Upregulation and intrarenal redistribution of heat shock proteins 90alpha and 90beta by low-sodium diet in the rat

The Link Between Heat Shock Proteins, Renin-Angiotensin System, and the Coagulation Cascade in the Pathogenesis of the Coronavirus-19 Disease

INTRODUCTION

Understanding the pathogenesis of COVID-19 is integral for its successful treatment.

METHODS

Available literature on the relationship between COVID-19, heat shock proteins (HSP), and the renin-angiotensin-aldosterone (RAAS) system were searched and used to hypothesize how HSP can be targeted in COVID-19.

RESULTS

During SARS-CoV-2 cellular entry, the ACE-2 receptor is downregulated. This leads to the augmentation of angiotensin-2/AT1 receptor axis along with attenuation of the ACE-2/angiotensin_1-7/Mas axis. Heat shock proteins are key stabilizing molecules in various pathways.In the heart and vessels, HSP-90 and HSP-60 can facilitate angiotensin-2-mediated myocardial injury and endothelial cell activation. HSP-60-TLR4/CD14 complex formation stabilizes IκB-kinase (IKK) potentiating NF-κB activation. HSPs in lungs and kidneys have antioxidant, vasodilatory, and anti-inflammatory actions and may be protective against the effects of RAAS. Stress-induced HSP-70 has a role in complement-mediated microvascular injury such as has been demonstrated in COVID-19. SARS-CoV-2 can induce autophagy via Beclin-1 and ER (endoplasmic reticular) stress via BIP. These two can be potential targets in the HSP environment.

CONCLUSION

Various HSP molecules can modulate the effects of the renin-angiotensin-aldosterone (RAAS) system and thus may have a potential role in the pathogenesis of COVID-19.

Proteome changes in renal cortex and medulla induced by dietary supplementation with inulin-type fructans in growing pigs

The aim of the study was to evaluate the influence of dietary supplementation with inulin extract from chicory root and dried chicory root on the protein profile of the renal cortex and medulla of growing pigs. The experiment was carried out on renal cortex and medulla tissue collected from 24 50-day-old PIC x Penarlan P76 crossbred piglets (males). Animals were divided into three dietary groups (n = 8) and fed with a control diet, diet supplemented with 2% inulin extract from chicory root and a diet supplemented with 4% dried chicory root. Kidney samples were collected after 40 days of feeding, and renal cortex and medulla proteins were separated by two-dimensional electrophoresis. Protein identification was performed using MALDI-TOF mass spectrometry. The diet supplemented with 2% chicory inulin induced significant expression changes of 20 and 26 protein spots in the renal cortex and medulla respectively. Supplementation with 4% dried chicory root triggered changes in the expression of 44 and 24 proteins in the renal cortex and medulla respectively. Both forms of chicory inulin-type fructans effectively affected the expression of proteins involved in energy metabolism, heat shock proteins and other chaperones, cytoskeletal and cytoskeleton-related proteins, as well as other proteins. Additionally, changes in transferrin abundance in both experimental groups suggested the significance of chicory fructan supplementation for iron absorption and bioavailability. In conclusion, 2% inulin extract from chicory root and 4% dried chicory root exerted a similar effect on changes in renal protein expression; however, more pronounced alterations were induced by dried chicory root. Nevertheless, further studies are needed for better understanding the mechanism underlying the effect of chicory inulin-type fructans and their fermentation end products on the kidneys of growing pigs.

Geraniin is a diuretic by inhibiting the Na+-K+-2Cl- cotransporter NKCC2

Geranium seemannii Peyr is a perennial plant endemic to central Mexico that has been widely used for its diuretic effect, but the responsible compound of this effect is unknown as well as the mechanism by which the diuretic effect is achieved. Geraniin is one of the compounds isolated from this kind of geranium. This study was designed to determinate whether geraniin possesses diuretic activity and to elucidate the mechanism of action. Geraniin was extracted and purified from Geranium seemannii Peyr. Male Wistar rats were divided into four groups: 1) Control, 2) 75 mg/kg of geraniin, 3) 20 mg/kg of furosemide, and 4) 10 mg/kg of hydrochlorothiazide. Each treatment was administered by gavage every 24 h for 7 days. The urinary excretion of electrolytes and the fractional excretion of sodium (FENa) were determined. To uncover the molecular target of geraniin, Xenopus laevis oocytes were microinjected with cRNAs encoding the Na⁺-Cl^- cotransporter (NCC) and the Na⁺-K⁺-2Cl^- cotransporter NKCC2 to functionally express these cotransporters. Geraniin significantly increased diuresis, natriuresis, and calciuresis to a similar extent as was observed in the furosemide-treated rats. Consistent with the furosemide-like effect, in X. laevis oocytes, geraniin significantly reduced the activity of NKCC2, with no effect on NCC activity. In contrast to furosemide, the effect of geraniin on NKCC2 was irreversible, apparently due to its inhibitory effect on heat shock protein 90. Our observations suggest that geraniin could have a potential role in the treatment of hypertension or edematous states.

Interleukin-6, Interleukin-10 and Heat Shock Protein-90 Expression in Renal Epithelial Neoplasias and Surrounding Normal-Appearing Renal Parenchyma

Cytokines, notably the interleukins IL-6 and IL-10, have an important role in the development and progression of renal-cell carcinomas, acting in the host-tumor interaction and in tumor bulk. Heat shock proteins (HSP), in particular HSP-90, may have a regulatory role in cytokine biosynthesis and prognostic implication in some tumors. To define the roles of the cytokines IL-6 and IL-10 and HSP-90 in the progression of renal-cell carcinoma we analyzed immunohistochemical expression of these proteins in human renal-cell carcinomas from 95 total nephrectomies. IL-6, IL-10 and HSP-90 proteins were more strongly expressed in epithelium and stroma of the renal tumoral compartment than in adjacent normal peritumoral tissue. But the difference reached significance only for HSP-90 protein. The percentage of cells expressing IL-6, IL-10 and HSP-90 immunoreactivity was higher in benign epithelial tumors, than in normal peritumoral tissue, but lower than in renal-cell carcinomas. Whereas HSP-90 immunoreactivity seemed higher in more aggressive histological phenotypes (collecting-duct carcinoma) of renal-cell carcinomas, IL-10 protein levels were higher in more advanced TNM stage (pT3) tumors. Our observation suggests that IL-6 and IL-10 and HSP-90 may be useful markers associated with the development and progression of renal-cell carcinomas and have independent functional roles in this malignant condition.

Intra-renal transfection of heat shock protein 90 alpha or beta (Hsp90α or Hsp90β) protects against ischemia/reperfusion injury

BACKGROUND

We previously reported that radicicol (Hsp90 inhibitor) induced a reduction in the renal blood flow and glomerular filtration rate, in part due to a reduction in urinary NO2/NO3 excretion, suggesting that Hsp90 regulates renal vascular tone in physiological conditions. However, there is a lack of information concerning Hsp90α or Hsp90β role on eNOS activity and their association with acute kidney injury (AKI) characterized by an inadequate NO production. This study evaluated the effects of Hsp90α or Hsp90β intra-renal transfection under ischemia/reperfusion (IR) injury.

METHODS

Uninephrectomized (Nx) rats were intra-renally transfected through injections with Hsp90α or Hsp90β cloned into pcDNA3.1(+) or empty vector (EV) at 48 h before inducing IR, as indicated in the following groups: (i) Nx+sham, (ii) Nx+IR, (iii) Nx+IR+EV, (iv) Nx+IR+Hsp90α and (v) Nx+IR+Hsp90β. After 24 h, physiological, histopathological, biochemical and molecular studies were performed.

RESULTS

IR-induced renal dysfunction, structural injury, tubular proliferation, the elevation of urinary Hsp72 and the reduction of urinary NO2/NO3 excretion. These alterations were associated with reduced eNOS-Hsp90 coupling and changes in the eNOS phosphorylation state mediated through a reduction in PKCα and increased Rho kinase expression. In contrast, intra-renal transfection of Hsp90α or Hsp90β prevented IR injury that was associated with the restoration of eNOS-Hsp90 coupling, eNOS activating phosphorylation and PKCα and Rho kinase levels.

CONCLUSIONS

Here we showed that eNOS-Hsp90 uncoupling plays a critical role in promoting NO reduction during IR. This effect was effectively reversed through Hsp90α or Hsp90β intra-renal transfection, suggesting their implication in regulating NO/eNOS pathway and the renal vascular tone.

Rapid nongenomic action of aldosterone on protein expressions of Hsp90( α and β ) and pc-Src in rat kidney

Previous in vitro studies indicated that aldosterone nongenomically phosphorylates epidermal growth factor receptor (EGFR) through activation of upstream signals, heat shock protein 90 β (Hsp90 β ), and cytosolic (c)-Src kinase. We demonstrated that aldosterone rapidly elevates EGFR phosphorylation in rat kidney. There are no in vivo data regarding renal Hsp90( α and β ) and phosphorylated (p)c-Src protein expressions. The present study further investigates the expressions of these proteins. Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (Aldo: 150 μ g/kg BW). After 30 minutes, abundances and localizations of these proteins were determined. Aldosterone enhanced renal Hsp90 β protein abundance (P < 0.001), but Hsp90 α and pc-Src protein levels remained unaltered. Expression of Hsp90( α and β ) was induced prominently in the proximal convoluted tubules (PCTs). Activation of Hsp90 α was observed in vascular and outer medulla regions, whereas Hsp90 β was induced in the cortex. Immunoreactivity of pc-Src was elevated in PCT with obvious staining at the luminal membrane. This in vivo study is the first to demonstrate that aldosterone nongenomically elevates Hsp90( α and β ) protein expressions in rat kidney. Aldosterone had no effect on pc-Src protein levels but modulated localization. These results indicate that aldosterone regulates upstream mediators of EGFR transactivation in vivo.

Gene expression analysis reveals the cell cycle and kinetochore genes participating in ischemia reperfusion injury and early development in kidney

Background

The molecular mechanisms that mediate the ischemia-reperfusion (I/R) injury in kidney are not completely understood. It is also largely unknown whether such mechanisms overlap with those governing the early development of kidney.

Methodology/Principal Findings

We performed gene expression analysis to investigate the transcriptome changes during regeneration after I/R injury in the rat (0 hr, 6 hr, 24 hr, and 120 hr after reperfusion) and early development of mouse kidney (embryonic day 16 p.c. and postnatal 1 and 7 day). Pathway analysis revealed a wide spectrum of molecular functions that may participate in the regeneration and developmental processes of kidney as well as the functional association between them. While the genes associated with cell cycle, immunity, inflammation, and apoptosis were globally activated during the regeneration after I/R injury, the genes encoding various transporters and metabolic enzymes were down-regulated. We also observed that these injury-associated molecular functions largely overlap with those of early kidney development. In particular, the up-regulation of kinases and kinesins with roles in cell division was common during regeneration and early developmental kidney as validated by real-time PCR and immunohistochemistry.

Conclusions

In addition to the candidate genes whose up-regulation constitutes an overlapping expression signature between kidney regeneration and development, this study lays a foundation for studying the functional relationship between two biological processes.

Natural annual cycle of heat shock protein expression in land snails: desert versus Mediterranean species of Sphincterochila

Land snails are subject to daily and seasonal variations in temperature and in water availability, and have evolved annual cycles of activity and aestivation as part of their survival strategy. We tested in the field whether adaptation to different habitats affects the endogenous levels of heat shock proteins (HSPs) in two closely related Sphincterochila snail species, a desiccation-resistant desert species, Sphincterochila zonata, and a Mediterranean-type, desiccation-sensitive species, S. cariosa. We examined HSP levels in various tissues of snails during aestivation and after resumption of activity. Our study shows that, during aestivation, S. cariosa had higher standing stocks of Hsp70 in the foot and the hepatopancreas, and of small HSPs (sHSPs) in all the examined tissues, whereas S. zonata had higher stocks of Hsp70 in the kidney and of Hsp90 in the kidney and in the hepatopancreas. Arousal induced a general upregulation of HSPs, except for Hsp90, the expression of which in the foot was higher during aestivation. We suggest that the stress protein machinery is upregulated during arousal in anticipation of possible oxidative stress ensuing from the accelerating metabolic rate and the exit from the deep hypometabolic state. Our findings support the concept that, in land snails, aestivation and activity represent two distinct physiological states, and suggest that land snails use HSPs as important components of the aestivation mechanism, and as part of their survival strategy during and after arousal. Our study also indicates that adaptation to different habitats results in the development of distinct strategies of HSP expression with likely consequences for the ecology and distribution of land snails.

Heat shock proteins and resistance to desiccation in congeneric land snails

Land snails are subject to daily and seasonal variations in temperature and in water availability and depend on a range of behavioral and physiological adaptations for coping with problems of maintaining water, ionic, and thermal balance. Heat shock proteins (HSPs) are a multigene family of proteins whose expression is induced by a variety of stress agents. We used experimental desiccation to test whether adaptation to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desiccation-resistant, desert species Sphincterochila zonata, and a Mediterranean-type, desiccation-sensitive species Sphincterochila cariosa. We examined the HSP response in the foot, hepatopancreas, and kidney tissues of snails exposed to normothermic desiccation. Our findings show variations in the HSP response in both timing and magnitude between the two species. The levels of endogenous Hsp72 in S. cariosa were higher in all the examined tissues, and the induction of Hsp72, Hsp74, and Hsp90 developed earlier than in S. zonata. In contrary, the induction of sHSPs (Hsp25 and Hsp30) was more pronounced in S. zonata compared to S. cariosa. Our results suggest that land snails use HSPs as part of their survival strategy during desiccation and as important components of the aestivation mechanism in the transition from activity to dormancy. Our study underscores the distinct strategy of HSP expression in response to desiccation, namely the delayed induction of Hsp70 and Hsp90 together with enhanced induction of sHSPs in the desert-dwelling species, and suggests that evolution in harsh environments will result in selection for reduced Hsp70 expression.

Radicicol, a heat shock protein 90 inhibitor, reduces glomerular filtration rate

The heat shock protein subfamily of 90 kDa (HSP90) is composed of five isoforms. The more abundant proteins of this subfamily are cytosolic isoforms known as HSP90α and HSP90β. More than 100 client proteins have been found to be regulated by HSP90. Several studies have shown that HSP90 regulates nitric oxide synthesis that is dependent on endothelial nitric oxide synthase (eNOS). Because eNOS regulates renal vascular tone and glomerular filtration rate (GFR), the present study was designed to evaluate the effect of acute HSP90 inhibition with radicicol on GFR and the eNOS pathway. Twenty male Wistar rats were divided into two groups: control vehicle animals and radicicol-infused animals (25 μg·ml−1·min−1). Basal levels were taken before experimental measurements. Mean arterial pressure and renal blood flow (RBF) were recorded, as well as GFR, urinary nitrite and nitrate excretion (UNO2/NO3V). Additionally, we evaluated eNOS expression, Ser1177 and Thr495 eNOS phosphorylation levels, the eNOS dimer-to-monomer ratio, as well as oxidative stress by assessing renal lipoperoxidation and urinary isoprostane F2α and hydrogen peroxide. HSP90 inhibition with radicicol produced a fall in RBF and GFR that was associated with a significant reduction of UNO2/NO3V. The effects of radicicol were in part mediated by a significant decrease in eNOS phosphorylation and in the eNOS dimer-to-monomer ratio. Our findings suggest that GFR is in part maintained by HSP90-eNOS interaction.

Proteomic identification of proteins associated with the osmoregulatory transcription factor TonEBP/OREBP: functional effects of Hsp90 and PARP-1

Hypertonicity (e.g., high NaCl) activates the transcription factor tonicity-responsive enhancer/osmotic response element-binding protein (TonEBP/OREBP), increasing transcription of protective genes. In the present studies, by stably expressing amino acids 1-547 of TonEBP/OREBP in HEK 293 cells and immunoprecipitating it plus associated proteins from the nuclei of cells exposed to high NaCl, we identify 14 proteins that are physically associated with TonEBP/OREBP. The associated proteins fall into several classes: 1) DNA-dependent protein kinase, both its catalytic subunit and regulatory subunit, Ku86; 2) RNA helicases, namely RNA helicase A, nucleolar RNA helicase II/Gu, and DEAD-box RNA helicase p72; 3) small or heterogeneous nuclear ribonucleoproteins (snRNPs or hnRNPs), namely U5 snRNP-specific 116 kDa protein, U5 snRNP-specific 200 kDa protein, hnRNP U, hnRNP M, hnRNP K, and hnRNP F; 4) heat shock proteins, namely Hsp90beta and Hsc70; and 5) poly(ADP-ribose) polymerase-1 (PARP-1). We confirm identification of most of the proteins by Western analysis and also demonstrate by electrophoretic mobility-shift assay that they are present in the large complex that binds specifically along with TonEBP/OREBP to its cognate DNA element. In addition, we find that PARP-1 and Hsp90 modulate TonEBP/OREBP activity. PARP-1 expression reduces TonEBP/OREBP transcriptional activity and the activity of its transactivating domain. Hsp90 enhances those activities and sustains the increased abundance of TonEBP/OREBP protein in cells exposed to high NaCl.

Renocortical mRNA expression of vasoactive factors during spironolactone protective effect in chronic cyclosporine nephrotoxicity

We showed that spironolactone reduced structural damage and prevented renal dysfunction in chronic cyclosporine (CsA) nephrotoxicity. These findings evidenced an aldosterone renal vascular effect under this condition. To investigate aldosterone’s role in modulating renal vascular tone, renocortical vasoactive pathways mRNA levels in chronic CsA nephrotoxicity as well as spironolactone’s effect on renal function in acute CsA nephrotoxicity were evaluated. Two experimental sets were designed. For chronic nephrotoxicity, rats fed with low-sodium diet were divided into groups receiving vehicle, spironolactone (Sp), CsA, and CsA+Sp, for 21 days. Creatinine clearance, survival percentage, and renocortical mRNA levels of pro-renin, angiotensinogen (Ang), angiotensin receptors (AT1A, AT1B, and AT2), preproendothelin, endothelin receptors (ETA, ETB), cyclooxygenase-2 (COX-2), and adenosine receptors (Ad1, Ad2A, Ad2B, and Ad3) were analyzed. For acute nephrotoxicity, similar groups fed with a standard chow diet for 7 days were included. Serum potassium and sodium, glomerular filtration rate (GFR), and renal blood flow (RBF) were determined. In chronic model, CsA produced pro-renin and ET upregulation, altered adenosine receptors expression, and reduced Ang, AT1A, AT1B, ETB, and COX-2 mRNA levels. Spironolactone protective effect in chronic nephrotoxicity was associated with prevention of pro-renin upregulation and increased AT2, together with ETBreduction. In acute nephrotoxicity, spironolactone completely prevented GFR and RBF reduction induced by CsA. Our results suggest that aldosterone contributes to renal vasoconstriction observed in CsA nephrotoxicity and that renoprotection conferred by spironolactone was related to modification of renocortical vasoactive pathways expression, in which pro-renin normalization was the most evident change in chronic nephropathy. Finally, our data point to spironolactone as a potential treatment to reduce CsA nephrotoxicity in transplant patients.

Recent advances in the regulation of nitric oxide in the kidney

Nitric oxide (NO) plays important roles in the regulation of renal function and the long-term control of blood pressure. New roles of NO have been proposed recently in diabetes, nephrotoxicity, and pregnancy. NO derived from all 3 NOS isoforms contributes to the overall regulation of kidney function, and recent advances in our understanding of their regulation have been made lately. In this regard, substrate and cofactor availability play important roles in regulating nitric oxide synthase (NOS) activity not only by limiting enzyme activity but also by influencing the coupling of NOS with its cofactors, tetrahydrobiopterin and NADPH. Protein-protein interactions are now recognized to be important negative and positive regulators of NOS. Phosphorylation is another component of the mechanism whereby NOS is activated or deactivated. Increased NOS expression can also influence enzyme activity; however, the degree of expression does not always correlate with enzyme activity because increased NO levels can result in inhibition of NOS. Finally, other potential regulators of NOS such as endogenous L-arginine analogs may also be important. In this article, we summarize recent advances in the regulation of activity and expression of the NOS isoforms within the kidney.