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Purpose:To determine the pharmacokinetics and skin toxicity profile of sorafenib in children with refractory/relapsed malignancies.Patients and Methods:Sorafenib was administered concurrently or sequentially with clofarabine and cytarabine to patients with leukemia or with bevacizumab and cyclophosphamide to patients with solid tumor malignancies. The population pharmacokinetics (PPK) of sorafenib and its metabolites and skin toxicities were evaluated.Results:In PPK analysis, older age, bevacizumab and cyclophosphamide regimen, and higher creatinine were associated with decreased sorafenib apparent clearance (CL/f; P < 0.0001 for all), and concurrent clofarabine and cytarabine administration was associated with decreased sorafenib N-oxide CL/f (P = 7e−4). Higher bilirubin was associated with decreased sorafenib N-oxide and glucuronide CL/f (P = 1e−4). Concurrent use of organic anion-transporting polypeptide 1B1 inhibitors was associated with increased sorafenib and decreased sorafenib glucuronide CL/f (P < 0.003). In exposure–toxicity analysis, a shorter time to development of grade 2–3 hand–foot skin reaction (HFSR) was associated with concurrent (P = 0.0015) but not with sequential (P = 0.59) clofarabine and cytarabine administration, compared with bevacizumab and cyclophosphamide, and with higher steady-state concentrations of sorafenib (P = 0.0004) and sorafenib N-oxide (P = 0.0275). In the Bayes information criterion model selection, concurrent clofarabine and cytarabine administration, higher sorafenib steady-state concentrations, larger body surface area, and previous occurrence of rash appeared in the four best two-predictor models of HFSR. Pharmacokinetic simulations showed that once-daily and every-other-day sorafenib schedules would minimize exposure to sorafenib steady-state concentrations associated with HFSR.Conclusions:Sorafenib skin toxicities can be affected by concurrent medications and sorafenib steady-state concentrations. The described PPK model can be used to refine exposure–response relations for alternative dosing strategies to minimize skin toxicity.

Acute myeloid leukemia (AML) with mutations in the tumor suppressor gene TP53 confers a dismal prognosis with 3-year overall survival of

Oral anticancer drugs suffer from significant variability in pharmacokinetics and pharmacodynamics partially due to limited bioavailability. The limited bioavailability of anticancer drugs is due to both pharmaceutical limitations and physiological barriers. Pharmacokinetic boosting is a strategy to enhance the oral bioavailability of a therapeutic drug by inhibiting physiological barriers through an intentional drug-drug interaction (DDI). This type of strategy has proven effective across several therapeutic indications including anticancer treatment. Pharmacokinetic boosting could improve anticancer drugs lacking or with otherwise unacceptable oral formulations through logistic, economic, pharmacodynamic, and pharmacokinetic benefits. Despite these benefits, pharmacokinetic boosting strategies could result in unintended DDIs and are only likely to benefit a limited number of targets. Highlighting this concern, pharmacokinetic boosting has mixed results depending on the boosted drug. While pharmacokinetic boosting did not significantly improve certain drugs, it has resulted in the commercial approval of boosted oral formulations for other drugs. Pharmacokinetic boosting to improve oral anticancer therapy is an expanding area of research that is likely to improve treatment options for cancer patients.

Dofetilide is a rapid delayed rectifier potassium current inhibitor widely used to prevent the recurrence of atrial fibrillation and flutter. The clinical use of this drug is associated with increases in QTc interval, which predispose patients to ventricular cardiac arrhythmias. The mechanisms involved in the disposition of dofetilide, including its movement in and out of cardiomyocytes, remain unknown. Using a xenobiotic transporter screen, we identified MATE1 (SLC47A1) as a transporter of dofetilide and found that genetic knockout or pharmacological inhibition of MATE1 in mice was associated with enhanced retention of dofetilide in cardiomyocytes and increased QTc prolongation. The urinary excretion of dofetilide was also dependent on the MATE1 genotype, and we found that this transport mechanism provides a mechanistic basis for previously recorded drug-drug interactions of dofetilide with various contraindicated drugs, including bictegravir, cimetidine, ketoconazole, and verapamil. The translational significance of these observations was examined with a physiologically-based pharmacokinetic model that adequately predicted the drug-drug interaction liabilities in humans. These findings support the thesis that MATE1 serves a conserved cardioprotective role by restricting excessive cellular accumulation and warrant caution against the concurrent administration of potent MATE1 inhibitors and cardiotoxic substrates with a narrow therapeutic window.

Glycochenodeoxycholate-3-sulfate (GCDCA-S) and chenodeoxycholate-24-glucuronide (CDCA-24G) are bile acid metabolites that potentially serve as endogenous biomarkers for drug-drug interactions mediated by the hepatic uptake transporters OATP1B1 and OATP1B3. We developed and validated a novel UHPLC-MS/MS method for the quantitative determination of GCDCA-S and CDCA-24G in mouse and human plasma with a lower limit of quantitation of 0.5 ng/mL. Chromatographic separation was achieved on an Accucore aQ column (50 mm × 2.1 mm, dp = 2.6 μm) maintained at 20 °C and a gradient mobile phase comprising 2 mM ammonium acetate in water and methanol. The extraction recoveries of GCDCA-S and CDCA-24G were80 %, and linear (r

Peripheral neurotoxicity is a debilitating toxicity that afflicts up to 90% of patients with colorectal cancer receiving oxaliplatin-containing therapy. Although emerging evidence has highlighted the importance of various solute carriers to the toxicity of anticancer drugs, the contribution of these proteins to oxaliplatin-induced peripheral neurotoxicity remains controversial. Among candidate transporters investigated in genetically-engineered mouse models, we provide evidence for a critical role of the organic cation transporter 2 (OCT2) in satellite glial cells to oxaliplatin-induced neurotoxicity, and demonstrate that targeting OCT2 using genetic and pharmacological approaches ameliorates acute and chronic forms of neurotoxicity. The relevance of this transport system was verified in transporter-deficient rats as a secondary model organism, and translational significance of preventative strategies was demonstrated in preclinical models of colorectal cancer. These studies suggest that pharmacological targeting of OCT2 could be exploited to afford neuroprotection in cancer patients requiring treatment with oxaliplatin.

Despite the clinical benefit associated with gilteritinib in relapsed/refractory acute myeloid leukemia (AML), most patients eventually develop resistance through unknown mechanisms. To delineate the mechanistic basis of resistance to gilteritinib, we performed targeted sequencing and scRNASeq on primary FLT3-ITD-mutated AML samples. Co-occurring mutations in RAS pathway genes were the most common genetic abnormalities, and unresponsiveness to gilteritinib was associated with increased expression of bone marrow-derived hematopoietic cytokines and chemokines. In particular, we found elevated expression of the TEK-family kinase, BMX, in gilteritinib-unresponsive patients pre- and post-treatment. BMX contributed to gilteritinib resistance in FLT3-mutant cell lines in a hypoxia-dependent manner by promoting pSTAT5 signaling, and these phenotypes could be reversed with pharmacological inhibition and genetic knockout. We also observed that inhibition of BMX in primary FLT3-mutated AML samples decreased chemokine secretion and enhanced the activity of gilteritinib. Collectively, these findings indicate a crucial role for microenvironment-mediated factors modulated by BMX in the escape from targeted therapy and have implications for the development of novel therapeutic interventions to restore sensitivity to gilteritinib.

Ibrutinib (Imbruvica; PCI-32765) is an orally administered inhibitor of Bruton's tyrosine kinase that has transformed the treatment of B-cell malignancies. However, ibrutinib has very low oral bioavailability that contributes to significant variability in systemic exposure between patients, and this has the potential to affect both efficacy and toxicity. We hypothesized that the oral bioavailability of ibrutinib is limited by CYP3A isoform–mediated metabolism, and that this pathway can be inhibited to improve the pharmacokinetic properties of ibrutinib. Pharmacokinetic studies were performed in wild-type mice and mice genetically engineered to lack all CYP3A isoforms (CYP3A−/−) that received ibrutinib alone or in combination with CYP3A inhibitors cobicistat or ketoconazole. Computational modeling was performed to derive doses of ibrutinib that, when given after a CYP3A inhibitor, results in therapeutically relevant drug levels. Deficiency of CYP3A in mice was associated with an approximately 10-fold increase in the AUC of ibrutinib. This result could be phenocopied by administration of cobicistat before ibrutinib in wild-type mice, but cobicistat did not influence levels of ibrutinib in CYP3A−/− mice. Population pharmacokinetic and prospectively validated physiologically based pharmacokinetic models established preclinical and clinical doses of ibrutinib that could be given safely in combination with cobicistat without negatively affecting antileukemic properties. These findings signify a dominant role for CYP3A-mediated metabolism in the elimination of ibrutinib, and suggest a role for pharmacologic inhibitors of this pathway to intentionally modulate the plasma levels and improve the therapeutic use of this clinically important agent. Significance: Ibrutinib has limited oral bioavailability, which contributes to significant interindividual pharmacokinetic variability. Using engineered mouse models, we here report a causal relationship between CYP3A-mediated metabolism and ibrutinib's bioavailability and drug–drug interaction with cobicistat. These results offer a mechanistic basis for reported pharmacokinetic interactions with ibrutinib, and in conjunction with a newly developed computational model, allow for the rational design of clinical trials aimed at improving the therapeutic use of ibrutinib.

Purpose: To determine the pharmacokinetics and skin toxicity profile of sorafenib in children with refractory/relapsed malignancies. Patients and Methods: Sorafenib was administered concurrently or sequentially with clofarabine and cytarabine to patients with leukemia or with bevacizumab and cyclophosphamide to patients with solid tumor malignancies. The population pharmacokinetics (PPK) of sorafenib and its metabolites and skin toxicities were evaluated. Results: In PPK analysis, older age, bevacizumab and cyclophosphamide regimen, and higher creatinine were associated with decreased sorafenib apparent clearance (CL/f; P < 0.0001 for all), and concurrent clofarabine and cytarabine administration was associated with decreased sorafenib N-oxide CL/f (P = 7e−4). Higher bilirubin was associated with decreased sorafenib N-oxide and glucuronide CL/f (P = 1e−4). Concurrent use of organic anion-transporting polypeptide 1B1 inhibitors was associated with increased sorafenib and decreased sorafenib glucuronide CL/f (P < 0.003). In exposure–toxicity analysis, a shorter time to development of grade 2–3 hand–foot skin reaction (HFSR) was associated with concurrent (P = 0.0015) but not with sequential (P = 0.59) clofarabine and cytarabine administration, compared with bevacizumab and cyclophosphamide, and with higher steady-state concentrations of sorafenib (P = 0.0004) and sorafenib N-oxide (P = 0.0275). In the Bayes information criterion model selection, concurrent clofarabine and cytarabine administration, higher sorafenib steady-state concentrations, larger body surface area, and previous occurrence of rash appeared in the four best two-predictor models of HFSR. Pharmacokinetic simulations showed that once-daily and every-other-day sorafenib schedules would minimize exposure to sorafenib steady-state concentrations associated with HFSR. Conclusions: Sorafenib skin toxicities can be affected by concurrent medications and sorafenib steady-state concentrations. The described PPK model can be used to refine exposure–response relations for alternative dosing strategies to minimize skin toxicity.

• Individuals with posttraumatic stress disorder (PTSD) are at increased risk for cardiovascular disease. We previously reported that a predator-based model of PTSD increases myocardial sensitivity to ischemic injury. Heightened sympathetic signaling has a well-established role in the formation of anxiety associated with PTSD and may also contribute to worsening of myocardial injury in the ischemic heart. Thus, we examined whether suppression of sympathetic tone protects the ischemic heart in rats subjected to this model of PTSD. Rats were treated with saline or clonidine throughout the 31-day stress paradigm. Behavior on the elevated plus maze (EPM) was assessed on Day 32, and hearts were subjected to an ischemic insult on day 33. Stressed rats exhibited increased anxiety on the EPM and significantly larger myocardial infarcts following ischemia. Clonidine reversed the anxiety-like behavior but had no impact on infarct size. In a subsequent experiment, rats were treated with propranolol in their drinking water throughout the stress paradigm. Propranolol had no effect on either anxiety or myocardial sensitivity to ischemic injury. These findings suggest that the myocardial hypersensitivity to ischemic injury observed in this model is not caused by increased sympathetic tone or chronic β-adrenergic receptor signaling.

Doxorubicin is a commonly used anticancer agent that can cause debilitating and irreversible cardiac injury. The initiating mechanisms contributing to this side effect remain unknown, and current preventative strategies offer only modest protection. Using stem-cell–derived cardiomyocytes from patients receiving doxorubicin, we probed the transcriptomic landscape of solute carriers and identified organic cation transporter 3 (OCT3) (SLC22A3) as a critical transporter regulating the cardiac accumulation of doxorubicin. Functional validation studies in heterologous overexpression models confirmed that doxorubicin is transported into cardiomyocytes by OCT3 and that deficiency of OCT3 protected mice from acute and chronic doxorubicin-related changes in cardiovascular function and genetic pathways associated with cardiac damage. To provide proof-of-principle and demonstrate translational relevance of this transport mechanism, we identified several pharmacological inhibitors of OCT3, including nilotinib, and found that pharmacological targeting of OCT3 can also preserve cardiovascular function following treatment with doxorubicin without affecting its plasma levels or antitumor effects in multiple models of leukemia and breast cancer. Finally, we identified a previously unrecognized, OCT3-dependent pathway of doxorubicin-induced cardiotoxicity that results in a downstream signaling cascade involving the calcium-binding proteins S100A8 and S100A9. These collective findings not only shed light on the etiology of doxorubicin-induced cardiotoxicity, but also are of potential translational relevance and provide a rationale for the implementation of a targeted intervention strategy to prevent this debilitating side effect.

Organic cation transporter 1 (OCT1) is a transporter that regulates the hepatic uptake and subsequent elimination of diverse cationic compounds. Although OCT1 has been involved in drug-drug interactions and causes pharmacokinetic variability of many prescription drugs, details of the molecular mechanisms that regulate the activity of OCT1 remain incompletely understood. Based on an unbiased phospho-proteomics screen, we identified OCT1 as a tyrosine-phosphorylated transporter, and functional validation studies using genetic and pharmacological approaches revealed that OCT1 is highly sensitive to small molecules that target the protein kinase YES1, such as dasatinib. In addition, we found that dasatinib can inhibit hepatic OCT1 function in mice as evidenced from its ability to modulate levels of isobutyryl L-carnitine, a hepatic OCT1 biomarker identified from a targeted metabolomics analysis. These findings provide novel insight into the post-translational regulation of OCT1 and suggest that caution is warranted with polypharmacy regimes involving the combined use of OCT1 substrates and kinase inhibitors that target YES1.

Effective treatment for AML is challenging due to the presence of clonal heterogeneity and the evolution of polyclonal drug resistance. Here, we report that TP-0903 has potent activity against protein kinases related to STAT, AKT, and ERK signaling, as well as cell cycle regulators in biochemical and cellular assays. In vitro and in vivo, TP-0903 was active in multiple models of drug-resistant FLT3 mutant AML, including those involving the F691L gatekeeper mutation and bone marrow microenvironment–mediated factors. Furthermore, TP-0903 demonstrated preclinical activity in AML models with FLT3-ITD and common co-occurring mutations in IDH2 and NRAS genes. We also showed that TP-0903 had ex vivo activity in primary AML cells with recurrent mutations including MLL-PTD, ASXL1, SRSF2, and WT1, which are associated with poor prognosis or promote clinical resistance to AML-directed therapies. Our preclinical studies demonstrate that TP-0903 is a multikinase inhibitor with potent activity against multiple drug-resistant models of AML that will have an immediate clinical impact in a heterogeneous disease like AML., TP-0903, a multikinase inhibitor, demonstrates preclinical activity in models of drug-resistant AML, including those involving FLT3 mutations, bone marrow microenvironment-mediated factors and recurrent mutations.

Prior studies have demonstrated an organic anion transporter 6 (OAT6)-mediated accumulation of sorafenib in keratinocytes. The OAT6 inhibitor probenecid decreases sorafenib uptake in skin and might, therefore, decrease sorafenib-induced cutaneous adverse events. Here, the influence of probenecid on sorafenib pharmacokinetics and toxicity was investigated. Pharmacokinetic sampling was performed in 16 patients on steady-state sorafenib treatment at days 1 and 15 of the study. Patients received sorafenib (200&ndash, 800 mg daily) in combination with probenecid (500 mg two times daily (b.i.d.)) on days 2&ndash, 15. This study was designed to determine bioequivalence with geometric mean Area under the curve from zero to twelve hours (AUC0&ndash, 12 h) as primary endpoint. During concomitant probenecid, sorafenib plasma AUC0&ndash, 12 h decreased by 27% (90% CI: &minus, 38% to &minus, 14%, P &lt, 0.01). Furthermore, peak and trough levels of sorafenib, as well as sorafenib concentrations in skin, decreased to a similar extent in the presence of probenecid. The metabolic ratio of sorafenib-glucuronide to parent drug increased (+29%) in the presence of probenecid. A decrease in systemic sorafenib concentrations during probenecid administration seems to have influenced cutaneous concentrations. Since sorafenib-glucuronide concentrations increased compared with sorafenib and sorafenib-N-oxide, probenecid may have interrupted enterohepatic circulation of sorafenib by inhibition of the organic anion transporting polypeptides 1B1 (OATP1B1). Sorafenib treatment with probenecid is, therefore, not bioequivalent to sorafenib monotherapy. A clear effect of probenecid on sorafenib toxicity could not be identified in this study.

A rapid and sensitive analytical method was developed to quantify venetoclax, an oral BH3-mimetic that blocks the anti-apoptotic protein BCL-2, in mouse plasma using ultra-high-performance liquid chromatography with electrospray ionization tandem mass spectrometric detection. Plasma protein precipitation was performed on 5 µL samples, and separation of the analytes was accomplished on an Accucore aQ column using gradient elution at a flow rate of 0.4 mL/min. The calibration curve was linear (R2 ≥ 0.99) over the concentration range of 5–1,000 ng/mL, and the lower limit of quantitation was 5 ng/mL. The intra-day and inter-day precisions (RSD%) were

Post-traumatic stress disorder (PTSD) is a debilitating psychological disorder typified by diagnostic symptom clusters including hyperarousal, avoidance, negative cognitions and mood, and intrusive re-experiencing of the traumatic event. Patients with PTSD have been reported to self-medicate with alcohol to ameliorate hyperarousal symptoms associated with the disorder. Research utilizing rodent models of PTSD to emulate this behavioral phenomenon has thus far yielded inconsistent results. In the present study, we examined the effects of a predator-based psychosocial stress model of PTSD on voluntary ethanol consumption. In the first of two experiments, following exposure to a 31-day stress or control paradigm, rats were singly housed during the dark cycle with free access to 1% sucrose solution or 10% ethanol, which was also sweetened with 1% sucrose. Over the course of a 20-day period of ethanol access, stressed rats consumed significantly less ethanol than non-stressed rats. These counterintuitive results prompted the completion of a second experiment which was identical to the first, except rats were also exposed to the two-bottle paradigm for 20 days before the stress or control paradigm. In the second experiment, after the stress manipulation, stressed rats exhibited significantly greater ethanol preference than non-stressed rats. These findings suggest that prior exposure to ethanol influences the subsequent effect of stress on ethanol intake. They also validate the use of the present model of PTSD to examine potential mechanisms underlying stress-related changes in ethanol-seeking behavior.

While clinical benefit has been observed with gilteritinib in patients with FLT3 mutated relapsed/refractory acute myeloid leukemia (AML), most patients relapse through mechanisms that are incompletely understood. In this study, to investigate mechanisms of gilteritinib sensitivity and resistance, we performed targeted sequencing (21 patients) and scRNASeq analysis (8 patients) of FLT3-ITD-positive AML samples obtained before and during treatment. Before treatment, co-occurring mutations were observed in 33 genes among 21 patients. Mutations in RAS pathway genes (PTPN11, KRAS, NRAS, CBL) were the most common and observed in 57% (12/21) of patients. Seven patients pretreatment already contained RAS pathway mutations, of which 6 of these mutations were maintained over the course of treatment. During treatment, 9 patients showed emerging RAS mutations, 4 of which initially presented with a different RAS pathway mutation pre-treatment. Other mutations that arose during treatment were observed in CEBPA, IDH1, SF1 and WT1; as well as CSF3R, CUX1, PLEKHG5, and XPO1, not previously identified in gilteritinib-treated patients. Mutational clonality was generally maintained over treatment in both responders and non-responders. scRNASeq revealed global gene expression differences in myeloblast populations between gilteritinib-responsive and -unresponsive patients. Previous studies in vitro have shown that bone marrow-derived hematopoietic and inflammatory cytokines/chemokines confer resistance to FLT3 inhibitors. In the unresponsive group, we observed an increase in expression of CCL5, CXCL1, CXCL2, CXCL8, FLT3, IL6R, IL3RA, and CSF2RA during gilteritinib treatment, supporting the concept from preclinical studies that AML microenvironment-mediated factors play a critical role in drug resistance. Baseline expression of the Tec kinase BMX was significantly higher in unresponsive patients (Log2FoldChange, 6.65; adjusted P value, 0.00186), and this was maintained in the expanding myeloblast populations during treatment. Previously, upregulated BMX was shown to contribute to sorafenib resistance in patients with FLT3-ITD-positive AML, through cell-nonautonomous microenvironment hypoxia-dependent effects. Further in vitro investigation confirmed gilteritinib resistance could be reversed through genetic and pharmacological manipulation of BMX. Gene module analysis showed associations between gilteritinib responsive and upregulation of genes and pathways involved in lymphocyte differentiation and myeloid leukocyte activation, including TBX21, GATA3, CD33, and LYZ. By contrast, there was association between unresponsiveness to gilteritinib and upregulation of cell-cycle, DNA, and RNA metabolic processes, including pathways involving METTL1 and DNMT3A, as well as pre-treatment expression of pathways associated with protein translation. Together, these data provide support for microenvironment-dependent escape from targeted therapy and suggest that BMX may contribute to gilteritinib resistance. High-dimensional analysis with scRNA-seq provides a deeper understanding of targets and pathways for potential therapeutic intervention to restore gilteritinib sensitivity. Disclosures Blachly: INNATE: Consultancy, Honoraria; KITE: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria.

Sleep deprivation is associated with increased risk of myocardial infarction. However, it is unknown whether the effects of sleep deprivation are limited to increasing the likelihood of experiencing a myocardial infarction or if sleep deprivation also increases the extent of myocardial injury. In this study, rats were deprived of paradoxical sleep for 96 h using the platform-over-water method. Control rats were subjected to the same condition except the control platform was large enough for the rats to sleep. Hearts from sleep deprived and control rats were subjected to 20 min ischemia on a Langendorff isolated heart system. Infarct size and post ischemic recovery of contractile function were unaffected by sleep deprivation in male hearts. In contrast, hearts from sleep-deprived females exhibited significantly larger infarcts than hearts from control females. Post ischemic recovery of rate pressure product and + dP/dT were significantly attenuated by sleep deprivation in female hearts, and post ischemic recovery of end diastolic pressure was significantly elevated in hearts from sleep deprived females compared to control females, indicating that post ischemic recovery of both systolic and diastolic function were worsened by sleep deprivation. These data provide evidence that sleep deprivation increases the extent of ischemia-induced injury in a sex-dependent manner.

Cardiovascular disease is the largest cause of mortality worldwide, and stress is a significant contributor to the development of cardiovascular disease. The relationship between acute and chronic stress and cardiovascular disease is well-evidenced. Acute stress can lead to arrhythmias and ischemic injury. However, recent evidence in rodent models suggests that acute stress can decrease sensitivity to myocardial ischemia-reperfusion injury. Conversely, chronic stress is arrythmogenic and increases sensitivity to myocardial ischemia-reperfusion injury. Few studies have examined the impact of validated animal models of stress-related psychological disorders on the ischemic heart. This review examines the work that has been completed using rat models to study the effects of stress on myocardial sensitivity to ischemic injury. Utilization of animal models of stress-related psychological disorders is critical in the prevention and treatment of cardiovascular disorders in patients experiencing stress-related psychiatric conditions.

Individuals with post-traumatic stress disorder (PTSD) experience many debilitating symptoms, including intrusive memories, persistent anxiety and avoidance of trauma-related cues. PTSD also results in numerous physiological complications, including increased risk for cardiovascular disease (CVD). However, characterization of PTSD-induced cardiovascular alterations is lacking, especially in preclinical models of the disorder. Thus, we examined the impact of a psychosocial predator-based animal model of PTSD on myocardial sensitivity to ischemic injury. Male and female Sprague-Dawley rats were exposed to psychosocial stress or control conditions for 31 days. Stressed rats were given two cat exposures, separated by a period of 10 days, and were subjected to daily social instability throughout the paradigm. Control rats were handled daily for the duration of the experiment. Rats were tested on the elevated plus maze (EPM) on day 32, and hearts were isolated on day 33 and subjected to 20 min ischemia and 2 h reperfusion on a Langendorff isolated heart system. Stressed male and female rats gained less body weight relative to controls, but only stressed males exhibited increased anxiety on the EPM. Male, but not female, rats exposed to psychosocial stress exhibited significantly larger infarcts and attenuated post-ischemic recovery of contractile function compared to controls. Our data demonstrate that predator stress combined with daily social instability sex-dependently increases myocardial sensitivity to ischemic injury. Thus, this manipulation may be useful for studying potential mechanisms underlying cardiovascular alterations in PTSD, as well as sex differences in the cardiovascular stress response.

Background: Posttraumatic stress disorder (PTSD) is a psychological disorder characterized by the formation of traumatic memories following exposure to a life threatening event. In addition to psychological manifestations, PTSD promotes atherosclerosis and increases the incidence of myocardial infarction. However, it is unknown whether the effects of PTSD are limited to increasing the incidence of myocardial infarction or if PTSD also increases infarct severity. Therefore, we used an animal model of PTSD to determine whether posttraumatic stress influences infarct size and postischemic recovery of cardiac contractile function. Methods: Rats were subjected to a well-established animal model of PTSD that is based on predator exposure and psychosocial stress (Zoladz et al., Stress 11:259-281). Rats subjected to this model exhibit many PTSD-like characteristics including the formation of traumatic memories, increased anxiety, increased startle reflex, hypertension, and alterations in the hypothalamic-pituitary adrenal axis. Male rats (7 weeks of age) were either subjected to psychosocial stress (n = 9) or continuously housed in their home cages (n = 8) for 31 days. Hearts were subsequently isolated and subjected to 20 minutes of ischemia and 2 hours reperfusion on a Langendorff isolated heart system. Results: Stressed rats exhibited significantly elevated corticosterone concentrations and anxiety-like behavior in the elevated plus maze. Infarct sizes were significantly larger in hearts from stressed rats (44.7 ± 1.7 % of area at risk) compared to nonstressed rats (31.0 ± 5.4 % of area at risk). Consistent with increased myocardial injury, postischemic recovery of rate pressure product (stressed = 16,922 ± 1,554 mmHg*bpm; nonstressed = 26,407 ± 2,977 mmHg*bpm) and +dP/dT (stressed = 1,901 ± 189 mmHg/sec; nonstressed =3,259 ± 498 mmHg/sec) were significantly attenuated in hearts from stressed rats. Furthermore, postischemic end diastolic pressure was significantly elevated in hearts from stressed (57 ± 6 mmHg) compared to nonstressed (32 ± 7 mmHg) rats. Conclusion: This animal model suggests that PTSD may make the myocardium more sensitive to ischemic injury through a mechanism that is independent from its ability to promote atherosclerosis.