In vivo 17β-estradiol treatment contributes to podocyte actin stabilization in female db/db mice

Catalase, a therapeutic target in the reversal of estrogen-mediated aging

Despite increasing interest in the reversal of age-related processes, there is a paucity of data regarding the effects of post-menopausal-associated estrogen loss on cellular function. We studied human adipose-derived mesenchymal stem cells (hASCs) isolated from women younger than 45 years old (pre-menopause, pre-hASC) or older than 55 years old (post-menopause, post-hASC). In this study, we provide proof of concept that the age-related ineffective functionality of ASCs can be reversed to improve their ability in promoting tissue repair. We found reduced estrogen receptor expression, decreased estrogen receptor activation, and reduced sensitivity to 17β-estradiol in post-hASCs. This correlated with decreased antioxidants (catalase and superoxide dismutase [SOD] expression) and increased oxidative stress compared with pre-hASCs. Increasing catalase expression in post-hASCs restored estrogen receptor (ER) expression and their functional capacity to promote tissue repair as shown in human skin ex vivo wound healing and in vivo mouse model of lung injury. Our results suggest that the consequences of 17β-estradiol decline on the function of hASCs may be reversible by changing the oxidative stress/antioxidant composition.

Sex Differences in Glomerular Protein Expression and Effects of Soy-Based Diet on Podocyte Signaling

Background:

Kidney disease is a major public health issue arising from loss of glomerular podocyte function, and there are considerable sex differences in its prognosis. Evidence suggests a renoprotective effect of estrogen and soy diet-derived phytoestrogens, although the molecular basis for this is poorly understood.

Objective:

Here, we aim to assess sex differences in expression of key proteins associated with podocyte survival and determine the effects of dietary soy on glomerular and podocyte signaling.

Methods:

Male and female FVB mice were fed control, low (1%), and high (20%) doses of isolated soy protein (ISP) in utero and until 100 days of age. Spot urine was collected to measure proteinuria and isolated glomeruli were used to quantify activated and total levels of nephrin, Akt, and ERK1/2. To investigate protective effects of specific soy phytoestrogens, cultured podocytes were treated with or without daidzein and subject to control or high glucose as a model of podocyte injury.

Results:

Nephrin and Akt were elevated at baseline in glomeruli from females compared to males. Both sexes that were fed 1% and 20% ISP displayed robust increases in total glomerular Akt compared to controls, and these effects were more prominent in females. A similar trend at both doses in both sexes was observed with activated Akt and total nephrin. Notably, males exclusively showed increased phosphorylation of nephrin and extracellular signal-regulated kinase (ERK) at the 1% ISP dose; however, no overt changes in urinary albumin excretion or podocin levels were observed, suggesting that the soy diets did not impair podocyte function. Finally, in cultured male and female podocytes, daidzein treatment suppressed high glucose-induced ERK activation.

Conclusions:

Together, our findings reveal a putative mechanism to explain the protective influence of sex on kidney disease progression, and they provide further evidence to support a beneficial role for dietary soy in preserving glomerular function.

Diabetic condition induces hypertrophy and vacuolization in glomerular parietal epithelial cells

Diabetic nephropathy (DN) is accompanied by characteristic changes in the glomerulus, but little is known about the effect of diabetes on parietal epithelial cells (PECs). In this study, a descriptive analysis of PECs was undertaken in diabetic db/db mice and in diabetic patients. PEC hypertrophy was significantly more prominent in diabetic mice than in nondiabetic mice, and this was evident even at the early stage. Additionally, the number of vacuoles in PECs was markedly increased in diabetic mice, suggesting the presence of cellular injury in PECs in DN. Although rare, binuclear cells were observed in mice with early diabetes. In cultured PECs, a high glucose condition, compared with normal glucose condition, induced cellular hypertrophy and apoptosis. Flow cytometry showed that some PECs in the G0 phase reentered the cell cycle but got arrested in the S phase. Finally, in human diabetic subjects, hypertrophy and vacuolization were observed in the PECs. Our data showed that PECs undergo substantial changes in DN and may participate in rearrangement for differentiation into podocytes.

Estrogen and estrogen receptors in kidney diseases

Acute kidney injury (AKI) and chronic kidney disease (CKD) are posing great threats to global health within this century. Studies have suggested that estrogen and estrogen receptors (ERs) play important roles in many physiological processes in the kidney. For instance, they are crucial in maintaining mitochondrial homeostasis and modulating endothelin-1 (ET-1) system in the kidney. Estrogen takes part in the kidney repair and regeneration via its receptors. Estrogen also participates in the regulation of phosphorus homeostasis via its receptors in the proximal tubule. The ERα polymorphisms have been associated with the susceptibilities and outcomes of several renal diseases. As a consequence, the altered or dysregulated estrogen/ERs signaling pathways may contribute to a variety of kidney diseases, including various causes-induced AKI, diabetic kidney disease (DKD), lupus nephritis (LN), IgA nephropathy (IgAN), CKD complications, etc. Experimental and clinical studies have shown that targeting estrogen/ERs signaling pathways might have protective effects against certain renal disorders. However, many unsolved problems still exist in knowledge regarding the roles of estrogen and ERs in distinct kidney diseases. Further research is needed to shed light on this area and to enable the discovery of pathway-specific therapies for kidney diseases.

Parp1 protects against Aag-dependent alkylation-induced nephrotoxicity in a sex-dependent manner

Nephrotoxicity is a common toxic side-effect of chemotherapeutic alkylating agents. Although the base excision repair (BER) pathway is essential in repairing DNA alkylation damage, under certain conditions the initiation of BER produces toxic repair intermediates that damage healthy tissues. We have shown that the alkyladenine DNA glycosylase, Aag (a.k.a. Mpg), an enzyme that initiates BER, mediates alkylation-induced whole-animal lethality and cytotoxicity in the pancreas, spleen, retina, and cerebellum, but not in the kidney. Cytotoxicity in both wild-type and Aag-transgenic mice (AagTg) was abrogated in the absence of Poly(ADP-ribose) polymerase-1 (Parp1). Here we report that Parp1-deficient mice expressing increased Aag (AagTg/Parp1^−/−) develop sex-dependent kidney failure upon exposure to the alkylating agent, methyl methanesulfonate (MMS), and suffer increased whole-animal lethality compared to AagTg and wild-type mice. Macroscopic, histological, electron microscopic and immunohistochemical analyses revealed morphological kidney damage including dilated tubules, proteinaceous casts, vacuolation, collapse of the glomerular tuft, and deterioration of podocyte structure. Moreover, mice exhibited clinical signs of kidney disease indicating functional damage, including elevated blood nitrogen urea and creatinine, hypoproteinemia and proteinuria. Pharmacological Parp inhibition in AagTg mice also resulted in sensitivity to MMS-induced nephrotoxicity. These findings provide in vivo evidence that Parp1 modulates Aag-dependent MMS-induced nephrotoxicity in a sex-dependent manner and highlight the critical roles that Aag-initiated BER and Parp1 may play in determining the side-effects of chemotherapeutic alkylating agents.

EFhd2/swiprosin-1 regulates LPS-induced macrophage recruitment via enhancing actin polymerization and cell migration

Macrophage motility is vital in innate immunity, which contributes strategically to the defensive inflammation process. During bacterial infection, lipopolysaccharide (LPS) potently activates the migration of macrophages via the NF-κB/iNOS/c-Src signaling pathway. However, the downstream region of c-Src that participates in macrophage migration is unclear. EFhd2, a novel actin bundling protein, was evaluated for its role in LPS-stimulated macrophage migration in this study. We found that LPS stimulated the up-regulation, tyrosine phosphorylation and membrane translocation of EFhd2 in macrophages. The absence of EFhd2 inhibited the recruitment of macrophages in the lungs of LPS-induced septic mice. LPS-induced macrophage migration was neutralized by the deletion of EFhd2. EFhd2-mediated up-regulation of NFPs (including Rac1/Cdc42, N-WASP/WAVE2 and Arp2/3 complex) induced by LPS could be used to explain the role of EFhd2 in promoting actin polymerization. Furthermore, the purified EFhd2 could directly promote actin polymerization in vitro. Dasatinib, a c-Src specific inhibitor, inhibited the up-regulation of EFhd2 stimulated by LPS. Therefore, our study demonstrated that EFhd2 might be involved in LPS-stimulated macrophage migration, which provides a potential target for LPS-activated c-Src during macrophage mobilization.

Gender Differences in the Acute Kidney Injury to Chronic Kidney Disease Transition

This study evaluated if there is a sexual dimorphism in the acute kidney injury (AKI) to chronic kidney disease (CKD) transition and the time-course of the potential mechanisms involved in the dimorphic response. Female and male rats were divided into sham-operated or underwent 45-min renal ischemia (F + IR, and M + IR). All groups were studied at 24-h and 1, 2, 3, or 4-months post-ischemia. Additionally, oophorectomized rats were divided into sham or IR groups. After 24-h, AKI extent was simllar in females and males, but female rats exhibited less oxidative stress and increased renal GSH content. After 4-months and despite similar AKI, the M + IR group developed CKD characterized by proteinuria, tubulointerstitial fibrosis, glomerular hypertrophy, increased oxidative stress and a reduction in HIF1α and VEGF from the 1^st-month and persisting throughout the time-course studied. Interestingly, the F + IR group did not develop CKD due to lesser oxidative stress and increased eNOS, TGFβ and HIF1α mRNA levels from the 1^st-month after IR. Whereas, oophorectomized rats did develop CKD. We found a sexual dimorphic response in the AKI to CKD transition. Early antioxidant defense and higher TGFβ, HIF1α and eNOS were among the renoprotective mechanisms that the F + IR group demonstrated.

Estrogen receptor subtype ratio change protects against podocyte damage

Women are relatively protected against the development and progression of glomerulosclerosis (GS) prior to menopause. However, the "female advantage" is lost in women who are either diabetic, post-menopausal or both. We showed that 17β-estradiol (E₂) was effective in prevention of diabetic GS development in part through the stabilization of podocyte cytoskeleton and a change in estrogen receptor (ER) subtype ratio. The objective of this study was to examine whether resveratrol (RSV), reported to have estrogen-like action and renoprotective activity against diabetic GS, would affect similar pathways. After in vitro treatment with RSV we found a change in the ERα and ERβ expression ratio in favor of ERβ, suppression of heat shock protein 25 (Hsp25) expression and increase in β1-integrin expression, important for maintaining podocyte cytoskeleton. We noted a reduction of insulin-like growth factor 1 receptor (IGFR1) expression, decrease in extracellular signal-regulated kinase (ERK) activation, decrease in reactive oxygen species (ROS), and decrease in cleaved-caspase 3 expression. We found an increase in [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) and an increase in matrix metalloproteinases (MMP-2 and MMP-9) activity. Using cre-loxP strategy we developed podocyte-specific ERα knockout mice to show the importance of ERβ. In isolated podocytes, we confirmed reduction of ERα expression in conjunction with a decrease in IGFR1 expression, ERK and increase of MMP-2 similar to that of our in vitro treatment with RSV. Taken together these data suggest an important role for ERβ and ER subtype ratio in podocyte stabilization. Therefore RSV or other regulators of ER pathways could offer protection against diabetic and age-related podocyte changes.

Hormone replacement therapy, renal function and heart ultrasonographic parameters in postmenopausal women: an observational study

BACKGROUND AND AIM

A certain degree of impaired kidney function is related to an increased cardiovascular risk. The cardiovascular protection exerted in the postmenopausal state by the hormone replacement therapy (HRT) is debated. No studies have so far explored the relationship between menopause, renal function and cardiovascular risk profile in healthy menopausal women in relation with HRT.

SUBJECTS AND METHODS

A total of 362 postmenopausal healthy women with normal albumin excretion rate were recruited and divided into two groups (HRT+ and HRT-) according to the presence or absence of HRT. All participants underwent a complete routine biochemical analyses and an echocardiogram.

RESULTS

Clinical characteristics of the two groups were similar, but HRT+ showed a significantly higher estimated glomerular filtration rate (GFR; by CKD-EPI formula). Regarding the heart ultrasonography, HRT+ had a significantly lower size of the aortic root and left atrium diameter (p = 0.038 and p = 0.012, respectively); no differences were found in the ejection fraction and Left Ventricular Mass Index (LVMI). In the whole study group, eGFR correlated inversely with LVMI and with the size of the aortic root (both p < 0.0001), being GFR the only determinant of the former by a stepwise regression. Dividing the study population according to an eGFR cut-off (> 80 and < 80 ml/min/1.73 m(2)); > 80 women, in comparison with < 80, showed a significantly lower LVMI and lower size of aortic bulb, further reduced in the HRT+.

CONCLUSION

In a cohort of healthy, drug-naïve, postmenopausal women, HRT seems to positively affect glomerular filtration and is associated with lower values of left ventricular mass and aortic root size, thus offering a further mechanism through female hormones exert cardioprotection.

A Podocyte-Based Automated Screening Assay Identifies Protective Small Molecules

Podocyte injury and loss mark an early step in the pathogenesis of various glomerular diseases, making these cells excellent targets for therapeutics. However, cell-based high-throughput screening assays for the rational development of podocyte-directed therapeutics are currently lacking. Here, we describe a novel high-content screening-based phenotypic assay that analyzes thousands of podocytes per assay condition in 96-well plates to quantitatively measure dose-dependent changes in multiple cellular features. Our assay consistently produced a Z' value >0.44, making it suitable for compound screening. On screening with >2100 pharmacologically active agents, we identified 24 small molecules that protected podocytes against injury in vitro (1% hit rate). Among the identified hits, we confirmed an β1-integrin agonist, pyrintegrin, as a podocyte-protective agent. Treatment with pyrintegrin prevented damage-induced decreases in F-actin stress fibers, focal adhesions, and active β1-integrin levels in cultured cells. In vivo, administration of pyrintegrin protected mice from LPS-induced podocyte foot process effacement and proteinuria. Analysis of the murine glomeruli showed that LPS administration reduced the levels of active β1 integrin in the podocytes, which was prevented by cotreatment with pyrintegrin. In rats, pyrintegrin reduced peak proteinuria caused by puromycin aminonucleoside-induced nephropathy. Our findings identify pyrintegrin as a potential therapeutic candidate and show the use of podocyte-based screening assays for identifying novel therapeutics for proteinuric kidney diseases.

Endogenous female sex hormones delay the development of renal dysfunction in apolipoprotein E-deficient mice

Background

Hypercholesterolemia is a well-established risk factor for the development of kidney injury. Considering that female sex hormones may play a preventative role in both cardiovascular and renal diseases, the aim of the present study was to evaluate the effects of female sex hormones on hypercholesterolemia-induced renal dysfunction.

Methods

Apolipoprotein E-deficient (ApoE) and C57 control female mice underwent an ovariectomy (OVX) or sham surgery and after 2 months, creatinine clearance, uremia and proteinuria were determined. Renal oxidative stress and lipid deposition were also quantified. Values are presented as mean ± SEM. Statistical analyses were performed using Two-way ANOVA followed by Tukey’s post hoc test.

Results

Creatinine clearance (μL/min) was similar between C57 (171 ± 17) and ApoE (140 ± 26) mice underwent sham surgery. OVX resulted in a reduced glomerular filtration rate in both C57 (112 ± 8, ~ − 35%, p < 0.05) and ApoE (61 ± 10, ~ − 56%, p < 0.05) animals. Plasma levels of urea (mg/dL) were higher in both ApoE groups (Sham: 73 ± 7; OVX: 73 ± 8, p < 0.05) when compared to C57 animals (Sham: 49 ± 3; OVX: 60 ± 4), with no changes among ovariectomized groups. Proteinuria levels (mg/24 h) were similar between C57 (Sham: 25.1 ± 5.7; OVX: 33.7 ± 4.7) and ApoE sham animals (26.4 ± 3.5), however, 24-h urine protein excretion was augmented in ApoE OVX animals (49.6 ± 5.8, p < 0.05). Histological kidney analysis demonstrated that the absence of female sex hormones resulted in increased oxidative stress, which was more severe in ApoE mice (C57 Sham: 9.2 ± 0.4; C57 OVX: 22.9 ± 1.0; ApoE Sham: 13.9 ± 0.7; ApoE OVX: 34.0 ± 1.4 au x 10³, p < 0.05). As expected, ApoE mice presented higher lipid deposition, which was not affected by OVX (C57 Sham: 0 ± 0; C57 OVX: 0 ± 0; ApoE Sham: 6.8 ± 1.6; ApoE OVX: 5.2 ± 0.8% x 10⁻², p < 0.05). Ovariectomy resulted in a similar reduction in ER-α protein expression in the renal cortex (C57: 0.78 ± 0.04; ApoE: 0.81 ± 0.04 au, p < 0.05) when compared to sham animals (C57:1.00 ± 0.04; ApoE: 1.03 ± 0.03 au).

Conclusion

Taken together these data indicate that female sex hormones may delay hypercholesterolemia-induced renal dysfunction and emphasizes the importance of plasma cholesterol control in post-menopausal women.

Podocytes, signaling pathways, and vascular factors in diabetic kidney disease

Alterations and injury to glomerular podocytes play a key role in the initiation and progression of diabetic kidney disease (DKD). Multiple factors in diabetes cause abnormalities in podocyte signaling that lead to podocyte foot process effacement, hypertrophy, detachment, loss, and death. Alterations in insulin action and mammalian target of rapamycin activation have been well documented to lead to pathology. Reduced insulin action directly leads to albuminuria, increased glomerular matrix accumulation, thickening of the glomerular basement membrane, podocyte apoptosis, and glomerulosclerosis. In addition, podocytes generate factors that alter signaling in other glomerular cells. Prominent among these is vascular endothelial growth factor-A, which maintains glomerular endothelium viability but causes endothelial cell pathology when generated at too high a level. Finally, circulating vascular factors (eg, activated protein C) have a profound effect on podocyte stability and survival. This cytoprotective factor is critical for podocyte health, and its deficiency promotes podocyte injury and apoptosis. Thus, the podocyte sits in the center of a network of paracrine and hormonal signaling systems that in health keep the podocyte adaptable and viable, but in diabetes they can lead to pathologic changes, detachment, and death.