Contributor:

Piwkowska, Agnieszka (Promotor)

Place of publishing:

Warszawa

Degree name:

PhD

Level of degree:

2

Degree discipline :

biologia medyczna

Degree grantor:

Instytut Medycyny Doświadczalnej i Klinicznej im. M. Mossakowskiego PAN

Abstract:

Podocytes constitute a key element of glomerular filtration barrier mainly through a well-developed contractile apparatus formed by actin and myosin filament bundles. The podocyte foot processes along with the slit diaphragm proteins modulate the actin cytoskeleton dynamics and subsequent glomerular filtration. AMP-activated protein kinase (AMPK) is an essential enzyme responsible for maintaining energy homeostasis and proper metabolic response depending on changing environmental conditions, including stress conditions. Podocytes covering the external surface of the glomerular capillary seem to be a sensitive to a high glucose concentration or mechanical stress during glomerulopathies, including diabetic nephropathy. In pathological conditions release of nucleotides into extracellular space from glomeruli and podocytes is increased. Extracellular nucleotides act as signaling molecules through the P2 nucleotide receptors regulating vasoconstriction, thus contributing to the regulation of the glomerular filtration rate. The main goal of the study was investigation of the role of AMPK in hyperglycemia and P2 receptors in regulation of podocytes actin cytokeleton and permeability of glomerular filtration barrier. The experiments were performed using such experimental models as isolated rat glomeruli and primary culture of rat podocytes. This work demonstrated a decrease of AMPK phosphorylation level in podocytes with high level of glucose and increase of phosphorylation level after AMPK stimulation by metformin. Moreover, we observed that the changes mentioned above are correlated with the amount of TPRC6, which was increased in hyperglycemic conditions and then was restored to control values after AMPK activation. We showed a similar dependence in immunofluorescence staining and the degree of colocalization between AMPK and TRPC6, which was decreased in high glucose concentration and increased by AMPK stimulation. In this study we demonstrated a reduction of the amount of nephrin and changes in intracellular actin distribution in podocytes exposed to high glucose concentrations. Metformin treatment caused restoration of high glucose-induced changes in amount and intracellular location of proteins modulating actin cytoskeleton. Moreover, metformin through AMPK activation caused a reduction of permeability to albumin in podocytes under hyperglycemic conditions and diminution of glomerular permeability in diabetic rats. We showed that nucleotide stimulation in podocytes has an effect on restoration of energy homeostasis through AMPK activation and maintaining the oxidative balance through decreased ROS generation. Purinergic activation regulates the amount of synthesis of cyclic nucleotides (cGMP and cAMP) controlling the contractility of blood vessels. Furthermore, P2 activation, notably P2Y4, leads to a reorganization of actin cytoskeleton with accompanying an increase of permeability to albumin across podocyte monolayer. The process seems to be coupled with protein kinase A, whose suppression of activity prevented nucleotides-induced changes. In conclusion, the results of the present study offer evidence supporting a role for AMPK and purinergic signaling in regulating glomerular filtration through podocyte cytoskeleton remodeling. We believe that the proposed studies may become helpful in recognizing and understanding new defense mechanisms on the podocytes functioning, glomerular protection and preservation of normal renal function.

Detailed Resource Type:

PhD Dissertations

Resource Identifier:

oai:rcin.org.pl:193695

Source:

IMDiK PAN, sygn. ZS405 ; click here to follow the link

Language:

pol

Language of abstract:

eng

Rights:

Creative Commons Attribution BY 4.0 license

Terms of use:

Copyright-protected material. [CC BY 4.0] May be used within the scope specified in Creative Commons Attribution BY 4.0 license, full text available at: ; -

Digitizing institution:

Mossakowski Medical Research Institute PAS

Original in:

Library of the Mossakowski Medical Research Institute PAS

Projects co-financed by:

Operational Program Digital Poland, 2014-2020, Measure 2.3: Digital accessibility and usefulness of public sector information; funds from the European Regional Development Fund and national co-financing from the state budget.

Access:

Open