thymosin-beta(4) and Kidney-Diseases

Substantial evidence demonstrates a link of increased plasminogen activator inhibitor-1 (PAI-1) and glomerulosclerosis and kidney fibrosis, providing a novel therapeutic option for prevention and treatment of chronic kidney diseases. Several mechanisms contributing to increased PAI-1 will be addressed, including classic key profibrotic factors such as the renin-angiotensin-system (RAS) and transforming growth factor-beta (TGF-b???and novel molecules identified by proteomic analysis, such as thymosin- b4. The fibrotic sequelae caused by increased PAI-1 in kidney depend not only on its classic inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA), but also its influence on cell migration.

Topics: Angiotensins; Animals; Chronic Disease; Disease Models, Animal; Fibrosis; Humans; Kidney Diseases; Mice; Oligopeptides; Organ Specificity; Plasminogen Activator Inhibitor 1; Renin-Angiotensin System; Thymosin; Transforming Growth Factor beta1

Plasma ultrafiltration in the kidney occurs across glomerular capillaries, which are surrounded by epithelial cells called podocytes. Podocytes have a unique shape maintained by a complex cytoskeleton, which becomes disrupted in glomerular disease resulting in defective filtration and albuminuria. Lack of endogenous thymosin β4 (TB4), an actin sequestering peptide, exacerbates glomerular injury and disrupts the organisation of the podocyte actin cytoskeleton, however, the potential of exogenous TB4 therapy to improve podocyte injury is unknown. Here, we have used Adriamycin (ADR), a toxin which injures podocytes and damages the glomerular filtration barrier leading to albuminuria in mice. Through interrogating single-cell RNA-sequencing data of isolated glomeruli we demonstrate that ADR injury results in reduced levels of podocyte TB4. Administration of an adeno-associated viral vector encoding TB4 increased the circulating level of TB4 and prevented ADR-induced podocyte loss and albuminuria. ADR injury was associated with disorganisation of the podocyte actin cytoskeleton in vitro, which was ameliorated by treatment with exogenous TB4. Collectively, we propose that systemic gene therapy with TB4 prevents podocyte injury and maintains glomerular filtration via protection of the podocyte cytoskeleton thus presenting a novel treatment strategy for glomerular disease.

Topics: Albuminuria; Animals; Cells, Cultured; Doxorubicin; Genetic Therapy; Kidney Diseases; Kidney Glomerulus; Mice; Podocytes; Thymosin

The antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is released from thymosin-β4 (Tβ4) by the meprin-α and prolyl oligopeptidase (POP) enzymes and is hydrolyzed by angiotensin-converting enzyme (ACE). Ac-SDKP is present in urine; however, it is not clear whether de novo tubular release occurs or if glomerular filtration is the main source. We hypothesized that Ac-SDKP is released into the lumen of the nephrons and that it exerts an antifibrotic effect. We determined the presence of Tβ4, meprin-α, and POP in the kidneys of Sprague-Dawley rats. The stop-flow technique was used to evaluate Ac-SDKP formation in different nephron segments. Finally, we decreased Ac-SDKP formation by inhibiting the POP enzyme and evaluated the long-term effect in renal fibrosis. The Tβ4 precursor and the releasing enzymes meprin-α and POP were expressed in the kidneys. POP enzyme activity was almost double that in the renal medulla compared with the renal cortex. With the use of the stop-flow technique, we detected the highest Ac-SDKP concentrations in the distal nephron. The infusion of a POP inhibitor into the kidney decreased the amount of Ac-SDKP in distal nephron segments and in the proximal nephron to a minor extent. An ACE inhibitor increased the Ac-SDKP content in all nephron segments, but the increase was highest in the distal portion. The chronic infusion of a POP inhibitor increased kidney medullary fibrosis, which was prevented by Ac-SDKP. We conclude that Ac-SDKP is released by the nephron and is part of an important antifibrotic system in the kidney.

Topics: Animals; Disease Models, Animal; Fibrosis; Kidney Diseases; Kidney Medulla; Male; Metalloendopeptidases; Nephrons; Oligopeptides; Prolyl Oligopeptidases; Rats, Sprague-Dawley; Serine Endopeptidases; Signal Transduction; Thymosin

Previously, we found thymosin β4 (Tβ4) is upregulated in glomerulosclerosis and required for angiotensin II-induced expression of plasminogen activator inhibitor-1 (PAI-1) in glomerular endothelial cells. Tβ4 has beneficial effects in dermal and corneal wound healing and heart disease, yet its effects in kidney disease are unknown. Here we studied renal fibrosis in wild-type and PAI-1 knockout mice following unilateral ureteral obstruction to explore the impact of Tβ4 and its prolyl oligopeptidase tetrapeptide degradation product, N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), in renal fibrosis. Additionally, we explored interactions of Tβ4 with PAI-1. Treatment with Ac-SDKP significantly decreased fibrosis in both wild-type and PAI-1 knockout mice, as observed by decreased collagen and fibronectin deposition, fewer myofibroblasts and macrophages, and suppressed profibrotic factors. In contrast, Tβ4 plus a prolyl oligopeptidase inhibitor significantly increased fibrosis in wild-type mice. Tβ4 alone also promoted repair and reduced late fibrosis in wild-type mice. Importantly, both profibrotic effects of Tβ4 plus the prolyl oligopeptidase inhibitor, and late reparative effects of Tβ4 alone, were absent in PAI-1 knockout mice. Thus, Tβ4 combined with prolyl oligopeptidase inhibition is consistently profibrotic, but by itself has antifibrotic effects in late-stage fibrosis, while Ac-SDKP has consistent antifibrotic effects in both early and late stages of kidney injury. These effects of Tβ4 are dependent on PAI-1.

Topics: Animals; Collagen; Disease Models, Animal; Fibronectins; Fibrosis; Kidney; Kidney Diseases; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myofibroblasts; Oligopeptides; Plasminogen Activator Inhibitor 1; Prolyl Oligopeptidases; Serine Endopeptidases; Serine Proteinase Inhibitors; Thymosin; Time Factors; Ureteral Obstruction; Urological Agents