Ischemia Reperfusion Injury Produces, and Ischemic Preconditioning Prevents, Rat Cardiac Fibroblast Differentiation: Role of KATP Channels

Abstract

Ischemic preconditioning (IPC) and activation of ATP-sensitive potassium channels (KATP) protect cardiac myocytes from ischemia reperfusion (IR) injury. We investigated the influence of IR injury, IPC and KATP in isolated rat cardiac fibroblasts. Hearts were removed under isoflurane anesthesia. IR was simulated in vitro by application and removal of paraffin oil over pelleted cells. Ischemia (30, 60 and 120 min) followed by 60 min reperfusion resulted in significant differentiation of fibroblasts into myofibroblasts in culture (mean % fibroblasts ± SEM in IR vs. time control: 12 ± 1% vs. 63 ± 2%, 30 min ischemia; 15 ± 3% vs. 71 ± 4%, 60 min ischemia; 8 ± 1% vs. 55 ± 2%, 120 min ischemia). IPC (15 min ischemia, 30 min reperfusion) significantly attenuated IR-induced fibroblast differentiation (52 ± 3%) compared to 60 min IR. IPC was mimicked by opening KATP with pinacidil (50 μM; 43 ± 6%) and by selectively opening mitochondrial KATP (mKATP) with diazoxide (100 μM; 53 ± 3%). Furthermore, IPC was attenuated by inhibiting KATP with glibenclamide (10 μM; 23 ± 5%) and by selectively blocking mKATP with 5-hydroxydecanoate (100 μM; 22 ± 9%). These results suggest that (a) IR injury evoked cardiac fibroblast to myofibroblast differentiation, (b) IPC attenuated IR-induced fibroblast differentiation, (c) KATP were involved in IPC and (d) this protection involved selective activation of mKATP.

Ca2+ Signaling in Cardiac Fibroblasts and Fibrosis-Associated Heart Diseases

“…Another significant K + conductance in fibroblasts is the ATP-activated potassium channel, K ATP [51,52,54]. Activation of K ATP in mouse cardiac fibroblasts increases cell proliferation, reduces IL-6 secretion [54], and inhibits fibroblast differentiation induced by ischemic injury in vitro [55]. Functional K ATP expression in fibroblasts in vivo can be induced by myocardial infarction in the scar and border zone, which may influence the electrophysiological properties of myocytes [56].…”

Channelling the Force to Reprogram the Matrix: Mechanosensitive Ion Channels in Cardiac Fibroblasts

“…There are three known subtypes of K ATP channels found within the heart: cardiac mitochondria K ATP (mK ATP ), cardiac sarcolemma K ATP (sK ATP ), and plasma membrane K ATP (pK ATP ), with mK ATP being 2000-fold more sensitive to the K ATP agonist diazoxide than the other two [ 261 , 262 ]. Within mouse and rat hearts, K ATP channels have been shown to be expressed in CM, CF, and in the SMC and EC of coronary arteries [ 262 , 263 ]. In rodents, K ATP channels are expressed in CF isolated from normal heart tissue [ 264 ], but may not be functional under physiological conditions [ 265 ].…”

“…Despite this descriptive evidence that K ATP channel activity and expression correlate with development of the MF phenotype, numerous studies in both rodent and human CF, which utilise pharmacological modulators of K ATP channels, indicate that CF K ATP activity more likely opposes transdifferentiation of CF to MF [ 262 , 271 , 272 ]. Within cultured rat CF, K ATP expression has been associated with MF maturation.…”

“…Within cultured rat CF, K ATP expression has been associated with MF maturation. Treatment of CF with the K ATP activators diazoxide and pinacidil delayed MF maturation, while the K ATP inhibitor glibenclamide increased MF maturation [ 262 ]. Schultz and co-workers found treatment of cultured human foetal CF with ursodeoxycholic acid hyperpolarised cells, downregulated αSMA expression, and prevented CF-to-MF differentiation [ 272 ].…”

Ca2+ signalling in fibroblasts and the therapeutic potential of KCa3.1 channel blockers in fibrotic diseases

“…Whereas the role of K ir currents in human lung fibrosis has not been elucidated, data reporting differences in K ir currents between non‐fibrotic and IPF‐derived fibroblasts (Roach et al, ) suggest a possible role for K ir channels in airway remodelling during fibrogenesis. Modulation of ATP‐sensitive K + channels (K ir 6.1) increased mouse cardiac fibroblast proliferation (Benamer et al, ) and activation of ATP‐sensitive K + channels (K ATP ) reduces fibroblast differentiation and protects cardiac myocytes from ischaemia–reperfusion injury (Pertiwi et al, ). There is no literature, as yet, supporting a role or the expression of Kir6.x/K ATP channels in kidney, lung and liver fibrosis.…”