after taking into account inter-subject variability in the parameters. To cope with these limitations, we developed a mechanistic latent variable model based on the physiology of the male genital tract and surrogate markers. We employ a Bayesian approach and perform a sensitivity analysis on the distributional assumptions on the random effects and priors. The model and Bayesian approach are validated on experimental data where the concentration of a drug should be (biologically) differentially distributed between the two glands. In this example, the Bayesian model-based conclusions are found to be robust to model specification and this hierarchical approach leads to more scientifically valid conclusions than the original methodology. In particular, unlike existing methods, the proposed model-based approach was not affected by a common form of outliers.

Tissue distribution, ontogeny and induction of the transporters Multidrug and toxin extrusion (MATE) 1 and MATE2 mRNA expression levels in mice

Transporters are expressed in a wide variety of tissues where they perform the critical function of enabling anionic and cationic chemicals of exogenous and endogenous origin to cross otherwise impermeable cell membranes. The Multidrug and toxin extrusion (MATE) transporters mediate cellular efflux of a variety of organic cations, including many drugs. The purpose of the current study was to determine (1) constitutive expression levels of MATE mRNA in various tissues, (2) whether there are gender differences in the expression of MATEs, (3) the ontogenic expression pattern of MATE1 in kidney and (4) whether MATEs are pharmacologically inducible in liver via activation of known transcription factors. In both male and female mice, MATE1 mRNA levels were highest in the kidney, where male expression was higher than female. MATE2 mRNA expression levels were the highest in the testis, where high expression was localized to Sertoli cells, a critical cell type of the blood testis barrier. In female mice, MATE2 mRNA levels were expressed most highly in the colon. The ontogenic pattern of expression of MATE1 mRNA in the kidneys of both males and females was gradual, with levels increasing steadily from prenatal day -2 to 45 days of age, and a gender difference appearing at day 30. Of the transcription factor activators examined (AhR, CAR, Nrf2, PPARalpha and PXR), none were capable of altering MATE1 or MATE2. The current findings support a potential role for MATE1 and MATE2 in a wide range of tissues and, notably, a unique role for MATE2 in the blood-testis barrier.

Semen Quality and Drug Concentrations in Seminal Plasma of Patients Using a Didanosine or Didanosine Plus Tenofovir Containing Antiretroviral Regimen

Data on the concentrations of didanosine (ddI) and tenofovir (TFV) in seminal plasma are sparse. Subtherapeutic drug concentrations within the lumen of the male genital tract may have implications for selection and transmission of drug-resistant HIV strains. On the other hand, sufficient penetration of these drugs into the male genital tract has potential toxic effects on the spermatozoa and their precursors. In the current study, the authors obtained paired semen and blood samples at variable time points after drug intake from 30 HIV-1-infected patients using a ddI (n = 15) or ddI + TFV (n = 15) containing an antiretroviral regimen. Didanosine and TFV concentrations were measured in seminal and blood plasma and semen quality was assessed. Both ddI and TFV penetrated well into seminal plasma. Whereas blood plasma ddI concentrations dropped to near or below the lower limit of quantification of 0.017 microg/mL 9 hours after drug intake, the ddI concentration in seminal plasma remained detectable during the whole dosing interval with a median of 0.20 and 0.21 microg/mL in the ddI and ddI + TFV groups, respectively. Tenofovir was detectable during the whole dosing interval in both blood and seminal plasma with a median concentration of 0.12 and 0.25 microg/mL, respectively, and a median seminal-to-blood-plasma ratio of 3.3. Semen quality was within the normal range according to the criteria of the World Health Organization, except for the percentage of progressively motile sperm, which was low in both groups of patients. The authors conclude that ddI and TFV penetrate well into seminal plasma and that the reduced sperm motility deserves further study.