The mechanisms contributing to diabetic cardiomyopathy, as well as the protective pathways of the kallikrein-kinin-system (KKS), are incompletely understood. In a kallikrein-overexpressing rat model of streptozotocin (STZ)-induced diabetic cardiomyopathy, we investigated the involvement of inflammatory pathways, endothelial dysfunction, and oxidative stress. Six weeks after STZ injection, impairment of left ventricular (LV) function parameters measured by a Millar-tip catheter (peak LV systolic pressure; dP/dtmax; dP/dtmin) was accompanied by a significant increment of ICAM-1 and VCAM-1 (CAMs) expression, as well as of beta2-leukocyte-integrins+ (CD18+, CD11a+, CD11b+) and cytokine (TNF-alpha and IL-1beta)-expressing infiltrates in male Sprague-Dawley (SD-STZ) rats compared with normoglycemic littermates. Furthermore, SD-STZ rats demonstrated a significant impairment of endothelium-dependent relaxation evoked by acetylcholine and significantly increased plasma TBARS (plasma thiobarbituric acid reactive substances) levels as a measure of oxidative stress. These diabetic cardiomyopathy-associated alterations were significantly attenuated (P<0.05) in diabetic transgenic rats expressing the human kallikrein 1 (hKLK1) gene with STZ-induced diabetes. CAMs expression, beta2-leukocyte-integrins+, and cytokine-expressing infiltrates correlated significantly with all evaluated LV function parameters. The multiple protective effects of the KKS in experimental diabetic cardiomyopathy comprise the inhibition of intramyocardial inflammation (CAMs expression, beta2-leukocyte-integrins+ infiltration and cytokine expression), an improvement of endothelium-dependent relaxation and the attenuation of oxidative stress. These insights might have therapeutic implications also for human diabetic cardiomyopathy.