Delayed neutrophil apoptosis mediates intermittent hypoxia-induced progressive heart failure in pressure-overloaded rats

Reduction of IL-6, IL-8 and β2-ADRENOCEPTOR mRNA levels in circulating polymorphonuclear leukocytes after adenotonsillectomy in children with Obstructive Sleep Apnea Syndrome

BACKGROUND

Obstructive Sleep Apnea Syndrome (OSAS) affects approximately 1-5% of children and is linked to cardiovascular, metabolic, and neurobehavioral complications. Dysregulation of inflammatory process and sympathetic nervous system overstimulation leading to increased catecholamine production may contribute to OSAS pathogenesis. Polymorphonuclear Neutrophils (PMN), key cells in the inflammatory process, express adrenergic receptors, including β2-adrenergic receptor (ADRB2), which modulate their functions through an autocrine/paracrine loop. In this pilot study, we aimed to investigate the relationship between OSAS severity, ADRB2 expression in PMN and patient's inflammatory profile before and after adenotonsillectomy.

PATIENTS/METHODS

In this pilot study we enrolled OSAS pediatric patients in which ADRB2, IL-6 and IL-8 mRNA expression levels were evaluated in circulating PMN by RT-PCR.

RESULTS

9 OSAS pediatric patients, ranged from 3 to 8 years of age, were enrolled in the study. We found that adenotonsillectomy significantly reduced ADRB2 as well as IL-6, IL-8 mRNA expression levels in PMN.

CONCLUSIONS

These findings offer valuable insights into the underlying immune and inflammatory mechanisms of OSAS and open the way for the development of novel therapeutic approaches.

Association between obstructive sleep apnea and cardiovascular diseases

Obstructive sleep apnea (OSA) is a common respiratory disorder characterized by partial obstruction of upper respiratory tract and repetitive cessation of breathing during sleep. The etiology behind OSA is associated with the occurrence of intermittent hypoxemia, recurrent arousals and intrathoracic pressure swings. These contributing factors may turn on various signaling mechanisms including elevated sympathetic tone, oxidative stress, inflammation, endothelial dysfunction, cardiovascular variability, abnormal coagulation and metabolic defect ( e.g., insulin resistance, leptin resistance and altered hepatic metabolism). Given its close tie with major cardiovascular risk factors, OSA is commonly linked to the pathogenesis of a wide array of cardiovascular diseases (CVDs) including hypertension, heart failure, arrhythmias, coronary artery disease, stroke, cerebrovascular disease and pulmonary hypertension (PH). The current standard treatment for OSA using adequate nasal continuous positive airway pressure (CPAP) confers a significant reduction in cardiovascular morbidity. Nonetheless, despite the availability of effective therapy, patients with CVDs are still deemed highly vulnerable to OSA and related adverse clinical outcomes. A better understanding of the etiology of OSA along with early diagnosis should be essential for this undertreated disorder in the clinical setting.

Polymorphonuclear neutrophils promote endothelial apoptosis by enhancing adhesion upon stimulation by intermittent hypoxia

PURPOSE

This study explored the interactive effects between polymorphonuclear neutrophils (PMNs) and vascular endothelial cells under intermittent hypoxia (IH) and investigated the mechanisms underlying these effects.

METHODS

Endothelial cells were co-cultured with PMNs isolated from rats exposed to normoxia or IH. The PMN apoptotic rate was determined using flow cytometry. Expression of apoptosis-related proteins in the endothelial cells were evaluated using Western blotting, and the levels of intercellular adhesion molecules in the co-culture supernatants were measured using enzyme-linked immunosorbent assay.

RESULTS

The PMN apoptotic rate in the IH-exposed rat group was significantly lower than that of the normoxia control group. There was a positive relationship between the PMN apoptotic rate and IH exposure time. In endothelial cells co-cultured with PMNs isolated from IH-exposed rats, a significant increase in the protein expression levels of Bax, Bcl-2, and caspase-3 and a significant decrease in the Bcl-2/Bax ratio were observed. Furthermore, the intercellular cell adhesion molecule-1(ICAM-1) and E-select element (E-S) levels were elevated significantly in the co-cultured supernatants of endothelial cells and PMNs from IH-exposed rats compared to that from controls. The above IH-induced alterations were partially restored by tempol pretreatment.

CONCLUSIONS

The apoptotic rate was low in PMNs from IH-exposed rats, which consequently increased the apoptotic signals in endothelial cells in vitro. This may be associated with the increased levels of intercellular adhesion molecules. Further, tempol partially attenuates the PMN-mediated pro-apoptotic effects on endothelial cells under IH.

Obstructive sleep apnea and cardiovascular comorbidity: common pathophysiological mechanisms to cardiovascular disease

Obstructive sleep apnea (OSA) is associated with many cardiovascular and metabolic diseases. Sleep apnea causes intermittent hypoxemia, chest pressure fluctuations and a reaction from the cerebral cortex in the form of a short awakening during sleep (EEG-activation). The consequences of pathological pathways are studied in experimental models involving cell cultures, animals, and healthy volunteers. At present, the negative impact of intermittent hypoxemia on a variety of pathophysiological disorders of the heart and blood vessels (vascular tone fluctuations, thickening of the intimamedia complex in the vascular wall, direct damaging effect on the myocardium) has a great evidence base. Two other pathological components of OSA (pressure fluctuations and EEG-activation) can also affect cardiovascular system, mainly affecting the increase in blood pressure and changing cardiac hemodynamics. Although these reactions are considered separately in the review, with the development of sleep apnea they occur sequentially and are closely interrelated. As a result, these pathological pathways trigger further pathophysiological mechanisms acting on the heart and blood vessels. It is known that these include excessive sympathetic activation, inflammation, oxidative stress and metabolic dysregulation. In many respects being links of one process, these mechanisms can trigger damage to the vascular wall, contributing to the formation of atherosclerotic lesions. The accumulated data with varying degrees of reliability confirm the participation of OSA through these processes in the formation of cardiovascular disorders. There are factors limiting direct evidence of this interaction (sleep deprivation, causing similar changes, as well as the inability to share the contribution of other risk factors for cardiovascular diseases, in particular arterial hypertension, obesity, which are often associated with OSA). It is necessary to continue the study of processes that implement the pathological effect of OSA on the cardiovascular system.

Expression profile of long non-coding RNAs in rat models of OSA-induced cardiovascular disease: new insight into pathogenesis

PURPOSE

Long non-coding RNAs (lncRNAs) are a recently identified class of regulatory molecules involved in the regulation of numerous biological processes, but their functions in a rat model of chronic intermittent hypoxia (CIH) remain largely unknown. Therefore, for further investigation, we aimed to explore lncRNA expression profiles and reveal their potential functional roles in rat models of CIH.

METHODS

We used a well-established CIH rat model and conducted lncRNA microarray experiments on the heart samples of rats with CIH and under normoxia control. Differentially expressed lncRNAs and mRNAs were identified via fold-change filtering and verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bioinformatics analyses were applied to reveal the potential roles of key lncRNAs. Co-expression analysis was conducted to determine the transcriptional regulatory relationship of lncRNAs and mRNAs between the two groups.

RESULTS

Our data indicated that 157 lncRNAs and 319 mRNAs were upregulated, while 132 lncRNAs and 428 mRNAs were downregulated in the rat model of CIH compared with sham control. Pathway analyses showed that 31 pathways involved in upregulated transcripts and 28 pathways involved in downregulated transcripts. Co-expression networks were also constructed to explore the potential roles of differentially expressed lncRNAs on mRNAs. LncRNAs, namely, XR_596701, XR_344474, XR_600374, ENSRNOT00000065561, XR_590196, and XR_597099, were validated by the use of qRT-PCR.

CONCLUSIONS

The present study first revealed lncRNAs expression profiles in a rat model of CIH, providing new insight into the pathogenesis of obstructive sleep apnea-induced cardiovascular disease.

Mechanisms of cardiovascular disease in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is recognized as a major public health burden conveying a significant risk of cardiovascular diseases (CVD) and mortality. Continuous positive airway pressure (CPAP) is the treatment of choice for the majority of patients with OSA but the benefit of CPAP on CVD is uncertain. Thus, a greater understanding of the mechanisms by which OSA leads to CVD might identify novel therapeutic approaches. Intermittent hypoxia (IH), a hallmark feature of OSA, plays a key role in the pathogenesis and experimental studies using animal and cell culture studies suggest that IH mediates CVD through activation of multiple mechanistic pathways such as sympathetic excitation, inflammation, oxidative stress or metabolic dysregulation. Recurrent arousals, intrathoracic pressure swings and concomitant obesity likely play important additive roles in this process. In this review, the available evidence of the pathophysiological mechanisms of CVD in OSA is explored with a specific emphasis on IH, recurrent arousals and intrathoracic pressure swings as the main pathophysiological triggers.

Effects of Antioxidant Tempol on Systematic Inflammation and Endothelial Apoptosis in Emphysematous Rats Exposed to Intermittent Hypoxia

PURPOSE

Obstructive sleep apnea and chronic obstructive pulmonary disease are independent risk factors of cardiovascular disease (CVD), and their coexistence is known as overlap syndrome (OS). Endothelial dysfunction is the initial stage of CVD; however, underlying mechanisms linking OS and CVD are not well understood. The aim of this study was to explore whether OS can lead to more severe inflammation and endothelial apoptosis by promoting endothelial dysfunction, and to assess the intervention effects of antioxidant tempol.

MATERIALS AND METHODS

Male Wistar rats (n=66) were exposed to normal oxygen [normal control (NC) group], intermittent hypoxia (IH group), cigarette smoke (CH group), as well as cigarette smoke and IH (OS group). Tempol intervention was assessed in OS group treated with tempol (OST group) or NaCl (OSN group). After an 8-week challenge, lung tissues, serum, and fresh blood were harvested for analysis of endothelial markers and apoptosis.

RESULTS

The levels of intracellular adhesion molecule-1, vascular cellular adhesion molecule-1, and apoptosis in circulating epithelial cells were the highest in OS group and the lowest in NC group. These levels were all greater in IH group than in CH group, and were lower in OST group than in OS and OSN groups (all p<0.001).

CONCLUSION

Synergistic effects of IH with cigarette smoke-induced emphysema produce a greater inflammatory status and endothelial apoptosis. OS-related inflammation and endothelial cell apoptosis may play important roles in promoting cardiovascular dysfunction, and antioxidant tempol could achieve a partial protective effect.

Hydrogen gas reduces chronic intermittent hypoxia-induced hypertension by inhibiting sympathetic nerve activity and increasing vasodilator responses via the antioxidation

Molecular hydrogen is reported to be used medically to ameliorate various systemic pathological conditions. This study aimed to investigate the effect of hydrogen (H₂ ) gas on hypertension induced by intermittent hypoxia in rats. The adult rats were exposed to chronic intermittent hypoxia (CIH) 8 hours/day for 5 weeks and/or H ₂ gas 2 hours/day. We found that the systolic and diastolic blood pressure (BP) increased significantly in rats exposed to intermittent hypoxia, both of which were markedly attenuated after H treatment. Furthermore, intermittent hypoxia exposure elevated renal sympathetic nerve activity, consistent with plasma norepinephrine. Additionally, H ₂ gas significantly improved CIH-induced abnormal vascular relaxation. Nevertheless, inhalation of H ₂ gas alone did not cause such changes. Moreover, H ₂ gas-treated rats exposed to CIH showed a significant reduction in 8-hydroxy-2 deoxyguanosine content and increases in superoxide dismutase activity, indicating improved oxidative stress. Taken together, these results indicate that H ₂ gas has significant effects on the reduction of BP without any side effects. Mechanistically, inhibition of sympathetic activity and reduction of systemic vascular resistance may participate in this process via the antioxidant activity of H ₂ .

Berberine inhibits cardiac remodeling of heart failure after myocardial infarction by reducing myocardial cell apoptosis in rats

The effects of berberine on cardiac function of heart failure after myocardial infarction and its possible mechanism were investigated. The anterior descending branches of 50 female Wistar rats were ligatured to establish the model of heart failure after myocardial infarction. At 4 weeks after successful modeling, the rats were randomly divided into two groups receiving 4-week gavage with saline (Sal group) and berberine (Ber group), while the sham-operation group (Sham group) was set up. After 4 weeks, the hemodynamics and serum BNP in rats were measured. The hearts of rats were taken to detect the degree of myocardial fibrosis. The myocardial cell apoptosis was detected. The expressions and changes in myocardial apoptosis-related proteins, including Bcl-2, Bax and caspase-3, were detected. The expression and changes in GRP78, CHOP and caspase-12 in myocardial tissue were detected. The results showed that Berberine improved the cardiac function of rats after myocardial infarction. After myocardial infarction, myocardial fibrosis and apoptosis were observed around the infarction area, berberine improved the myocardial fibrosis and reduced cell apoptosis. Furthermore, berberine alleviated endoplasmic reticulum stress (ERS) after myocardial infarction. In conclusion, Berberine can inhibit the myocardium cell apoptosis of heart failure after myocardial infarction, and its mechanism may be realized by affecting the ERS in myocardial tissue of heart failure after myocardial infarction and CHOP and caspase-12 apoptotic signaling pathway, upregulating Bcl-2/Bax expression and downregulating caspase-3 expression, thus inhibiting the cardiac remodeling and protecting the cardiac function.

Arsenite renal apoptotic effects in chickens co-aggravated by oxidative stress and inflammatory response

The kidney is the most crucial site for the excretion of arsenic and its metabolites.

Chronic intermittent hypoxia induces cardiac inflammation and dysfunction in a rat obstructive sleep apnea model

Chronic intermittent hypoxia is considered to play an important role in cardiovascular pathogenesis during the development of obstructive sleep apnea (OSA). We used a well-described OSA rat model induced with simultaneous intermittent hypoxia. Male Sprague Dawley rats were individually placed into plexiglass chambers with air pressure and components were electronically controlled. The rats were exposed to intermittent hypoxia 8 hours daily for 5 weeks. The changes of cardiac structure and function were examined by ultrasound. The cardiac pathology, apoptosis, and fibrosis were analyzed by H&E staining, TUNNEL assay, and picosirius staining, respectively. The expression of inflammation and fibrosis marker genes was analyzed by quantitative real-time PCR and Western blot. Chronic intermittent hypoxia/low pressure resulted in significant increase of left ventricular internal diameters (LVIDs), end-systolic volume (ESV), end-diastolic volume (EDV), and blood lactate level and marked reduction in ejection fraction and fractional shortening. Chronic intermittent hypoxia increased TUNNEL-positive myocytes, disrupted normal arrangement of cardiac fibers, and increased Sirius stained collagen fibers. The expression levels of hypoxia induced factor (HIF)-1α, NF-kB, IL-6, and matrix metallopeptidase 2 (MMP-2) were significantly increased in the heart of rats exposed to chronic intermittent hypoxia. In conclusion, the left ventricular function was adversely affected by chronic intermittent hypoxia, which is associated with increased expression of HIF-1α and NF-kB signaling molecules and development of cardiac inflammation, apoptosis and fibrosis.

Targeting the ROS-HIF-1-endothelin axis as a therapeutic approach for the treatment of obstructive sleep apnea-related cardiovascular complications

Obstructive sleep apnea (OSA) is now recognized as an independent and important risk factor for cardiovascular diseases such as hypertension, coronary heart disease, heart failure and stroke. Clinical and experimental data have confirmed that intermittent hypoxia is a major contributor to these deleterious consequences. The repetitive occurrence of hypoxia-reoxygenation sequences generates significant amounts of free radicals, particularly in moderate to severe OSA patients. Moreover, in addition to hypoxia, reactive oxygen species (ROS) are potential inducers of the hypoxia inducible transcription factor-1 (HIF-1) that promotes the transcription of numerous adaptive genes some of which being deleterious for the cardiovascular system, such as the endothelin-1 gene. This review will focus on the involvement of the ROS-HIF-1-endothelin signaling pathway in OSA and intermittent hypoxia and discuss current and potential therapeutic approaches targeting this pathway to treat or prevent cardiovascular disease in moderate to severe OSA patients.