Gender differences in the pathophysiology, clinical presentation, and outcomes of ischemic heart failure

Echocardiographic evaluation of patients presenting with acutely decompensated heart failure in the setting of dietary or medication noncompliance-Is there a role?

BACKGROUND

Reevaluating patients who are admitted with heart failure (HF) exacerbation using echocardiogram is a common and appropriate indication. However, it is unknown whether it is appropriate to reevaluate such patients when the exacerbation is attributed to patients' noncompliance with self-care behaviors, where the presumption is that the underlying HF biology is stable.

METHODS

Echocardiograms on all patients hospitalized for HF exacerbation attributed to dietary or medication noncompliance were retrospectively assessed for the presence of significant changes from prior echocardiogram.

RESULTS

A total of 559 charts of patients admitted with heart failure exacerbation were reviewed, of which 125 patients (22%) were thought to have dietary or medication noncompliance as the etiology. Fifty-three patients (42%) had a follow-up echocardiogram performed during the index admission. The likelihood of being reevaluated by an echocardiogram during admission was not affected by the clinical service that the patient was admitted to, the patient's gender, or age. Eighty percent of echocardiograms performed within a year of prior study and 78% of echocardiograms performed >1 year revealed at least one significant change. The most common changes identified were an increase in left atrium diameter, worsening of pulmonary artery systolic pressure and worsening ejection fraction. There was no correlation between the time interval of between echocardiograms and the likelihood of a significant change.

CONCLUSIONS

Repeat echocardiograms in patients admitted with HF exacerbation due to noncompliance revealed significant changes in the majority of patients studied. The changes may reflect worsening in cardiac function in addition to the presumed etiology of noncompliance.

Thymosin Beta-4 Is Elevated in Women With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Thymosin beta-4 (TB4) is an X-linked gene product with cardioprotective properties. Little is known about plasma concentration of TB4 in heart failure (HF), and its relationship with other cardiovascular biomarkers. We sought to evaluate circulating TB4 in HF patients with preserved (HFpEF) or reduced (HFrEF) ejection fraction compared to non-HF controls.

METHODS AND RESULTS

TB4 was measured using a liquid chromatography and mass spectrometry assay in age- and sex-matched HFpEF (n=219), HFrEF (n=219) patients, and controls (n=219) from a prospective nationwide study. Additionally, a 92-marker multiplex proximity extension assay was measured to identify biomarker covariates. Compared with controls, plasma TB4 was elevated in HFpEF (985 [421-1723] ng/mL versus 1401 [720-2379] ng/mL, P<0.001), but not in HFrEF (1106 [556-1955] ng/mL, P=0.642). Stratifying by sex, only women (1623 [1040-2625] ng/mL versus 942 [386-1891] ng/mL, P<0.001), but not men (1238.5 [586-1967] ng/mL versus 1004 [451-1538] ng/mL, P=1.0), had significantly elevated TB4 in the setting of HFpEF. Adjusted for New York Heart Association class, N-terminal pro B-type natriuretic peptide, age, and myocardial infarction, hazard ratio to all-cause mortality is significantly higher in women with elevated TB4 (1.668, P=0.036), but not in men (0.791, P=0.456) with HF. TB4 is strongly correlated with a cluster of 7 markers from the proximity extension assay panel, which are either X-linked, regulated by sex hormones, or involved with NF-κB signaling.

CONCLUSIONS

We show that plasma TB4 is elevated in women with HFpEF and has prognostic information. Because TB4 can preserve EF in animal studies of cardiac injury, the relation of endogenous, circulating TB4 to X chromosome biology and differential outcomes in female heart disease warrants further study.

MiR-486 regulates cardiomyocyte apoptosis by p53-mediated BCL-2 associated mitochondrial apoptotic pathway

BACKGROUND

Cardiomyocyte apoptosis is a common pathological manifestation that occurs in several heart diseases. This study aimed to explore the mechanism of microRNA-486 (miR-486) in cardiomyocyte apoptosis by interfering with the p53-activated BCL-2 associated mitochondrial pathway.

METHODS

miR-486 mimics and inhibitors were transfected into the primary cardiomyocytes of suckling Sprague-Dawley rat pups, and H₂O₂ was used to induce apoptosis. Flow cytometry and TUNEL were both used to detect cardiomyocyte apoptosis, while the relative mRNA transcript and protein levels of miR-486, p53, Bbc3, BCL-2, and cleaved caspase-3 were detected using RT-PCR and western blot analysis, respectively.

RESULTS

miR-486 overexpression significantly decreased the expressions of p53, Bbc3 and cleaved caspase-3 (P < 0.05), and BCL-2 expression was significantly increased (P < 0.05), which in turn caused a significant decrease in the rate of cardiomyocyte apoptosis (P < 0.05). In contrast, miR-486 silencing resulted in an elevated rate of cardiomyocyte apoptosis (P < 0.05).

CONCLUSION

miR-486 may regulate cardiomyocyte apoptosis via p53-mediated BCL-2 associated mitochondrial apoptotic pathway. Therefore, up-regulating miR-486 expression in cardiomyocytes can effectively reduce the activation of the BCL-2 associated mitochondrial apoptotic pathway, consequently protecting cardiomyocytes.

Mortality in HIV-infected women, heterosexual men, and men who have sex with men in Rio de Janeiro, Brazil: an observational cohort study

BACKGROUND

Mortality in HIV-infected individuals might differ by sex and mode of HIV acquisition. We aimed to study mortality in HIV-infected women, heterosexual men, and men who have sex with men (MSM) in a cohort from Rio de Janeiro, Brazil.

METHODS

In this observational cohort study, we included HIV-infected women, heterosexual men, and MSM (aged ≥18 years) from the Instituto Nacional de Infectologia Evandro Chagas database who were enrolled between Jan 1, 2000, and Oct 30, 2011, and who had at least 60 days of follow-up. Causes of deaths, defined with the Coding of Death in HIV protocol, were documented. Cox proportional hazards models accounting for competing risks were used to explore risk factors for AIDS-related and non-AIDS-related deaths.

FINDINGS

We had 10 142 person-years of follow-up from 2224 individuals: 817 (37%) women, 554 (25%) heterosexual men, and 853 (38%) MSM. Of 103 deaths occurred, 64 were AIDS related, 31 were non-AIDS related, and eight were of unknown causes. In unadjusted analyses, compared with women, the hazard of AIDS-related deaths was higher for heterosexual men (hazard ratio [HR] 3·52, 95% CI 1·30-9·08; p=0·009) and for MSM (2·30, 0·89-5·94; p=0·084). After adjustment for age, CD4 cell counts, last HIV viral load, antiretroviral therapy use, and AIDS-defining infection, AIDS-defining malignant disease, and hospital admission during follow-up, the excess risk of AIDS-related death decreased for heterosexual men (adjusted HR 1·99, 0·75-5·25; p=0·163) but was unchanged for MSM (2·24, 0·82-6·11; p=0·114). Non-AIDS-related mortality did not differ by group.

INTERPRETATION

Compared with women, increased risk of AIDS-related death in heterosexual men was partly mitigated by risk factors for AIDS mortality, whereas the excess risk in MSM was unchanged. Further study of reasons for disparity in AIDS-related mortality by mode of transmission is needed.

FUNDING

US National Institutes of Health, Brazilian National Council of Technological and Scientific Development (CNPq), and Research Funding Agency of the State of Rio de Janeiro (FAPERJ).

Does aircraft noise exposure increase the risk of hypertension in the population living near airports in France?

OBJECTIVES

The largest study until now around 6 major European airports, the HYENA (HYpertension and Exposure to Noise near Airports) study, reported an excess risk of hypertension related to long-term aircraft noise exposure. The DEBATS (Discussion on the health effects of aircraft noise) study investigated the relationship between this exposure and the risk of hypertension in men and in women near French airports.

METHODS

Blood pressure of 1244 participants older than 18 years of age was measured. Information about health, socioeconomic and lifestyle factors was collected by means of a face-to-face questionnaire performed at home by an interviewer. Aircraft noise exposure was assessed for each participant's home address using noise maps. They were calculated with the Integrated Noise Model with a 1 dB(A)-resolution. The major potential confounders being risk factors for hypertension were included in the logistic regression models: age, occupational activity, body mass index, physical activity and alcohol consumption.

RESULTS

After adjustment for the main potential confounders, an exposure-response relationship was evidenced between the risk of hypertension and aircraft noise exposure at night for men only. A 10-dB(A) increase in L_night was associated with an OR of 1.34 (95% CI 1.00 to 1.97).

CONCLUSIONS

These findings contribute to the overall evidence suggesting that aircraft noise exposure at night-time may increase the risk of hypertension in men. Hypertension is a well-known and established risk factor for cardiovascular disease. The association reported in the present study between aircraft noise and hypertension implies that aircraft noise might be a risk factor also for cardiovascular disease.

Differences of psychological features in patients with heart failure with regard to gender and aetiology - Results of a CAPS-LOCK-HF (Complex Assessment of Psychological Status Located in Heart Failure) study

OBJECTIVE

Objective of the study was to assess the psychological state of HF patients with reduced ejection fraction (HFrEF) with regard to gender and aetiology.

METHODS

758 patients with HFrEF (mean age - 64±11years, men - 79%, NYHA class III-IV - 40%, ischemic aetiology - 61%) in a prospective Polish multicenter Caps-Lock-HF study. Scores on five different self-report inventories: CISS, MHLC, GSES, BDI and modified Mini-MAC were compared between the sexes taking into account the aetiology of HFrEF.

RESULTS

There were differences in the CISS and BDI score between the genders - women had higher CISS (emotion- and avoidance-oriented) and BDI (general score - 14.2±8.7 vs 12.3±8.6, P<0.05; subscale - somatic score - 7.3±3.7 vs 6.1±3.7, P<0.05). In the ischemic subpopulation, women had higher BDI (general and subscales) than men. In the non-ischemic subpopulation the differences between genders were limited to CISS scale. In a multivariable analysis with demographic and clinical data female sex, NYHA class, atrial fibrillation and diabetes mellitus determined BDI score. Similarly, in the ischemic subpopulation, the female sex, NYHA class and atrial fibrillation determined the BDI, while in the non-ischemic population NYHA class was the only factor that influenced the BDI score. Adding the psychological data made a significant additional contribution to the prediction of depression status.

CONCLUSIONS

There are distinct differences in psychological features with regard to gender in patients with HFrEF. Women demonstrate less favourable psychological characteristics. Gender-related differences in BDI score are especially explicit in patients with ischemic aetiology of HF. The BDI score is related to psychological predisposition.

Sex-related differences in intrinsic myocardial properties influence cardiac function in middle-aged rats during infarction-induced left ventricular remodeling

We previously determined that residual left ventricular (LV) myocardium of middle-aged rats had sex-related differences in regional tissue properties 4 weeks after a large myocardial infarction (MI). However, the impact of such differences on cardiac performance remained unclear. Therefore, our current study aimed to elucidate whether sex-related changes in MI-induced myocardial remodeling can influence cardiac function. A similar-sized MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. The cardiac function was monitored for 2 months after MI and then various LV parameters were compared between sexes. We found that although two sex groups had a similar pattern of MI-induced decline in LV function, F-MI rats had greater cardiac performance compared to M-MI rats, considering the higher values of EF (39.9 ± 3.4% vs. 26.7 ± 7.7%, P < 0.05), SW index (40.4 ± 2.1 mmHg • mL/kg vs. 20.2 ± 3.3 mmHg • mL/kg, P < 0.001), and CI (139.2 ± 7.9 mL/min/kg vs. 74.9 ± 14.7 mL/min/kg, P < 0.01). The poorer pumping capacity in M-MI hearts was associated with markedly reduced LV compliance and prolonged relaxation. On the tissue level, F-MI rats revealed a higher, than in M-MI rats, density of cardiac myocytes in the LV free wall (2383.8 ± 242.6 cells/mm(2) vs. 1785.7 ± 55.9 cells/mm(2), P < 0.05). The latter finding correlated with a lower density of apoptotic cardiac myocytes in residual LV myocardium of F-MI rats (0.18 ± 0.08 cells/mm(2) vs. 0.91 ± 0.30 cells/mm(2) in males, P < 0.01). Thus, our data suggested that F-MI rats had markedly attenuated decline in cardiac performance compared to males due to ability of female rats to better retain functionally favorable intrinsic myocardial properties.

Using MRI to predict future adverse cardiac remodelling in a male mouse model of myocardial infarction

Background

Mice are frequently used in research to examine outcomes of myocardial infarction (MI) and to investigate therapeutic interventions at an early pre-clinical stage. The MI model is generated by surgically occluding a major coronary artery, but natural variation in murine coronary anatomy can generate variable outcomes that will inevitably affect the accuracy of such investigations. The aim of this study was to use MRI to derive the most sensitive early variable that could be used to predict subsequent adverse cardiac remodelling in a male mouse model of MI.

Methods

Using a longitudinal study design, heart structure and function were evaluated using cardiac MRI at one week following surgical MI to generate the early measurements and again at four weeks, when the scar had matured. The primary variables measured at week one were left ventricular volumes at end systole (LV-ESV) and at end diastole (LV-EDV), infarct size, LV-cardiac mass, and ejection fraction (EF).

Results

Univariate and multiple regression analyses showed that LV-ESV at one week following MI could be used to accurately predict various parameters of adverse LV remodelling at four weeks post-MI. However, the highest correlation was between LV-ESV at one week following MI and LV-EDV at four weeks (r = 0.99; p < 0.0001), making LV-ESV at one week a valuable predictor variable of future adverse ventricular remodelling after MI.

Conclusion

Using MRI to determine LV-ESV at an early stage following MI enables a more robust analysis of potential therapeutic interventions to ameliorate adverse cardiac remodelling.

Cardiomyocyte-specific overexpression of oestrogen receptor β improves survival and cardiac function after myocardial infarction in female and male mice

The study provides new insights into cardiomyocyte-specific effects of ERβ in the setting of chronic MI using a transgenic mouse model. ERβ-overexpressing mice of both sexes showed improved survival, less maladaptive LV remodelling, better cardiac function and less heart failure development.

Biomechanics of Cardiac Function

The heart pumps blood to maintain circulation and ensure the delivery of oxygenated blood to all the organs of the body. Mechanics play a critical role in governing and regulating heart function under both normal and pathological conditions. Biological processes and mechanical stress are coupled together in regulating myocyte function and extracellular matrix structure thus controlling heart function. Here, we offer a brief introduction to the biomechanics of left ventricular function and then summarize recent progress in the study of the effects of mechanical stress on ventricular wall remodeling and cardiac function as well as the effects of wall mechanical properties on cardiac function in normal and dysfunctional hearts. Various mechanical models to determine wall stress and cardiac function in normal and diseased hearts with both systolic and diastolic dysfunction are discussed. The results of these studies have enhanced our understanding of the biomechanical mechanism in the development and remodeling of normal and dysfunctional hearts. Biomechanics provide a tool to understand the mechanism of left ventricular remodeling in diastolic and systolic dysfunction and guidance in designing and developing new treatments.

Mitochondrial maintenance failure in aging and role of sexual dimorphism

Gene expression changes during aging are partly conserved across species, and suggest that oxidative stress, inflammation and proteotoxicity result from mitochondrial malfunction and abnormal mitochondrial-nuclear signaling. Mitochondrial maintenance failure may result from trade-offs between mitochondrial turnover versus growth and reproduction, sexual antagonistic pleiotropy and genetic conflicts resulting from uni-parental mitochondrial transmission, as well as mitochondrial and nuclear mutations and loss of epigenetic regulation. Aging phenotypes and interventions are often sex-specific, indicating that both male and female sexual differentiation promote mitochondrial failure and aging. Studies in mammals and invertebrates implicate autophagy, apoptosis, AKT, PARP, p53 and FOXO in mediating sex-specific differences in stress resistance and aging. The data support a model where the genes Sxl in Drosophila, sdc-2 in Caenorhabditis elegans, and Xist in mammals regulate mitochondrial maintenance across generations and in aging. Several interventions that increase life span cause a mitochondrial unfolded protein response (UPRmt), and UPRmt is also observed during normal aging, indicating hormesis. The UPRmt may increase life span by stimulating mitochondrial turnover through autophagy, and/or by inhibiting the production of hormones and toxic metabolites. The data suggest that metazoan life span interventions may act through a common hormesis mechanism involving liver UPRmt, mitochondrial maintenance and sexual differentiation.

How cardiomyocyte excitation, calcium release and contraction become altered with age

Cardiovascular disease is the main cause of death globally, accounting for over 17 million deaths each year. As the incidence of cardiovascular disease rises markedly with age, the overall risk of cardiovascular disease is expected to increase dramatically with the aging of the population such that by 2030 it could account for over 23 million deaths per year. It is therefore vitally important to understand how the heart remodels in response to normal aging for at least two reasons: i) to understand why the aged heart is increasingly susceptible to disease; and ii) since it may be possible to modify treatment of disease in older adults if the underlying substrate upon which the disease first develops is fully understood. It is well known that age modulates cardiac function at the level of the individual cardiomyocyte. Generally, in males, aging reduces cell shortening, which is associated with a decrease in the amplitude of the systolic Ca(2+) transient. This may arise due to a decrease in peak L-type Ca(2+) current. Sarcoplasmic reticulum (SR) Ca(2+) load appears to be maintained during normal aging but evidence suggests that SR function is disrupted, such that the rate of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA)-mediated Ca(2+) removal is reduced and the properties of SR Ca(2+) release in terms of Ca(2+) sparks are altered. Interestingly, Ca(2+) handling is modulated by age to a lesser degree in females. Here we review how cellular contraction is altered as a result of the aging process by considering expression levels and functional properties of key proteins involved in controlling intracellular Ca(2+). We consider how changes in both electrical properties and intracellular Ca(2+) handling may interact to modulate cardiomyocyte contraction. We also reflect on why cardiovascular risk may differ between the sexes by highlighting sex-specific variation in the age-associated remodeling process. This article is part of a Special Issue entitled CV Aging.

Testosterone modulates cardiac contraction and calcium homeostasis: cellular and molecular mechanisms

The incidence of cardiovascular disease rises dramatically with age in both men and women. Because a woman's risk of cardiovascular disease rises markedly after the onset of menopause, there has been growing interest in the effect of estrogen on the heart and its role in the pathophysiology of these diseases. Much less attention has been paid to the impact of testosterone on the heart, even though the levels of testosterone also decline with age and low-testosterone levels are linked to the development of cardiovascular diseases. The knowledge that receptors for all major sex steroid hormones, including testosterone, are present on individual cardiomyocytes suggests that these hormones may influence the heart at the cellular level. Indeed, it is well established that there are male-female differences in intracellular Ca(2+) release and contraction in isolated ventricular myocytes. Growing evidence suggests that these differences arise from effects of sex steroid hormones on processes involved in intracellular Ca(2+) homeostasis. This review considers how myocardial contractile function is modified by testosterone, with a focus on the impact of testosterone on processes that regulate Ca(2+) handling at the level of the ventricular myocyte. The idea that testosterone regulates Ca(2+) handling in the heart is important, as Ca(2+) dysregulation plays a key role in the pathogenesis of a variety of different cardiovascular diseases. A better understanding of sex hormone regulation of myocardial Ca(2+) homeostasis may reveal new targets for the treatment of cardiovascular diseases in all older adults.

Risk assessment of post-infarction heart failure. Systematic review on the role of emerging biomarkers

The prognostic significance of cardiospecific troponins and natriuretic peptides in patients with myocardial ischemia is well established, and their measurement is now endorsed by the most important guidelines and recommendations for diagnosis and management of heart failure (HF). Additional biomarkers have also been investigated to support clinical judgment and diagnostic imaging in the stratification of risk of cardiac dysfunction in patients with myocardial infarction (MI). We have performed a systematic analysis of the current scientific literature regarding the most important biomarkers of HF, selecting all prospective studies with adequate sample size (i.e. >100 patients) that have assessed, during the early phase of myocardial ischemia, the prognostic value of emergent biomarkers for new-onset HF or deterioration of cardiac function in patients with MI. This analysis has provided some good evidence suggesting that, in most cases, the use of diagnostic biomarkers of cardiac dysfunction does not translate into efficient risk prediction of HF. However, some notable exceptions were found, including biomarkers of cardiac fibrosis (especially galectin-3), growth differentiation factor-15 (GDF-15), osteoprotegerin, C-reactive protein (CRP), and red blood cell distribution width (RDW). Nevertheless, future studies with well-defined characteristics including the use of larger sample sizes, standardized end points, and replication populations, along with benchmark analyses against other consolidated biomarkers (i.e. cardiospecific troponins and natriuretic peptides), should be planned. Such evaluations will help to establish whether an integrated approach including biomarkers of different pathogenetic pathways - for example, apoptosis, stress of cardiomyocytes, cardiac fibrosis, inflammation, and extra-cardiac involvement - may be cost effective for identifying patients at increased risk of developing HF, and who, therefore, may benefit from a tailored therapeutic strategy.

Mineralocorticoid receptors and the heart, multiple cell types and multiple mechanisms: a focus on the cardiomyocyte

MR (mineralocorticoid receptor) activation in the heart plays a central role in the development of cardiovascular disease, including heart failure. The MR is present in many cell types within the myocardium, including cardiomyocytes, macrophages and the coronary vasculature. The specific role of the MR in each of these cell types in the initiation and progression of cardiac pathophysiology is not fully understood. Cardiomyocyte MRs are increasingly recognized to play a role in regulating cardiac function, electrical conduction and fibrosis, through direct signal mediation and through paracrine MR-dependent activity. Although MR blockade in the heart is an attractive therapeutic option for the treatment of heart failure and other forms of heart disease, current antagonists are limited by side effects owing to MR inactivation in other tissues (including renal targets). This has led to increased efforts to develop therapeutics that are more selective for cardiac MRs and which may have reduced the occurrence of side effects in non-cardiac tissues. A major clinical consideration in the treatment of cardiovascular disease is of the differences between males and females in the incidence and outcomes of cardiac events. There is clinical evidence that female sensitivity to endogenous MRs is more pronounced, and experimentally that MR-targeted interventions may be more efficacious in females. Given that sex differences have been described in MR signalling in a range of experimental settings and that the MR and oestrogen receptor pathways share some common signalling intermediates, it is becoming increasingly apparent that the mechanisms of MRs need to be evaluated in a sex-selective manner. Further research targeted to identify sex differences in cardiomyocyte MR activation and signalling processes has the potential to provide the basis for the development of cardiac-specific MR therapies that may also be sex-specific.

More than hormones: sex differences in cardiovascular parameters after sleep loss in rats

Although the influence of sex on sleep pattern and cardiovascular parameters is well known, knowledge regarding the effects of sleep loss on heart responses in both sexes is scarce. The present study investigated the effects of paradoxical sleep deprivation (PSD) and chronic sleep restriction (SR) on cardiovascular parameters and adrenocorticotropic hormone (ACTH) levels in male and female rats. Both groups were randomly assigned to PSD for 96 h, SR for 21 days or home-cage control. Mean arterial pressure (MAP), heart rate (HR), baroreflex sensitivity (bradycardia and tachycardia responses) and ACTH levels were evaluated. The results showed that PSD induced a significant increase in HR and ACTH levels in both sexes, although male rats presented higher levels of ACTH hormone compared to females. In addition to sex-specific responses, PSD decreased the tachycardia only in male rats. SR, induced a significant increase in MAP and decrease in bradycardia in both sexes. Male rats were more affected by sleep deprivation protocols than females for MAP, bradycardia response, and ACTH levels. The results showed that the effects of sleep loss on cardiovascular parameters are associated with the protocol of sleep deprivation and that sex can modulate these effects. We suggested this experimental model as a suitable tool for further investigations of the relationship between cardiovascular parameters and sleep.

Sex-specific differences in hyperoxic lung injury in mice: implications for acute and chronic lung disease in humans

Sex-specific differences in pulmonary morbidity in humans are well documented. Hyperoxia contributes to lung injury in experimental animals and humans. The mechanisms responsible for sex differences in the susceptibility towards hyperoxic lung injury remain largely unknown. In this investigation, we tested the hypothesis that mice will display sex-specific differences in hyperoxic lung injury. Eight week-old male and female mice (C57BL/6J) were exposed to 72 h of hyperoxia (FiO2>0.95). After exposure to hyperoxia, lung injury, levels of 8-iso-prostaglandin F2 alpha (8-iso-PGF 2α) (LC-MS/MS), apoptosis (TUNEL) and inflammatory markers (suspension bead array) were determined. Cytochrome P450 (CYP)1A expression in the lung was assessed using immunohistochemistry and western blotting. After exposure to hyperoxia, males showed greater lung injury, neutrophil infiltration and apoptosis, compared to air-breathing controls than females. Pulmonary 8-iso-PGF 2α levels were higher in males than females after hyperoxia exposure. Sexually dimorphic increases in levels of IL-6 (F>M) and VEGF (M>F) in the lungs were also observed. CYP1A1 expression in the lung was higher in female mice compared to males under hyperoxic conditions. Overall, our results support the hypothesis that male mice are more susceptible than females to hyperoxic lung injury and that differences in inflammatory and oxidative stress markers contribute to these sex-specific dimorphic effects. In conclusion, this paper describes the establishment of an animal model that shows sex differences in hyperoxic lung injury in a temporal manner and thus has important implications for lung diseases mediated by hyperoxia in humans.