Effects of tenofovir on cytokines and nucleotidases in HIV-1 target cells and the mucosal tissue environment in the female reproductive tract.

Tenofovir (TFV) is a reverse transcriptase inhibitor used in microbicide preexposure prophylaxis trials to prevent HIV infection. Recognizing that changes in cytokine/chemokine secretion and nucleotidase biological activity can influence female reproductive tract (FRT) immune protection against HIV infection, we tested the hypothesis that TFV regulates immune protection in the FRT. Epithelial cells, fibroblasts, CD4(+) T cells, and CD14(+) cells were isolated from the endometrium (Em), endocervix (Cx), and ectocervix (Ecx) following hysterectomy. The levels of proinflammatory cytokines (macrophage inflammatory protein 3α [MIP-3α], interleukin 8 [IL-8], and tumor necrosis factor alpha [TNF-α]), the expression levels of specific nucleotidases, and nucleotidase biological activities were analyzed in the presence or absence of TFV. TFV influenced mRNA and/or protein cytokines and nucleotidases in a cell- and site-specific manner. TFV significantly enhanced IL-8 and TNF-α secretion by epithelial cells from the Em and Ecx but not from the Cx. In contrast, in response to TFV, IL-8 secretion was significantly decreased in Em and Cx fibroblasts but increased with fibroblasts from the Ecx. When incubated with CD4(+) T cells from the FRT, TFV increased IL-8 (Em and Ecx) and TNF-α (Cx and Ecx) secretion levels. Moreover, when incubated with Em CD14(+) cells, TFV significantly increased MIP-3α, IL-8, and TNF-α secretion levels relative to those of the controls. In contrast, nucleotidase biological activities were significantly decreased by TFV in epithelial (Cx) and CD4(+) T cells (Em) but increased in fibroblasts (Em). Our findings indicate that TFV modulates proinflammatory cytokines, nucleotidase gene expression, and nucleotidase biological activity in epithelial cells, fibroblasts, CD4(+) T cells, and CD14(+) cells at distinct sites within the FRT.

Sex hormones regulate tenofovir-diphosphate in female reproductive tract cells in culture.

The conflicting results of recent pre-exposure prophylaxis (PrEP) trials utilizing tenofovir (TFV) to prevent HIV infection in women led us to evaluate the accumulation of intracellular TFV-diphosphate (TFV-DP) in cells from the female reproductive tract (FRT) and whether sex hormones influence the presence of TFV-DP in these cells. Following incubation with TFV, isolated epithelial cells, fibroblasts, CD4+ T cells and CD14+ cells from the FRT as well as blood CD4+ T cells and monocyte-derived macrophages convert TFV to TFV-DP. Unexpectedly, we found that TFV-DP concentrations (fmol/million cells) vary significantly with the cell type analyzed and the site within the FRT. Epithelial cells had 5-fold higher TFV-DP concentrations than fibroblasts; endometrial epithelial cells had higher TFV-DP concentrations than cells from the ectocervix. Epithelial cells had 125-fold higher TFV-DP concentrations than FRT CD4+ T cells, which were comparable to that measured in peripheral blood CD4+ T cells. These findings suggest the existence of a TFV-DP gradient in the FRT where epithelial cells > fibroblasts > CD4+ T cells and macrophages. In other studies, estradiol increased TFV-DP concentrations in endometrial and endocervical/ectocervical epithelial cells, but had no effect on fibroblasts or CD4+ T cells from FRT tissues. In contrast, progesterone alone and in combination with estradiol decreased TFV-DP concentrations in FRT CD4+ T cells. Our results suggest that epithelial cells and fibroblasts are a repository of TFV-DP that is under hormonal control. These cells might act either as a sink to decrease TFV availability to CD4+ T cells and macrophages in the FRT, or upon conversion of TFV-DP to TFV increase TFV availability to HIV-target cells. In summary, these results indicate that intracellular TFV-DP varies with cell type and location in the FRT and demonstrate that estradiol and/or progesterone regulate the intracellular concentrations of TFV-DP in FRT epithelial cells and CD4+ T cells.

Monomethylated trivalent arsenic species disrupt steroid receptor interactions with their DNA response elements at non-cytotoxic cellular concentrations.

Arsenic (As) is considered a top environmental chemical of human health because it has been linked to adverse health effects including cancer, diabetes, cardiovascular disease, and reproductive and developmental problems. In several cell culture and animal models, As acts as an endocrine disruptor, which may underlie many of its health effects. Previous work showed that steroid receptor (SR)-driven gene expression is disrupted in cells treated with inorganic As (arsenite, iAs(+3)). In those studies, low iAs(+3) concentrations (0.1-0.7 µM) stimulated hormone-inducible transcription, whereas somewhat higher but still non-cytotoxic levels (1-3 µM) inhibited transcription. This investigation focuses on the mechanisms underlying these inhibitory effects and evaluates the role of methylated trivalent As metabolites on SR function. Recent evidence suggests that, compared with iAs, methylated forms may have distinct biochemical effects. Here, fluorescence polarization (FP) experiments utilizing purified, hormone-bound human glucocorticoid (GR) and progesterone receptor (PR) have demonstrated that neither inorganic (iAs(+3)) nor dimethylated (DMA(+3)) species of trivalent As affect receptor interactions with glucocorticoid DNA response elements (GREs). However, monomethylated forms (monomethylarsenite, MMA(+3) and monomethylarsonic diglutathione, MADG) strongly inhibit GR-GRE and PR-GRE binding. Additionally, speciation studies of iAs(+3)-treated H4IIE rat hepatoma cells show that, under treatment conditions that cause inhibition of hormone-inducible gene transcription, the intracellular concentration of MADG is sufficient to inhibit GR-GRE and PR-GRE interactions in vivo. These results indicate that arsenic's inhibitory endocrine disruption effects are probably caused in part by methylated metabolites' disruption of SR ability to bind DNA response elements that are crucial to hormone-driven gene transcription.

Effect of tenofovir on nucleotidases and cytokines in HIV-1 target cells.

Tenofovir (TFV) has been widely used for pre-exposure prophylaxis of HIV-1 infection with mixed results. While the use of TFV in uninfected individuals for prevention of HIV-1 acquisition is actively being investigated, the possible consequences of TFV exposure for the HIV-target cells and the mucosal microenvironment are unknown. In the current study, we evaluated the effects of TFV treatment on blood-derived CD4⁺ T cells, monocyte-derived macrophages and dendritic cells (DC). Purified HIV-target cells were treated with different concentrations of TFV (0.001-1.0 mg/ml) for 2 to 24 hr. RNA was isolated and RT-PCR was performed to compare the levels of mRNA expression of nucleotidases and pro-inflammatory cytokine genes (MIP3α, IL-8 and TNFα) in the presence or absence of TFV. We found that TFV increases 5'-ecto-nucleotidase (NT5E) and inhibits mitochondrial nucleotidase (NT5M) gene expression and increases 5' nucleotidase activity in macrophages. We also observed that TFV stimulates the expression and secretion of IL-8 by macrophages, DC, and activated CD4⁺ T cells and increases the expression and secretion of MIP3α by macrophages. In contrast, TFV had no effect on TNFα secretion from macrophages, DC and CD4⁺ T cells. Our results demonstrate that TFV alters innate immune responses in HIV-target cells with potential implications for increased inflammation at mucosal surfaces. As new preventive trials are designed, these findings should provide a foundation for understanding the effects of TFV on HIV-target cells in microbicide trials.

Estradiol regulation of nucleotidases in female reproductive tract epithelial cells and fibroblasts.

The use of topical and oral adenosine derivatives in HIV prevention that need to be maintained in tissues and cells at effective levels to prevent transmission prompted us to ask whether estradiol could influence the regulation of catabolic nucleotidase enzymes in epithelial cells and fibroblasts from the upper and lower female reproductive tract (FRT) as these might affect cellular TFV-DP levels. Epithelial cells and fibroblasts were isolated from endometrium (EM), endocervix (CX) and ectocervix (ECX) tissues from hysterectomy patients, grown to confluence and treated with or without estradiol prior to RNA isolation. The expression of nucleotidase (NT) genes was measurable by RT-PCR in epithelial cells and fibroblasts from all FRT tissues. To determine if sex hormones have the potential to regulate NT, we evaluated NT gene expression and NT biological activity in FRT cells following hormone treatment. Estradiol increased expression of Cytosolic 5'-nucleotidase after 2 or 4 h in endometrial epithelial cells but not epithelial cells or fibroblasts from other sites. In studies using a modified 5'-Nucleotidase biological assay for nucleotidases, estradiol increased NT activity in epithelial cells and fibroblasts from the EM, CX and ECX at 24 and 48 h. In related studies, HUVEC primary cells and a HUVEC cell line were unresponsive to estradiol in terms of nucleotidase expression or biological activity. Our findings of an increase in nucleotidase expression and biological activity induced by estradiol do not directly assess changes in microbicide metabolism. However, they do suggest that when estradiol levels are elevated during the menstrual cycle, FRT epithelial cells and fibroblasts from the EM, CX and ECX have the potential to influence microbicide levels that could enhance protection of HIV-target cells (CD4+T cells, macrophages and dendritic cells) throughout the FRT.

New approaches to making the microenvironment of the female reproductive tract hostile to HIV.

The studies presented in this review explore three distinct areas with potential for inhibiting HIV infection in women. Based on emerging information from the physiology, endocrinology and immunology of the female reproductive tract (FRT), we propose unique 'works in progress' for protecting women from HIV. Various aspects of FRT immunity are suppressed by estradiol during the menstrual cycle, making women more susceptible to HIV infection. By engineering commensal Lactobacillus to secrete the anti-HIV molecule Elafin as estradiol levels increase, women could be protected from HIV infection. Selective estrogen response modifiers enhance barrier integrity and enhance secretion of protective anti-HIV molecules. Finally, understanding the interactions and regulation of FRT endogenous antimicrobials, proteases, antiproteases, etc., all of which are under hormonal control, will open new avenues to therapeutic manipulation of the FRT mucosal microenvironment. By seeking new alternatives to preventing HIV infection in women, we may finally disrupt the HIV pandemic.

Arsenic as an endocrine disruptor: effects of arsenic on estrogen receptor-mediated gene expression in vivo and in cell culture.

Arsenic (As) contamination of drinking water is considered a serious worldwide environmental health threat that is associated with increased disease risks including skin, lung, bladder, and other cancers; type 2 diabetes; vascular and cardiovascular diseases; reproductive and developmental effects; and neurological and cognitive effects. Increased health risks may occur at as low as 10-50 ppb, while biological effects have been observed in experimental animal and cell culture systems at much lower levels. We previously reported that As is a potent endocrine disruptor, altering gene regulation by the closely related glucocorticoid, mineralocorticoid, progesterone, and androgen steroid receptors (SRs) at concentrations as low as 0.01 microM ( approximately 0.7 ppb). Very low doses enhanced hormone-mediated gene transcription, whereas slightly higher but still noncytotoxic doses were suppressive. We report here that As also disrupts the more distally related estrogen receptor (ER) both in vivo and in cell culture. At noncytotoxic doses (1-50 micromol/kg arsenite) As strongly suppressed ER-dependent gene transcription of the 17beta-estradiol (E2)-inducible vitellogenin II gene in chick embryo liver in vivo. In cell culture, noncytotoxic levels (0.25-3 microM, approximately 20-225 ppb) of As significantly inhibited E2-mediated gene activation of an ER-regulated reporter gene and the native ER-regulated GREB1 gene in human breast cancer MCF-7 cells. While the effects of As on ER-dependent gene regulation were generally similar to As effects on the other SRs, there were specific differences, particularly the lack of significant enhancement at the lowest doses, that may provide insights into possible mechanisms.

Arsenic disruption of steroid receptor gene activation: Complex dose-response effects are shared by several steroid receptors.

Chronic intake of arsenic (As) has been associated with increased risk of cancer, diabetes, developmental and reproductive problems, and cardiovascular disease. Recent studies suggest increased health risks with drinking water levels as low as 5-10 ppb. We previously reported that As disrupts glucocorticoid receptor (GR) mediated transcription in a very complex fashion. Low As levels (0.1-0.7 microM) stimulated transcription, whereas slightly higher levels (1-3 microM) were inhibitory. The DNA binding domain (DBD) was the minimal region of GR required for the response to As. Mutations in the DBD that alter the conformation of the dimerization domain (D-loop) to a DNA-bound GR conformation abolished the stimulatory effect and enhanced the inhibitory response to As. Here we report that receptors for progesterone (PR) and mineralocorticoids display a complex As response similar to that of the GR, suggesting a common mechanism for this effect. The complex response to As is not due to altered steroid or receptor levels. Moreover, a well-characterized GR dimerization mutant displayed a wild-type biphasic response to As for several divergent reporter genes, suggesting that dimerization is not critical for the response to As. Fluorescence polarization studies with purified PR and GR demonstrated that the specific PR/GR-DNA interaction is not altered in the presence of As. These results indicate that the numerous and diverse human health effects associated with As exposure may be mediated, at least in part, through its ability to simultaneously disrupt multiple hormone receptor systems.

Arsenic at very low concentrations alters glucocorticoid receptor (GR)-mediated gene activation but not GR-mediated gene repression: complex dose-response effects are closely correlated with levels of activated GR and require a functional GR DNA binding domain.

Arsenic (As) contamination of drinking water is considered a principal environmental health threat throughout the world. Chronic intake is associated with an increased risk of cancer, diabetes, and cardiovascular disease, and recent studies suggest increased health risks at levels as low as 5-10 ppb. We report here that 0.05-1 microM (6-120 ppb) As showed stimulatory effects on glucocorticoid receptor (GR)-mediated gene activation in rat EDR3 hepatoma cells of both the endogenous tyrosine aminotransferase (TAT) gene and the reporter genes containing TAT glucocorticoid response elements. At slightly higher concentrations (1-3 microM), the effects of As became inhibitory. Thus, over this narrow concentration range, the effects of As changed from a 2- to 4-fold stimulation to a greater than 2-fold suppression in activity. Interestingly, the inhibitory effect of GR on both AP1- and NF-kappa B-mediated gene activation was not affected by As. The magnitude of GR stimulation and inhibition by As was highly dependent on the cellular level of hormone-activated GR. Mutational deletion studies indicated that the central DNA binding domain (DBD) of GR is the minimal region required for the As effect and does not require free sulfhydryls. Point mutations located within the DBD that have known structural consequences significantly altered the GR response to As. In particular, point mutations in the DBD that confer a DNA-bound GR confirmation abolished the low dose As stimulatory effect but enhanced the inhibitory response, further indicating that the DBD is important for mediating these As effects.