Abstract P184: Exploring Sex Differences in Immune Cell Profiles of Male, Premenopausal Female, and Postmenopausal Female Mice to Understand Susceptibility to Immune Mediated Hypertension

T cells are required for the development of hypertension in male and postmenopausal female mice while premenopausal females are protected from T cell mediated hypertension. To better understand sex differences in immune-cell mediated hypertensive responses, we sought to determine if there were any significant differences in the immune cell profiles of premenopausal female (F), VCD-treated postmenopausal female (PMF), and male (M) mice. Spleens were collected from all mice and processed for flow cytometric analysis of T cell populations (n=8/group). Analysis of splenic T cell populations revealed no significant difference in the frequency of CD3+ or CD4+ T cells between groups (CD3+: F 33.4%, PMF 30.3%, M 30.2% of total lymphocytes, CD4+: F 64.8%, PMF 70.7%, M 67.5% of CD3+ cells). However, postmenopausal females had a significantly lower frequency of splenic CD8+ T cells compared to both males and premenopausal females (CD8+: F 27.9%, PMF 19.5%*, M 25.3% of CD3+ cells *p<0.05 vs M and F). Additionally, premenopausal females displayed significantly increased expression of the memory marker CD44 and the anti-inflammatory marker CTLA-4 on CD4+ cells compared to both males and postmenopausal females (MFI CD44: F 334.8*, PMF 269.4, M 280.4, MFI CTLA-4: F 100.7*, PMF 80.9, M 86.8 *p<0.01 vs M and PMF). Additional flow cytometric staining was performed to evaluate sex differences in splenic Antigen Presenting Cell (APC) populations (n=8/group). The frequency of CD11b+ APCs, thought to primarily represent macrophage populations, were significantly reduced in postmenopausal females compared to premenopausal females but there was no significant difference from males (CD11b +: F 14.6%, PMF 11.8%*, M 12.9% of monocytes *p<0.05 vs F). Additionally, CD11c+ dendritic cell populations were found to be significantly reduced in postmenopausal females compared to both males and premenopausal females (CD11c+: F 4.1%, PMF 2.8%*, M 3.9% of all monocytes *p<0.01 vs M and F). Taken together, these results indicate a significant difference in the baseline immune environment between male, premenopausal female and postmenopausal females which likely contribute to sex-differences in susceptibility to immune-mediated hypertension.

Abstract P148: Transcriptomic and Proteomic Analysis of CD4 + T Cells to Identify Sex Differences in Angiotensin II Signaling Pathways

T cells are involved in hypertension pathogenesis in both males and postmenopausal females while premenopausal females are resistant to T cell-mediated Ang II-induced hypertension. The goals of this study were (1) to identify T cell specific proteomic pathways associated with postmenopausal susceptibility to hypertension (2) to identify T cell specific transcriptomic changes associated with premenopausal protection from hypertension. Proteomic analysis was performed on splenic CD4 + T cells isolated from premenopausal and postmenopausal females (VCD, 160 mg/kg/day i.p. 20d) following Ang II infusion (800 ng/kg/min 14d). 384 proteins from CD4 + T cells were identified as differentially expressed following Ang II infusion in premenopausal females. 285 proteins from CD4 + T cells were identified as differentially expressed between premenopausal and postmenopausal females following Ang II infusion. Gene ontology (GO) analysis of pre vs. postmenopausal proteins identified enriched pathways associated with RNA binding, chaperone activity and cellular stress responses. Transcriptomic changes were analyzed, via RNAseq, on isolated splenic CD4 + T cells from premenopausal females, with and without Ang II infusion. Thirty-four genes were identified as differentially expressed in CD4 + T cells following Ang II infusion. GO analysis of Ang II upregulated genes revealed an enrichment of five distinct molecular functions, including antioxidant activity. In a subsequent study to validate the RNAseq, we confirmed that Ang II increased CD4 + T cell mRNA expression of calprotectin (S100a8/S100a9), a calcium and zinc binding protein complex that contributes to antioxidant defense (S100a8: Con 1.0 ± 0.4 vs Ang II 5.0 ± 0.8*; S100a9: Con 1.0 ± 0.4 vs Ang II 6.0 ± 0.8*, *P<0.05 vs Con). Furthermore, we determined that Ang II did not increase calprotectin expression in mice lacking estrogen receptor α (ERKO) (S100a8: ERKO 0.1 ± 0.4 vs ERKO/Ang II 0.3 ± 0.7; S100a9: ERKO 0.2 ± 0.5 vs ERKO/Ang II 0.3 ± 0.6). The current studies demonstrate a role for estrogen in Ang II-induced T cell gene expression and signal transduction, and begin to elucidate the molecular mechanisms of female protection from T cell-mediated hypertension.

Menopause and FOXP3+ Treg cell depletion eliminate female protection against T cell-mediated angiotensin II hypertension

Although it is known that the prevalence and severity of hypertension increases in women after menopause, the contribution of T cells to this process has not been explored. Although the immune system is both necessary and required for the development of angiotensin II (ANG II) hypertension in men, we have demonstrated that premenopausal women are protected from T cell-mediated hypertension. The goal of the current study was to test the hypotheses that 1) female protection against T cell-mediated ANG II hypertension is eliminated following progression into menopause and 2) T regulatory cells (Tregs) provide premenopausal protection against ANG II-induced hypertension. Menopause was induced in Rag-1^-/- mice (via 4-vinylcyclohexene diepoxide), and all mice received a 14-day ANG II infusion. Donor CD3⁺ T cells were adoptively transferred 3 wk before ANG II infusion. In the absence of T cells, systolic blood pressure responses to ANG II were similar to those seen in premenopausal mice (Δ12 mmHg). After adoptive transfer of T cells, ANG II significantly increased systolic blood pressure in postmenopausal females (Δ28 mmHg). A significant increase in F4/80 positive renal macrophages, an increase in renal inflammatory gene expression, along with a reduction in renal expression of mannose receptor C-type 1, a marker for M2 macrophages, accompanied the increase in systolic blood pressure (SBP). Flow cytometric analysis identified that Tregs were significantly decreased in the spleen and kidneys of Rag-1^-/- menopausal mice versus premenopausal females, following ANG II infusion. In a validation study, an anti-CD25 antibody was used to deplete Tregs in premenopausal mice, which induced a significant increase in SBP. These results demonstrate that premenopausal protection against T cell-mediated ANG II hypertension is eliminated once females enter menopause, suggesting that a change in hormonal status upregulates macrophage-induced proinflammatory and T cell-dependent responses. Furthermore, we are the first to report that the presence of Tregs are required to suppress ANG II hypertension in premenopausal females.NEW & NOTEWORTHY Whether progression into menopause eliminated female protection against T cell-mediated hypertension was examined. Menopausal mice without T cells remained protected against angiotensin II (ANG II) hypertension; however, in the presence of T cells, blood pressure responses to ANG II increased significantly in menopause. Underlying mechanisms examined were anti-inflammatory protection provided by T regulatory cells in premenopausal females and renal inflammatory processes involving macrophage infiltration and cytokine activation.

Renoprotective impact of estrogen receptor-α and its splice variants in female mice with type 1 diabetes

Estrogen has been implicated in the regulation of growth and immune function in the kidney, which expresses the full-length estrogen receptor-α (ERα66), its ERα splice variants, and estrogen receptor-β (ERβ). Thus, we hypothesized that these splice variants may inhibit the glomerular enlargement that occurs early in type 1 diabetes (T1D). T1D was induced by streptozotocin (STZ) injection in 8- to 12-wk-old female mice lacking ERα66 (ERα66KO) or all ERα variants (αERKO), and their wild-type (WT) littermates. Basal renal ERα36 protein expression was reduced in the ERα66KO model and was downregulated by T1D in WT mice. T1D did not alter ERα46 or ERβ in WT-STZ; however, ERα46 was decreased modestly in ERα66KO mice. Renal hypertrophy was evident in all diabetic mice. F4/80-positive immunostaining was reduced in ERα66KO compared with WT and αERKO mice but was higher in STZ than in Control mice across all genotypes. Glomerular area was greater in WT and αERKO than in ERα66KO mice, with T1D-induced glomerular enlargement apparent in WT-STZ and αERKO-STZ, but not in ERα66KO-STZ mice. Proteinuria and hyperfiltration were evident in ERα66KO-STZ and αERKO-STZ, but not in WT-STZ mice. These data indicate that ERα splice variants may exert an inhibitory influence on glomerular enlargement and macrophage infiltration during T1D; however, effects of splice variants are masked in the presence of the full-length ERα66, suggesting that ERα66 acts in opposition to its splice variants to influence these parameters. In contrast, hyperfiltration and proteinuria in T1D are attenuated via an ERα66-dependent mechanism that is unaffected by splice variant status.

Early Retinal Neuronal Dysfunction in Diabetic Mice: Reduced Light-Evoked Inhibition Increases Rod Pathway Signaling

Purpose

Recent studies suggest that the neural retinal response to light is compromised in diabetes. Electroretinogram studies suggest that the dim light retinal rod pathway is especially susceptible to diabetic damage. The purpose of this study was to determine whether diabetes alters rod pathway signaling.

Methods

Diabetes was induced in C57BL/6J mice by three intraperitoneal injections of streptozotocin (STZ; 75 mg/kg), and confirmed by blood glucose levels > 200 mg/dL. Six weeks after the first injection, whole-cell voltage clamp recordings of spontaneous and light-evoked inhibitory postsynaptic currents from rod bipolar cells were made in dark-adapted retinal slices. Light-evoked excitatory currents from rod bipolar and AII amacrine cells, and spontaneous excitatory currents from AII amacrine cells were also measured. Receptor inputs were pharmacologically isolated. Immunohistochemistry was performed on whole mounted retinas.

Results

Rod bipolar cells had reduced light-evoked inhibitory input from amacrine cells but no change in excitatory input from rod photoreceptors. Reduced light-evoked inhibition, mediated by both GABA_A and GABA_C receptors, increased rod bipolar cell output onto AII amacrine cells. Spontaneous release of GABA onto rod bipolar cells was increased, which may limit GABA availability for light-evoked release. These physiological changes occurred in the absence of retinal cell loss or changes in GABA_A receptor expression levels.

Conclusions

Our results indicate that early diabetes causes deficits in the rod pathway leading to decreased light-evoked rod bipolar cell inhibition and increased rod pathway output that provide a basis for the development of early diabetic visual deficits.

ANG II-induced hypertension in the VCD mouse model of menopause is prevented by estrogen replacement during perimenopause

Premenopausal females are resistant to the development of hypertension, and this protection is lost after the onset of menopause, resulting in a sharp increase in disease onset and severity. However, it is unknown how a fluctuating ovarian hormone environment during the transition from perimenopause to menopause impacts the onset of hypertension, and whether interventions during perimenopause prevent disease onset after menopause. A gradual transition to menopause was induced by repeated daily injections of 4-vinylcyclohexene diepoxide (VCD). ANG II (800 ng·kg(-1)·min(-1)) was infused into perimenopausal and menopausal female mice for 14 days. A separate cohort of mice received 17β-estradiol replacement during perimenopause. ANG II infusion produced significantly higher mean arterial pressure (MAP) in menopausal vs. cycling females, and 17β-estradiol replacement prevented this increase. In contrast, MAP was not significantly different when ANG II was infused into perimenopausal and cycling females, suggesting that female resistance to ANG II-induced hypertension is intact during perimenopause. ANG II infusion caused a significant glomerular hypertrophy, and hypertrophy was not impacted by hormonal status. Expression levels of aquaporin-2 (AQP2), a collecting duct protein, have been suggested to reflect blood pressure. AQP2 protein expression was significantly downregulated in the renal cortex of the ANG II-infused menopause group, where blood pressure was increased. AQP2 expression levels were restored to control levels with 17β-estradiol replacement. This study indicates that the changing hormonal environment in the VCD model of menopause impacts the severity of ANG II-induced hypertension. These data highlight the utility of the ovary-intact VCD model of menopause as a clinically relevant model to investigate the physiological mechanisms of hypertension that occur in women during the transition into menopause.

Abstract P618: Foxp3+ Regulatory T cell Depletion Eliminates Ang II-Induced Hypertension Resistance in Female Mice

Compared to males, premenopausal females are resistant to the development of Ang II hypertension. In males, Ang II induces hypertension, in part, through mechanisms requiring T effector lymphocytes. Recently, our lab has demonstrated that females can prevent the T lymphocyte-dependent increase in blood pressure (SBP and MAP) and expression of pro-inflammatory cytokines in the kidney in response to Ang II infusion. Because Foxp3 + T regulatory cells suppress the pro-inflammatory and hypertensive actions of T effector cells, we sought to determine whether Foxp3 + T regulatory cells contribute to this resistance in females. Premenopausal (8 week old) 129SVE female mice were infused with Ang II (800ng/kg/min, 14d) and received 4 doses of the anti-CD25 antibody PC-61 to transiently deplete Foxp3 + T regulatory cells (every 84 hours beginning 12 hours prior to Ang II infusion, 250μg/dose, i.p., vehicle control). Blood pressure was measured before and after Ang II infusion via non-invasive tail cuff. Ang II induced a significant increase in systolic blood pressure in Foxp3 + -depleted mice, while resistance was retained in vehicle-treated mice (Con Δ5 ± 5mmHg, Ang II Δ10 ± 7mmHg, PC-61 Δ28 ± 9 * mmHg, * p<0.05 vs Con). Flow cytometric analysis demonstrated that PC-61-treatment significantly reduced the number of Foxp3 + splenic T cells compared to control (Con 1.7x10 6 cells, Ang II 2.3x10 6 cells, PC-61 8.3x10 5* cells, * P<0.05 vs Con) without changing CD3 + and CD4 + T cell counts. The number of Foxp3 + T cells residing in the kidney was also significantly reduced by PC-61 (Con 1,152 ± 368 cells, Ang II 686 ± 389 cells, PC-61 210 ± 35 * cells, * P<0.05 vs Con). Quantitative real-time PCR demonstrated that whole kidney expression of MCP-1 and ENaC alpha were significantly increased in Foxp3 + -depleted mice (MCP-1- Con 1.0 ± 0.1, Ang II 1.6 ± 0.4, PC-61 1.8 ± 0.2 * ; ENaC-α- Con 1.0 ± 0.1, Ang II 1.6 ± 0.2, PC-61 2.1 ± 0.1 * , * P<0.05 vs Con). These data suggest that the anti-inflammatory Foxp3 + T regulatory cells play a significant role in mediating the resistance to Ang II hypertension in premenopausal female mice, and may influence renal inflammation and sodium retention during chronic Ang II infusion.

Rapamycin inhibition of mTORC1 reverses lithium-induced proliferation of renal collecting duct cells

Nephrogenic diabetes insipidus (NDI) is the most common renal side effect in patients undergoing lithium therapy for bipolar affective disorders. Approximately 2 million US patients take lithium of whom ∼50% will have altered renal function and develop NDI (2, 37). Lithium-induced NDI is a defect in the urinary concentrating mechanism. Lithium therapy also leads to proliferation and abundant renal cysts (microcysts), commonly in the collecting ducts of the cortico-medullary region. The mTOR pathway integrates nutrient and mitogen signals to control cell proliferation and cell growth (size) via the mTOR Complex 1 (mTORC1). To address our hypothesis that mTOR activation may be responsible for lithium-induced proliferation of collecting ducts, we fed mice lithium chronically and assessed mTORC1 signaling in the renal medulla. We demonstrate that mTOR signaling is activated in the renal collecting ducts of lithium-treated mice; lithium increased the phosphorylation of rS6 (Ser240/Ser244), p-TSC2 (Thr1462), and p-mTOR (Ser2448). Consistent with our hypothesis, treatment with rapamycin, an allosteric inhibitor of mTOR, reversed lithium-induced proliferation of medullary collecting duct cells and reduced levels of p-rS6 and p-mTOR. Medullary levels of p-GSK3β were increased in the renal medullas of lithium-treated mice and remained elevated following rapamycin treatment. However, mTOR inhibition did not improve lithium-induced NDI and did not restore the expression of collecting duct proteins aquaporin-2 or UT-A1.

Midkine, a heparin-binding protein, is increased in the diabetic mouse kidney postmenopause

Estrogen is thought to protect against the development of chronic kidney disease, and menopause increases the development and severity of diabetic kidney disease. In this study, we used streptozotocin (STZ) to induce diabetes in the 4-vinylcyclohexene diepoxide (VCD)-treated mouse model of menopause. DNA microarrays were used to identify gene expression changes in the diabetic kidney postmenopause. An ANOVA model, CARMA, was used to isolate the menopause effect between two groups of diabetic mice, diabetic menopausal (STZ/VCD) and diabetic cycling (STZ). In this diabetic study, 8,864 genes of the possible 15,600 genes on the array were included in the ANOVA; 99 genes were identified as demonstrating a >1.5-fold up- or downregulation between the STZ/VCD and STZ groups. We randomly selected genes for confirmation by real-time PCR; midkine (Mdk), immediate early response gene 3 (IEX-1), mitogen-inducible gene 6 (Mig6), and ubiquitin-specific protease 2 (USP2) were significantly increased in the kidneys of STZ/VCD compared with STZ mice. Western blot analysis confirmed that Mdk and IEX-1 protein abundance was significantly increased in the kidney cortex of STZ/VCD compared with STZ mice. In a separate study, DNA microarrays and CARMA analysis were used to identify the effect of menopause on the nondiabetic kidney; VCD-treated mice were compared with cycling mice. Of the possible 15,600 genes on the array, 9,142 genes were included in the ANOVA; 20 genes were identified as demonstrating a >1.5-fold up- or downregulation; histidine decarboxylase and vanin 1 were among the genes identified as differentially expressed in the postmenopausal nondiabetic kidney. These data expand our understanding of how hormone status correlates with the development of diabetic kidney disease and identify several target genes for further studies.

Loss of ovarian function in the VCD mouse-model of menopause leads to insulin resistance and a rapid progression into the metabolic syndrome

Factors comprising the metabolic syndrome occur with increased incidence in postmenopausal women. To investigate the effects of ovarian failure on the progression of the metabolic syndrome, female B(6)C(3)F(1) mice were treated with 4-vinylcyclohexene diepoxide (VCD) and fed a high-fat (HF) diet for 16 wk. VCD destroys preantral follicles, causing early ovarian failure and is a well-characterized model for the gradual onset of menopause. After 12 wk on a HF diet, VCD-treated mice had developed an impaired glucose tolerance, whereas cycling controls were unaffected [12 wk AUC HF mice 13,455 +/- 643 vs. HF/VCD 17,378 +/- 1140 mg/dl/min, P < 0.05]. After 16 wk on a HF diet, VCD-treated mice had significantly higher fasting insulin levels (HF 5.4 +/- 1.3 vs. HF/VCD 10.1 +/- 1.4 ng/ml, P < 0.05) and were significantly more insulin resistant (HOMA-IR) than cycling controls on a HF diet (HF 56.2 +/- 16.7 vs. HF/VCD 113.1 +/- 19.6 mg/dl x microU/ml, P < 0.05). All mice on a HF diet gained more weight than mice on a standard diet, and weight gain in HF/VCD mice was significantly increased compared with HF cycling controls. Interestingly, even without a HF diet, progression into VCD-induced menopause caused a significant increase in cholesterol and free fatty acids. Furthermore, in mice fed a standard diet (6% fat), insulin resistance developed 4 mo after VCD-induced ovarian failure. Insulin resistance following ovarian failure (menopause) was prevented by estrogen replacement. Studies here demonstrate that ovarian failure (menopause) accelerates progression into the metabolic syndrome and that estrogen replacement prevents the onset of insulin resistance in VCD-treated mice. Thus, the VCD model of menopause provides a physiologically relevant means of studying how sex hormones influence the progression of the metabolic syndrome.

Embryo transfer rederivation of C.B-17/Icr-Prkdc(scid) mice experimentally infected with mouse parvovirus 1

We determined whether embryos derived from C.B-17/Icr-Prkdc(scid) (SCID) mice infected with mouse parvovirus (MPV) 1b and mated to MPV-naive B6C3F1 mice would transmit virus to naive recipient female mice and rederived progeny. Viral DNA was detected by quantitative PCR (qPCR) in lymphoid tissues, gonad, sperm, and feces of all MPV1b-inoculated SCID mice. Viral DNA was detected in 1 of 16 aliquots of embryos from infected male SCID mice and in 12 of 18 aliquots of embryos from infected female SCID mice. All recipient female mice implanted with embryos from infected SCID male mice and their progeny were negative by serology and qPCR. In contrast, 3 of 5 recipient female mice implanted with embryos from infected SCID female mice and 14 of 15 progeny mice from these recipients were seropositive by multiplex fluorescent immunoassay (MFI) for MPV capsid antigen (rVP2). All of these mice were negative by MFI for parvovirus nonstructural protein antigen (rNS1) and by qPCR, with the exception of 1 recipient female mouse that displayed weak rNS1 seroreactivity and low levels of MPV DNA in lymphoid tissues. Seroreactivity to rVP2 declined over time in all progeny mice from infected SCID female mice until all were seronegative by 20 wk of age, consistent with maternal antibody transfer. Given that the high levels of MPV contamination detected in our experimentally infected SCID mice are unlikely in naturally infected immunocompetent mice, these data indicate that embryo transfer rederivation is effective for the eradication of MPV from infected colonies.

Hormonal status affects the progression of STZ-induced diabetes and diabetic renal damage in the VCD mouse model of menopause

Changes in the estrogen/testosterone balance at menopause may negatively influence the development of diabetic kidney disease. Furthermore, recent studies suggest that changes in hormone levels during perimenopause may influence disease development. Injection of 4-vinylcyclohexene diepoxide (VCD) in B(6)C(3)F(1) mice induces gradual ovarian failure, preserving both the perimenopausal (peri-ovarian failure) and menopausal (post-ovarian failure) periods. To address the impact of the transition into menopause on the development of diabetes and diabetic kidney damage, we used streptozotocin (STZ)-induced diabetes in the VCD model of menopause. After 6 wk of STZ-induced diabetes, blood glucose was significantly increased in post-ovarian failure (post-OF) diabetic mice compared with cycling diabetic mice. In peri-ovarian failure (peri-OF) diabetic mice, blood glucose levels trended higher but were not significantly different from cycling diabetic mice, suggesting a continuum of worsening blood glucose across the menopausal transition. Cell proliferation, an early marker of damage in the kidney, was increased in post-OF diabetic mice compared with cycling diabetic mice, as measured by PCNA immunohistochemistry. In post-OF diabetic mice, mRNA abundance of early growth response-1 (Egr-1), collagen-4alpha1, and matrix metalloproteinase-9 were increased and 3beta-hydroxysteroid dehydrogenase 4 (3beta-HSD4) and transforming growth factor-beta(2) (TGF-beta(2)) were decreased compared with cycling diabetic mice. In peri-OF diabetic mice, mRNA abundance of Egr-1 and 3beta-HSD4 were increased, and TGF-beta(2) was decreased compared with cycling diabetic mice. This study highlights the importance and utility of the VCD model of menopause, as it provides a physiologically relevant system for determining the impact of the menopausal transition on diabetes and diabetic kidney damage.