Estrogen preserves split renal function in a chronic complete unilateral ureteral obstruction animal model

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.

Estrogen receptor alpha expression in renal tissue and its relationship with prognosis in immunoglobulin A nephropathy

OBJECTIVE

Epidemiologic studies have shown that, compared to men, women have better prognoses in chronic renal diseases. This indicates that gender hormones may have some effect on renal function. The present study aimed to investigate the expression and relationship with prognosis of estrogen receptor alpha (ERα) in renal tissue of immunoglobulin A nephropathy (IgAN) patients.

METHODS

Expression of ERα was detected by immunohistochemistry. Specimens were collected from forty-five IgAN patients and five normal healthy participants. In addition to expression, the relationship of ERα with clinical data, prognosis, and the degree of glomerular damage were analyzed.

RESULTS

ERα was expressed in the glomeruli and renal tubules. The expression of ERα in the glomeruli of IgAN renal tissue decreased gradually (P = 0.001, P < 0.05) with the increasing severity of disease and its expression was associated with estimated glomerular filtration rate (eGFR), serum creatinine (Scr) and pathological grade (r = 0.876, -0.818 and -0.736, P < 0.05). In addition, the expression of ERα was significantly decreased in hypertensive IgAN patients compared with the non-hypertensive group (P = 0.011). We found that ERα was of great significance for the prognosis of IgAN (P = 0.01, P < 0.05).

CONCLUSIONS

The expression of ERα in the renal tissue of IgAN patients was reduced and there was a correlation with the degree of kidney damage and prognosis, suggesting that ERα may play a role in the progression of IgAN.

Estrogen regulates aquaporin-2 expression in the kidney

Estrogens are primarily identified as sex hormones that, for a long time, have been known as important regulators of female reproductive physiology. However, our understanding of the role of estrogens has changed over the past years. It is now well accepted that estrogens are also involved in other physiological and pathological processes in both genders. This is due to the fact that estrogen can act both local as well as on a systemic level. Next to its role in reproductive physiology, there is accumulating evidence that estrogen influences multiple systems involved in water homeostasis. This chapter will delineate the regulatory effects of estrogen on the water channel aquaporin-2 (AQP2) found in the renal collecting duct. We will first provide an introduction to estrogen, the estrogen receptors and their role in renal physiology as well as describe the effect of selective estrogen receptor modulators (SERMs) on the kidney. Subsequently, we will focus on how estrogen and SERMs influence water balance and regulate AQP2 expression in principal cells of the collecting duct. Finally, we will describe how estrogen regulates AQP2 functionality in other organ systems.

Cellular senescence in the aging and diseased kidney

The program of cellular senescence is involved in both the G1 and G2 phase of the cell cycle, limiting G1/S and G2/M progression respectively, and resulting in prolonged cell cycle arrest. Cellular senescence is involved in normal wound healing. However, multiple organs display increased senescent cell numbers both during natural aging and after injury, suggesting that senescent cells can have beneficial as well as detrimental effects in organismal aging and disease. Also in the kidney, senescent cells accumulate in various compartments with advancing age and renal disease. In experimental studies, forced apoptosis induction through the clearance of senescent cells leads to better preservation of kidney function during aging. Recent groundbreaking studies demonstrate that senescent cell depletion through INK-ATTAC transgene-mediated or cell-penetrating FOXO4-DRI peptide induced forced apoptosis, reduced age-associated damage and dysfunction in multiple organs, in particular the kidney, and increased performance and lifespan. Senescence is also involved in oncology and therapeutic depletion of senescent cells by senolytic drugs has been studied in experimental and human cancers. Although studies with senolytic drugs in models of kidney injury are lacking, their dose limiting side effects on other organs suggest that targeted delivery might be needed for successful application of senolytic drugs for treatment of kidney disease. In this review, we discuss (i) current understanding of the mechanisms and associated pathways of senescence, (ii) evidence of senescence occurrence and causality with organ injury, and (iii) therapeutic strategies for senescence depletion (senotherapy) including targeting, all in the context of renal aging and disease.

The effect and safety of postmenopausal hormone therapy and selective estrogen receptor modulators on kidney outcomes in women: a protocol for systematic review and meta-analysis

BACKGROUND

The prevalence of menopause in women with or at risk of chronic kidney disease is increasing globally. Although international guidelines on menopause recommend the use of postmenopausal hormone therapy with or without selective estrogen receptor modulators for control of vasomotor symptoms, the effects of these treatments on kidney function and albuminuria are unclear. Furthermore, women with chronic kidney disease are at significantly increased risk of venous thromboembolism and malignancy, well-documented adverse effects of postmenopausal hormone therapy. Our study aims to establish the effect of these treatments on kidney function and albuminuria in women, as well as determine the safety of these treatments in the chronic kidney disease population.

METHODS

We will conduct a systematic review and meta-analysis addressing the effect and safety of postmenopausal hormone therapy and selective estrogen receptor modulators on kidney outcomes in women. We plan to search for published (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), tables of contents of relevant journals) and unpublished (ongoing studies, conference proceedings) studies in all languages examining the effect of postmenopausal hormone therapy, including selective estrogen receptor modulators, on kidney function and albuminuria, as well as the risk of adverse outcomes of these treatments in women with chronic kidney disease. Two independent investigators will screen identified abstracts and select studies that examine the effect of postmenopausal hormone therapy and selective estrogen receptor modulators on kidney outcomes in the general population or adverse outcomes in the chronic kidney disease population. Data on study population, intervention, outcomes, as well as study quality and risk of bias will be independently extracted from each eligible study. Along with descriptive presentation of data, outcome measures will be presented as meta-analyses using a random effects model. Planned subgroup analyses will be completed, and meta-regression will be performed if significant heterogeneity is noted.

DISCUSSION

By examining the effects of postmenopausal hormone therapy and selective estrogen receptor modulators on kidney function and albuminuria, the results of this systematic review and meta-analysis will inform management of postmenopausal women in the general population. Furthermore, it will evaluate the safety, including the risks of known adverse outcomes of postmenopausal hormone therapy and selective estrogen receptor modulators, in the already vulnerable chronic kidney disease population.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016050651.

Tamoxifen for induction of Cre-recombination may confound fibrosis studies in female mice

A variety of conditional knock-out mice relying on Tamoxifen-driven ERT2/Cre -mediated recombination are available and have been used to study involvement of specific genes in kidney disease. However, recent data suggest that Tamoxifen itself might attenuate fibrosis when administered during experimental models of kidney disease. It has remained unclear whether this still applies also if kidney damage is initiated after a wash-out period has been implemented. Here we report that the commonly applied regimen of administration of 4 alternate day doses of 1mg Tamoxifen per mouse until 14 days prior to start of the actual experiment, in this case the induction of obstructive nephropathy by Unilateral Ureteral Obstruction (UUO), still attenuated fibrosis in female obstructed mouse kidneys, whereas this effect was not seen in male obstructed kidneys. Attenuation of fibrosis was accompanied by a reduction in nuclear ERα positivity despite absence of detectable levels of the active tamoxifen metabolite endoxifen throughout the UUO experiment. In conclusion, these results indicate that the Tamoxifen dosing regimen commonly applied in conditional gene targeting experiments might have prolonged confounding effects in female mice through attenuation of renal fibrosis independent of modulation of the expression of the targeted gene(s).

Imaging technologies for monitoring the safety, efficacy and mechanisms of action of cell-based regenerative medicine therapies in models of kidney disease

The incidence of end stage kidney disease is rising annually and it is now a global public health problem. Current treatment options are dialysis or renal transplantation, which apart from their significant drawbacks in terms of increased morbidity and mortality, are placing an increasing economic burden on society. Cell-based Regenerative Medicine Therapies (RMTs) have shown great promise in rodent models of kidney disease, but clinical translation is hampered due to the lack of adequate safety and efficacy data. Furthermore, the mechanisms whereby the cell-based RMTs ameliorate injury are ill-defined. For instance, it is not always clear if the cells directly replace damaged renal tissue, or whether paracrine effects are more important. Knowledge of the mechanisms responsible for the beneficial effects of cell therapies is crucial because it could lead to the development of safer and more effective RMTs in the future. To address these questions, novel in vivo imaging strategies are needed to monitor the biodistribution of cell-based RMTs and evaluate their beneficial effects on host tissues and organs, as well as any potential adverse effects. In this review we will discuss how state-of-the-art imaging modalities, including bioluminescence, magnetic resonance, nuclear imaging, ultrasound and an emerging imaging technology called multispectral optoacoustic tomography, can be used in combination with various imaging probes to track the fate and biodistribution of cell-based RMTs in rodent models of kidney disease, and evaluate their effect on renal function.

Differences in Factors Associated with Albuminuria according to Gender and Comorbidities of Hypertension and Diabetes

Background

This study examined the differences in factors associated with albuminuria according to gender and comorbidities of hypertension (HTN) and diabetes mellitus (DM).

Methods

We included 3,859 participants aged 20 to 79 years (55% female) from the 5th Korea National Health and Nutrition Examination Survey. Participants were excluded if they took antihypertensive or anti-diabetic medication, had chronic renal failure, had malignant tumor, were pregnant or menstruating during the health examination, or had missing urine albumin data. Albuminuria was defined by the participant's urine albumin-creatinine ratio (uACR). Relationships between dependent and independent variables were analyzed using the Pearson's correlation test and simple linear regression. Due to possible muticollinearity, multiple linear regression analysis was used to determine whether the association between the dependent and independent variables of interest remained significant after adjustment for other potentially confounding independent variables.

Results

The variables significantly correlated with uACR were different between the genders and between subjects with HTN or DM as a comorbidity. In the multiple linear regression models, hemoglobin A1c (P=0.01) was positively associated with uACR in men without HTN and DM. In men with HTN or DM, systolic blood pressure and fasting glucose (P<0.01) were positively associated with uACR. In women with HTN or DM, waist circumference (P=0.011) and gamma-glutamyl transpeptidase (P<0.001) were positively correlated with uACR (P<0.05) and glucose level (P=0.019) was negatively correlated with uACR.

Conclusion

The study suggested factors correlated with albuminuria were different for men and women according to comorbidities such as HTN and DM.