Κ-opioid receptor stimulation improves endothelial function in hypoxic pulmonary hypertension

κ-Opioid Receptors Improve Vascular Endothelial Dysfunction in Salt-Sensitive Hypertension via PI3K/Akt/eNOS Signaling Pathway

κ-Opioid receptors (κ-OR) are widely used to regulate the activity of the cardiovascular system. To explore the effect and mechanism of κ-OR on salt-sensitive hypertensive endothelial dysfunction, we used Dah1 rats to construct a rat model of salt-sensitive hypertension on a high-salt (HS) diet. Then, the rats were treated with κ-OR activators U50,488H (1.25 mg/kg) and inhibitor nor-BNI (2.0 mg/kg) for 4 weeks, respectively. The rat aortas were collected to detect the contents of NO, ET-1, AngII, NOS, T-AOC, SO, and NT. Protein expression was determined for NOS, Akt, and Caveolin-1. In addition, the vascular endothelial cells were extracted, and the levels of NO, TNF-α, IL-1, IL-6, IL-8, IL-10, p-Akt, and p-eNOS in cell supernatants were detected. In vivo results showed that compared with the HS group, treated with U50,488H promoted rats' vasodilation by increasing the NO content and decreasing ET-1 and AngII contents. U50,488H reduced endothelial cell apoptosis and attenuated vascular, smooth muscle cell and endothelial cell injury. U50,488H also enhanced the rats' response to oxidative stress by increasing the NOS and T-AOC contents. Moreover, U50,488H increased the eNOS, p-eNOS, Akt, and p-AKT expression and decreased the iNOS and Caveolin-1 expression. In vitro results showed that U50,488H promoted NO, IL-10, p-Akt, and p-eNOS levels in endothelial cell supernatants versus the HS group. And U50,488H reduced the adhesion of peripheral blood mononuclear cells and polymorphonuclear neutrophils to endothelial cells and the migration function of polymorphonuclear neutrophils. Our study suggested that κ-OR activation may improve vascular endothelial dysfunction in salt-sensitive hypertensive rats through the PI3K/Akt/eNOS signaling pathway. This may be a potential therapeutic approach in the treatment of hypertension.

κ-opioid receptor stimulation alleviates rat vascular smooth muscle cell calcification via PFKFB3-lactate signaling

In the present study, the effects and mechanism of action of U50,488H (a selective κ-opioid receptor agonist) on calcification of rat vascular smooth muscle cells (VSMCs) induced by β-glycerophosphate (β-GP) were investigated. VSMCs were isolated and cultured in traditional FBS-based media. A calcification model was established in VSMCs under hyperphosphatemia and intracellular calcium contents. Alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and lactate were detected in cell culture supernatants before and after treatment. Alizarin red staining was used to detect the degree of calcification of VSMCs. Expression levels of key molecules of osteogenic markers, fructose-2,6-biphosphatase 3 (PFKFB3), and proline hydroxylase 2 (PHD2), were determined using western blotting. Further, vascular calcification was induced by vitamin D3 plus nicotine in rats and isolated thoracic aortas, calcium concentration was assessed in rat aortic rings in vitro. We demonstrated that U50,488H inhibited VSMC calcification in a concentration-dependent manner. Moreover, U50,488H significantly inhibited osteogenic differentiation and ALP activity in VSMCs pretreated with β-GP. Further studies confirmed that PFKFB3 expression, LDH level, and lactate content significantly increased during calcification of VSMCs; U50,488H reversed these changes. PHD2 expression showed the opposite trend compared to PFKFB3 expression. nor-BNI or 3-PO abolished U50,488H protective effects. Besides, U50,488H inhibited VSMC calcification in rat aortic rings ex vivo. Collectively, our experiments show that κ-opioid receptor activation inhibits VSMC calcification by reducing PFKFB3 expression and lactate content, providing a potential drug target and strategy for the clinical treatment of vascular calcification.

The Protective Effects of Butorphanol on Pulmonary Function of Patients with Obesity Undergoing Laparoscopic Bariatric Surgery: a Double-Blind Randomized Controlled Trial

BACKGROUND

Obesity is a risk factor for postoperative pulmonary complications (PPCs). Recent studies have reported the pulmonary protective role of the kappa opioid receptor (KOR). Butorphanol is a narcotic with strong KOR agonist action, and the role in pulmonary protection is uncertain. Here, we hypothesized that butorphanol exerts protective effects on pulmonary function in patients with obesity undergoing laparoscopic bariatric surgery.

METHODS

Patients with a body mass index ≥ 30 kg/m² scheduled for laparoscopic bariatric surgery were randomized to receive butorphanol or normal saline. Butorphanol was administered as an initial loading dose of 10 μg/kg at 5 min before induction followed by 5 μg/(kg h) during surgery. The primary outcome was arterial-alveolar oxygen tension ratio (a/A ratio). Secondary outcomes included other pulmonary variables, biomarkers reflecting pulmonary injury, and incidence of PPCs within 7 days after surgery.

RESULTS

Patients in the butorphanol group had a significantly higher a/A ratio at 1 h after the operation began (68 ± 7 vs. 55 ± 8, P < 0.001), end of the operation (73 ± 8 vs. 59 ± 7, P < 0.001), and 1 h after extubation (83 ± 9 vs. 70 ± 5, P < 0.001) compared with those in the control group. In addition, in the butorphanol group, dead space to tidal volume ratios were significantly lower than those in the control group at the same time points (all P < 0.001). In the control group, the levels of biomarkers reflecting pulmonary injury were significantly higher than those in the butorphanol group at 3 h, 6 h, 12 h, and 24 h postoperatively (P < 0.001). The incidence of PPCs was similar in both groups.

CONCLUSION

Butorphanol administration protected pulmonary function by improving oxygenation and reducing dead space ventilation in patients with obesity undergoing laparoscopic bariatric surgery. Butorphanol may therefore provide clinical benefits in patients with obesity.

Participation of the opioid receptor - nitric oxide - cGMP - K+ channel pathway in the peripheral antinociceptive effect of nalbuphine and buprenorphine in rats

The aim of this study was to examine if the peripheral antinociceptive effects of the opioid agonist/antagonist nalbuphine and buprenorphine involve the sequential participation of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) synthesis followed by K⁺ channel opening in the formalin test. Wistar rats (180-220 g) were injected in the dorsal surface of the right hind paw with formalin (1%). Rats received a subcutaneous (s.c.) injection into the dorsal surface of the paw of vehicles or increasing doses of nalbuphine (50-200 μg/paw) or buprenorphine (1-5 μg/paw) 20 min before formalin injection into the paw. Nalbuphine antinociception was reversed by the s.c. injection into the paw of the inhibitor of NO synthesis (N^G-nitro-l-arginine methyl ester (L-NAME)), by the inhibitor of guanylyl cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ)), by the K_ir6.1-2, ATP-sensitive K⁺ channel inhibitors (glibenclamide and glipizide), by the K_Ca2.1-3, small conductance Ca²⁺-activated K⁺ channel blocker (apamin), by the K_Ca1.1, large conductance Ca²⁺-activated K⁺ channel blocker (charybdotoxin), and by the K_V, voltage-dependent K⁺ channel inhibitors (4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA)). The antinociceptive effect produced by buprenorphine was blocked by the s.c. injection of 4-AP and TEA but not by L-NAME, ODQ, glibenclamide, glipizide, apamin, or charybdotoxin. The present results provide evidence for differences in peripheral mechanisms of action between these opioid drugs.

The effect of activated κ-opioid receptor (κ-OR) on the role of calcium sensing receptor (CaSR) in preventing hypoxic pulmonary hypertension development

κ-opioid receptor (κ-OR) plays a key role in preventing hypoxic pulmonary hypertension (HPH) development after activated by exogenous agonist U50,488H. Calcium sensing receptor (CaSR) activation induces HPH by promoting vasoconstriction and vascular remodeling. The activated κ-OR is reported to inhibit the expression of CaSR in pulmonary artery smooth muscle cells (PASMCs). Thus, in this study, we aimed to explore the effect of activated κ-OR on the role of CaSR in preventing HPH development. An HPH rat model was constructed using Sprague-Dawley rats. Changes in mean pulmonary arterial pressure (mPAP) and right ventricular pressure (RVP) mediated by κ-OR agonist U50,488H and CaSR inhibitor NPS2143 were observed. The effects of CaSR agonist spermine and inhibitor NPS2143 on pulmonary artery tension were tested. The expression and localization of κ-OR and CaSR were measured in isolated PASMCs. A cell-counting kit-8 assay was performed to evaluate the effect of spermine in PASMC proliferation. Expression of proliferating cell nuclear antigen (PCNA), Erk, and p-Erk was evaluated by western blot analysis. Results showed that κ-OR and CaSR were co-expressed and colocalized in PASMCs under normoxic and hypoxic conditions. Interactions between κ-OR and CaSR were also observed. Spermine improved vasoconstriction in the pulmonary artery in HPH rats, which was abolished by U50,488H. RVP and mPAP were significantly increased in HPH rats under CaSR stimulation, but were significantly reduced when the rats were pretreated with U50,488H and NPS2143 (P < 0.01). Spermine treatment significantly promoted PASMC proliferation, which was significantly inhibited by U50,488H, p38 inhibitor SB203580, JNK inhibitor SP600125, Erk inhibitor SCH772984, and MEK inhibitor U0126, especially Erk inhibitor (P < 0.01). Spermine significantly increased PCNA and P-Erk expression in hypoxic conditions, which was inhibited by U50,488H and NPS2143. κ-OR stimulation prevented HPH development via the CaSR/MAPK signaling pathway.

κ-Opioid receptor stimulation reduces palmitate-induced apoptosis via Akt/eNOS signaling pathway

Background

This study was designed to test the hypothesis that κ-opioid receptor (κ-OR) stimulation reduces palmitate-induced HUVECs apoptosis and to investigate its mechanisms.

Methods

HUVECs were subjected to sodium palmitate, apoptosis and cell viability were determined, HUVECs were treated with specific inhibitors to PI3K, Akt, eNOS and siRNAs targeting κ-OR and Akt. Groups were divided as follows: the control group, the sodium palmitate group, the sodium palmitate+U50,488H (a selective κ-OR agonist) group and the sodium palmitate+U50,488H + nor-BNI (a selective κ-OR antagonist) group.

Results

Treatment with sodium palmitate significantly reduced cell viability and increased apoptosis rate which were significantly alleviated by pretreatment with U50,488H, the effect of U50,488H was abolished by nor-BNI. Phosphorylation of Akt and eNOS, as well as NO production were attenuated and accompanied by an increased expression of caspase 3 when HUVECs were subjected to sodium palmitate, and all these changes were restored by pretreatment with U50,488H, the effects of U50,488H were abolished by nor-BNI, and specific inhibitors to PI3K, Akt, eNOS, respectively. SiRNAs targeting κ-OR or Akt abolished the effects of U50,488H on phosphorylation of Akt and eNOS as well as the expressions of caspase 3, Bax and Bcl-2. SiRNAs targeting Akt elicited no effect on the expression of κ-OR.

Conclusion

This study provides the evidence for the first time that κ-OR stimulation possesses anti-palmitate-induced apoptosis effect, which is mediated by PI3K/Akt/eNOS signaling pathway.

Protective effects of astragaloside IV against hypoxic pulmonary hypertension

The present study aimed to evaluate the protective effects of astragaloside IV (As-IV) against hypoxic pulmonary hypertension (HPH) and its mechanisms of action. Sprague-Dawley rats were used in a model of HPH induced by chronic hypoxia. After hypoxia, the mean pulmonary arterial pressure (mPAP), right ventricular pressure (RVP), and right ventricular hypertrophy index (RVHI) were monitored. Relaxation of the pulmonary artery in response to As-IV was measured. The levels of endothelin-1 (ET-1), angiotensin II (Ang II), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in serum were assessed. Cell proliferation was detected by the cell counting kit-8 (CCK-8) assay. Treatment with As-IV significantly decreased mPAP, RVP and RV/(LV + S) and attenuated the development of HPH. Moreover, As-IV time-dependently relaxed the pulmonary arteries from HPH rats. In addition, As-IV decreased the levels of ET-1, Ang II, TNF-α, and IL-6 in serum of HPH rats. In vitro experiments demonstrated that As-IV also significantly inhibited the proliferation of pulmonary artery smooth muscle cells (PASMCs) subjected to hypoxia. Our findings suggested the therapeutic potential of As-IV in the treatment of pulmonary hypertension.

A current view of G protein-coupled receptor - mediated signaling in pulmonary hypertension: finding opportunities for therapeutic intervention

Pathological vascular remodeling is observed in various cardiovascular diseases including pulmonary hypertension (PH), a disease of unknown etiology that has been characterized by pulmonary artery vasoconstriction, right ventricular hypertrophy, vascular inflammation, and abnormal angiogenesis in pulmonary circulation. G protein-coupled receptors (GPCRs) are the largest family in the genome and widely expressed in cardiovascular system. They regulate all aspects of PH pathophysiology and represent therapeutic targets. We overview GPCRs function in vasoconstriction, vasodilation, vascular inflammation-driven remodeling and describe signaling cross talk between GPCR, inflammatory cytokines, and growth factors. Overall, the goal of this review is to emphasize the importance of GPCRs as critical signal transducers and targets for drug development in PH.

Quaternary ammonium salt of U50,488H elicits protective effects against hypoxic pulmonary hypertension

The present study aimed to investigate the role of quaternary ammonium salt of U50,488H (Q-U50,488H) in hypoxic pulmonary hypertension (HPH) and underlying mechanisms involved. A HPH animal model was established in rats under hypoxia and the mean pulmonary arterial pressure (mPAP) and right ventricular pressure (RVP) were measured. Relaxation of the pulmonary artery in response to Q-U50,488H was determined. In addition, expression and activity of endothelial nitric oxide (NO) synthase (eNOS) and inducible NO synthase (iNOS) with NO content, Akt expression, total antioxidant capacity (T-AOC), and gp91phox were evaluated. Cell viability was determined by the cell counting kit-8 (CCK-8) assay. We demonstrated that both the molecular weight and solubility of Q-U50,488H were higher than that of U50,488H. Q-U50,488H reduced mPAP and RVP and prevented the development of HPH. Moreover, Q-U50,488H relaxed the pulmonary arteries from both normal and HPH rats in a time-dependent manner. Under hypoxic conditions, Q-U50,488H significantly increased Akt phosphorylation, eNOS phosphorylation, NO content in serum, and T-AOC in pulmonary arteries of HPH rats. In addition, the activity of eNOS was elevated, but the activity of iNOS was reduced when Q-U50,488H was given under hypoxia. Q-U50,488H significantly counteracted the increase of gp91phox expression in pulmonary arteries under hypoxia. In addition, in vitro studies suggested that Q-U50,488H inhibited pulmonary artery smooth muscle cells (PASMCs) proliferation under hypoxic conditions and that the effects of Q-U50,488H were blocked by nor-binaltorphimine (nor-BNI). Thus, our results provided evidence that Q-U50,488H plays a protective role against HPH via κ-opioid receptor stimulation.

Hypoxia-Induced Mitogenic Factor Acts as a Nonclassical Ligand of Calcium-Sensing Receptor, Therapeutically Exploitable for Intermittent Hypoxia-Induced Pulmonary Hypertension

Hypoxia-induced mitogenic factor (HIMF) is an inflammatory cytokine playing important role(s) in the development of hypoxic pulmonary hypertension. The molecular target mediating HIMF-stimulated downstream events remains unclear. The coimmunoprecipitation screen identified extracellular calcium-sensing receptor (CaSR) as the binding partner for HIMF in pulmonary artery smooth muscle cells. The yeast 2-hybrid assay then revealed the binding of HIMF to the intracellular, not the extracellular, domain of extracellular CaSR. The binding of HIMF enhanced the activity of extracellular CaSR and mediated hypoxia-evoked proliferation of pulmonary artery smooth cells and the development of pulmonary vascular remodeling and pulmonary hypertension, all of which was specifically attenuated by a synthesized membrane-permeable peptide flanking the core amino acids of the intracellular binding domain of extracellular CaSR. Thus, HIMF induces pulmonary hypertension as a nonclassical ligand of extracellular CaSR, and the binding motif of extracellular CaSR can be therapeutically exploitable.

Functional pharmacological characterization of SER100 in cardiovascular health and disease

BACKGROUND AND PURPOSE

SER100 is a selective nociceptin (NOP) receptor agonist with sodium-potassium-sparing aquaretic and anti-natriuretic activity. This study was designed to characterize the functional cardiovascular pharmacology of SER100 in vitro and in vivo, including experimental models of cardiovascular disease.

EXPERIMENTAL APPROACH

Haemodynamic, ECG parameters and heart rate variability (HRV) were determined using radiotelemetry in healthy, conscious mice. The haemodynamic and vascular effects of SER100 were also evaluated in two models of cardiovascular disease, spontaneously hypertensive rats (SHR) and murine hypoxia-induced pulmonary hypertension (PH). To elucidate mechanisms underlying the pharmacology of SER100, acute blood pressure recordings were performed in anaesthetized mice, and the reactivity of rodent aorta and mesenteric arteries in response to electrical- and agonist-stimulation assessed.

KEY RESULTS

SER100 caused NOP receptor-dependent reductions in mean arterial blood pressure and heart rate that were independent of NO. The hypotensive and vasorelaxant actions of SER100 were potentiated in SHR compared with Wistar Kyoto. Moreover, SER100 reduced several indices of disease severity in experimental PH. Analysis of HRV indicated that SER100 decreased the low/high frequency ratio, an indicator of sympatho-vagal balance, and in electrically stimulated mouse mesenteric arteries SER100 inhibited sympathetic-induced contractions.

CONCLUSIONS AND IMPLICATIONS

SER100 exerts a chronic hypotensive and bradycardic effects in rodents, including models of systemic and pulmonary hypertension. SER100 produces its cardiovascular effects, at least in part, by inhibition of cardiac and vascular sympathetic activity. SER100 may represent a novel therapeutic candidate in systemic and pulmonary hypertension.

Punicalagin Prevents Hypoxic Pulmonary Hypertension via Anti-Oxidant Effects in Rats

Punicalagin (PG), a major bioactive ingredient in pomegranate juice, has been proven to have anti-oxidative stress properties and to exert protective effects on acute lung injuries induced by lipopolysaccharides. This study aimed to investigate the effects of PG treatment on hypoxic pulmonary hypertension (HPH) and the underlying mechanisms responsible for the effects. Rats were exposed to 10% oxygen for 2 wk (8 h/day) to induce the HPH model. PG (5, 15, 45[Formula: see text]mg/kg) was orally administered 10[Formula: see text]min before hypoxia each day. PG treatments at the doses of 15 and 45[Formula: see text]mg/kg/d decreased the mean pulmonary arterial pressure (mPAP) and alleviated right ventricular hypertrophy and vascular remodeling in HPH rats. Meanwhile, PG treatment attenuated the hypoxia-induced endothelial dysfunction of pulmonary artery rings. The beneficial effects of PG treatment were associated with improved nitric oxide (NO)-cGMP signaling and reduced oxidative stress, as evidenced by decreased superoxide generation, gp91[Formula: see text] expression and nitrotyrosine content in the pulmonary arteries. Furthermore, tempol’s scavenging of oxidative stress also increased NO production and attenuated endothelial dysfunction and pulmonary hypertension in HPH rats. Combining tempol and PG did not exert additional beneficial effects compared to tempol alone. Our study indicated for the first time that PG treatment can protect against hypoxia-induced endothelial dysfunction and pulmonary hypertension in rats, which may be induced via its anti-oxidant actions.

κ-Opioid Receptor Stimulation Improves Endothelial Function via Akt-stimulated NO Production in Hyperlipidemic Rats

This study was designed to investigate the effect of U50,488H (a selective κ-opioid receptor agonist) on endothelial function impaired by hyperlipidemia and to determine the role of Akt-stimulated NO production in it. Hyperlipidemic model was established by feeding rats with a high-fat diet for 14 weeks. U50,488H and nor-BNI (a selective κ-opioid receptor antagonist) were administered intraperitoneally. In vitro, the involvement of the PI3K/Akt/eNOS pathway in the effect of U50,488H was studied using cultured endothelial cells subjected to artificial hyperlipidemia. Serum total cholesterol and low-density lipoprotein cholesterol concentrations dramatically increased after high-fat diet feeding. Administration of U50,488H significantly alleviated endothelial ultrastructural destruction and endothelium-dependent vasorelaxation impairment caused by hyperlipidemia. U50,488H also increased Akt/eNOS phosphorylation and serum/medium NO level both in vivo and in vitro. U50,488H increased eNOS activity and suppressed iNOS activity in vivo. The effects of U50,488H were abolished in vitro by siRNAs targeting κ-opioid receptor and Akt or PI3K/Akt/eNOS inhibitors. All effects of U50,488H were blocked by nor-BNI. These results demonstrate that κ-opioid receptor stimulation normalizes endothelial ultrastructure and function under hyperlipidemic condition. Its mechanism is related to the preservation of eNOS phosphorylation through activation of the PI3K/Akt signaling pathway and downregulation of iNOS expression/activity.

Calorie Restriction Attenuates Monocrotaline-induced Pulmonary Arterial Hypertension in Rats

Calorie restriction (CR) is one of the most effective nonpharmacological interventions protecting against cardiovascular disease, such as hypertension in the systemic circulation. However, whether CR could attenuate pulmonary arterial hypertension (PAH) is largely unknown. The PAH model was developed by subjecting the rats to a single subcutaneous injection of monocrotaline. CR lowered mean pulmonary arterial pressure (mPAP) and reduced vascular remodeling and right ventricular hypertrophy in PAH rats. Meanwhile, CR attenuated endothelial dysfunction as evidenced by increased relaxation in response to acetylcholine. The beneficial effects of CR were associated with restored sirtuin-1 (SIRT1) expression and endothelial nitric oxide synthase (eNOS) phosphorylation and reduced eNOS acetylation in pulmonary arteries of PAH rats. To further clarify the role of SIRT1 in the protective effects of CR, adenoviral vectors for overexpression of SIRT1 were administered intratracheally at 1 day before monocrotaline injection. Overexpression of SIRT1 exhibited similar beneficial effects on mPAP and endothelial function, and increased eNOS phosphorylation and reduced eNOS acetylation in the absence of CR. Moreover, SIRT1 overexpression attenuated the increase in mPAP in hypoxia-induced PAH animals. Overall, the present data demonstrate that CR may serve as an effective treatment of PAH, and targeting the SIRT1/eNOS pathway may improve treatment of PAH.

Activation of κ-opioid receptor by U50,488H improves vascular dysfunction in streptozotocin-induced diabetic rats

BACKGROUND

Evidence suggests that activation of κ-opioid receptor (KOR) by U50,488H exhibits potential cardiovascular protective properties. However, the effects of U50,488H on vascular dysfunction in diabetes mellitus (DM) are still not clear. The present study was designed to investigate the effects of U50,488H on vascular dysfunction in diabetic rats and explore the underlying mechanisms involved.

METHODS

Rats were randomly divided into control, DM, DM + vehicle, DM + U50,488H and DM + nor-binaltorphimine (nor-BNI) groups. Streptozotocin injection was used to induce DM. Weight, blood glucose, blood pressure and plasma insulin for each group were measured. Arterial functions were assessed with isolated vessels mounted for isometric tension recordings. Angiotensin II (ANG II), soluble intercellular adhesion molecule-1 (sICAM-1), interleukin (IL)-6 and IL-8 levels were measured by ELISA, and endothelial nitric oxide synthase (eNOS) phosphorylation and NF-κB p65 translocation were measured by Western blot.

RESULTS

Activation of KOR by U50,488H reduced the enhanced contractility of aortas to KCl and noradrenaline and increased acetylcholine-induced vascular relaxation, which could also protect the aortal ultrastructure in DM. U50,488H treatment resulted in reduction in ANG II, sICAM-1, IL-6 and IL-8 levels and elevation in NO levels, while these effects were abolished by nor-BNI treatment. Further more, eNOS phosphorylation was increased, and NF-κB p65 translocation was decreased after U50,488H treatment.

CONCLUSIONS

Our study demonstrated that U50,488H may have therapeutic effects on diabetic vascular dysfunction by improving endothelial dysfunction and attenuating chronic inflammation, which may be dependent on phosphorylation of eNOS and downstream inhibition of NF-кB.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Effect of chronic continual- and intermittent hypoxia-induced systemic inflammation on the cardiovascular system in rats

PURPOSE

Obstructive sleep apnea syndrome (OSAS) has been recognized as an important risk factor for cardiovascular morbidity and mortality. However, the underlying mechanisms are poorly understood. Present study aimed to investigate the role of NF-κB-dependent inflammation pathways in pathophysiological responses of cardiovascular system in OSAS.

METHODS

Thirty male specific pathogen-free (SPF) Sprague-Dawley rats were randomly assigned to normoxia (N) group, continual hypoxia (CH) group, and intermittent hypoxia (IH) group (n = 10) and were exposed to N (21% O2), CH (8% O2), or IH (6-11% O2 for 10 s and 21% O2 for 80 s in every 90 s) for 8 h/day for 35 days. The hemodynamic and pathomorphologic effects of IH and CH exposure were investigated as well as the expression of NF-κB-dependent inflammation factors.

RESULTS

Chronic IH or CH significantly increased mean pulmonary arterial pressure (mPAP) in rats, while no significant changes occurred in mean carotid arterial pressure (mCAP). The ratio of right ventricle (RV) to left ventricle (LV) + septum (S) was significantly increased by both IH and CH, suggesting RV hypertrophy was induced by IH or CH. Elastic fiber staining showed an irregular pattern of elastic fiber distribution after hypoxia, and aortic tunica media thickness was increased. Both chronic IH and CH upregulated the expressions of transcription factor NF-κB and related pro-inflammatory cytokines and adhesion molecules.

CONCLUSIONS

The current study expands our understanding that both IH and CH could activate the expression of NF-κB and related inflammatory factors as well as cause pathophysiologic damage to the cardiovascular system in OSAS. All these results provide further support to an emerging hypothesis that activation of NF-κB-dependent inflammation may play a central role in the pathophysiology of cardiovascular dysfunction in OSAS.