Endothelin A receptor antagonist, atrasentan, attenuates renal and cardiac dysfunction in Dahl salt-hypertensive rats in a blood pressure independent manner

Novel Approaches in Chronic Renal Failure without Renal Replacement Therapy: A Review

Chronic kidney disease (CKD) is characterized by renal parenchymal damage leading to a reduction in the glomerular filtration rate. The inflammatory response plays a pivotal role in the tissue damage contributing to renal failure. Current therapeutic options encompass dietary control, mineral salt regulation, and management of blood pressure, blood glucose, and fatty acid levels. However, they do not effectively halt the progression of renal damage. This review critically examines novel therapeutic avenues aimed at ameliorating inflammation, mitigating extracellular matrix accumulation, and fostering renal tissue regeneration in the context of CKD. Understanding the mechanisms sustaining a proinflammatory and profibrotic state may offer the potential for targeted pharmacological interventions. This, in turn, could pave the way for combination therapies capable of reversing renal damage in CKD. The non-replacement phase of CKD currently faces a dearth of efficacious therapeutic options. Future directions encompass exploring vaptans as diuretics to inhibit water absorption, investigating antifibrotic agents, antioxidants, and exploring regenerative treatment modalities, such as stem cell therapy and novel probiotics. Moreover, this review identifies pharmaceutical agents capable of mitigating renal parenchymal damage attributed to CKD, targeting molecular-level signaling pathways (TGF-β, Smad, and Nrf2) that predominate in the inflammatory processes of renal fibrogenic cells.

Sustained rubber hand illusion after the end of visuotactile stimulation with a similar time course for the reduction of subjective ownership and proprioceptive drift

The rubber hand illusion is a perceptual illusion in which participants experience an inanimate rubber hand as their own when they observe this model hand being stroked in synchrony with strokes applied to the person’s real hand, which is hidden. Earlier studies have focused on the factors that determine the elicitation of this illusion, the relative contribution of vision, touch and other sensory modalities involved and the best ways to quantify this perceptual phenomenon. Questionnaires serve to assess the subjective feeling of ownership, whereas proprioceptive drift is a measure of the recalibration of hand position sense towards the rubber hand when the illusion is induced. Proprioceptive drift has been widely used and thought of as an objective measure of the illusion, although the relationship between this measure and the subjective illusion is not fully understood. Here, we examined how long the illusion is maintained after the synchronous visuotactile stimulation stops with the specific aim of clarifying the temporal relationship in the reduction of both subjective ownership and proprioceptive drift. Our results show that both the feeling of ownership and proprioceptive drift are sustained for tens of seconds after visuotactile stroking has ceased. Furthermore, our results indicate that the reduction of proprioceptive drift and the feeling of ownership follow similar time courses in their reduction, suggesting that the two phenomena are temporally correlated. Collectively, these findings help us better understand the relationships of multisensory stimulation, subjective ownership, and proprioceptive drift in the rubber hand illusion.

Renoprotection Provided by Additional Diuretic Treatment in Partially Nephrectomized Ren-2 Transgenic Rats Subjected to the Combined RAS and ETA Blockade

Objective

Our previous study in heterozygous Ren-2 transgenic rats (TGR) demonstrated that long-term treatment with endothelin receptor A (ET_A) blocker atrasentan added to the renin-angiotensin system (RAS) blockade had renoprotective effects in a model of chronic kidney disease (CKD) induced by partial nephrectomy. Since ET_A blockade is known to cause edema, we were interested whether diuretic treatment added to this therapy would be beneficial.

Design and Methods

Partial nephrectomy (NX) was performed at the age of 3 months in TGR rats which were subjected to: (i) RAS blockade alone (angiotensin receptor blocker losartan and angiotensin converting enzyme inhibitor trandolapril), (ii) combined RAS (losartan and trandolapril) and ET_A receptor blockade (atrasentan), or (iii) diuretic (hydrochlorothiazide) added to the combined RAS + ET_A blockade for 50 weeks following NX.

Results

At the end of the study systolic blood pressure and cardiac hypertrophy were similarly decreased in all treated groups. Survival was significantly improved by ET_A receptor blockade added to RAS blockade with no further effects of diuretic treatment. However, additional diuretic treatment combined with RAS + ET_A blockade decreased body weight and had beneficial renoprotective effects - reductions of both kidney weight and kidney damage markers. Proteinuria gradually increased in rats treated with RAS blockade alone, while it was substantially lowered by additional ET_A blockade. In rats treated with additional diuretic, proteinuria was progressively reduced throughout the experiment.

Conclusion

A diuretic added to the combined RAS and ET_A blockade has late renoprotective effects in CKD induced by partial nephrectomy in Ren-2 transgenic rats. The diuretic improved: renal function (evaluated as proteinuria and creatinine clearance), renal morphology (kidney mass, glomerular volume), and histological markers of kidney damage (glomerulosclerosis index, tubulointerstitial injury).

Estrogen Contributions to Microvascular Dysfunction Evolving to Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a syndrome involving microvascular dysfunction. No treatment is available yet and as the HFpEF patient group is expanding due to the aging population, more knowledge on dysfunction of the cardiac microvasculature is required. Endothelial dysfunction, impaired angiogenesis, (perivascular) fibrosis and the pruning of capillaries (rarefaction) may all contribute to microvascular dysfunction in the heart and other organs, e.g., the kidneys. The HFpEF patient group consists mainly of post-menopausal women and female sex itself is a risk factor for this syndrome. This may point toward a role of estrogen depletion after menopause in the development of HFpEF. Estrogens favor the ratio of vasodilating over vasoconstricting factors, which results in an overall lower blood pressure in women than in men. Furthermore, estrogens improve angiogenic capacity and attenuate (perivascular) fibrosis formation. Therefore, we hypothesize that the drop of estrogen levels after menopause contributes to myocardial microvascular dysfunction and renders post-menopausal women more vulnerable for heart diseases that involve the microvasculature. This review provides a detailed summary of molecular targets of estrogen, which might guide future research and treatment options.

Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt-induced renal injury and inflammation

AIM

Chronic high salt intake exaggerates renal injury and inflammation, especially with the loss of functional ET_B receptors. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and bile salt that is approved for the treatment of hepatic diseases. Our aim was to determine whether TUDCA is reno-protective in a model of ET_B receptor deficiency with chronic high salt-induced renal injury and inflammation.

METHODS

ET_B -deficient and transgenic control rats were placed on normal (0.8% NaCl) or high salt (8% NaCl) diet for 3 weeks, receiving TUDCA (400 mg/kg/d; ip) or vehicle. Histological and biochemical markers of kidney injury, renal cell death and renal inflammation were assessed.

RESULTS

In ET_B -deficient rats, high salt diet significantly increased glomerular and proximal tubular histological injury, proteinuria, albuminuria, excretion of tubular injury markers KIM-1 and NGAL, renal cortical cell death and renal CD4⁺ T cell numbers. TUDCA treatment increased proximal tubule megalin expression as well as prevented high salt diet-induced glomerular and tubular damage in ET_B -deficient rats, as indicated by reduced kidney injury markers, decreased glomerular permeability and proximal tubule brush border restoration, as well as reduced renal inflammation. However, TUDCA had no significant effect on blood pressure.

CONCLUSIONS

TUDCA protects against the development of glomerular and proximal tubular damage, decreases renal cell death and inflammation in the renal cortex in rats with ET_B receptor dysfunction on a chronic high salt diet. These results highlight the potential use of TUDCA as a preventive tool against chronic high salt induced renal damage.

Renoprotective effects of ET(A) receptor antagonists therapy in experimental non-diabetic chronic kidney disease: Is there still hope for the future?

Chronic kidney disease (CKD) is a life-threatening disease arising as a frequent complication of diabetes, obesity and hypertension. Since it is typically undetected for long periods, it often progresses to end-stage renal disease. CKD is characterized by the development of progressive glomerulosclerosis, interstitial fibrosis and tubular atrophy along with a decreased glomerular filtration rate. This is associated with podocyte injury and a progressive rise in proteinuria. As endothelin-1 (ET-1) through the activation of endothelin receptor type A (ET(A)) promotes renal cell injury, inflammation, and fibrosis which finally lead to proteinuria, it is not surprising that ET(A) receptors antagonists have been proven to have beneficial renoprotective effects in both experimental and clinical studies in diabetic and non-diabetic CKD. Unfortunately, fluid retention encountered in large clinical trials in diabetic CKD led to the termination of these studies. Therefore, several advances, including the synthesis of new antagonists with enhanced pharmacological activity, the use of lower doses of ET antagonists, the addition of diuretics, plus simply searching for distinct pathological states to be treated, are promising targets for future experimental studies. In support of these approaches, our group demonstrated in adult subtotally nephrectomized Ren-2 transgenic rats that the addition of a diuretic on top of renin-angiotensin and ET(A) blockade led to a further decrease of proteinuria. This effect was independent of blood pressure which was normalized in all treated groups. Recent data in non-diabetic CKD, therefore, indicate a new potential for ET(A) antagonists, at least under certain pathological conditions.

Drugs and Targets in Fibrosis

Fibrosis contributes to the development of many diseases and many target molecules are involved in fibrosis. Currently, the majority of fibrosis treatment strategies are limited to specific diseases or organs. However, accumulating evidence demonstrates great similarities among fibroproliferative diseases, and more and more drugs are proved to be effective anti-fibrotic therapies across different diseases and organs. Here we comprehensively review the current knowledge on the pathological mechanisms of fibrosis, and divide factors mediating fibrosis progression into extracellular and intracellular groups. Furthermore, we systematically summarize both single and multiple component drugs that target fibrosis. Future directions of fibrosis drug discovery are also proposed.