Flávia Fernandes Mesquita

Involvement of Renal Corpuscle microRNA Expression on Epithelial-to-Mesenchymal Transition in Maternal Low Protein Diet in Adult Programmed Rats

Prior study shows that maternal protein-restricted (LP) 16-wk-old offspring have pronounced reduction of nephron number and arterial hypertension associated with unchanged glomerular filtration rate, besides enhanced glomerular area, which may be related to glomerular hyperfiltration/overflow and which accounts for the glomerular filtration barrier breakdown and early glomerulosclerosis. In the current study, LP rats showed heavy proteinuria associated with podocyte simplification and foot process effacement. TGF-β1 glomerular expression was significantly enhanced in LP. Isolated LP glomeruli show a reduced level of miR-200a, miR-141, miR-429 and ZEB2 mRNA and upregulated collagen 1α1/2 mRNA expression. By western blot analyzes of whole kidney tissue, we found significant reduction of both podocin and nephrin and enhanced expression of mesenchymal protein markers such as desmin, collagen type I and fibronectin. From our present knowledge, these are the first data showing renal miRNA modulation in the protein restriction model of fetal programming. The fetal-programmed adult offspring showed pronounced structural glomerular disorders with an accentuated and advanced stage of fibrosis, which led us to state that the glomerular miR-200 family would be downregulated by TGF-β1 action inducing ZEB 2 expression that may subsequently cause glomeruli epithelial-to-mesenchymal transition.

Maternal undernutrition and the offspring kidney: from fetal to adult life

Maternal dietary protein restriction during pregnancy is associated with low fetal birth weight and leads to renal morphological and physiological changes. Different mechanisms can contribute to this phenotype: exposure to fetal glucocorticoid, alterations in the components of the renin-angiotensin system, apoptosis, and DNA methylation. A low-protein diet during gestation decreases the activity of placental 11ß-hydroxysteroid dehydrogenase, exposing the fetus to glucocorticoids and resetting the hypothalamic-pituitary-adrenal axis in the offspring. The abnormal function/expression of type 1 (AT1(R)) or type 2 (AT2(R)) AngII receptors during any period of life may be the consequence or cause of renal adaptation. AT1(R) is up-regulated, compared with control, on the first day after birth of offspring born to low-protein diet mothers, but this protein appears to be down-regulated by 12 days of age and thereafter. In these offspring, AT2(R) expression differs from control at 1 day of age, but is also down-regulated thereafter, with low nephron numbers at all ages: from the fetal period, at the end of nephron formation, and during adulthood. However, during adulthood, the glomerular filtration rate is not altered, due to glomerulus and podocyte hypertrophy. Kidney tubule transporters are regulated by physiological mechanisms; Na(+)/K(+)-ATPase is inhibited by AngII and, in this model, the down-regulated AngII receptors fail to inhibit Na(+)/K(+)-ATPase, leading to increased Na(+) reabsorption, contributing to the hypertensive status. We also considered the modulation of pro-apoptotic and anti-apoptotic factors during nephrogenesis, since organogenesis depends upon a tight balance between proliferation, differentiation and cell death.

Long-term exercise attenuates blood pressure responsiveness and modulates kidney angiotensin II signalling and urinary sodium excretion in SHR

Observations have been made regarding the effects of long-term exercise training on blood pressure, renal sodium handling and renal renin–angiotensin–aldosterone (RAS) intracellular pathways in conscious, trained Okamoto–Aoki spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKy) normotensive rats, compared with appropriate age-matched sedentary SHR and WKy. To evaluate the influence of exercise training on renal function and RAS, receptors and intracellular angiotensin II (AngII) pathway compounds were used respectively, and lithium clearance and western blot methods were utilised. The current study demonstrated that increased blood pressure in SHR was blunted and significantly reduced by long-term swim training between the ages of 6 and 16 weeks. Additionally, the investigators observed an increased fractional urinary sodium excretion in trained SHR (SHRT) rats, compared with sedentary SHR (SHRS), despite a significantly decreased creatinine clearance (CCr). Furthermore, immunoblotting analysis demonstrated a decreased expression of AT1R in the entire kidney of TSHR rats, compared with SSHR. Conversely, the expression of the AT2R, in both sedentary and trained SHR, was unchanged. The present study may indicate that, in the kidney, long-term exercise exerts a modulating effect on AngII receptor expression. In fact, the present study indicates an association of increasing natriuresis, reciprocal changes in renal AngII receptors and intracellular pathway proteins with the fall in blood pressure levels observed in TSHR rats compared with age-matched SSHR rats.

Fetal kidney programming by severe food restriction: Effects on structure, hormonal receptor expression and urinary sodium excretion in rats:

Introduction: The present study investigates, in 23-day-old and adult male rats, the effect of severe food restriction in utero on blood pressure (BP), and its association with nephron structure and function changes, angiotensin II (AT1R/AT2R), glucocorticoid (GR) and mineralocorticoid (MR) receptor expression. Materials and methods: The daily food supply to pregnant rats was measured and one group (n=15) received normal quantity of food (NF) while the other received 50% of that (FR50%) (n=15). Kidneys were processed to AT1R, AT2R, MR, and GR immunolocalization and for western blotting analysis. The renal function was estimated by creatinine and lithium clearances in 12-week-old offspring. Results: By stereological analyses, FR50% offspring present a reduction of nephron numbers (35%) with unchanged renal volume. Expression of AT1R and AT2R was significantly decreased in FR50% while the expression of GR and MR increased in FR50%. We also verified a pronounced decrease in urinary sodium excretion accompanied by increased BP in 12-week-old FR50% offspring. Conclusion: The current data suggest that changes in renal function are conducive to excess sodium tubule reabsorption, and this might potentiate the programming of adult hypertension. It is plausible to arise in the current study an association between decreasing natriuresis, reciprocal changes in renal AngII and steroid receptors with the hypertension development found in FR50% compared with age-matched NF offspring.

Fetal Kidney Programming by Maternal Smoking Exposure: Effects on Kidney Structure, Blood Pressure and Urinary Sodium Excretion in Adult Offspring

Introduction: Fetal programming by different insults results in low birth weight and reduction in nephron number increasing the risk for adult development of cardiovascular and renal diseases. Maternal smoking is an important modifiable adverse fetal exposure worldwide and leads to a decrease in the offsprings birth weight. Thus far, the specific adverse fetal smoking exposures and mechanisms underlying these associations on renal development and functional disorder are unclear. Methods: The present study investigates, in adult male rats, the effect of smoking exposure (Sk) in uteri on blood pressure (BP) by an indirect tail-cuff method using an electrosphygmomanometer, and its association with nephron structure by stereological estimation, immunohistochemical and histological techniques, in parallel with kidney function creatinine and lithium clearance. Results: The current study showed in a 16-week old Sk offspring enhanced arterial blood pressure associated with, reduced urinary sodium excretion and higher TGF-β1 glomerular expression. Sk glomeruli also presented an upregulated collagen and fibronectin deposition intrinsically related to fibrotic process as compared to age-matched control group. Conclusion: Here, we demonstrate that fetal-programmed Sk offspring present pronounced glomerular TGF-β1 and fibrotic marker expression that may, subsequently, promote a glomerular epithelial-mesenchymal transition activated process in an Sk offspring. Although the precise mechanism responsible for the subsequently renal morphological and functional response in Sk offspring is incompletely known, the current data suggest that changes in renal function are conducive to excess sodium tubule reabsorption that is associated with enhanced TGF-β1, fibronectin and collagen deposition, intrinsically related to fibrotic process, might potentiate the programming of adult hypertension.

Early changes of hypothalamic angiotensin II receptors expression in gestational protein-restricted offspring: effect on water intake, blood pressure and renal sodium handling

The current study examines changes in the postnatal hypothalamic angiotensin receptors by maternal protein restriction (LP), and its impact on in uteri programming of hypertension in adult life. The data show that LP male pup body weight was significantly reduced when compared to that of control (NP) pups. Also, immunoblotting analysis demonstrated a significantly decreased expression of type 1 AngII receptors (AT1R) in the entire hypothalamic tissue extract of LP rats at 12 days of age compared to age-matched NP offspring. Conversely, the expression of the type 2 AngII (AT2R) receptors in 12-day- and 16-week-old LP hypothalamus was significantly increased. The current data show the influence of central AngII administration on water consumption in a concentration-dependent fashion, but also demonstrate that the water intake response to AngII was strikingly attenuated in 16-week-old LP. These results may be related to decreased brain arginine vasopressin (AVP) expression appearing in maternal protein-restricted offspring. The present investigation shows an early decrease in fractional urinary sodium excretion in maternal protein-restricted offspring. The decreased fractional sodium excretion was accompanied by a fall in proximal sodium excretion and occurred despite unchanged creatinine clearance. These effects were associated with a significant enhancement in arterial blood pressure in the LP group, but the precise mechanism of these phenomena remains unknown.

Impact of taurine supplementation on blood pressure in gestational protein-restricted offspring: Effect on the medial solitary tract nucleus cell numbers, angiotensin receptors, and renal sodium handling

Objective: The current study considers changes of the postnatal brainstem cell number and angiotensin receptors by maternal protein restriction (LP) and LP taurine supplementation (LPT), and its impact on arterial hypertension development in adult life. Methods and results: The brain tissue studies were performed by immunoblotting, immunohistochemistry, and isotropic fractionator analysis. The current study shows that elevated blood pressure associated with decreased fractional urinary sodium excretion (FENa) in adult LP offspring was reverted by diet taurine supplementation. Also, that 12-day-old LP pups present a reduction of 21% of brainstem neuron counts, and, immunohistochemistry demonstrates a decreased expression of type 1 angiotensin II receptors (AT1R) in the entire medial solitary tract nuclei (nTS) of 16-week-old LP rats compared to age-matched NP and LPT offspring. Conversely, the immunostained type 2 AngII (AT2R) receptors in 16-week-old LP nTS were unchanged. Conclusion: The present investigation shows a decreased FENa that occurs despite unchanged creatinine clearance. It is plausible to hypothesize an association of decreased postnatal nTS cell number, AT1R/AT2R ratio and FENa with the higher blood pressure levels found in taurine-deficient progeny (LP) compared with age-matched NP and LPT offspring.

Early potential impairment of renal sensory nerves in streptozotocin-induced diabetic rats: role of neurokinin receptors

BACKGROUND Electrophysiological studies in the mammalian kidney have identified two major classes of sensory receptors of the afferent renal nerves; chemoreceptors (CR) and mechanoreceptors (MR). The localization of calcitonin gene-related peptide (CGRP) and substance P (SP) in these renal pelvic sensory neurons provides an anatomical basis for a possible functional interaction between the two neuropeptides and SP receptor. The present study was performed to examine the possible changes in the responsiveness of renal sensory SP and CGRP receptors in rats with streptozotocin (STZ)-induced diabetes mellitus. Due to the crucial role of renal pelvic SP and CGRP receptors in the activation of renal sensory neurons by various stimuli, we examined whether the responsiveness of MR or CR activation and the dorsal root ganglia content of neuropeptides and neurokinin 1 receptors (NK(1)R) were altered in diabetic rats compared with non-diabetic rats. METHODS Afferent renal nerve activity (ARNA) was recorded from the peripheral portion of the cut end of one renal nerve branch placed on a bipolar silver wire electrode. T(13) dorsal root ganglia (DRG) immunoreactivity was performed to NK(1)R, SP and CGRP. RESULTS The results of the current study confirmed that the stimulation of renal MR and CR elicited a renorenal reflex response, and that the renal pelvic administration of SP and CGRP increased ipsilateral ARNA and contralateral urinary sodium excretion with no changes in arterial pressure. We also found a decrease in NK(1)R expression followed by an increase in SP and CGRP levels in the DRG of diabetic rats. The ARNA response, produced by renal pelvic MR and CR stimulation, was found to be significantly attenuated in the STZ-induced diabetic model. Conclusions. These data may indicate a compensatory synthesis and/or abnormal axonal delivery of neurokinins from the cell body to synaptic portions of the neuron as the underlying reason for attenuated ARNA in renal sensory neurons of diabetic rats.