Theaflavin 3,3′‐digallate reverses the downregulation of connexin 43 and autophagy induced by high glucose via AMPK activation in cardiomyocytes

Abstract

Theaflavin 3,3′‐digallate (TF3), is reported to protect cardiomyocytes from lipotoxicity and reperfusion injury. However, the role of TF3 in the protection of high‐glucose injury is still poorly understood. This study investigated the protective effects of TF3 on gap junctions and autophagy in neonatal cardiomyocytes (NRCMs). NRCMs preincubated with high glucose were coincubated with TF3. The expression of connexins and autophagy‐related proteins was determined. The functioning of gap‐junctional intercellular communication (GJIC) was measured by a dye transfer assay. Adenosine monophosphate‐activated protein kinase (AMPK) activity was determined by western blot. Moreover, AMPK was activated with aminoimidazole‐4‐carboxamide‐1‐β‐d‐ribofuranoside (AICAR) or inhibited by AMPKα small interfering RNA (siRNA) to explore the role of AMPK in the modulation of connexin 43 (Cx43) and autophagy. Meanwhile, autophagy was activated or blocked to observe the change in Cx43 expression. It was found that the protein expression of Cx43 and autophagy‐related proteins was increased in a TF3 dose‐ and time‐dependent manner under high glucose. TF3 also recovered the reduced GJIC function induced by high glucose concentrations. TF3 activated phosphorylated AMPK in a time‐dependent way. AMPKα siRNA abrogated the protection of TF3, while AICAR showed similar results compared to the TF3 treatment. Meanwhile, autophagy activation caused decreased Cx43, while cotreatment with baf A1 enhanced Cx43 expression further compared with the TF3 treatment alone under high glucose. We concluded that TF3 partly reversed the inhibition of Cx43 expression and autophagy induced by high glucose in NRCMs, partly by restoring AMPK activity. Inhibition of autophagy might be protective by preserving Cx43 expression in NRCMs stimulated by high glucose.

Blocking Connexin-43 mediated hemichannel activity protects against early tubular injury in experimental chronic kidney disease

“…In CKD, diabetic nephropathy accounts for approximately 50% of patients presenting with end-stage renal failure [1]. Hyperglycemia and downstream changes in connexin expression are critical in the development and progression of secondary micro-vascular complications, [12][13][14][15] with glucose decreasing gap junction conductance and disrupting cellular homeostasis in a variety of cell types [16][17][18][19]. Evidence that connexin expression is linked to renal damage in CKD [9,11,12,[20][21][22][23][24], suggests that they represent a viable therapeutic target for treatment of the disease.…”

Identification of differentially expressed genes in the endothelial precursor cells of patients with type 2 diabetes mellitus by bioinformatics analysis

“…The expression data were normalized to the reference GAPDH. FCs of relative mRNA expression were calculated using the change-in-threshold method (2 −ΔΔCq ) (37). The primer sets used for qPCR are listed in Table I.…”

Role of Herbal Teas in Regulating Cellular Homeostasis and Autophagy and Their Implications in Regulating Overall Health

“…It is believed that theaflavins partly reversed the inhibition of connexin expression and autophagy induced by high glucose in neonatal cardiomyocytes, partly by restoring AMPK activity. Inhibition of autophagy might be protective by preserving connexin expression in cells stimulated by high glucose [ 171 ].…”