Mapping the correlations between bandgap, HOMO, and LUMO trends for meta substituted Zn-MOFs.

Bandgap is a key property that determines electrical and optical properties in materials. Modulating the bandgap thus is critical in developing novel materials particularly semiconductors with improved features. This study examines the bandgap, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energy level trends in a metal organic framework, metal-organic framework 5 (MOF-5), as a function of Hammett substituent effect (with the constant σm in the meta-position of the benzene ring) and solvent dielectric effect (with the constant ε). Specifically, experimental design and response surface methodologies helped to assess the significance of trends and correlations between these molecular properties with σm and ε. While the HOMO and LUMO decrease with increasing σm, the LUMO exhibits greater sensitivity to the substituent's electron withdrawing capability. The relative difference in these trends helps to explain why the bandgap tends to decrease with increasing σm.

Factors associated with acute esophagitis during radiation therapy for lung cancer.

INTRODUCTION: Limiting acute esophagitis remains a clinical challenge during the treatment of locally advanced non-small cell lung cancer (NSCLC). METHODS: Demographic, dosimetric, and acute toxicity data were prospectively collected for patients undergoing definitive radiation therapy +/- chemotherapy for stage II-III NSCLC from 2012 to 2022 across a statewide consortium. Logistic regression models were used to characterize the risk of grade 2 + and 3 + esophagitis as a function of dosimetric and clinical covariates. Multivariate regression models were fitted to predict the 50 % risk of grade 2 esophagitis and 3 % risk of grade 3 esophagitis. RESULTS: Of 1760 patients, 84.2 % had stage III disease and 85.3 % received concurrent chemotherapy. 79.2 % of patients had an ECOG performance status ≤ 1. Overall rates of acute grade 2 + and 3 + esophagitis were 48.4 % and 2.2 %, respectively. On multivariate analyses, performance status, mean esophageal dose (MED) and minimum dose to the 2 cc of esophagus receiving the highest dose (D2cc) were significantly associated with grade 2 + and 3 + esophagitis. Concurrent chemotherapy was associated with grade 2 + but not grade 3 + esophagitis. For all patients, MED of 29 Gy and D2cc of 61 Gy corresponded to a 3 % risk of acute grade 3 + esophagitis. For patients receiving chemotherapy, MED of 22 Gy and D2cc of 50 Gy corresponded to a 50 % risk of acute grade 2 + esophagitis. CONCLUSIONS: Performance status, concurrent chemotherapy, MED and D2cc are associated with acute esophagitis during definitive treatment of NSCLC. Models that quantitatively account for these factors can be useful in individualizing radiation plans.

Factors Associated With Cardiac Radiation Dose Reduction After Hypofractionated Radiation Therapy for Localized, Left-Sided Breast Cancer in a Large Statewide Quality Consortium.

PURPOSE: Limiting cardiac radiation dose is important for minimizing long-term cardiac toxicity in patients with left-sided early-stage breast cancer. METHODS AND MATERIALS: Prospectively collected dosimetric data were analyzed for patients undergoing moderately hypofractionated radiation therapy to the left breast within the Michigan Radiation Oncology Quality Consortium from 2016 to 2022. The mean heart dose (MHD) goal was progressively tightened from ≤2 Gy in 2016 to MHD ≤ 1.2 Gy in 2018. In 2021, a planning target volume (PTV) coverage goal was added, and the goal MHD was reduced to ≤1 Gy. Multivariate logistic regression models were developed to assess for covariates associated with meeting the MHD goals in 2016 to 2020 and the combined MHD/PTV coverage goal in 2021 to 2022. RESULTS: In total, 4165 patients were analyzed with a median age of 64 years. Overall average cardiac metric compliance was 91.7%. Utilization of motion management increased from 41.8% in 2016 to 2020 to 46.5% in 2021 to 2022. Similarly, use of prone positioning increased from 12.2% to 22.2% in these periods. On multivariate analysis in the 2016 to 2020 cohort, treatment with motion management (odds ratio [OR], 5.20; 95% CI, 3.59-7.54; P < .0001) or prone positioning (OR, 3.21; 95% CI, 1.85-5.57; P < .0001) was associated with meeting the MHD goal, while receipt of boost (OR, 0.25; 95% CI, 0.17-0.39; P < .0001) and omission of hormone therapy (OR, 0.65; 95% CI, 0.49-0.88; P = .0047) were associated with not meeting the MHD goal. From 2021 to 2022, treatment with motion management (OR, 1.89; 95% CI, 1.12-3.21; P = .018) or prone positioning (OR, 3.71; 95% CI, 1.73-7.95; P = .0008) was associated with meeting the combined MHD/PTV goal, while larger breast volume (≥1440 cc; OR, 0.34; 95% CI, 0.13-0.91; P = .031) was associated with not meeting the combined goal. CONCLUSIONS: In our statewide consortium, high rates of compliance with aggressive targets for limiting cardiac dose were achievable without sacrificing target coverage.

National Long-term Survival Estimates After Radical Prostatectomy for Prostate Cancer.

OBJECTIVE: To examine survival and disease control outcomes, including metastasis-related survival outcomes, in a large contemporary cohort of patients undergoing radical prostatectomy for localized prostate cancer. METHODS: We conducted a retrospective study of men with localized prostate cancer treated with radical prostatectomy from 2005 to 2015 with follow-up through 2019 in the Veterans Health Administration. We defined biochemical recurrence (BCR) as a prostate-specific antigen ≥0.2 ng/mL. We used a validated natural language processing encoded dataset to identify incident metastatic prostate cancer. We estimated overall survival from time of surgery, time of BCR, and time of first metastasis using the Kaplan-Meier method. We then estimated time from surgery to BCR, BCR to metastatic disease, and prostate-cancer-specific survival from various time points using cumulative incidence considering competing risk of death. RESULTS: Of 21,992 men undergoing radical prostatectomy, we identified 5951 (27%) who developed BCR. Of men with BCR, 677 (11%) developed metastases. We estimated the 10-year cumulative incidence of BCR and metastases after BCR were 28% and 20%, respectively. Median overall survival after BCR was 14years, with 10-year survival of 70%. From the time of metastasis, median overall survival approached 7years, with 10-year overall survival of 34%. Prostate cancer-specific survival for the entire cohort at 10years was 94%. CONCLUSION: In this large contemporary national cohort, survival for men with biochemically recurrent prostate cancer is longer than historical cohorts. When counseling patients and designing clinical studies, these updated estimates may serve as more reliable reflections of current outcomes.

A Phase II Study of Optimized Individualized Adaptive Radiotherapy for Hepatocellular Carcinoma.

PURPOSE: We hypothesized that optimizing the utility of stereotactic body radiotherapy (SBRT) based on the individual patient's probability for tumor control and risk of liver injury would decrease toxicity without sacrificing local control in patients with impaired liver function or tumors not amenable to thermal ablation. PATIENTS AND METHODS: Patients with Child-Pugh (CP) A to B7 liver function with aggregate tumor size >3.5 cm, or CP ≥ B8 with any size tumor were prospectively enrolled on an Institutional Review Board-approved phase II clinical trial to undergo SBRT with baseline and midtreatment dose optimization using a quantitative, individualized utility-based analysis. Primary endpoints were change in CP score of ≥2 points within 6 months and local control. Protocol-treated patients were compared with patients receiving conventional SBRT at another cancer center using overlap weighting. RESULTS: A total of 56 patients with 80 treated tumors were analyzed with a median follow-up of 11.2 months. Two-year cumulative incidence of local progression was 6.4% [95% confidence interval (CI, 2.4-13.4)]. Twenty-one percent of patients experienced treatment-related toxicity within 6 months, which is similar to the rate for SBRT in patients with CP A liver function. An analysis using overlap weighting revealed similar local control [HR, 0.69; 95% CI (0.25-1.91); P = 0.48] and decreased toxicity [OR, 0.26; 95% CI (0.07-0.99); P = 0.048] compared with conventional SBRT. CONCLUSIONS: Treatment of individuals with impaired liver function or tumors not amenable to thermal ablation with a treatment paradigm designed to optimize utility may decrease treatment-related toxicity while maintaining tumor control.

Outcomes after definitive radiation therapy for localized prostate cancer in a national health care delivery system.

PURPOSE: Accurate information regarding real-world outcomes after contemporary radiation therapy for localized prostate cancer is important for shared decision-making. Clinically relevant end points at 10 years among men treated within a national health care delivery system were examined. METHODS: National administrative, cancer registry, and electronic health record data were used for patients undergoing definitive radiation therapy with or without concurrent androgen deprivation therapy within the Veterans Health Administration from 2005 to 2015. National Death Index data were used through 2019 for overall and prostate cancer-specific survival and identified date of incident metastatic prostate cancer using a validated natural language processing algorithm. Metastasis-free, prostate cancer-specific, and overall survival using Kaplan-Meier methods were estimated. RESULTS: Among 41,735 men treated with definitive radiation therapy, the median age at diagnosis was 65 years and median follow-up was 8.7 years. Most had intermediate (42%) and high-risk (33%) disease, with 40% receiving androgen deprivation therapy as part of initial therapy. Unadjusted 10-year metastasis-free survival was 96%, 92%, and 80% for low-, intermediate-, and high-risk disease. Similarly, unadjusted 10-year prostate cancer-specific survival was 98%, 97%, and 90% for low-, intermediate-, and high-risk disease. The unadjusted overall survival was lower across increasing disease risk categories at 77%, 71%, and 62% for low-, intermediate-, and high-risk disease (p < .001). CONCLUSIONS: These data provide population-based 10-year benchmarks for clinically relevant end points, including metastasis-free survival, among patients with localized prostate cancer undergoing radiation therapy using contemporary techniques. The survival rates for high-risk disease in particular suggest that outcomes have recently improved.

Advances in Radiation Therapy for Primary Liver Cancer.

During the past 30 years, several advances have been made allowing for safer and more effective treatment of patients with liver cancer. This report reviews recent advances in radiation therapy for primary liver cancers including hepatocellular carcinoma and intrahepatic cholangiocarcinoma. First, studies focusing on liver stereotactic body radiation therapy (SBRT) are reviewed focusing on lessons learned and knowledge gained from early pioneering trials. Then, new technologies to enhance SBRT treatments are explored including adaptive therapy and MRI-guided and biology-guided radiation therapy. Finally, treatment with Y-90 transarterial radioembolization is reviewed with a focus on novel approaches focused on personalized therapy.

Cardiac and Pulmonary Dosimetric Parameters in Patients With Lung Cancer Undergoing Postoperative Radiation Therapy Across a Statewide Consortium.

PURPOSE: The recently published Lung Adjuvant Radiotherapy Trial (Lung ART) reported increased rates of cardiac and pulmonary toxic effects in the postoperative radiation therapy (PORT) arm. It remains unknown whether the dosimetric parameters reported in Lung ART are representative of contemporary real-world practice, which remains relevant for patients undergoing PORT for positive surgical margins. The purpose of this study was to examine heart and lung dose exposure in patients receiving PORT for non-small cell lung cancer across a statewide consortium. METHODS AND MATERIALS: From 2012 to 2022, demographic and dosimetric data were prospectively collected for 377 patients at 27 academic and community centers within the Michigan Radiation Oncology Quality Consortium undergoing PORT for nonmetastatic non-small cell lung cancer. Dosimetric parameters for target coverage and organ-at-risk exposure were calculated using data from dose-volume histograms, and rates of 3-dimensional conformal radiation therapy (3D-CRT) and intensity modulated radiation therapy (IMRT) utilization were assessed. RESULTS: Fifty-one percent of patients in this cohort had N2 disease at the time of surgery, and 25% had a positive margin. Sixty-six percent of patients were treated with IMRT compared with 32% with 3D-CRT. The planning target volume was significantly smaller in patients treated with 3D-CRT (149.2 vs 265.4 cm3; P < .0001). The median mean heart dose for all patients was 8.7 Gy (interquartile range [IQR], 3.5-15.3 Gy), the median heart volume receiving at least 5 Gy (V5) was 35.2% (IQR, 18.5%-60.2%), and the median heart volume receiving at least 35 Gy (V35) was 9% (IQR, 3.2%-17.7%). The median mean lung dose was 11.4 Gy (IQR, 8.1-14.3 Gy), and the median lung volume receiving at least 20 Gy (V20) was 19.6% (IQR, 12.7%-25.4%). These dosimetric parameters did not significantly differ by treatment modality (IMRT vs 3D-CRT) or in patients with positive versus negative surgical margins. CONCLUSIONS: With increased rates of IMRT use, cardiac and lung dosimetric parameters in this statewide consortium were slightly lower than those reported in Lung ART. These data provide useful benchmarks for treatment planning in patients undergoing PORT for positive surgical margins.

Cannabis Use in Patients Seen in an Academic Radiation Oncology Department.

PURPOSE: Cannabis use rates are increasing in the United States. Patients with cancer use cannabis for many reasons, even without high-quality supporting data. This study sought to characterize cannabis use among patients seen in radiation oncology in a state that has legalized adult nonmedical use cannabis and to identify key cannabis-related educational topics. METHODS AND MATERIALS: Cannabis history was documented by providers using a structured template at patient visits in an academic radiation oncology practice October 2020 to November 2021. Cannabis use data, including recency/frequency of use, reason, and mode of administration, were summarized, and logistic regression was used to explore associations between patient and disease characteristics and recent cannabis use. A multivariable model employed stepwise variable selection using the Akaike Information Criterion. RESULTS: Of 3143 patients total, 91 (2.9%) declined to answer cannabis use questions, and 343 (10.9%) endorsed recent use (≤1 month ago), 235 (7.5%) noted nonrecent use (>1 month ago), and 2474 (78.7%) denied history of cannabis use. In multivariable analyses, those ≥50 years old (odds ratio [OR], 0.409; 95% confidence interval [CI], 0.294-0.568; P < .001) or with history of prior courses of radiation (OR, 0.748; 95% CI, 0.572-0.979; P = .034) were less likely, and those with a mental health diagnosis not related to substance use (OR, 1.533; 95% CI, 1.171-2.005; P = .002) or who smoked tobacco (OR, 3.003; 95% CI, 2.098-4.299; P < .001) were more likely to endorse recent cannabis use. Patients reported pain, insomnia, and anxiety as the most common reasons for use. Smoking was the most common mode of administration. CONCLUSIONS: Patients are willing to discuss cannabis use with providers and reported recent cannabis use for a variety of reasons. Younger patients new to oncologic care and those with a history of mental illness or tobacco smoking may benefit most from discussions about cannabis given higher rates of cannabis use in these groups.

Effect of Education and Standardization of Cardiac Dose Constraints on Heart Dose in Patients With Lung Cancer Receiving Definitive Radiation Therapy Across a Statewide Consortium.

PURPOSE: Cardiac radiation exposure is associated with an increased rate of adverse cardiac events in patients receiving radiation therapy for locally advanced non-small cell lung carcinoma (NSCLC). Previous analysis of practice patterns within the Michigan Radiation Oncology Quality Consortium (MROQC) revealed 1 in 4 patients received a mean heart dose >20 Gy and significant heterogeneity existed among treatment centers in using cardiac dose constraints. The purpose of this study is to analyze the effect of education and initiation of standardized cardiac dose constraints on heart dose across a statewide consortium. METHODS AND MATERIALS: From 2012 to 2020, 1681 patients from 27 academic and community centers who received radiation therapy for locally advanced NSCLC were included in this analysis. Dosimetric endpoints including mean heart dose (MHD), mean lung dose, and mean esophagus dose were calculated using data from dose-volume histograms. These dose metrics were grouped by year of treatment initiation for all patients. Education regarding data for cardiac dose constraints first occurred in small lung cancer working group meetings and then consortium-wide starting in 2016. In 2018, a quality metric requiring mean heart dose <20 Gy while maintaining dose coverage (D95) to the target was implemented. Dose metrics were compared before (2012-2016) versus after (2017-2020) initiation of interventions targeting cardiac constraints. Statistical analysis was performed using the Wilcoxon rank sum test. RESULTS: After education and implementation of the heart dose performance metric, mean MHD declined from an average of 12.2 Gy preintervention to 10.4 Gy postintervention (P < .0001), and the percentage of patients receiving MHD >20 Gy was reduced from 21.1% to 10.3% (P < .0001). Mean lung dose and mean esophagus dose did not increase, and target coverage remained unchanged. CONCLUSIONS: Education and implementation of a standardized cardiac dose quality measure across a statewide consortium was associated with a reduction of mean heart dose in patients receiving radiation therapy for locally advanced NSCLC. These dose reductions were achieved without sacrificing target coverage, increasing mean lung dose, or increasing mean esophagus dose. Analysis of the clinical ramifications of the reduction in cardiac doses is ongoing.

Long-term outcome comparison for standard fractionation (>59 Gy) versus hyperfractionated (>45 Gy) radiotherapy plus concurrent chemotherapy for limited-stage small-cell lung cancer.

BACKGROUND: Concurrent chemoradiotherapy (CCRT) is commonly employed in limited-stage small-cell lung cancer (LS-SCLC); however, the optimal radiotherapy regimen is still unknown. This 3-institution analysis compares long-term disease control and survival outcomes for once- (QD) versus twice-daily (BID) radiotherapy at contemporary doses. METHODS AND MATERIALS: Data were collected for LS-SCLC patients treated with platinum-based CCRT and planned RT doses of >5940 cGy at >180 cGy QD or >4500 cGy at 150 cGy BID. Comparative outcome analyses were performed for treatment groups. RESULTS: From 2005 through 2014, 132 patients met inclusion criteria for analysis (80 QD, 52 BID). Treatment groups were well-balanced, excepting higher rate of advanced mediastinal staging, longer interval from biopsy to treatment initiation, and lower rate of prophylactic cranial irradiation for the QD group, as well as institutional practice variation. At median survivor follow-up of 33.5 months (range, 4.6-105.8), 80 patients experienced disease failure (44 QD, 36 BID), and 106 died (62 QD, 44 BID). No differences in disease control or survival were demonstrated between treatment groups. CONCLUSION: The present analysis did not detect a difference in disease control or survival outcomes for contemporary dose QD versus BID CCRT in LS-SCLC.

Regulation of metabolism by mitochondrial enzyme acetylation in cardiac ischemia-reperfusion injury.

Ischemia reperfusion injury (I/R injury) contributes significantly to morbidity and mortality following myocardial infarction (MI). Although rapid reperfusion of the ischemic myocardium was established decades ago as a highly beneficial therapy for MI, significant cell death still occurs after the onset of reperfusion. Mitochondrial dysfunction is closely associated with I/R injury, resulting in the uncontrolled production of reactive oxygen species (ROS). Considerable efforts have gone into understanding the metabolic perturbations elicited by I/R injury. Recent work has identified the critical role of reversible protein acetylation in maintaining normal mitochondrial biologic function and energy metabolism both in the normal heart and during I/R injury. Several studies have shown that modification of class I HDAC and/or Sirtuin (Sirt) activity is cardioprotective in the setting of I/R injury. A better understanding of the role of these metabolic pathways in reperfusion injury and their regulation by reversible protein acetylation presents a promising way forward in improving the treatment of cardiac reperfusion injury. Here we briefly review some of what is known about how acetylation regulates mitochondrial metabolism and how it relates to I/R injury.

Angiokine Wisp-1 is increased in myocardial infarction and regulates cardiac endothelial signaling.

Myocardial infarctions (MIs) cause the loss of myocytes due to lack of sufficient oxygenation and latent revascularization. Although the administration of histone deacetylase (HDAC) inhibitors reduces the size of infarctions and improves cardiac physiology in small-animal models of MI injury, the cellular targets of the HDACs, which the drugs inhibit, are largely unspecified. Here, we show that WNT-inducible secreted protein-1 (Wisp-1), a matricellular protein that promotes angiogenesis in cancers as well as cell survival in isolated cardiac myocytes and neurons, is a target of HDACs. Further, Wisp-1 transcription is regulated by HDACs and can be modified by the HDAC inhibitor, suberanilohydroxamic acid (SAHA/vorinostat), after MI injury. We observe that, at 7 days after MI, Wisp-1 is elevated 3-fold greater in the border zone of infarction in mice that experience an MI injury and are injected daily with SAHA, relative to MI alone. Additionally, human coronary artery endothelial cells (HCAECs) produce WISP-1 and are responsive to autocrine WISP-1-mediated signaling, which functionally promotes their proangiogenic behavior. Altering endogenous expression of WISP-1 in HCAECs directly impacts their network density in vitro. Therapeutic interventions after a heart attack define the extent of infarct injury, cell survival, and overall prognosis. Our studies shown here identify a potentially novel cardiac angiokine, Wisp-1, that may contribute to beneficial post-MI treatment modalities.

HDAC1 localizes to the mitochondria of cardiac myocytes and contributes to early cardiac reperfusion injury.

RATIONALE: Recent evidence indicates that histone deacetylase enzymes (HDACs) contribute to ischemia reperfusion (I/R) injury, and pan-HDAC inhibitors have been shown to be cardioprotective when administered either before an ischemic insult or during reperfusion. We have shown previously that selective inhibition of class I HDACs provides superior cardioprotection when compared to pan-HDAC inhibition in a pretreatment model, but selective class I HDAC inhibition has not been tested during reperfusion, and specific targets of class I HDACs in I/R injury have not been identified. OBJECTIVE: We hypothesized that selective inhibition of class I HDACs with the drug MS-275 (entinostat) during reperfusion would improve recovery from I/R injury in the first hour of reperfusion. METHODS AND RESULTS: Hearts from male Sprague-Dawley rats were subjected to ex vivo I/R injury±MS-275 class I HDAC inhibition during reperfusion alone. MS-275 significantly attenuated I/R injury, as indicated by improved LV function and tissue viability at the end of reperfusion. Unexpectedly, we observed that HDAC1 is present in the mitochondria of cardiac myocytes, but not fibroblasts or endothelial cells. We then designed mitochondria-restricted and mitochondria-excluded HDAC inhibitors, and tested both in our ex vivo I/R model. The selective inhibition of mitochondrial HDAC1 attenuated I/R injury to the same extent as MS-275, whereas the mitochondrial-excluded inhibitor did not. Further assays demonstrated that these effects are attributable to a decrease in SDHA activity and subsequent metabolic ROS production in reperfusion. CONCLUSIONS: We demonstrate for the first time that HDAC1 is present within the mitochondria of cardiac myocytes, and mitochondrial HDAC1 contributes significantly to I/R injury within the first hour of reperfusion.

Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts.

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for myocardial infarction and cardiac complications of thoracic surgery. The ability of certain drugs to precondition the myocardium against ischemia reperfusion injury has led to multiple clinical trials, with little success. The isolated heart model allows acute observation of the functional effects of ischemia reperfusion injury in real time, including the effects of various pharmacological interventions administered at any time-point before or within the ischemia-reperfusion injury window. Since brief periods of ischemia can precondition the heart against ischemic injury, in situ aortic cannulation is performed to allow for functional assessment of non-preconditioned myocardium. A saline filled balloon is placed into the left ventricle to allow for real-time measurement of pressure generation. Ischemic injury is simulated by the cessation of perfusion buffer flow, followed by reperfusion. The duration of both ischemia and reperfusion can be modulated to examine biochemical events at any given time-point. Although the Langendorff isolated heart model does not allow for the consideration of systemic events affecting ischemia and reperfusion, it is an excellent model for the examination of acute functional and biochemical events within the window of ischemia reperfusion injury as well as the effect of pharmacological intervention on cardiac pre- and postconditioning. The goal of this protocol is to demonstrate how to perform in situ aortic cannulation and heart excision followed by ischemia/reperfusion injury in the Langendorff model.

Histone Deacetylases Exert Class-Specific Roles in Conditioning the Brain and Heart Against Acute Ischemic Injury.

Ischemia-reperfusion (IR) injury comprises a significant portion of morbidity and mortality from heart and brain diseases worldwide. This enduring clinical problem has inspired myriad reports in the scientific literature of experimental interventions seeking to elucidate the pathology of IR injury. Elective cardiac surgery presents perhaps the most viable scenario for protecting the heart and brain from IR injury due to the opportunity to condition the organs prior to insult. The physiological parameters for the preconditioning of vital organs prior to insult through mechanical and pharmacological maneuvers have been heavily examined. These investigations have revealed new insights into how preconditioning alters cellular responses to IR injury. However, the promise of preconditioning remains unfulfilled at the clinical level, and research seeking to implicate cell signals essential to this protection continues. Recent discoveries in molecular biology have revealed that gene expression can be controlled through posttranslational modifications, without altering the chemical structure of the genetic code. In this scenario, gene expression is repressed by enzymes that cause chromatin compaction through catalytic removal of acetyl moieties from lysine residues on histones. These enzymes, called histone deacetylases (HDACs), can be inhibited pharmacologically, leading to the de-repression of protective genes. The discovery that HDACs can also alter the function of non-histone proteins through posttranslational deacetylation has expanded the potential impact of HDAC inhibitors for the treatment of human disease. HDAC inhibitors have been applied in a very small number of experimental models of IR. However, the scientific literature contains an increasing number of reports demonstrating that HDACs converge on preconditioning signals in the cell. This review will describe the influence of HDACs on major preconditioning signaling pathways in the heart and brain.

Selective inhibition of class I but not class IIb histone deacetylases exerts cardiac protection from ischemia reperfusion.

While inhibition of class I/IIb histone deacetylases (HDACs) protects the mammalian heart from ischemia reperfusion (IR) injury, class selective effects remain unexamined. We hypothesized that selective inhibition of class I HDACs would preserve left ventricular contractile function following IR in isolated hearts. Male Sprague Dawley rats (n=6 per group) were injected with vehicle (dimethylsulfoxide, 0.63mg/kg), the class I/IIb HDAC inhibitor trichostatin A (1mg/kg), the class I HDAC inhibitor entinostat (MS-275, 10mg/kg), or the HDAC6 (class IIb) inhibitor tubastatin A (10mg/kg). After 24h, hearts were isolated and perfused in Langendorff mode for 30min (Sham) or subjected to 30min global ischemia and 120min global reperfusion (IR). A saline filled balloon attached to a pressure transducer was placed in the LV to monitor contractile function. After perfusion, LV tissue was collected for measurements of antioxidant protein levels and infarct area. At the conclusion of IR, MS-275 pretreatment was associated with significant preservation of developed pressure, rate of pressure generation, rate of pressure relaxation and rate pressure product, as compared to vehicle treated hearts. There was significant reduction of infarct area with MS-275 pretreatment. Contractile function was not significantly restored in hearts treated with trichostatin A or tubastatin A. Mitochondrial superoxide dismutase (SOD2) and catalase protein and mRNA in hearts from animals pretreated with MS-275 were increased following IR, as compared to Sham. This was associated with a dramatic enrichment of nuclear FOXO3a transcription factor, which mediates the expression of SOD2 and catalase. Tubastatin A treatment was associated with significantly decreased catalase levels after IR. Class I HDAC inhibition elicits protection of contractile function following IR, which is associated with increased expression of endogenous antioxidant enzymes. Class I/IIb HDAC inhibition with trichostatin A or selective inhibition of HDAC6 with tubastatin A was not protective. This study highlights the need for the development of new strategies that target specific HDAC isoforms in cardiac ischemia reperfusion.