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Introduction: We demonstrated Toll-like receptor (TLR) 4 in the pathogenesis of angiotensin II (AngII)-mediated abdominal aortic aneurysm (AAA) formation. Here, we study TLR2 in the AAA formation., Methods: Male ApoE-/- and ApoE-/-TLR2-/- mice were treated with AngII. Mice were injected with the TLR2 agonist Pam3CSK4. The incidence and severity of AAA were determined. MCP-1, MCP-5, RANTES, CXCL10, CCR5, and CXCR3 were analyzed. M1 and M2 macrophages in the aorta were detected by flow cytometry., Results: These studies demonstrated an increase in AAA formation in TLR2-/- mice and a decrease by Pam3CSK4. Pam3CSK4 decreased the ratio of M1/M2 and the levels of RANTES, CXCL10, CCR5, and CXCR3. Furthermore, Pam3CSK4 treatment 1 week following AngII retarded the progression of AAA., Conclusion: These data demonstrated a protective effect of TLR2 signaling on AAA in association with a decrease in the ratio of M1 to M2 macrophages and the expression of chemokines and their receptors. Furthermore, the treatment of Pam3CSK4 after AngII demonstrated a marked retardation of lesion progression. Given the fact that most AAA patients are detected late in the disease process, these findings suggest that TLR2 stimulation may play a therapeutic role in retarding disease progression., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

The pathophysiology of pulmonary hypertension (PH) and heart failure (HF) includes fibrogenic remodeling associated with the loss of pulmonary arterial (PA) and cardiac compliance. We and others have previously identified transglutaminase 2 (TG2) as a participant in adverse fibrogenic remodeling. However, little is known about the biologic mechanisms that regulate TG2 function. We examined physiological mouse models of experimental PH, HF, and type 1 diabetes that are associated with altered glucose metabolism/glycolysis and report here that TG2 expression and activity are elevated in pulmonary and cardiac tissues under all these conditions. We additionally used PA adventitial fibroblasts to test the hypothesis that TG2 is an intermediary between enhanced tissue glycolysis and fibrogenesis. Our in vitro results show that glycolytic enzymes and TG2 are upregulated in fibroblasts exposed to high glucose, which stimulates cellular glycolysis as measured by Seahorse analysis. We examined the relationship of TG2 to a terminal glycolytic enzyme, pyruvate kinase M2 (PKM2), and found that PKM2 regulates glucose-induced TG2 expression and activity as well as fibrogenesis. Our studies further show that TG2 inhibition blocks glucose-induced fibrogenesis and cell proliferation. Our findings support a novel role for glycolysis-mediated TG2 induction and tissue fibrosis associated with experimental PH, HF, and hyperglycemia., (© 2019 Federation of American Societies for Experimental Biology.)

Type 1 diabetic Akita mice develop severe cardiac parasympathetic dysfunction that we have previously demonstrated is due at least in part to an abnormality in the response of the end organ to parasympathetic stimulation. Specifically, we had shown that hypoinsulinemia in the diabetic heart results in attenuation of the G-protein coupled inward rectifying K channel (GIRK) which mediates the negative chronotropic response to parasympathetic stimulation due at least in part to decreased expression of the GIRK1 and GIRK4 subunits of the channel. We further demonstrated that the expression of GIRK1 and GIRK4 is under the control of the Sterol Regulatory element Binding Protein (SREBP-1), which is also decreased in response to hypoinsulinemia. Finally, given that hyperactivity of Glycogen Synthase Kinase (GSK)3β, had been demonstrated in the diabetic heart, we demonstrated that treatment of Akita mice with Li+, an inhibitor of GSK3β, increased parasympathetic responsiveness and SREBP-1 levels consistent with the conclusion that GSK3β might regulate IKACh via an effect on SREBP-1. However, inhibitor studies were complicated by lack of specificity for GSK3β. Here we generated an Akita mouse with cardiac specific inducible knockout of GSK3β. Using this mouse, we demonstrate that attenuation of GSK3β expression is associated with an increase in parasympathetic responsiveness measured as an increase in the heart rate response to atropine from 17.3 ± 3.5% (n = 8) prior to 41.2 ± 5.4% (n = 8, P = 0.017), an increase in the duration of carbamylcholine mediated bradycardia from 8.43 ± 1.60 min (n = 7) to 12.71 ± 2.26 min (n = 7, P = 0.028) and an increase in HRV as measured by an increase in the high frequency fraction from 40.78 ± 3.86% to 65.04 ± 5.64 (n = 10, P = 0.005). Furthermore, patch clamp measurements demonstrated a 3-fold increase in acetylcholine stimulated peak IKACh in atrial myocytes from GSK3β deficiency mice compared with control. Finally, western blot analysis of atrial extracts from knockout mice demonstrated increased levels of SREBP-1, GIRK1 and GIRK4 compared with control. Taken together with our prior observations, these data establish a role of increased GSK3β activity in the pathogenesis of parasympathetic dysfunction in type 1 diabetes via the regulation of IKACh and GIRK1/4 expression., Competing Interests: The authors have declared that no competing interests exist.

Background: The incidence of sudden arrhythmic death is markedly increased in diabetics., Objective: The purpose of this study was to develop a mouse model for postmyocardial infarction (post-MI) ventricular tachycardia (VT) in the diabetic heart and determine the mechanism of an antiarrhythmic effect of statins., Methods: ECG transmitters were implanted in wild-type (WT), placebo, and pravastatin-treated type I diabetic Akita mice. MIs were induced by coronary ligation, and Ca 2+ transients were studied by optical mapping, and Ca 2+ transients and sparks in left ventricular myocytes (VM) by the Ionoptix system and confocal microscopy., Results: Burst pacing of Akita mouse hearts resulted in rate-related QRS/T-wave alternans, which was attenuated in pravastatin-treated mice. Post-MI Akita mice developed QRS/T-wave alternans and VT at 2820 ± 879 beats per mouse, which decreased to 343 ± 115 in pravastatin-treated mice (n = 13, P <.05). Optical mapping demonstrated pacing-induced VT originating in the peri-infarction zone and Ca 2+ alternans, both attenuated in hearts of statin-treated mice. Akita VM displayed Ca 2+ alternans, and triggered activity as well as increased Ca 2+ transient decay time (Tau), Ca 2+ sparks, and cytosolic Ca 2+ and decreased SR Ca 2+ stores all of which were in part reversed in cells from statin treated mice. Homogenates of Akita ventricles demonstrated decreased SERCA2a/PLB ratio and increased ratio of protein phosphatase (PP-1) to the PP-1 inhibitor PPI-1 which were reversed in homogenates of pravastatin-treated Akita mice., Conclusion: Pravastatin decreased the incidence of post-MI VT and Ca 2+ alternans in Akita mouse hearts in part by revering abnormalities of Ca 2+ handling via the PP-1/PPI-1 pathway., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Abdominal Aortic Aneurysm (AAA) is a major cause of mortality and morbidity in men over 65 years of age. Male apolipoprotein E knockout (ApoE(-/-)) mice infused with angiotensin II (AngII) develop AAA. Although AngII stimulates both JAK/STAT and Toll-like receptor 4 (TLR4) signaling pathways, their involvement in AngII mediated AAA formation is unclear. Here we used the small molecule STAT3 inhibitor, S3I-201, the TLR4 inhibitor Eritoran and ApoE(-/-)TLR4(-/-) mice to evaluate the interaction between STAT3 and TLR4 signaling in AngII-induced AAA formation. ApoE(-/-) mice infused for 28 days with AngII developed AAAs and increased STAT3 activation and TLR4 expression. Moreover, AngII increased macrophage infiltration and the ratio of M1 (pro-inflammatory)/M2 (healing) macrophages in aneurysmal tissue as early as 7-10 days after AngII infusion. STAT3 inhibition with S3I-201 decreased the incidence and severity of AngII-induced AAA formation and decreased MMP activity and the ratio of M1/M2 macrophages. Furthermore, AngII-mediated AAA formation, MMP secretion, STAT3 phosphorylation and the ratio of M1/M2 macrophages were markedly decreased in ApoE(-/-)TLR4(-/-) mice, and in Eritoran-treated ApoE(-/-) mice. TLR4 and pSTAT3 levels were also increased in human aneurysmal tissue. These data support a role of pSTAT3 in TLR4 dependent AAA formation and possible therapeutic roles for TLR4 and/or STAT3 inhibition in AAA., (Copyright © 2015 Elsevier Ltd. All rights reserved.)