Ischemic preconditioning affects phosphosites and accentuates myocardial stunning while reducing infarction size in rats.

Background and aims: Ischemic preconditioning (IPC), i.e., brief periods of ischemia, protect the heart from subsequent prolonged ischemic injury, and reduces infarction size. Myocardial stunning refers to transient loss of contractility in the heart after myocardial ischemia that recovers without permanent damage. The relationship between IPC and myocardial stunning remains incompletely understood. This study aimed primarily to examine the effects of IPC on the relationship between ischemia duration, stunning, and infarct size in an ischemia-reperfusion injury model. Secondarily, this study aimed to examine to which extent the phosphoproteomic changes induced by IPC relate to myocardial contractile function. Methods and results: Rats were subjected to different durations of left anterior descending artery (LAD) occlusion, with or without preceding IPC. Echocardiograms were acquired to assess cardiac contraction in the affected myocardial segment. Infarction size was evaluated using triphenyl tetrazolium chloride staining. Phosphoproteomic analysis was performed in heart tissue from preconditioned and non-preconditioned animals. In contrast to rats without IPC, reversible akinesia was observed in a majority of the rats that were subjected to IPC and subsequently exposed to ischemia of 13.5 or 15 min of ischemia. Phosphoproteomic analysis revealed significant differential regulation of 786 phosphopeptides between IPC and non-IPC groups, with significant associations with the sarcomere, Z-disc, and actin binding. Conclusion: IPC induces changes in phosphosites of proteins involved in myocardial contraction; and both accentuates post-ischemic myocardial stunning and reduces infarct size.

Voluntary Exercise-Mediated Protection in TNBS-Induced Rat Colitis: The Involvement of NETosis and Prdx Antioxidants.

Inflammatory bowel diseases (IBDs) are autoimmune disorders of the gut. It is increasingly clear that voluntary exercise (VE) may exert protection against IBDs, but the exact background mechanism needs to be elucidated. In the present study, we aimed to investigate the possible role of NETosis and the antioxidant peroxiredoxin (Prdx) enzyme family in VE-induced protection. Wistar Han rats were randomly divided into two groups: sedentary (SED) and VE. After the 6-week voluntary wheel running, animals were treated with 2,4,6-trinitrobenzene sulphonic acid (TNBS) as a model of colitis. Here, we found that VE significantly decreased inflammation and ulceration of the colon in the VE TNBS group compared with SED TNBS. We also found that VE significantly decreased the expression of protein arginine deiminase 4 (PAD4) and myeloperoxidase (MPO), and markedly reduced citrullinated histone H3 (citH3) compared with SED TNBS. Furthermore, VE caused a significant increase in the levels of Prdx6 in the control and TNBS groups. Taken together, we found that a prior 6-week VE effectively reduces inflammation in TNBS-induced colitis, and we suggest that the protective effect of VE may be mediated via the inhibition of NETosis and upregulation of Prdx6 antioxidant.

Co-administration with A1M does not influence apoptotic response of 177Lu-octreotate in GOT1 neuroendocrine tumors.

Recombinant α1-microglobulin (A1M) is a proposed radioprotector during 177Lu-octreotate therapy of neuroendocrine tumors (NETs). To ensure a maintained therapeutic effect, we previously demonstrated that A1M does not affect the 177Lu-octreotate induced decrease in GOT1 tumor volume. However, the underlying biological events of these findings are still unknown. The aim of this work was to examine the regulation of apoptosis-related genes in GOT1 tumors short-time after i.v. administration of 177Lu-octreotate with and without A1M or A1M alone. Human GOT1 tumor-bearing mice received 30 MBq 177Lu-octreotate or 5 mg/kg A1M or co-treatment with both. Animals were sacrificed after 1 or 7 days. Gene expression analysis of apoptosis-related genes in GOT1 tissue was performed with RT-PCR. In general, similar expression patterns of pro- and anti-apoptotic genes were found after 177Lu-octreotate exposure with or without co-administration of A1M. The highest regulated genes in both irradiated groups compared to untreated controls were FAS and TNFSFRS10B. Administration of A1M alone only resulted in significantly regulated genes after 7 days. Co-administration of A1M did not negatively affect the transcriptional apoptotic response of 177Lu-octreotate in GOT1 tumors.

Differences between cardiac troponin I vs. T according to the duration of myocardial ischaemia.

AIMS: Cardiac troponin T (cTnT) and troponin I (cTnI) are expressed as an obligate 1:1 complex in the myocardium. However, blood levels of cTnI often rise much higher than that of cTnT in myocardial infarction (MI), whereas cTnT is often higher in patients with stable conditions such as atrial fibrillation. Here we examine high-sensitive (hs) cTnI and hs-cTnT after different durations of experimental cardiac ischaemia. METHODS AND RESULTS: hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were measured in plasma samples from rats before and at 30 and 120 min after 5, 10, 15, and 30 min of myocardial ischaemia. The animals were killed after 120 min of reperfusion, and the infarct volume and volume at risk were measured. hs-cTnI, hs-cTnT, and the hs-cTnT/hs-cTnI ratio were also measured in plasma samples collected from patients with ST-elevation myocardial infarction (STEMI). hs-cTnT and hs-cTnI increased over 10-fold in all rats subjected to ischaemia. The increase of hs-cTnI and hs-cTnT after 30 min was similar, resulting in a hs-cTnI/hs-cTnT ratio around 1. The hs-cTnI/hs-cTnT ratio was also around 1 in blood samples collected at 120 min in rats subjected to 5 or 10 min of ischaemia where no localized necrosis was observed. In contrast, the hs-cTnI/hs-cTnT ratio at 2 h was 3.6-5.5 after longer ischaemia that induced cardiac necrosis. The large hs-cTnI/hs-cTnT ratio was confirmed in patients with anterior STEMI. CONCLUSION: Both hs-cTnI and hs-cTnT increased similarly after brief periods of ischaemia that did not cause overt necrosis, whereas the hs-cTnI/hs-cTnT ratio tended to increase following longer ischaemia that induced substantial necrosis. A low hs-cTnI/hs-cTnT ratio around 1 may signify non-necrotic cTn release.

Novel Potentials of the DPP-4 Inhibitor Sitagliptin against Ischemia-Reperfusion (I/R) Injury in Rat Ex-Vivo Heart Model.

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of oral anti-diabetic drugs, implicated in pleiotropic secondary cardioprotective effects. The aim of the study was to unveil the unknown and possible cardioprotective targets that can be exerted by sitagliptin (Sitg) against ischemia-reperfusion (I/R) injury. Male wistar rats received 2 weeks' Sitg oral treatment of different doses (25, 50, 100, and 150 mg/kg/day), or saline as a Control. Hearts were then isolated and subjected to two different I/R injury protocols: 10 min perfusion, 45 min regional ischemia, and 120 min reperfusion for infarct size (IS) measurement, or: 10 min perfusion, 45 min regional ischemia and 10 min reperfusion for biochemical analysis: nitric oxide synthases (NOSs) and DPP-4 activity, glucagon-like peptide-1 (GLP-1), Calcium, transient receptor potential vanilloid (TRPV)-1 and calcitonin gene-related peptide (CGRP) levels, transient receptor potential canonical (TRPC)-1 and e-NOS protein expression. NOS inhibitor (L-NAME) and TRPV-1 inhibitor (Capsazepine) were utilized to confirm the implication of both signaling mechanisms in DPP-4 inhibition-induced at the level of IS. Findings show that Sitg (50 mg) resulted in significant decrease in IS and DPP-4 activity, and significant increase in GLP-1, NOS activity, e-NOS expression, TRPV-1 level and TRPC-1 expression, compared to controls. Results of CGRP are in line with TRPV-1, as a downstream regulatory effect. NOS system and transient receptor potential (TRP) channels can contribute to DPP-4 inhibition-mediated cardioprotection against I/R injury using Sitagliptin.

Role of Exercise-Induced Cardiac Remodeling in Ovariectomized Female Rats.

Myocardial extracellular matrix (ECM) is essential for proper cardiac function and structural integrity; thus, the disruption of ECM homeostasis is associated with several pathological processes. Female Wistar rats underwent surgical ovariectomy (OVX) or sham operation (SO) and were then divided into eight subgroups based on the type of diet (standard chow or high-triglyceride diet/HT) and exercise (with or without running). After 12 weeks, cardiac MMP-2 activity, tissue inhibitor of metalloproteinase-2, content of collagen type I, the level of nitrotyrosine (3-NT) and glutathione (GSH), and the ratio of infarct size were determined. Our results show that OVX and HT diet caused an excessive accumulation of collagen; however, this increase was not observed in the trained animals. Twelve weeks of exercise promoted elevation in the levels of 3-NT and GSH and similarly an increase in MMP-2 activity of both SO and OVX animals. The high infarct-size ratio caused by OVX and HT diet was mitigated by physical exercise. Our findings demonstrate that ovarian estrogen loss and HT diet caused collagen accumulation and increased ratio of the infarct size. However, exercise-induced cardiac remodeling serves as a compensatory mechanism by enhancing MMP-2 activity and reducing fibrosis, thus minimizing the ischemia/reperfusion injury.

H2S confers colonoprotection against TNBS-induced colitis by HO-1 upregulation in rats.

Hydrogen sulfide (H2S) is an endogenous mediator that contributes to many important physiological processes including vasodilation and vascular smooth muscle relaxation; in turn, preventing tissue damage and reducing inflammation. Heme oxygenase (HO) enzymes, of which HO-1 is inducible by harmful stimuli, were found to regulate intestinal inflammation in experimental animal models of colitis. We aimed to investigate the protective effects of H2S against 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats, and whether HO enzyme system is involved in the H2S-induced colonic cytoprotection. Male Wistar rats were treated with TNBS to induce colitis, and H2S donor (Lawesson's reagent) was prepared two times/day at different concentrations, and delivered per os (from day 1 to day 3). Our results suggest that daily treatment (2 times/day) with H2S donor, could significantly decrease the extent of colonic inflammation compared to vehicle treatment, and the most effective daily dose of H2S donor against inflammation was 18.75 µM/kg/day. Per os administration of H2S donor increased the colonic HO enzyme activity; on the contrary, the protective effect of H2S was abolished by the co-treatment with HO inhibitor. Our findings suggest that H2S confers colonoprotection, probably by modulation of anti-inflammatory parameters and HO enzyme activity.

Experimental Diabetes Mellitus in Different Animal Models.

Animal models have historically played a critical role in the exploration and characterization of disease pathophysiology and target identification and in the evaluation of novel therapeutic agents and treatments in vivo. Diabetes mellitus disease, commonly known as diabetes, is a group of metabolic disorders characterized by high blood glucose levels for a prolonged time. To avoid late complications of diabetes and related costs, primary prevention and early treatment are therefore necessary. Due to its chronic symptoms, new treatment strategies need to be developed, because of the limited effectiveness of the current therapies. We overviewed the pathophysiological features of diabetes in relation to its complications in type 1 and type 2 mice along with rat models, including Zucker Diabetic Fatty (ZDF) rats, BB rats, LEW 1AR1/-iddm rats, Goto-Kakizaki rats, chemically induced diabetic models, and Nonobese Diabetic mouse, and Akita mice model. The advantages and disadvantages that these models comprise were also addressed in this review. This paper briefly reviews the wide pathophysiological and molecular mechanisms associated with type 1 and type 2 diabetes, particularly focusing on the challenges associated with the evaluation and predictive validation of these models as ideal animal models for preclinical assessments and discovering new drugs and therapeutic agents for translational application in humans.