Testosterone down-regulates ornithine aminotransferase gene and up-regulates arginase II and ornithine decarboxylase genes for polyamines synthesis in the murine kidney

Elevation of Arginase-II in Podocytes Contributes to Age-Associated Albuminuria in Male Mice

One of the manifestations of renal aging is podocyte dysfunction and loss, which are associated with proteinuria and glomerulosclerosis. Studies show a male bias in glomerular dysfunction and chronic kidney diseases, and the underlying mechanisms remain obscure. Recent studies demonstrate the role of an age-associated increase in arginase-II (Arg-II) in proximal tubules of both male and female mice. However, it is unclear whether Arg-II is also involved in aging glomeruli. The current study investigates the role of the sex-specific elevation of Arg-II in podocytes in age-associated increased albuminuria. Young (3-4 months) and old (20-22 months) male and female mice of wt and arginase-II knockout (arg-ii-/-) were used. Albuminuria was employed as a readout of glomerular function. Cellular localization and expression of Arg-II in glomeruli were analyzed using an immunofluorescence confocal microscope. A more pronounced age-associated increase in albuminuria was found in male than in female mice. An age-associated induction of Arg-II in glomeruli and podocytes (as demonstrated by co-localization of Arg-II with the podocyte marker synaptopodin) was also observed in males but not in females. Ablation of the arg-ii gene in mice significantly reduces age-associated albuminuria in males. Also, age-associated decreases in podocyte density and glomerulus hypertrophy are significantly prevented in male arg-ii-/- but not in female mice. However, age-associated glomerulosclerosis is not affected by arg-ii ablation in both sexes. These results demonstrate a role of Arg-II in sex-specific podocyte injury in aging. They may explain the sex-specific differences in the development of renal disease in humans during aging.

Methyl Group Metabolism in Differentiation, Aging, and Cancer

Methyl group metabolism belongs to a relatively understudied field of research. Its importance lies in the fact that methyl group metabolic pathways are crucial for the successful conversion of dietary nutrients into the basic building blocks to carry out any cellular methylation reaction. Methyl groups play essential roles in numerous cellular functions such as DNA methylation, nucleotide- and protein biosynthesis. Especially, DNA methylation is responsible for organizing the genome into transcriptionally silent and active regions. Ultimately, it is this proper annotation that determines the quality of expression patterns required to ensure and shape the phenotypic integrity and function of a highly specialized cell type. Life is characterized by constantly changing environmental conditions, which are addressed by changes in DNA methylation. This relationship is increasingly coming into focus as it is of fundamental importance for differentiation, aging, and cancer. The stability and permanence of these metabolic processes, fueling the supplementation of methyl groups, seem to be important criteria to prevent deficiencies and erosion of the methylome. Alterations in the metabolic processes can lead to epigenetic and genetic perturbations, causative for diverse disorders, accelerated aging, and various age-related diseases. In recent decades, the intake of methyl group compounds has changed significantly due to, e.g., environmental pollution and food additives. Based on the current knowledge, this review provides a brief overview of the highly interconnected relationship between nutrition, metabolism, changes in epigenetic modifications, cancer, and aging. One goal is to provide an impetus to additionally investigate changes in DNA methylation as a possible consequence of an impaired methyl group metabolism.

Role of tubular epithelial arginase-II in renal inflammaging

The aging kidney undergoes complex changes and is vulnerable to injury and development of chronic kidney disease (CKD) with preponderance affecting more women than men. Evidence has been presented that the type-II L-arginine:ureohydrolase, arginase-II (Arg-II) plays a role in the acceleration of aging. Arg-II is highly expressed in the kidney. However, the role of Arg-II in renal aging is not known. This study is to investigate whether Arg-II is involved in the kidney aging process dependently on sex. Arg-II level in the kidney of wild type (WT) mice is significantly elevated with aging, which is accompanied by an increase in expression of the inflammatory cytokines/chemokines, tissue macrophages, factors involved in fibrosis, and tubulointestitial fibrosis in both males and females. This renal aging phenotype is significantly suppressed in arg-II^−/− mice, mainly in the females in which Arg-II level is higher than in the males. Importantly, numerous factors such as IL-1β, MCP1, VCAM-1, and TGFβ1 are mainly localized in the proximal tubular S3 segment cells expressing Arg-II in the aging kidney. In human proximal tubular cells (HK-2), TNF-α enhances adhesion molecule expression dependently on Arg-II upregulation. Overexpression of Arg-II in the cells enhances TGFβ1 levels which is prevented by mitochondrial ROS inhibition. In summary, our study reveals that renal proximal tubular Arg-II plays an important role in the kidney aging process in females. Arg-II could be a promising therapeutic target for the treatment and prevention of aging-associated kidney diseases.

Racial disparity in prostate cancer in the African American population with actionable ideas and novel immunotherapies

Background

African Americans (AAs) in the United States are known to have a higher incidence and mortality for Prostate Cancer (PCa). The drivers of this epidemiological disparity are multifactorial, including socioeconomic factors leading to lifestyle and dietary issues, healthcare access problems, and potentially tumor biology.

Recent findings

Although recent evidence suggests once access is equal, AA men have equal outcomes to Caucasian American (CA) men, differences in PCa incidence remain, and there is much to do to reverse disparities in mortality across the USA. A deeper understanding of these issues, both at the clinical and molecular level, can facilitate improved outcomes in the AA population. This review first discusses PCa oncogenesis in the context of its diverse hallmarks before benchmarking key molecular and genomic differences for PCa in AA men that have emerged in the recent literature. Studies have emphasized the importance of tumor microenvironment that contributes to both the unequal cancer burden and differences in clinical outcome between the races. Management of comorbidities like obesity, hypertension, and diabetes will provide an essential means of reducing prostate cancer incidence in AA men. Although requiring further AA specific research, several new treatment strategies such as immune checkpoint inhibitors used in combination PARP inhibitors and other emerging vaccines, including Sipuleucel‐T, have demonstrated some proven efficacy.

Conclusion

Genomic profiling to integrate clinical and genomic data for diagnosis, prognosis, and treatment will allow physicians to plan a “Precision Medicine” approach to AA men. There is a pressing need for further research for risk stratification, which may allow early identification of AA men with higher risk disease based on their unique clinical, genomic, and immunological profiles, which can then be mapped to appropriate clinical trials. Treatment options are outlined, with a concise description of recent work in AA specific populations, detailing several targeted therapies, including immunotherapy. Also, a summary of current clinical trials involving AA men is presented, and it is important that policies are adopted to ensure that AA men are actively recruited. Although it is encouraging that many of these explore the lifestyle and educational initiatives and therapeutic interventions, there is much still work to be done to reduce incidence and mortality in AA men and equalize current racial disparities.

Arginase II Plays a Central Role in the Sexual Dimorphism of Arginine Metabolism in C57BL/6 Mice

BACKGROUND

Sex differences in plasma concentration of arginine and arginase activity of different tissues have been reported in mice. In addition, male but not female C57BL/6 mice have a dietary arginine requirement for growth.

OBJECTIVE

The goal of this research was to test the hypothesis that arginase II is a key factor in the sexual dimorphism of arginine metabolism.

METHODS

Young adult male and female wild type (WT), and heterozygous and arginase II knockout mice on a C57BL/6 background mice were infused with labeled citrulline, arginine, ornithine, phenylalanine, and tyrosine to determine the rates of appearance and interconversion of these amino acids. Tissue arginase activity was measured in the liver, heart, jejunum, kidney, pancreas, and spleen with an arginine radioisotope. The effect of genotype, sex, and their interaction was tested.

RESULTS

Female mice produced ∼36% more citrulline than their male littermates, which translated into a greater arginine endogenous synthesis, flux, and plasma concentration (42, 6, and 27%, respectively; P < 0.001). Female mice also had a greater phenylalanine flux (10%) indicating a greater rate of whole protein breakdown; however, they had a lower protein synthesis rate than males (18%; P < 0.001). The ablation of arginase II reduced the production of citrulline and the de novo synthesis of arginine in females and increased the rate of appearance of arginine and plasma arginine concentration in male mice (16 and 22%, respectively; P < 0.001). No effect of arginase II deletion, however, was observed for whole-body protein kinetics. Arginase II activity was present in the pancreas, kidney, jejunum, and spleen; WT females had a ∼2-fold greater renal arginase activity than their WT counterparts.

CONCLUSIONS

A clear sexual dimorphism exists in the endogenous synthesis of arginine and its disposal. Female mice have a greater arginine availability than their male littermates. The ablation of arginase II increases arginine availability in male mice.

Deficit of human ornithine aminotransferase in gyrate atrophy: Molecular, cellular, and clinical aspects

Gyrate Atrophy (GA) of the choroid and retina (MIM# 258870) is an autosomal recessive disorder due to mutations of the OAT gene encoding ornithine-delta-aminotransferase (OAT), associated with progressive retinal deterioration and blindness. The disease has a theoretical global incidence of approximately 1:1,500,000. OAT is mainly involved in ornithine catabolism in adults, thus explaining the hyperornithinemia as hallmark of the disease. Patients are treated with an arginine-restricted diet, to limit ornithine load, or the administration of Vitamin B6, a precursor of the OAT coenzyme pyridoxal phosphate. Although the clinical and genetic aspects of GA are known for many years, the enzymatic phenotype of pathogenic variants and their response to Vitamin B6, as well as the molecular mechanisms explaining retinal damage, are poorly clarified. Herein, we provide an overview of the current knowledge on the biochemical properties of human OAT and on the molecular, cellular, and clinical aspects of GA.

Putrescine regulates nitric oxide accumulation in Ganoderma lucidum partly by influencing cellular glutamine levels under heat stress

When fungi are subjected to abiotic stresses, the polyamines (PAs) level alter significantly. Here, we reveal that the polyamine putrescine (Put) could play an important role in alleviating heat stress(HS)-induced accumulation of nitric oxide (NO). Ornithine decarboxylase (ODC)-silenced mutants that were defective in Put biosynthesis exhibited significantly lower NO levels than the wild type (WT) when subjected to HS. With addition of 5 mM exogenous Put, the ODC-silenced mutant endogenous Put obviously increased under HS. At the same time, the contents of NO in the ODC-silenced mutants recovered to approximately WT levels after the administration of exogenous Put. However, the elevated NO content in the ODC-silenced mutants disappeared when exogenous Put and carboxy-PTIO (PTIO is a specific scavenger of NO) were added. Intriguingly, the content of glutamine (Gln) was significantly increased in the ODC-silenced strains. When exogenous Put was added to the WT, the Gln content was significantly decreased. The appearance of a high level of Gln was accompanied by nitrate reductase (NR) activity reduction. Further studies showed that Put influenced ganoderic acids (GAs) biosynthesis by regulating NO content, possibly through NR, under HS. Our work reported that Put regulates HS-induced NO accumulation by changing the cellular Gln level in filamentous fungi. IMPORTANCE: In our present work, it was HS as an ubiquitous environmental stress that affects the important pharmacological secondary metabolite (GAs) content in G. lucidum. Afterwards, we began to explore the network formed between multiple substances to jointly reduce the massive accumulation of GAs content caused by HS. We firstly focused on Put, a substance that enhances resistance to multiple stresses. Further, we discovered an influence on Put could changing the NO content, which has been shown to decrease the accumulation of GAs via HS. Then, we also found the change of NO content may be due to Put level that would affect intracellular Gln content. It has never been reported. And ultimately, it is Put related network that could reduce HS-inducing secondary metabolite mess in fungi.

A Metabolomics Approach to Screening for Autism Risk in the Children's Autism Metabolome Project

Autism spectrum disorder (ASD) is biologically and behaviorally heterogeneous. Delayed diagnosis of ASD is common and problematic. The complexity of ASD and the low sensitivity of available screening tools are key factors in delayed diagnosis. Identification of biomarkers that reduce complexity through stratification into reliable subpopulations can assist in earlier diagnosis, provide insight into the biology of ASD, and potentially suggest targeted interventions. Quantitative metabolomic analysis was performed on plasma samples from 708 fasting children, aged 18 to 48 months, enrolled in the Children's Autism Metabolome Project (CAMP). The primary goal was to identify alterations in metabolism helpful in stratifying ASD subjects into subpopulations with shared metabolic phenotypes (i.e., metabotypes). Metabotypes associated with ASD were identified in a discovery set of 357 subjects. The reproducibility of the metabotypes was validated in an independent replication set of 351 CAMP subjects. Thirty-four candidate metabotypes that differentiated subsets of ASD from typically developing participants were identified with sensitivity of at least 5% and specificity greater than 95%. The 34 metabotypes formed six metabolic clusters based on ratios of either lactate or pyruvate, succinate, glycine, ornithine, 4-hydroxyproline, or α-ketoglutarate with other metabolites. Optimization of a subset of new and previously defined metabotypes into a screening battery resulted in 53% sensitivity (95% confidence interval [CI], 48%-57%) and 91% specificity (95% CI, 86%-94%). Thus, our metabolomic screening tool detects more than 50% of the autistic participants in the CAMP study. Further development of this metabolomic screening approach may facilitate earlier referral and diagnosis of ASD and, ultimately, more targeted treatments. LAY SUMMARY: Analysis of a selected set of metabolites in blood samples from children with autism and typically developing children identified reproducible differences in the metabolism of about half of the children with autism. Testing for these differences in blood samples can be used to help screen children as young as 18 months for risk of autism that, in turn, can facilitate earlier diagnoses. In addition, differences may lead to biological insights that produce more precise treatment options. We are exploring other blood-based molecules to determine if still a higher percentage of children with autism can be detected using this strategy. Autism Res 2020, 13: 1270-1285. © 2020 The Authors. Autism Research published by International Society for Autism Research published by Wiley Periodicals LLC.

Altered Expression of Urea Cycle Enzymes in Amyloid-β Protein Precursor Overexpressing PC12 Cells and in Sporadic Alzheimer's Disease Brain

Urea cycle enzymes may play important yet poorly characterized roles in Alzheimer's disease (AD). Our previous results showed that amyloid-β (Aβ) affects urea cycle enzymes in rat pheochromocytoma (PC12) cells. The aim of the present study was to investigate the changes in arginases, other urea cycle enzymes, and nitric oxide synthases (NOSs) in PC12 cells transfected with AβPP bearing the double 'Swedish' mutation (APPsw, K670M/N671L) and in postmortem sporadic AD brain hippocampus; the mutation intensifies Aβ production and strongly associates with AD neuropathology. mRNA expression was analyzed using real-time PCR in cell cultures and DNA microarrays in hippocampal CA1 area of human AD brains. Arginase activity was measured spectrophotometrically, and arginine, ornithine, and citrulline levels by high-performance liquid chromatography. Our data demonstrated that the expression and activity of arginases (Arg1 and Arg2), as well as the expression of argininosuccinate synthase (Ass) were significantly reduced in APPsw cells compared to control. However, argininosuccinate lyase (Asl) was upregulated in APPsw cells. Real-time PCR analysis revealed significant elevation of neuronal nitric oxide synthase (Nnos) mRNA in APPsw cells, without changes in the endothelial Enos, whereas inducible Inos was undetectable. The changes were found to follow closely those observed in the human hippocampal CA1 region of sporadic AD brains. The changes in enzyme expression were accompanied in APPsw cells by significantly elevated citrulline, ornithine, and arginine. Our findings demonstrate that AβPP/Aβ alters arginine metabolism and induces a shift of cellular homeostasis that may support the oxidative/nitrosative stress observed in AD.

Effects of testosterone administration (and its 5-alpha-reduction) on parenchymal organ volumes in healthy young men: findings from a dose-response trial

Animal data shows that testosterone administration increases the volume of some parenchymal organs. However, the effects of exogenous testosterone on solid abdominal organs in humans remain unknown. The present study evaluated the effects of testosterone administration on the volume of liver, spleen and kidneys in a dose-response trial. Young healthy men aged 18-50 years participating in the 5α-Reductase (5aR) Trial. All participants received monthly injections of 7.5 mg leuprolide acetate to suppress endogenous testosterone secretion and weekly injections of 50, 125, 300 or 600 mg of testosterone enanthate, and were randomized to receive either 2.5 mg dutasteride (5 α-reductase inhibitor) or placebo daily for 20 weeks. Liver, spleen and kidney volumes were measured at baseline and the end of treatment using 1.5-Tesla magnetic resonance imaging. The dose-effect of testosterone on changes in the volume of parenchymal organs was evaluated by linear regression model. The association between changes in total testosterone (TT) levels and changes in organ volumes were assessed. Testosterone administration increased liver volume dose-dependently (17.4 cm3 per 100 mg of weekly testosterone enanthate; p = 0.031); the increase in liver volume was positively associated with changes in TT levels (R2  = 0.08, p = 0.024). A dose-dependent, but non-significant, increase in kidney volumes was also seen. Inclusion of dutasteride use into the models showed an independent association of randomization to dutasteride group with liver volume increase. In conclusion, Testosterone administration increased the liver volume in a dose-dependent manner. The potential changes in parenchymal organs should be considered when interpreting apparent changes in lean mass in response to anabolic interventions.

Arginase-II Promotes Tumor Necrosis Factor-α Release From Pancreatic Acinar Cells Causing β-Cell Apoptosis in Aging

Aging is associated with glucose intolerance. Arginase-II (Arg-II), the type-II L-arginine-ureahydrolase, is highly expressed in pancreas. However, its role in regulation of pancreatic β-cell function is not known. Here we show that female (not male) mice deficient in Arg-II (Arg-II^-/-) are protected from age-associated glucose intolerance and reveal greater glucose induced-insulin release, larger islet size and β-cell mass, and more proliferative and less apoptotic β-cells compared with the age-matched wild-type (WT) controls. Moreover, Arg-II is mainly expressed in acinar cells and is upregulated with aging, which enhances p38 mitogen-activated protein kinase (p38 MAPK) activation and release of tumor necrosis factor-α (TNF-α). Accordingly, conditioned medium of isolated acinar cells from old WT (not Arg-II^-/-) mice contains higher TNF-α levels than the young mice and stimulates β-cell apoptosis and dysfunction, which are prevented by a neutralizing anti-TNF-α antibody. In acinar cells, our study demonstrates an age-associated Arg-II upregulation, which promotes TNF-α release through p38 MAPK leading to β-cell apoptosis, insufficient insulin secretion, and glucose intolerance in female rather than male mice.

Ornithine Aminotransferase, an Important Glutamate-Metabolizing Enzyme at the Crossroads of Multiple Metabolic Pathways

Ornithine δ-aminotransferase (OAT, E.C. 2.6.1.13) catalyzes the transfer of the δ-amino group from ornithine (Orn) to α-ketoglutarate (aKG), yielding glutamate-5-semialdehyde and glutamate (Glu), and vice versa. In mammals, OAT is a mitochondrial enzyme, mainly located in the liver, intestine, brain, and kidney. In general, OAT serves to form glutamate from ornithine, with the notable exception of the intestine, where citrulline (Cit) or arginine (Arg) are end products. Its main function is to control the production of signaling molecules and mediators, such as Glu itself, Cit, GABA, and aliphatic polyamines. It is also involved in proline (Pro) synthesis. Deficiency in OAT causes gyrate atrophy, a rare but serious inherited disease, a further measure of the importance of this enzyme.

Mutational Landscape of Aggressive Prostate Tumors in African American Men

Prostate cancer is the most frequently diagnosed and second most fatal nonskin cancer among men in the United States. African American men are two times more likely to develop and die of prostate cancer compared with men of other ancestries. Previous whole genome or exome tumor-sequencing studies of prostate cancer have primarily focused on men of European ancestry. In this study, we sequenced and characterized somatic mutations in aggressive (Gleason ≥7, stage ≥T2b) prostate tumors from 24 African American patients. We describe the locations and prevalence of small somatic mutations (up to 50 bases in length), copy number aberrations, and structural rearrangements in the tumor genomes compared with patient-matched normal genomes. We observed several mutation patterns consistent with previous studies, such as large copy number aberrations in chromosome 8 and complex rearrangement chains. However, TMPRSS2-ERG gene fusions and PTEN losses occurred in only 21% and 8% of the African American patients, respectively, far less common than in patients of European ancestry. We also identified mutations that appeared specific to or more common in African American patients, including a novel CDC27-OAT gene fusion occurring in 17% of patients. The genomic aberrations reported in this study warrant further investigation of their biologic significant role in the incidence and clinical outcomes of prostate cancer in African Americans. Cancer Res; 76(7); 1860-8. ©2016 AACR.

Oxymetholone therapy of fanconi anemia suppresses osteopontin transcription and induces hematopoietic stem cell cycling

Androgens are widely used for treating Fanconi anemia (FA) and other human bone marrow failure syndromes, but their mode of action remains incompletely understood. Aged Fancd2^−/− mice were used to assess the therapeutic efficacy of oxymetholone (OXM) and its mechanism of action. Eighteen-month-old Fancd2^−/− mice recapitulated key human FA phenotypes, including reduced bone marrow cellularity, red cell macrocytosis, and peripheral pancytopenia. As in humans, chronic OXM treatment significantly improved these hematological parameters and stimulated the proliferation of hematopoietic stem and progenitor cells. RNA-Seq analysis implicated downregulation of osteopontin as an important potential mechanism for the drug’s action. Consistent with the increased stem cell proliferation, competitive repopulation assays demonstrated that chronic OXM therapy eventually resulted in stem cell exhaustion. These results expand our knowledge of the regulation of hematopoietic stem cell proliferation and have direct clinical implications for the treatment of bone marrow failure.

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OXM treatment causes loss of quiescence and stem cell exhaustion

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RNaseq analysis reveals transcriptional changes in key pathways in Fancd2^−/− HSPC

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OXM suppresses transcription of osteopontin, a known stem cell quiescence promoter

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Unlike previous notions, OXM has no effect on telomerase expression or EPO signaling

Expression and distribution of genes encoding for polyamine-metabolizing enzymes in the different zones of male and female mouse kidneys

The role of polyamines in renal physiology is only partially understood. Moreover, most of the data on the enzymes of polyamine metabolism come from studies using whole kidneys. The aim of the present study was to analyze the mRNA abundance of the genes implicated in both the polyamine biosynthetic and catabolic pathways in different renal zones of male and female mice, by means of the quantitative reverse transcription-polymerase chain reaction. Our results indicate that there is an uneven distribution of the different mRNAs studied in the five renal zones: superficial cortex, deep cortex, outer stripe of the outer medulla (OS), inner stripe of the outer medulla (IS), and the inner medulla + papilla (IM). The biosynthetic genes, ornithine decarboxylase (ODC) and spermine synthase, were more expressed in the cortex, whereas the mRNAs of the catabolic genes spermine oxidase (SMO) and diamine oxidase were more abundant in IS and IM. The genes involved in the regulation of polyamine synthesis (AZ1, AZ2 and AZIN1) were expressed in all the renal zones, predominantly in the cortex, while AZIN2 gene was more abundant in the OS. ODC, SMO, spermidine synthase and spermidine/spermine acetyl transferase expression was higher in males than in females. In conclusion, the genes encoding for the polyamine metabolism were specifically and quantitatively distributed along the corticopapillary axis of male and female mouse kidneys, suggesting that their physiological role is essential in defined renal zones and/or nephron segments.

Endocrine disruptors provoke differential modulatory responses on androgen receptor and pregnane and xenobiotic receptor: potential implications in metabolic disorders

A systematic comparison of the impact of some potential endocrine disruptors (EDs) on modulation of androgen receptor (AR) and pregnane and xenobiotic receptor (PXR) function was conducted in a multi-step analysis. Promoter-reporter-based transcription assays were performed in conjunction with receptor dynamic studies in living cells that helped implicating the suspected EDs for their deleterious effects. We demonstrate that most of the selected EDs not only inhibit AR transcriptional activity, but also alter its subcellular dynamics. Conversely, some of these anti-androgenic compounds were potent activator of xeno-sensing nuclear receptor, PXR. Interestingly, agonist-activated AR that associates with the mitotic chromatin fails to achieve this association when bound to anti-androgenic EDs. Conclusively, most EDs (except BCH) behaved like pure antagonist for AR while as agonist for PXR. Subsequent experiments with DDT treatment in mice model indicated that in testis AR and its regulated genes PEM and ODC levels are down-regulated, whereas in liver of same mice PEM is up-regulated while AR and ODC remain unchanged. On the contrary, PXR and its regulated genes CYP3A11 and MDR1 levels in mice liver were up-regulated while in testis PXR remained unchanged, CYP3A11 up-regulated and MDR1 were down-regulated. Based on a novel "Biopit" concept it is speculated that long-term exposure to endocrine disrupting chemicals may influence the epigenetic profile of target cells via transcription factors thereby making them vulnerable to onset of chemically induced endocrine-related malignancies or metabolic disorders.

Androgen-regulated expression of arginase 1, arginase 2 and interleukin-8 in human prostate cancer

Background

Prostate cancer (PCa) is the most frequently diagnosed cancer in North American men. Androgen-deprivation therapy (ADT) accentuates the infiltration of immune cells within the prostate. However, the immunosuppressive pathways regulated by androgens in PCa are not well characterized. Arginase 2 (ARG2) expression by PCa cells leads to a reduced activation of tumor-specific T cells. Our hypothesis was that androgens could regulate the expression of ARG2 by PCa cells.

Methodology/Principal Findings

In this report, we demonstrate that both ARG1 and ARG2 are expressed by hormone-sensitive (HS) and hormone-refractory (HR) PCa cell lines, with the LNCaP cells having the highest arginase activity. In prostate tissue samples, ARG2 was more expressed in normal and non-malignant prostatic tissues compared to tumor tissues. Following androgen stimulation of LNCaP cells with 10 nM R1881, both ARG1 and ARG2 were overexpressed. The regulation of arginase expression following androgen stimulation was dependent on the androgen receptor (AR), as a siRNA treatment targeting the AR inhibited both ARG1 and ARG2 overexpression. This observation was correlated in vivo in patients by immunohistochemistry. Patients treated by ADT prior to surgery had lower ARG2 expression in both non-malignant and malignant tissues. Furthermore, ARG1 and ARG2 were enzymatically active and their decreased expression by siRNA resulted in reduced overall arginase activity and l-arginine metabolism. The decreased ARG1 and ARG2 expression also translated with diminished LNCaP cells cell growth and increased PBMC activation following exposure to LNCaP cells conditioned media. Finally, we found that interleukin-8 (IL-8) was also upregulated following androgen stimulation and that it directly increased the expression of ARG1 and ARG2 in the absence of androgens.

Conclusion/Significance

Our data provides the first detailed in vitro and in vivo account of an androgen-regulated immunosuppressive pathway in human PCa through the expression of ARG1, ARG2 and IL-8.

Disruption of arginase II alters prostate tumor formation in TRAMP mice

BACKGROUND

Arginase II (AII) is involved in the polyamine synthetic pathway, and elevated levels of expression have been found in a high proportion of prostate cancer samples and patients. However, the biological function of arginase II in prostate cancer still remains to be elucidated. In this study, we utilized the TRAMP mouse prostate cancer model to better understand the contribution of AII on tumor development.

METHODS

AII expression was determined in prostates from TRAMP mice at 23 weeks of age by real-time RT-PCR and Western blot analysis. Additionally, AII expression was disrupted in the TRAMP model by crossbreeding arginase II knockout (AII KO) mice with TRAMP mice in order to generate the TRAMP/AII KO line. In each group, genito-urinary (GU) tract weights were determined and a pathological evaluation of the tumors was completed.

RESULTS

AII expression was only detectable in those mice without the presence of macroscopic tumors; it was also absent in the TRAMP-C2 cell line, which is characteristic of an advanced prostate tumor. Assessment of the GU weights revealed larger average GU weights in the TRAMP/AII KO mice compared to TRAMP mice. Additionally, a greater percentage of more advanced pathology was found in the TRAMP/AII KO group compared to the TRAMP cohort.

CONCLUSIONS

Based on these results, AII deficiency in the TRAMP model seems to accelerate prostate tumor progression, leading to an overall more advanced cancer stage in these mice. These findings support the possibility that prostatic arginase II could be a potentially useful marker of disease progression.

Overexpression of ornithine aminotransferase: consequences on amino acid homeostasis

Ornithine aminotransferase (OAT) is a reversible enzyme expressed mainly in the liver, kidney and intestine. OAT controls the interconversion of ornithine into glutamate semi-aldehyde, and is therefore involved in the metabolism of arginine and glutamine which play a major role in N homeostasis. We hypothesised that OAT could be a limiting step in glutamine–arginine interconversion. To study the contribution of the OAT enzyme in amino acid metabolism, transgenic mice that specifically overexpress human OAT in the liver, kidneys and intestine were generated. The transgene expression was analysed byin situhybridisation and real-time PCR. Tissue (liver, jejunum and kidney) OAT activity, and plasma and tissue (liver and jejunum) amino acid concentrations were measured. Transgenic male mice exhibited higher OAT activity in the liver (25 (sem4)v.11 (sem1) nmol/min per μg protein for wild-type (WT) mice;P < 0·05) but there were no differences in kinetic parameters (i.e.Kmand maximum rate of reaction (Vmax)) between WT and transgenic animals. OAT overexpression decreased plasma and liver ornithine concentrations but did not affect glutamine or arginine homeostasis. There was an inverse relationship between ornithine levels and OAT activity. We conclude that OAT overexpression has only limited metabolic effects, probably due to the reversible nature of the enzyme. Moreover, these metabolic modifications had no effect on phenotype.

Transplant recipient renal function is donor renal mass- and recipient gender-dependent

The effect of both donor renal mass and gender on renal function, in both gender recipients, was examined. Qualifying consecutive living-donor renal transplants (n = 730) were stratified into 4 donor-recipient groups: female-female (n = 177), male-female (n = 151), female-male (n = 240), male-male (n = 162). Groups were equivalent in age, race, body mass index (BMI), match, ischemia time, operative time, and estimated glomerular filtration rate (eGFR). Female recipients had lower serum creatinine (Cr(s)). Male recipients had higher Cr(s) wherever they received a female allograft. Male recipients of male kidneys had a higher eGFR than all other groups for 3 years. Renal function of the recipient correlated with the renal mass of the donor within each group. Male and female kidneys functioned equivalently in the female-recipient environment. Large nephron-mass male donor kidneys function more poorly in female recipients. The male kidney loses 15-20 ml/min eGFR in the female host. The diminished graft function may be related to androgen deprivation. Female and male donor kidneys function equivalently in the male recipient if adjusted for renal mass transplanted. Female kidneys improve eGFR by 7-10 ml/min by being transplanted into a male environment. Donor renal mass and gender affect recipient graft function Expectations of ultimate recipient renal function should take into account both the gender and mass disparity of the donor-recipient pair.

Nuclear and membrane receptor-mediated signalling pathways modulate polyamine biosynthesis and interconversion

Polyamines play an important role in cell growth and differentiation, while their overproduction has potentially oncogenic consequences. Polyamine homoeostasis, a critical determinant of cell fate, is precisely tuned at the level of biosynthesis, degradation and transport. The enzymes ODC (ornithine decarboxylase), AdoMetDC (S-adenosylmethionine decarboxylase) and SSAT (spermidine/spermine N(1)-acetyltransferase) are critical for polyamine pool maintenance. Our experiments were designed to examine the expression of these enzymes in testosterone-induced hypertrophic and antifolate-induced hyperplastic mouse kidney, characterized by activation of AR (androgen receptor) and HGF (hepatocyte growth factor) membrane receptor c-Met respectively. The expression of these key enzymes was up-regulated by antifolate CB 3717 injury-evoked activation of HGF/c-Met signalling. In contrast, activation of the testosterone/AR pathway remarkably induced a selective increase in ODC expression without affecting other enzymes. Studies in catecholamine-depleted kidneys point to a synergistic interaction between the signalling pathways activated via cell membrane catecholamine receptors and AR, as well as c-Met. We found that this cross-talk modulated the expression of ODC and AdoMetDC, enzymes limiting polyamine biosynthesis, but not SSAT. This is in contrast with the antagonistic cross-talk between AR- and c-Met-mediated signalling which negatively regulated the expression of ODC, but affected neither AdoMetDC nor SSAT.

Gender differences in kidney function

Sex hormones influence the development of female (F) and male (M) specific traits and primarily affect the structure and function of gender-specific organs. Recent studies also indicated their important roles in regulating structure and/or function of nearly every tissue and organ in the mammalian body, including the kidneys, causing gender differences in a variety of characteristics. Clinical observations in humans and studies in experimental animals in vivo and in models in vitro have shown that renal structure and functions under various physiological, pharmacological, and toxicological conditions are different in M and F, and that these differences may be related to the sex-hormone-regulated expression and action of transporters in the apical and basolateral membrane of nephron epithelial cells. In this review we have collected published data on gender differences in renal functions, transporters and other related parameters, and present our own microarray data on messenger RNA expression for various transporters in the kidney cortex of M and F rats. With these data we would like to emphasize the importance of sex hormones in regulation of a variety of renal transport functions and to initiate further studies of gender-related differences in kidney structure and functions, which would enable us to better understand occurrence and development of various renal diseases, pharmacotherapy, and drug-induced nephrotoxicity in humans and animals.

Sex-differential expression of ornithine aminotransferase in the mouse kidney

The mouse kidney expresses the gene of ornithine aminotransferase (Oat). Previous works suggest that Oat is differentially expressed in female and male mouse kidney (Alonso E, Rubio V. Biochem J 259: 131-138, 1989; Levillain O, Diaz JJ, Blanchard O, Dechaud H. Endocrinology 146: 950-959, 2005; Manteuffel-Cymborowska M, Chmurzynska W, Peska M, Grzelakowska-Sztabert B. Int J Biochem Cell Biol 27: 287-295, 1995; Natesan S, Reddy SR. Comp Biochem Physiol B Biochem Mol Biol 130: 585-595, 2001; Yu H, Yoo PK, Aguirre CC, Tsoa RW, Kern RM, Grody WW, Cederbaum SD, Iyer RK. J Histochem Cytochem 51: 1151-1160, 2003). This study was designed to provide a detailed description of the sexual dimorphism of Oat expression in the mouse kidney and to test the influence of sex hormones on its regulation. Experiments were performed on male and female Swiss OF1 mice during their postnatal development, at adulthood, and in orchidectomized and ovariectomized mice. Kidneys, dissected renal zones, and mitochondria were used to analyze OAT mRNA and protein levels and measure OAT activity. The results revealed that before puberty, Oat expression was similar between female and male kidneys whereas from puberty until adulthood Oat expression increased in the female kidney, becoming approximately 2.5-fold higher than in the male kidney. This sex-differential expression of Oat was associated with a sex-specific distribution of Oat along the corticopapillary axis and within the nephron. OAT was three- to fourfold more expressed in the female than the male cortex. In males, Oat was highly expressed in the medulla, mainly in the thick ascending limbs. Renal Oat distribution in orchidectomized mice resembled that in the females. Ovariectomy did not influence Oat expression. Sex differences are explained by the physiological increase in plasma testosterone in males. Expression of medium-chain acyl-CoA synthetase protein confirmed this finding. We report sexual dimorphism of Oat expression in the mouse kidney and show that Oat is naturally downregulated in the presence of testosterone.

Sexual dimorphism of ornithine decarboxylase in the mouse adrenal: influence of polyamine deprivation on catecholamine and corticoid levels

Adrenal sexual dimorphism is thought to be important in explaining sex-related differences regarding prevalent diseases and the responses to stress and drugs. We report here that in CD1 mice there is marked sexual dimorphism affecting not only gland size and corticoid hormone secretion but also adrenal ornithine decarboxylase (ODC), polyamine, and catecholamine levels in which testosterone appears to be a major determinant. Our results show that adrenal weight, ODC activity, and corticosterone and aldosterone secretion were higher in female than in male mice and that orchidectomy brought these male parameters closer to the values found in females. mRNA levels of steroidogenic proteins SF-1, Dax-1, steroid 21-hydroxylase, and aldosterone synthase appeared to be slightly higher in female than in male adrenals. Immunocytochemical analysis of adrenal ODC revealed that immunoreactivity was higher in females than in males and was located mainly in the cortical cells, and especially in zona glomerulosa, whereas no sex differences in ODC mRNA levels were observed. These results suggest that sex-associated differences in the expression of ODC in the mouse adrenal gland appear to be related mainly to posttranscriptional mechanisms. Combination treatment of mice with alpha-difluoromethylornithine (a suicide inhibitor of ODC) and a polyamine-deficient diet produced a marked decrease in adrenal polyamine and catecholamine levels and a significant reduction in plasma corticosterone and aldosterone concentrations that were not associated with a decrease in the mRNA levels of steroidogenic proteins. All of these data suggest a relevant role for testosterone, ODC, and polyamines in the mouse adrenal function.

Relaxin becomes upregulated during prostate cancer progression to androgen independence and is negatively regulated by androgens

BACKGROUND

Relaxin is a potent peptide hormone normally secreted by the prostate. This study characterized relaxin expression during prostate cancer progression to androgen independence (AI), and in response to androgens.

METHODS

The prostate cancer cell line, LNCaP, was assayed by microarrays and confirmatory Northern analysis to assess changes in relaxin levels due to androgen treatment and in LNCaP xenografts following castration. Relaxin protein levels were examined by immunohistochemistry (IHC) in tissue microarrays of human prostate cancer samples following androgen ablation.

RESULTS

Relaxin levels decreased in a time and concentration-dependent manner due to androgens in vitro, and increased in xenografts post-castration. Relaxin increased in radical prostatectomy specimens after 6 months of androgen ablation and in AI tumors, was highest in bone metastases.

CONCLUSIONS

Relaxin is negatively regulated by androgens in vitro and in vivo, which correlates to clinical prostate cancer specimens following androgen ablation. The role of relaxin in angiogenesis and tissue remodeling suggests it may contribute to prostate cancer progression.

Rat renal glucose transporter SGLT1 exhibits zonal distribution and androgen-dependent gender differences

SGLT1 (SLC5A1) mediates a part of glucose and galactose reabsorption in the mammalian proximal tubule (PT), but the detailed localization of the transporter along the tubule is still disputable. Here, we used several methods to localize rat SGLT1 (rSGLT1) in the kidneys of intact and variously treated male (M) and female (F) rats. In immunoblots of isolated cortical (C) and outer stripe (OS) brush-border membranes (BBM), a peptide-specific polyclonal antibody for rSGLT1 labeled a sharp inzone-, and gender-dependent ∼40-kDa protein and a broad ∼75-kDa band that exhibited strong zonal (OS > C) and gender differences (F > M). In tissue cryosections, the antibody strongly stained BBM of the S3 PT segments in the OS and medullary rays (F > M) and smooth muscles of the blood vessels and renal capsule (F ∼ M) and weakly stained the apical domain of other PT segments in the C (F ∼ M). The phlorizin-sensitive uptake of d-[3H]galactose in BBM vesicles, as well as the tissue abundance of rSGLT1-specific mRNA, matched the immunoblotting data related to the 75-kDa protein and the immunostaining in S3, proving zonal and gender differences in the functional transporter. Ovariectomy had no effect, castration upregulated, whereas treatment of castrated rats with testosterone, but not with estradiol or progesterone, downregulated the 75-kDa protein and the immunostaining in S3. We conclude that in the rat kidney, the expression of SGLT1 is represented by a 75-kDa protein localized largely in the PT S3 segments, where it exhibits gender differences (F > M) at both the protein and mRNA levels that are caused by androgen inhibition.

Gene Regulation in Spermatogenesis

Mammalian spermatogenesis is a complex hormone-dependent developmental program in which a myriad of events must take place to ensure that germ cells reach their proper stage of development at the proper time. Many of these events are controlled by cell type- and stage-specific transcription factors. The regulatory mechanisms involved provide an intriguing paradigm for the field of developmental biology and may lead to the development of new contraceptives an and innovative routs to treat male infertility. In this review, we address three aspects of the genetic regulatory mechanism that drive spermatogenesis. First, we detail what is known about how steroid hormones (both androgens and estrogens) and their cognate receptors initiate and maintain mammalian spermatogenesis. Steroids act through three mechanistic routes: (i) direct activation of genes through hormone-dependent promoter elements, (ii) secondary transcriptional responses through activation of hormone-dependent transcription factors, and (iii) rapid, transcription-independent (nonclassical) events induced by steroid hormones. Second, we provide a survey of transcription factors that function in mammalian spermatogenesis, including homeobox, zinc-finger, heat-shock, and cAMP-response family members. Our survey is not intended to cover all examples but to give a flavor for the gamut of biological roles conferred by transcription factors in the testis, particularly those defined in knockout mice. Third, we address how testis-specific transcription is achieved. In particular, we cover the evidence for and against the idea that some testis-specific genes are transcriptionally silent in somatic tissues as a result of DNA methylation.