Regulation of TLR4 expression mediates the attenuating effect of erythropoietin on inflammation and myocardial fibrosis in rat heart

Abstract

The mechanism underlying the anti-inflammatory or antifibrotic activity of erythropoietin (EPO) in myocardial fibrosis (MF) remains elusive. In the current study, abdominal aortic constriction (AAC) was performed on rats and EPO and/or Toll-like receptor (TLR)4 were overexpressed in rat hearts through intramyocardial administration of lentivirus expressing the EPO and TLR4 genes. Hematoxylin and eosin staining and Masson's trichrome staining were performed on tissue sections from rat hearts for histopathological examination. ELISA was used to determine the levels of inflammatory mediators in serum. Gene expression levels were determined by quantitative polymerase chain reaction analysis and protein expression levels were determined by western blot analysis and immunofluorescence staining. The results indicated that EPO overexpression improved MF in rat hearts, by inhibiting the release of transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, IL-17A, matrix metalloproteinase (MMP)-9 and MMP-2. Moreover, EPO overexpression suppressed the expression of TLR4, while promoting phosphoinositide 3-kinase (PI3K) and phosphorylated AKT serine/threonine kinase 1 (Akt) expression levels. However, the beneficial effects of EPO were attenuated by overexpression of TLR4. In addition, inhibition of PI3K/Akt signaling activity by treatment with LY294002 markedly reversed the protective effect of EPO on the AAC-induced MF. Taken together, the present study demonstrated that EPO may have a critical role against MF by activating PI3K/Akt signaling and by down-regulating TLR4 expression, thereby inhibiting the release of TGF-β1, TNF-α, IL-6, IL-1β, IL-17A, MMP-9 and MMP-2. These findings suggest that the PI3K/Akt/TLR4 signaling pathway is associated with the anti-inflammatory effects of EPO and may play a role in attenuating AAC-induced MF.

Inhibition of Interleukin‐6/glycoprotein 130 signalling by Bazedoxifene ameliorates cardiac remodelling in pressure overload mice

“…The underlying mechanisms that involved with IL‐6 signalling in HHD were yet to be disambiguated because of the complicated networks comprised of multiple biological process. It has been reported that the expression of IL‐6 is in positive correlation with that of MMP2 in several types of cardiovascular diseases such as aortic dissection, lipopolysaccharide‐induced cardiac fibrosis and pressure overload‐associated cardiac extracellular matrix (ECM) remodelling . In addition to the fact that an IL‐6 dependent increase of MMP2 and a MMP2‐dependent increase in IL‐6 are observed, STAT3 directly binds to the promoter of MMP2 to regulate cellular biological process .…”

PPAR γ/TLR4/TGF-β1 axis mediates the protection effect of erythropoietin on cyclosporin A-induced chronic nephropathy in rat

“…However, a series of studies have shown that indications benefiting from EPO treatment are clearly beyond the scope of anemia. In a variety of animal models, EPO exhibits multiple protective effects on tissues or organs, such as the pleiotropic effects on the cardiovascular system and kidney [7][8][9][10]. In preliminary experiment, we have observed that EPO could effectively improve the renal injury induced by cyclosporine A in rats.…”

Key Player in Cardiac Hypertrophy, Emphasizing the Role of Toll-Like Receptor 4

“…Consistent with a protective role for PI3K/Akt pathway, it is evident that the activation of the PI3K/Akt pathway is considered as a negative feedback regulator of TLR4 signaling in cardiac inflammation to control and limit the pro-inflammatory process (65,69,77,88). More recently, it was shown that erythropoietin exerts a protective role in myocardial fibrosis and cardiac hypertrophy, and the mechanism is associated with downregulating TLR4 expression by activating the PI3K/Akt signaling pathway (89). Notably, PI3K/Akt signaling also adversely affects the heart, possibly through the activation of PI3K different isoforms (p110α, p110γ).…”