Abstract
In heart failure Ca/calmodulin kinase (CaMK)II expression and reactive oxygen species (ROS) are increased. Both ROS and CaMKII can increase late I(Na) leading to intracellular Na accumulation and arrhythmias. It has been shown that ROS can activate CaMKII via oxidation. We tested whether CaMKIIδ is required for ROS-dependent late I(Na) regulation and whether ROS-induced Ca released from the sarcoplasmic reticulum (SR) is involved. 40 μmol/L H(2)O(2) significantly increased CaMKII oxidation and autophosphorylation in permeabilized rabbit cardiomyocytes. Without free [Ca](i) (5 mmol/L BAPTA/1 mmol/L Br(2)-BAPTA) or after SR depletion (caffeine 10 mmol/L, thapsigargin 5 μmol/L), the H(2)O(2)-dependent CaMKII oxidation and autophosphorylation was abolished. H(2)O(2) significantly increased SR Ca spark frequency (confocal microscopy) but reduced SR Ca load. In wild-type (WT) mouse myocytes, H(2)O(2) increased late I(Na) (whole cell patch-clamp). This increase was abolished in CaMKIIδ(-/-) myocytes. H(2)O(2)-induced [Na](i) and [Ca](i) accumulation (SBFI [sodium-binding benzofuran isophthalate] and Indo-1 epifluorescence) was significantly slowed in CaMKIIδ(-/-) myocytes (versus WT). CaMKIIδ(-/-) myocytes developed significantly less H(2)O(2)-induced arrhythmias and were more resistant to hypercontracture. Opposite results (increased late I(Na), [Na](i) and [Ca](i) accumulation) were obtained by overexpression of CaMKIIδ in rabbit myocytes (adenoviral gene transfer) reversible with CaMKII inhibition (10 μmol/L KN93 or 0.1 μmol/L AIP [autocamtide 2-related inhibitory peptide]). Free [Ca](i) and a functional SR are required for ROS activation of CaMKII. ROS-activated CaMKIIδ enhances late I(Na), which may lead to cellular Na and Ca overload. This may be of relevance in hear failure, where enhanced ROS production meets increased CaMKII expression.
Highlights
Rationale: In heart failure, Ca/calmodulin kinase (CaMK)II expression and reactive oxygen species (ROS) are increased
CaMKII␦ enhances late INa, which may lead to cellular Na and Ca overload
Na entering the cell via late INa leads to cytosolic Na accumulation,[6] favoring Ca entry via sarcolemmal Na/Ca exchange (NCX) and cellular Ca overload, contractile dysfunction, and hypercontracture.[5,11,12]
Summary
40 mol/L H2O2 significantly increased CaMKII oxidation and autophosphorylation in permeabilized rabbit cardiomyocytes. In wild-type (WT) mouse myocytes, H2O2 increased late INa (whole cell patch-clamp). This increase was abolished in CaMKII␦؊/؊ myocytes. Opposite results (increased late INa, [Na]i and [Ca]i accumulation) were obtained by overexpression of CaMKII␦ in rabbit myocytes (adenoviral gene transfer) reversible with CaMKII inhibition (10 mol/L KN93 or 0.1 mol/L AIP [autocamtide 2–related inhibitory peptide]). CaMKII␦ Knockout Mice and CaMKII␦ Overexpression in Rabbit Myocytes. Ventricular myocytes were isolated from CaMKII␦ knockout mice (CaMKII␦Ϫ/Ϫ)[17] and wild-type (WT) littermates. For CaMKII␦ overexpression, isolated rabbit ventricular myocytes were transfected with CaMKII␦C adenovirus (-galactosidase [Gal] as control).[5,13,21]. APs were continuously elicited by square current pulses of 1 to 2 nA amplitude and 1 to 5 ms duration at basic cycle length (BCL) of 2 seconds
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
