Nitric oxide modulates Leydig cell function in vitro: is this a way of communication between the immune and endocrine system in the testis?

Targeting Bacterial Antioxidant Systems for Antibiotics Development

The emergence of multidrug-resistant bacteria has become an urgent issue in modern medicine which requires novel strategies to develop antibiotics. Recent studies have supported the hypothesis that antibiotic-induced bacterial cell death is mediated by Reactive Oxygen Species (ROS). The hypothesis also highlighted the importance of antioxidant systems, the defense mechanism which contributes to antibiotic resistance. Thioredoxin and glutathione systems are the two major thiol-dependent systems which not only provide antioxidant capacity but also participate in various biological events in bacteria, such as DNA synthesis and protein folding. The biological importance makes them promising targets for novel antibiotics development. Based on the idea, ebselen and auranofin, two bacterial thioredoxin reductase inhibitors, have been found to inhibit the growth of bacteria lacking the GSH efficiently. A recent study combining ebselen and silver exhibited a strong synergistic effect against Multidrug-Resistant (MDR) Gram-negative bacteria which possess both thioredoxin and glutathione systems. These drug-repurposing studies are promising for quick clinical usage due to their well-known profile.

Remodeling the blood-brain barrier microenvironment by natural products for brain tumor therapy

Brain tumor incidence shows an upward trend in recent years; brain tumors account for 5% of adult tumors, while in children, this figure has increased to 70%. Moreover, 20%-30% of malignant tumors will eventually metastasize into the brain. Both benign and malignant tumors can cause an increase in intracranial pressure and brain tissue compression, leading to central nervous system (CNS) damage which endangers the patients' lives. Despite the many approaches to treating brain tumors and the progress that has been made, only modest gains in survival time of brain tumor patients have been achieved. At present, chemotherapy is the treatment of choice for many cancers, but the special structure of the blood-brain barrier (BBB) limits most chemotherapeutic agents from passing through the BBB and penetrating into tumors in the brain. The BBB microenvironment contains numerous cell types, including endothelial cells, astrocytes, peripheral cells and microglia, and extracellular matrix (ECM). Many chemical components of natural products are reported to regulate the BBB microenvironment near brain tumors and assist in their treatment. This review focuses on the composition and function of the BBB microenvironment under both physiological and pathological conditions, and the current research progress in regulating the BBB microenvironment by natural products to promote the treatment of brain tumors.

Nanoparticle-rich diesel exhaust may disrupt testosterone biosynthesis and metabolism via growth hormone

We previously reported that exposure to low (22.5+/-0.2 nm in diameter, 15.4+/-1.0 microg/m(3) in mass weight, 2.27x10(5)/cm(3) in mean number concentration), and medium (26.1+/-0.5 nm, 36.4+/-1.2 microg/m(3), 5.11x10(5)/cm(3)) concentrations of nanoparticle-rich diesel exhaust (NR-DE) for 1 and 2 months (5 h/day, 5 days/week) significantly increased plasma testosterone in male Fischer 344 rats, whereas exposure to a high concentration (27.1+/-0.5 nm, 168.8+/-2.7 microg/m(3), 1.36x10(6)/cm(3)) did not. The present study attempts to clarify the mechanism of this elevation. Low and medium exposures to NR-DE for 1 and 2 months significantly increased steroidogenic acute regulatory protein (StAR)- and cytochrome P450 side-chain cleavage (P450scc)-mRNA and their protein expressions in the testis of rats, in which the elevation pattern was very similar to that of plasma testosterone levels. Interestingly, both exposure levels for 1 month significantly increased growth hormone (GH) receptor expression in the testis, and low exposure also increased testicular insulin-like growth factor I-mRNA levels and hepatic microsomal cytochrome P450 2C11-mRNA and their protein levels in rats. These two factors are thought to be related to growth hormone secretion. Disruption of testosterone biosynthesis by NR-DE exposure may be a mode of action for reproductive toxicity, which may, in part, be regulated by increasing StAR and P450scc expressions via GH signalling.

Adaptive variation in testosterone levels in response to immune activation: empirical and theoretical perspectives

High testosterone levels reflect investment in male reproductive effort through the ability to produce and maintain muscle tissue and thus augment mate attraction and competitive ability. However, high testosterone levels can also compromise survivorship by increasing risk of prostate cancer, production of oxygen radicals, risk of injury due to hormonally-augmented behaviors such as aggression, violence and risk taking, reduced tissue and organ maintenance, negative energy balance from adipose tissue catabolism, and suppression of immune functions. Here, I briefly discuss how inter- and intra-individual variation in human male testosterone levels is likely an adaptive mechanism that facilitates the allocation of metabolic resources, particularly in response to injury, illness or otherwise immune activation. Maintaining low testosterone levels in resource-limited and/or high pathogen-risk environments may avoid some immunosuppression and suspend energetically-expensive anabolic functions. Augmenting testosterone levels in the presence of fertile and receptive mates, areas of high food resource availability, and low disease risk habitats will function to maximize lifetime reproductive success.

Calcium-sensing receptor activation induces nitric oxide production in H-500 Leydig cancer cells

Nitric oxide (NO) is a versatile second messenger. NO is produced by Leydig cells, where NO is a negative regulator of steroidogenesis. In cancer cells, NO is thought to have mutagenic and proliferative effects. We have previously shown that the calcium-sensing receptor (CaR) has promalignant effects in rat H-500 Leydig cancer cells, a model for humoral hypercalcemia of malignancy. Calcium, the major physiological ligand of the CaR, is a recognized intracellular cofactor in the process of NO production by virtue of its positive modulation of neuronal and endothelial nitric oxide synthase (NOS), but importantly, not of inducible (i) NOS activity. iNOS activity is regulated by changes in its expression level. Therefore, we investigated whether CaR activation changes iNOS expression. We found that high extracellular calcium (Cao2+) upregulates the level of mRNA for iNOS, whereas no change was seen in neuronal or endothelial NOS, as assessed by microarray and real-time PCR, respectively. The high Cao2+-induced iNOS upregulation was also detected by Northern and Western blotting. By quantitative real-time PCR, we showed that calcium maximally upregulates iNOS at 18 h. The effect of calcium was abolished by overexpression of a dominant-negative CaR (R185Q), confirming that the effect of Cao2+ was mediated by the CaR. Cells treated with high calcium had higher NO production than those treated with low calcium, as detected with the NO-specific DAF2-AM dye. This was confirmed in single-cell fluorescence determinations using confocal microscopy. In conclusion, high calcium upregulates the levels of iNOS mRNA and protein as well as NO production in H-500 cells, and the effect of Cao2+ on iNOS expression is mediated by the CaR.

Testosterone-mediated immune functions and male life histories

Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males. However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort. Defense against parasitic infection is an important force shaping life history evolution. Proper performance of immunological responses against infection is influenced by many physiological systems, including metabolic, reproductive, and stress hormones. Because androgens influence and modulate immune, reproductive, and somatic metabolic functions, assessing changes in testosterone and immune factors during infection may yield insight into male physiological ecology. In this review, we examine male life history trade-offs between immune and reproductive endocrine functions as well as provide a comprehensive review of testosterone-immunocompetence relationships. Emphasis is placed on testosterone because it is a primary hormone shown to be crucial to energy-allocation processes in vertebrates. Non-primate species have been used more extensively in this research than humans or non-human primates, and therefore this extensive literature is organized and reviewed in order to better understand potential parallel relationships in primates, especially humans. Furthermore, we attempt to reconcile the many inconsistent results obtained from field studies on immune-endocrine interactions as well as detail various methodologies that may be used to forward this research in evolutionary anthropology.

An alternative promoter of the human neuronal nitric oxide synthase gene is expressed specifically in Leydig cells

Neuronal nitric oxide synthase (nNOS) plays a modulatory role in the biology of a variety of neuroendocrine tissues and is especially relevant to gonadal function. We have previously reported the cloning and characterization of a variant of the nNOS protein, termed testis nNOS (TnNOS), the mRNA for which was restricted in expression to male gonadal tissues. To examine the cell-specificity of the testis-specific NOS regulatory regions we defined patterns of beta-galactosidase expression of an insertional transgene in which the reporter gene lacZ was under the transcriptional control of the human TnNOS promoter. beta-galactosidase activity was detected exclusively in the interstitial cells of the testis in transgenic mice. These cells also evidenced positive staining for nNOS protein and were identified as androgen-producing Leydig cells by staining with the Leydig cell marker, P(450)scc. Expression of the promoter was absent in cells of the seminiferous tubules, specifically germline cells of different stages and Sertoli cells. In contrast to the male gonad, beta-galactosidase activity was not detected in ovaries of adult female mice. Activity was also not evident in organs known to express full-length nNOS, such as skeletal muscle, kidney, or cerebellum. The same pattern of beta-galactosidase staining was observed in independent transgenic founders and was distinct from that observed for an endothelial NOS promoter/reporter transgene. In the testis of male adult eNOS promoter-reporter transgenic mice, beta-galactosidase activity was expressed only in endothelial cells of large- and medium-sized arterial blood vessels. Transcriptional activity of the human TnNOS promoter could not be detected in a variety of cell types, including Leydig cells, using episomal promoter-reporter constructs suggesting that a nuclear environment and higher order genomic complexity are required for appropriate promoter function. The restricted expression pattern of an nNOS variant in Leydig cells of the male gonad suggests an important role in the regulation of testosterone release and represents an intriguing model with which to dissect the molecular basis of Leydig cell-specific gene expression.