Protective Role of Klotho in Cardiomyocyte Injury Caused by Hypoxia-Reoxygenation via Regulation of the NF-κb Signaling Cascade

Summary

This protocol evaluates the protective role of klotho overexpression in H9C2 cardiomyocytes under hypoxia-reoxygenation using molecular and functional assays.

Abstract

This study aimed to investigate the protective role of klotho in cardiomyocytes subjected to hypoxia/reoxygenation (H/R) injury. An in vitro H/R model was established using H9C2 rat cardiomyoblasts, which were transfected with klotho-overexpressing lentiviral vectors. Cells were divided into six experimental groups: control, H/R, negative control (NC), klotho-overexpression, PDTC (an NF-κB inhibitor), and a combination group treated with klotho and lipopolysaccharide (LPS). Klotho expression levels were determined by quantitative real-time PCR and western blotting. Cell viability was measured via the MTT assay, while apoptosis was assessed using flow cytometry. The expression of proteins involved in the NF-κB signaling pathway was analyzed by western blotting, and the cellular expression of pro-inflammatory cytokines was evaluated through immunofluorescence staining. Klotho overexpression significantly elevated klotho levels in H9C2 cells and led to improved cell viability, reduced apoptosis, and decreased cellular expression of pro-inflammatory cytokines compared to the H/R group. Western blot analysis revealed that klotho overexpression, as well as PDTC treatment, suppressed NF-κB pathway activation, as indicated by a reduced p-P65/P65 ratio and increased p-IκBα/IκBα levels. These effects were partially reversed upon co-treatment with LPS. These results suggest that klotho confers cardioprotection against H/R-induced injury by modulating NF-κB signaling, reducing inflammation, and promoting cell survival. This protocol provides a reproducible method for studying the molecular mechanisms underlying myocardial ischemia-reperfusion injury and the therapeutic potential of klotho in cardiac inflammation.

Introduction

Acute myocardial infarction (AMI) is primarily caused by ischemia followed by reperfusion, which has prompted extensive research into the mechanisms of myocardial hypoxia/reoxygenation (H/R) injury^1,2,3. A pivotal aspect of myocardial H/R injury is cell apoptosis, which contributes significantly to the pathological progression of AMI^4,5.

Recent studies have implicated the nuclear factor kappa B (NF-κB) signaling pathway in myocardial H/R injury through its modulation of inflammatory re....

Protocol

All procedures involving the H9C2 rat cardiomyoblast cell line (ATCC, CRL-1446) were performed in compliance with institutional biosafety regulations. No animal or human subjects were directly involved in this study. Figure 1 illustrates the graphical workflow of the experimental design and analysis pipeline. The reagents and the equipment used are listed in the Table of Materials.

1. Cell culture

The H9C2 rat cardiomyoblast cell line (ATCC, CRL-1446) was cryopreserved in liquid nitrogen using a freezing medium composed of Dulbecco's Modified Eagle Medium (DMEM, hi....

Results

Klotho overexpression improves cell survival and attenuates NF-κB-mediated inflammatory injury

To confirm the efficiency of gene delivery, Klotho expression was quantified at both the mRNA and protein levels. Klotho-overexpressing cells showed a robust increase compared with both hypoxia/reoxygenation (H/R) and negative control groups (p < 0.05; Figure 2A,B). Functionally.......

Discussion

In this study, the protective role of Klotho in cardiomyocytes exposed to hypoxia/reoxygenation (H/R) injury was investigated, and Klotho overexpression was found to significantly improve cell viability, reduce apoptosis, and suppress pro-inflammatory cytokine expression. These effects were accompanied by reduced phosphorylation of p65 and enhanced phosphorylation of IκBα, suggesting that inhibition of NF-κB signaling contributes to the protective phenotype. Pharmacological inhibition of NF-κB by PDTC.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
4% Paraformaldehyde	Biosharp	XG1050
Annexin V APC/PI Staining Solution	Elabscience	E-CK-A217
cDNA Synthesis Kit	Qiagen	205410
DAPI Solution	BioFroxx	1155MG010
Dulbecco’s Modified Eagle Medium (DMEM)	HyClone	SH30243.01B
ECL Detection Reagent Kit	Meilunbio	MA0186-1
Electrophoresis Power Supply (POWER PAC 200)	Bio-Rad	POWER PAC 200
Fetal Bovine Serum (FBS)	VivaCell	C04001-500, C04002-500
Flow Cytometer (Gallios)	Beckman Coulter	Gallios
Fluorescence Microscope (BK6000)	Chongqing Optec	BK6000
Formazan Solvent	Solarbio	M1020
HRP-Conjugated Goat Anti-Rabbit IgG Antibody	Bethyl	A120-101P
LPS (NF-κB Pathway Agonist)	Sigma-Aldrich	L2630
Microplate Reader (Model K3)	Thermo	K3
Modular Incubator Chamber (Hypoxia Chamber)	Billups-Rothenberg	MIC-101
MTT Solution	Cayman	21795
PDTC (NF-κB Pathway Inhibitor)	Sigma-Aldrich	P8765
PE-Conjugated Goat Anti-Rabbit IgG Antibody	Bioss	bs-0295G-PE
Polybrene (Hexadimethrine Bromide)	Invitrogen	X2351
PVDF Membrane	Merck	ISEQ00010
Rabbit Anti-Rat IL-1β Antibody	Biorbyt	orb378927
Rabbit Anti-Rat IL-6 Antibody	ZEN BIO	384702
Rabbit Anti-Rat IκBα Antibody	Biorbyt	orb223182
Rabbit Anti-Rat Klotho Antibody	Biorbyt	orb333711
Rabbit Anti-Rat p65 Antibody	Biorbyt	orb229138
Rabbit Anti-Rat Phospho-IκBα Antibody	Biorbyt	orb223035
Rabbit Anti-Rat Phospho-NF-κB p65 Antibody	Biorbyt	orb304662
Rabbit Anti-Rat TNF-α Antibody	Biorbyt	orb106548
Rabbit Anti-Rat β-actin Antibody	Huabio	ET1702
Real-Time Quantitative PCR System (LightCycler 96)	Roche	Light Cycler96
RIPA Lysis Buffer	Mreda	MO52447
SDS-PAGE Gel Preparation Kit	Elabscience	E-IR-R305
TRIzol Reagent Kit	Life Technologies	15596-018