NLRP3-mediated inflammation in cardio-oncology: sterile yet harmful

Despite significant advances and the continuous development of novel, effective therapies to treat a variety of malignancies, cancer therapy-induced cardiotoxicity has been identified as a prominent cause of morbidity and mortality, closely competing with secondary malignancies. This unfortunate limitation has prompted the inception of the field of cardio-oncology with its purpose to provide the necessary knowledge and key information on mechanisms that support the use of the most efficacious cancer therapy with minimal or no interruption while paying close attention to preventing cardiovascular related morbidity and mortality. Several mechanisms that contribute to cancer therapy-induced cardiotoxicity have been proposed and studied. These mainly involve mitochondrial dysfunction and reactive oxygen species-induced oxidative stress, lysosomal damage, impaired autophagy, cell senescence, DNA damage, and sterile inflammation with the formation and activation of the NLRP3 inflammasome. In this review, we focus on describing the principal mechanisms for different classes of cancer therapies that lead to cardiotoxicity involving the NLRP3 inflammasome. We also summarize current evidence of cardio-protection with inflammasome inhibitors in the context of heart disease in general, and further highlight the potential application of this evidence for clinical translation in at risk patients for the purpose of preventing cancer therapy associated cardiovascular morbidity and mortality.

Replacement of Lost Substance P Reduces Fibrosis in the Diabetic Heart by Preventing Adverse Fibroblast and Macrophage Phenotype Changes

Reduced levels of the sensory nerve neuropeptide substance P (SP) have been reported in the diabetic rat heart, the consequence being a loss of cardioprotection in response to ischemic post-conditioning. We considered whether this loss of SP also predisposes the heart to non-ischemic diabetic cardiomyopathy in the form of fibrosis and hypertrophy. We report that diabetic Leprdb/db mice have reduced serum SP and that administration of exogenous replacement SP ameliorated cardiac fibrosis. Cardiac hypertrophy did not occur in Leprdb/db mice. Cardiac fibroblasts exposed to high glucose converted to a myofibroblast phenotype and produced excess extracellular matrix proteins; this was prevented by the presence of SP in the culture media. Cardiac fibroblasts exposed to high glucose produced increased amounts of the receptor for advanced glycation end products, reactive oxygen species and inflammatory cytokines, all of which were prevented by SP. Cultured macrophages assumed an M1 pro-inflammatory phenotype in response to high glucose as indicated by increased TNF-α, CCL2, and IL-6. SP promoted a shift to the reparative M2 macrophage phenotype characterized by arginase-1 and IL-10. Leprdb/db mice showed increased left ventricular M1 phenotype macrophages and an increase in the M1/M2 ratio. Replacement SP in Leprdb/db mice restored a favorable M1 to M2 balance. Together these findings indicate that a loss of SP predisposes the diabetic heart to developing fibrosis. The anti-fibrotic actions of replacement SP involve direct effects on cardiac fibroblasts and macrophages to oppose adverse phenotype changes. This study identifies the potential of replacement SP to treat diabetic cardiomyopathy.

Abstract 267: Histomorphometric Evaluation of Estrogen Effects on Coronary Artery Atherosclerosis: Inhibition of Plaque Formation, Reduction in Plaque Size and Promotion of Positive Remodeling Independent of Plaque Complications

Introduction: Whether and to what extent postmenopausal estrogen therapy has beneficial effects on progression of coronary artery atherosclerosis is controversial. In previous studies with monkey models we have shown that the stage of plaque progression modulates estrogen benefits and have led to the “timing hypothesis”. In this study, we used a histomorphometric approach to understand better the effects of estrogen therapy on critical components of atherosclerosis pathogenesis. Our hypothesis was that estrogen therapy would inhibit the initial development of atherosclerotic plaques, result in smaller but not less complicated plaques and among subjects that developed plaques, it would promote positive arterial remodeling.

Methods: Forty-eight surgically postmenopausal monkeys (Macaca fascicularis) were fed a moderately atherogenic diet and randomly assigned to receive no treatment (CTL) or a women’s equivalent dose of conjugated equine estrogen (CEE) (0.45 mg/day). The experimental period lasted for 20 months (equivalent to 5 years in humans). At the end of the experiment, prevalence of atherosclerotic plaques was determined. From those monkeys with affected arteries, plaque extent, severity and prevalence of stenosis were determined.

Results: Prevalence: The CEE treated group had significantly fewer monkeys with coronary artery atherosclerosis compared to the CTL group (CTL: 57 % vs. CEE: 33 % p=0.005). Extent: Among affected monkeys, the mean plaque size was significantly smaller in the CEE treated group compared to the CTL group (CTL: 0.30 ± 0.048 mm2 vs. CEE: 0.153 ± 0.028 mm2 p=0.015). Remodeling: The proportion of stenotic plaques was lower in the CEE group compared to the CTL group (CTL: 11.14 % vs. CEE: 1.34 % p= 0.008). Severity: CEE treatment did not have a beneficial effect on coronary artery severity (% of complicated [AHA grade≥ III] plaques- CTL: 52.34 % vs. 49.61 %, p=0.397).

Conclusions: These histomorphometric findings support previous evidence that beginning of estrogen therapy in the perimenopausal transition prevents plaque initiation. Among affected cases, estrogen treated monkeys had smaller plaques but were equally complicated. Notably, estrogen also promoted positive arterial remodeling among affected arteries.

Novel bacterial immobilization compound effectively decreases bacterial counts in healthy volunteers

Skin flora immobilization technology is similar in efficacy to Iodine-Povidone in healthy volunteers. We did a prospective study in a university clinic with 60 healthy volunteers. Right inguinal skin area on healthy volunteers was used to compare the antimicrobial properties of cyanoacrylate sealant (FloraSeal, Adhesion Biomedical, Wyomissing, PA) versus standard surgical preparation Povidone-iodine (Betadine, Purdue Productions, Stamford, CT). Bacterial counts were measured at different time intervals: 15 minutes, 4 hours, and 24 hours. Bacterial colony forming units were compared between Povidone-iodine and cyanoacrylate sealant. The absolute log reduction was 5.568 for Povidone-iodine (7 absolute CFU); 5.028 for cyanoacrylate (59 absolute CFU); and 5.568 for Povidone-iodine and cyanoacrylate combined (21 absolute CFU). Cyanoacrylate was able to sustain a reduction on bacterial counts at 4 hours and 24 hours of more than 99.8 per cent as compared with the control group. Cyanoacrylate microbial sealant successfully reduces bacterial counts on normal healthy skin. The results were similar to Povidone-iodine alone. We believe this technology may be an excellent means of mitigating incisional surgical site infection by reducing the risk of contamination by skin flora and warrants further testing.

Novel Bacterial Immobilization Compound Effectively Decreases Bacterial Counts in Healthy Volunteers

Skin flora immobilization technology is similar in efficacy to Iodine-Povidone in healthy volunteers. We did a prospective study in a university clinic with 60 healthy volunteers. Right inguinal skin area on healthy volunteers was used to compare the antimicrobial properties of cyanoacrylate sealant (FloraSeal, Adhesion Biomedical, Wyomissing, PA) versus standard surgical preparation Povidone-iodine (Betadine, Purdue Productions, Stamford, CT). Bacterial counts were measured at different time intervals: 15 minutes, 4 hours, and 24 hours. Bacterial colony forming units were compared between Povidone-iodine and cyanoacrylate sealant. The absolute log reduction was 5.568 for Povidone-iodine (7 absolute CFU); 5.028 for cyanoacrylate (59 absolute CFU); and 5.568 for Povidone-iodine and cyanoacrylate combined (21 absolute CFU). Cyanoacrylate was able to sustain a reduction on bacterial counts at 4 hours and 24 hours of more than 99.8 per cent as compared with the control group. Cyanoacrylate microbial sealant successfully reduces bacterial counts on normal healthy skin. The results were similar to Povidone-iodine alone. We believe this technology may be an excellent means of mitigating incisional surgical site infection by reducing the risk of contamination by skin flora and warrants further testing.