Improvement of defective sarcoplasmic reticulum Ca²⁺transport in diabetic heart of transgenic rats expressing the human kallikrein‐1 gene

Abstract

The bradykinin-forming enzyme kallikrein-1 is expressed in the heart. To examine whether contractile performance and sarcoplasmic reticulum Ca2+ transport of the diabetic heart can be rescued by targeting the kallikrein-kinin system, we studied left ventricular function and sarcoplasmic reticular Ca2+ uptake after induction of streptozotocin-induced diabetes mellitus in transgenic rats expressing the human tissue kallikrein-1 gene. Six weeks after a single injection of either streptozotocin (70 mg/kg ip) or vehicle, left ventricular performance was determined using a Millar-Tip catheter system. The Ca2+-transporting activity of reticulum-derived membrane vesicles was determined in left ventricular homogenates as oxalate-supported 45Ca2+ uptake. Western blot analysis was used to quantify the reticular Ca2+-ATPase SERCA2a, phospholamban, and the phosphorylation status of the latter. Contractile performance and Ca2+ uptake activity were similar in nondiabetic wild-type and transgenic rats. Severely diabetic wild-type animals exhibited impaired left ventricular performance and decreased reticular Ca2+ uptake (-39% vs. wild-type rats, P<0.05, respectively). These changes were attenuated in diabetic transgenic rats that, in addition, exhibited a markedly increased phospholamban phosphorylation at the Ca2+/calmodulin kinase-specific site threonine17 (2.2-fold vs. diabetic wild-type rats, P<0.05). These transgene-related effects were abolished after treatment with the bradykinin B2 receptor antagonist icatibant (Hoe 140). The SERCA2-to-phospholamban ratio, phosphoserine16-phospholamban levels, and the apparent affinity for Ca2+ of the uptake reaction did not differ between the groups. Increasing the activity of the kallikrein-kinin system by expressing a human kallikrein-1 transgene protects rat heart against diabetes-induced contractile and reticular Ca2+ transport dysfunctions. An increased phosphorylation of the SERCA2 regulatory protein phospholamban at threonine17 via a B2 receptor-mediated mechanism is thereby involved.

Cardioprotective and Anti-Inflammatory Effects of Interleukin Converting Enzyme Inhibition in Experimental Diabetic Cardiomyopathy

“…Diabetic cardiomyopathy is a distinct entity independent of coronary artery disease and commonly prevalent in the diabetic population (2). Pathophysiology of diabetic cardiomyopathy include, for example, microangiopathy, endothelial dysfunction, cardiac fibrosis, and disruption of the intracellular Ca 2ϩ transport, all triggered by the diabetic milieu (3)(4)(5). Additionally, inflammation with increased numbers of immunocompetent cells in the cardiac tissue plays a pivotal role in the pathophysiology of diabetic cardiomyopathy, as we were able to demonstrate recently in an experimental model of diabetes (6,7).…”

“…Diabetic cardiomyopathy is associated with left ventricular dysfunction (3,4,7,20). We recently showed that increased cytokine levels in the cardiac tissue correlate with the degree of cardiac failure in experimental diabetes (6), a finding that may explain their multiple cardiodepressive effects (21).…”

“…Two days after echocardiography, rats were intubated, artificially ventilated, and then subjected to open chest left ventricular catheterization under ketamin/xylazin anesthesia using a 2F pressure catheter (MillarInstruments, Houston, TX) as reported earlier (3,4). The left ventricular pressure (LVP) that developed and the peak rate of rise in LVP (dP/dt max ) characterizing systolic performance were analyzed.…”

Inhibition of p38 mitogen-activated protein kinase attenuates left ventricular dysfunction by mediating pro-inflammatory cardiac cytokine levels in a mouse model of diabetes mellitus

“…These abnormalities include, among others, cardiac fibrosis [5] and cardiac inflammation, which lead to left ventricular (LV) dysfunction, mediated mainly by the diabetic milieu (e.g. high glucose levels, oxidative stress, angiotensin II) [2,4,6]. Cardiac inflammation, not only in diabetic cardiomyopathy, but also in most kinds of heart failure, is accompanied by elevated cardiac protein levels of cytokines, such as TNF-α, IL1-β, IL6, and TGF-β1.…”

Usefulness of Mitral Annulus Velocity for the Early Detection of Left Ventricular Dysfunction in a Rat Model of Diabetic Cardiomyopathy

“…Diverse pathologic mechanisms, including microangiopathy, myocardial fibrosis, interstitial inflammation, oxidative damage, and abnormalities in calcium homeostasis, are known to contribute for the development of DMCMP. [4][5][6][7][8][9] As a consequence of above pathologic mechanism, functionally, diastolic and systolic functions of ventricle are impaired, 10)11) and subsequent structural changes are responsible for increased myocardial fibrosis and stiffness. 1)12) After far-advanced structural changes, the impairment of damaged myocardial function may be irreversible.…”