Role of ROS/Kv/HIF Axis in the Development of Hypoxia-Induced Pulmonary Hypertension.

Hypoxic pulmonary hypertension (HPH) is a common complication in patients with chronic obstructive pulmonary disease (COPD), sleep-disordered breathing, or dwellers in high altitude. The exact mechanisms underlying the development of HPH still remain unclear. Reactive oxygen species (ROS), hypoxia inducible factors (HIF), and potassium channels (KV) are believed as the main factors during the development of HPH. We propose that the "ROS/Kv/HIF axis" may play an important initiating role in the development of HPH. Being formed under a hypoxic condition, ROS affects the expression and function of HIFs or KV, and consequently triggers multiple downstream signaling pathways and genes expression that participate in promoting pulmonary vasoconstriction and arterial remodeling. Thus, further study determining the initiating role of "ROS/Kv/HIF axis" in the development of HPH could provide theoretic evidences to better understand the underlying mechanisms of HPH, and help identify new potential targets in the treatment of HPH.

Sodium hydrosulfide alleviates lung inflammation and cell apoptosis following resuscitated hemorrhagic shock in rats.

AIM: To investigate the protective effects of hydrogen sulfide (H2S) against inflammation, oxidative stress and apoptosis in a rat model of resuscitated hemorrhagic shock. METHODS: Hemorrhagic shock was induced in adult male SD rats by drawing blood from the femoral artery for 10 min. The mean arterial pressure was maintained at 35-40 mmHg for 1.5 h. After resuscitation the animals were observed for 200 min, and then killed. The lungs were harvested and bronchoalveolar lavage fluid was prepared. The levels of relevant proteins were examined using Western blotting and immunohistochemical analyses. NaHS (28 µmol/kg, ip) was injected before the resuscitation. RESULTS: Resuscitated hemorrhagic shock induced lung inflammatory responses and significantly increased the levels of inflammatory cytokines IL-6, TNF-α, and HMGB1 in bronchoalveolar lavage fluid. Furthermore, resuscitated hemorrhagic shock caused marked oxidative stress in lung tissue as shown by significant increases in the production of reactive oxygen species H2O2 and ·OH, the translocation of Nrf2, an important regulator of antioxidant expression, into nucleus, and the decrease of thioredoxin 1 expression. Moreover, resuscitated hemorrhagic shock markedly increased the expression of death receptor Fas and Fas-ligand and the number apoptotic cells in lung tissue, as well as the expression of pro-apoptotic proteins FADD, active-caspase 3, active-caspase 8, Bax, and decreased the expression of Bcl-2. Injection with NaHS significantly attenuated these pathophysiological abnormalities induced by the resuscitated hemorrhagic shock. CONCLUSION: NaHS administration protects rat lungs against inflammatory responses induced by resuscitated hemorrhagic shock via suppressing oxidative stress and the Fas/FasL apoptotic signaling pathway.

Leptin attenuates lipopolysaccharide or oleic acid-induced acute lung injury in mice.

Leptin is reported to be involved in acute lung injury (ALI). However, the role and underlying mechanisms of leptin in ALI remain unclear. The aim of this study was to determine whether leptin deficiency promoted the development of ALI. LPS or oleic acid (OA) were administered to wild-type and leptin deficient (ob/ob) mice to induce ALI. Leptin level, survival rate, and lung injury were examined. Results showed that leptin levels were predominantly increased in the lung, but also in the heart, liver, kidney, and adipose tissue after LPS adminiatration. Compared with wild-type mice, LPS- or OA-induced lung injury was worse and the survival rate was lower in ob/ob mice. Moreover, leptin deficiency promoted the release of proinflammatory cytokines. Exogenous administration of leptin reduced lethality in ob/ob mice and ameliorated lung injury partly through inhibiting the activation of NF-κB, p38, and ERK pathways. These results indicated that leptin deficiency contributed to the development of lung injury by enhancing inflammatory response, and a high level of leptin improved survival and protected against ALI.

Osthole improves acute lung injury in mice by up-regulating Nrf-2/thioredoxin 1.

Inhibiting reactive oxygen species (ROS) has been viewed as a therapeutic target for the treatment of acute lung injury (ALI). Osthole, an active component in Chinese herbal medicine, has drawn increasing attention because of its various pharmacological functions, including anti-inflammatory and anti-oxidative activities. The aim of the present study was to examine the effects of osthole on ALI induced by lipopolysaccharide (LPS) through intratracheal instillation. The mRNA and protein expression levels of thioredoxin 1 (Trx1) and the nuclear factor erythroid-2 related factor 2 (Nrf2) were detected by real-time PCR, reverse transcription PCR (RT-PCR) and Western blot, respectively. ROS production was measured by flow cytometry. Our results showed that osthole treatment improved the mice survival rates in the middle and high dosage groups, compared with the untreated LPS group. Moreover, osthole treatment significantly improved LPS-induced lung pathological damage, and it decreased the lung injury scores, lung wet/dry ratios and the total protein level in Bronchoalveolar lavage fluid (BALF). Osthole treatment dramatically reduced the H2O2, MDA and OH levels in the lung homogenates. LDH and ROS were markedly reduced in the osthole+LPS group in vitro. Furthermore, osthole increased Nrf2 and Trx1 expression in terms of mRNA and protein in vivo and in vitro. Nrf2 siRNA (siNrf2) could suppress the beneficial effects of osthole on ALI. In conclusion, the current study demonstrates that osthole exerted protective effects on LPS-induced ALI by up-regulating the Nrf-2/Trx-1 pathway.

Tanshinone IIA inhibits hypoxia-induced pulmonary artery smooth muscle cell proliferation via Akt/Skp2/p27-associated pathway.

We previously showed that tanshinone IIA ameliorated the hypoxia-induced pulmonary hypertension (HPH) partially by attenuating pulmonary artery remodeling. The hypoxia-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) is one of the major causes for pulmonary arterial remodeling, therefore the present study was performed to explore the effects and underlying mechanism of tanshinone IIA on the hypoxia-induced PASMCs proliferation. PASMCs were isolated from male Sprague-Dawley rats and cultured in normoxic (21%) or hypoxic (3%) condition. Cell proliferation was measured with 3 - (4, 5 - dimethylthiazal - 2 - yl) - 2, 5 - diphenyltetrazoliumbromide assay and cell counting. Cell cycle was measured with flow cytometry. The expression of of p27, Skp-2 and the phosphorylation of Akt were measured using western blot and/or RT-PCR respectively. The results showed that tanshinone IIA significantly inhibited the hypoxia-induced PASMCs proliferation in a concentration-dependent manner and arrested the cells in G1/G0-phase. Tanshinone IIA reversed the hypoxia-induced reduction of p27 protein, a cyclin-dependent kinase inhibitor, in PASMCs by slowing down its degradation. Knockdown of p27 with specific siRNA abolished the anti-proliferation of tanshinone IIA. Moreover, tanshinone IIA inhibited the hypoxia-induced increase of S-phase kinase-associated protein 2 (Skp2) and the phosphorylation of Akt, both of which are involved in the degradation of p27 protein. In vivo tanshinone IIA significantly upregulated the hypoxia-induced p27 protein reduction and downregulated the hypoxia-induced Skp2 increase in pulmonary arteries in HPH rats. Therefore, we propose that the inhibition of tanshinone IIA on hypoxia-induce PASMCs proliferation may be due to arresting the cells in G1/G0-phase by slowing down the hypoxia-induced degradation of p27 via Akt/Skp2-associated pathway. The novel information partially explained the anti-remodeling property of tanshinone IIA on pulmonary artery in HPH.

Osthole protects lipopolysaccharide-induced acute lung injury in mice by preventing down-regulation of angiotensin-converting enzyme 2.

The renin-angiotensin-aldosterone system (RAAS) plays an important role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Angiotensin converting enzyme 2 (ACE2) plays a protective role in acute lung injury. Osthole, a natural coumarin derivative extracted from traditional Chinese medicines, is known to have anti-inflammatory effect, but the effect of osthole on the ALI is largely unknown. The aim of this study is to explore whether and by what mechanisms osthole protects lipopolysaccharide(LPS)-induced acute lung injury. Herein, we found that osthole had a beneficial effect on LPS-induced ALI in mice. As revealed by survival study, pretreatment with high doses of osthole reduced the mortality of mice from ALI. Osthole pretreatment significantly improved LPS-induced lung pathological changes, reduced lung wet/dry weight ratios and total protein in BALF. Osthole also inhibited the release of inflammatory mediators TNF-α and IL-6. Meanwhile, osthole markedly prevented the loss of ACE2 and Ang1-7 in lung tissue of ALI mice. ACE2 inhibitor blocked the protective effect of osthole in NR 8383 cell lines. Taken together, our study showed that osthole improved survival rate and attenuated LPS-induced ALI and ACE2 may play a role in it.

Insulin reduces LPS-induced lethality and lung injury in rats.

Insulin is a main glucose homeostatic hormone in the body. Previous reports showed that insulin also exerted anti-inflammatory actions and attenuated systemic inflammatory response. Here, we observed the effects and the underlying mechanisms of insulin on lipopolysaccharide (LPS)-induced acute lung injury (ALI). As revealed by survival study, insulin reduced mortality of rats and prolonged their survival time. Meanwhile, insulin significantly reduced the levels of inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and high mobility group box 1 (HMGB1) in bronchoalveolar lavage fluid (BALF). Besides, insulin markedly inhibited the expression of toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB). Taken together, these data provided information that insulin attenuated LPS-induced ALI may attribute partly to the inhibition of the production of cytokines, and the expression of TLR2, TLR4 and NF-κB.

An exogenous hydrogen sulphide donor, NaHS, inhibits the nuclear factor κB inhibitor kinase/nuclear factor κb inhibitor/nuclear factor-κB signaling pathway and exerts cardioprotective effects in a rat hemorrhagic shock model.

Hemorrhagic shock (HS) is a common condition and leading cause of death in trauma patients universally. Severe inflammatory responses during HS finally lead to multiple-organ failure. Hydrogen sulphide (H2S) is increasingly recognized as an important signaling molecule with various protective effects. In the present study, we investigated the antiinflammatory and cardioprotective effects of an exogenous H2S donor, sodium hydrosulfide (NaHS), in an HS rat model. Male Sprague-Dawley rats were randomly divided into the sham-operated, sham-operated treated with NaHS (28 µmol/kg, intraperitoneally (i.p.)), HS, and HS treated with NaHS (28 µmol/kg, i.p.) groups. The HS groups were subjected to mimicked HS for 1 h and then treated with NaHS or left untreated. The rats were then resuscitated with Ringer lactate solution for 1 h. Myocardial enzymes and inflammatory cytokines were evaluated. Morphologic changes in cardiac tissue and ultrastructural injury were also analyzed. HS resulted in significant hemodynamic deterioration and increased myocardial enzyme and inflammatory cytokine levels. Intraperitoneal administration of NaHS significantly prevented hemodynamic deterioration and decreased the elevation of myocardial enzymes. NaHS also inhibited the nuclear factor κB inhibitor kinase (IKK)/nuclear factor κB inhibitor (IκB)/nuclear factor κB (NF-κB) signaling pathway. The results suggest that NaHS exerts cardioprotective effects against HS. The protective effects of NaHS may occur via down-regulation of the IKK/IκB/NF-κB signaling pathway.

Role of macrophage migration inhibitory factor in the proliferation of smooth muscle cell in pulmonary hypertension.

Pulmonary hypertension (PH) contributes to the mortality of patients with lung and heart diseases. However, the underlying mechanism has not been completely elucidated. Accumulating evidence suggests that inflammatory response may be involved in the pathogenesis of PH. Macrophage migration inhibitory factor (MIF) is a critical upstream inflammatory mediator which promotes a broad range of pathophysiological processes. The aim of the study was to investigate the role of MIF in the pulmonary vascular remodeling of hypoxia-induced PH. We found that MIF mRNA and protein expression was increased in the lung tissues from hypoxic pulmonary hypertensive rats. Intensive immunoreactivity for MIF was observed in smooth muscle cells of large pulmonary arteries (PAs), endothelial cells of small PAs, and inflammatory cells of hypoxic lungs. MIF participated in the hypoxia-induced PASMCs proliferation, and it could directly stimulate proliferation of these cells. MIF-induced enhanced growth of PASMCs was attenuated by MEK and JNK inhibitor. Besides, MIF antagonist ISO-1 suppressed the ERK1/2 and JNK phosphorylation induced by MIF. In conclusion, the current finding suggested that MIF may act on the proliferation of PASMCs through the activation of the ERK1/2 and JNK pathways, which contributes to hypoxic pulmonary hypertension.

Macrophage migration inhibitory factor contributes to hypoxic pulmonary vasoconstriction in rats.

BACKGROUND: Hypoxic pulmonary vasoconstriction may lead to pulmonary hypertension, but the underlying mechanisms of persistent vasoconstriction are still unclear. There is evidence that pulmonary inflammation contributes to the abnormalities of function in the pulmonary artery (PA) following chronic hypoxia exposure. Macrophage migration inhibitory factor (MIF) is an important pro-inflammatory cytokine, and we found that expression of MIF was increased in the smooth muscle of PA from hypoxic pulmonary hypertensive rats. Therefore, the aim of the study was to investigate the role of MIF in modulating vasoreactivity of isolated PA rings. METHODS: Sprague-Dawley rats were challenged by intermittent chronic hypoxia exposure for 4 weeks to establish hypoxic pulmonary hypertension models. Subsequently, immunohistochemistry and western blot assay were used to examine the MIF expression in pulmonary artery. Moreover, isometric force displacement was measured in isolated intrapulmonary artery. RESULTS: In the isolated PA, our results showed that MIF mediated the enhanced pulmonary arterial vasoconstriction in response to chronic hypoxia, and the delayed hypoxic constriction in a biphasic pattern of constriction occurs in response to acute hypoxia. We also present the finding that MIF had no effect on force on its own, but concentration-dependently potentiated constrictions pre-evoked by phenylephrine under normoxic condition. The potentiation was independent of the endothelium. MIF-induced potentiation of phenylephrine-evoked constriction was partially inhibited by PKC inhibitor chelerythrine, p38 inhibitor SB 203580, ERK1/2 inhibitor U0126, respectively. CONCLUSIONS: Our results suggested that MIF enhanced vasoconstriction of pulmonary artery elicited by agonist through PKC, p38 and ERK1/2 signal pathways, which may contributes to hypoxic pulmonary vasoconstriction.

Tanshinone IIA attenuates seawater aspiration-induced lung injury by inhibiting macrophage migration inhibitory factor.

Inflammation takes responsibility for the seawater aspiration-induced lung injury. Tanshinone IIA (TIIA) can protect lipopolysaccharide-induced lung injury in mice through the inhibition of inflammation, but it is not reported whether TIIA have a protective effect on lung injury induced by seawater aspiration. Macrophage migration inhibitory factor (MIF) plays an important role in acute lung injury. In this study, we observed the effect of TIIA on the seawater aspiration-induced lung injury and the role of MIF in it. Seawater was aspirated into trachea of rats to make the lung injury model. TIIA was administered to investigate its beneficial effect on seawater-induced acute lung injury. The results showed that seawater aspiration led to hyoxemia, pulmonary edema, neutrophil infiltration, and lung histopathologic changes, with the elevated MIF expression in the lung tissues and plasma. However, these changes were attenuated by TIIA. In macrophage cells we also demonstrated that TIIA could inhibit MIF expression, nuclear factor κB (NF-κB) activity and release of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) induced by seawater. Besides, pretreatment with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid (ISO-1), the MIF antagonist, elevated NF-κB and cytokines induced by seawater were also reduced markedly. Furthermore, rMIF treatment alone increased the phosphorylation level of NF-κB and release of cytokines, which was almost abolished by TIIA. Taken together, our results suggested that TIIA exert a protective effect on the seawater aspiration-induced lung injury partly through downregulation of MIF and the subsequent NF-κB activity, as well as expression of IL-6 and TNF-α.

Protective effect of bicyclol on lipopolysaccharide-induced acute lung injury in mice.

Bicyclol is synthesized based on schisandrin, which is one of the main active components of Chinese herb Fructus Schisandrae. The purpose of this study is to investigate whether bicyclol has a beneficial effect on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Bicyclol was given to mice by gavage for three times. ALI was induced by vena caudalis injection of LPS. The last dose of bicyclol was administrated 1 h before LPS given. Mice in each group were sacrificed at different time point after LPS administration. As revealed by survival study, pretreatment with high doses of bicyclol reduced the mortality of mice from ALI. Bicyclol pretreatment significantly improved LPS-induced lung pathological changes, inhibited myeloperoxidase (MPO) activity, and reduced lung/body and lung wet/dry weight ratios. Bicyclol also inhibited the release of TNF-α, IL-1ß and HMGB1, whereas simultaneously increased the expression of IL-10. Furthermore, the phosphorylation level of NF-κB p65 was markedly decreased by bicyclol. Taken together, our study showed that bicyclol improves survival rate and attenuates LPS-induced ALI. The protective mechanism may be due to the inhibition of NF-κB activation and regulation of cytokine secretion.

Beta-estradiol attenuates hypoxic pulmonary hypertension by stabilizing the expression of p27kip1 in rats.

BACKGROUND: Pulmonary vascular structure remodeling (PVSR) is a hallmark of pulmonary hypertension. P27(kip1), one of critical cyclin-dependent kinase inhibitors, has been shown to mediate anti-proliferation effects on various vascular cells. Beta-estradiol (ß-E2) has numerous biological protective effects including attenuation of hypoxic pulmonary hypertension (HPH). In the present study, we employed ß-E2 to investigate the roles of p27(kip1) and its closely-related kinase (Skp-2) in the progression of PVSR and HPH. METHODS: Sprague-Dawley rats treated with or without ß-E2 were challenged by intermittent chronic hypoxia exposure for 4 weeks to establish hypoxic pulmonary hypertension models, which resemble moderate severity of hypoxia-induced PH in humans. Subsequently, hemodynamic and pulmonary pathomorphology data were gathered. Additionally, pulmonary artery smooth muscle cells (PASMCs) were cultured to determine the anti-proliferation effect of ß-E2 under hypoxia exposure. Western blotting or reverse transcriptional polymerase chain reaction (RT-PCR) were adopted to test p27(kip1), Skp-2 and Akt-P changes in rat lung tissue and cultured PASMCs. RESULTS: Chronic hypoxia significantly increased right ventricular systolic pressures (RVSP), weight of right ventricle/left ventricle plus septum (RV/LV+S) ratio, medial width of pulmonary arterioles, accompanied with decreased expression of p27(kip1) in rats. Whereas, ß-E2 treatment repressed the elevation of RVSP, RV/LV+S, attenuated the PVSR of pulmonary arterioles induced by chronic hypoxia, and stabilized the expression of p27(kip1). Study also showed that ß-E2 application suppressed the proliferation of PASMCs and elevated the expression of p27(kip1) under hypoxia exposure. In addition, experiments both in vivo and in vitro consistently indicated an escalation of Skp-2 and phosphorylated Akt under hypoxia condition. Besides, all these changes were alleviated in the presence of ß-E2. CONCLUSIONS: Our results suggest that ß-E2 can effectively attenuate PVSR and HPH. The underlying mechanism may partially be through the increased p27(kip1) by inhibiting Skp-2 through Akt signal pathway. Therefore, targeting up-regulation of p27(kip1) or down-regulation of Skp-2 might provide new strategies for treatment of HPH.

Tanshinone IIA modulates pulmonary vascular response to agonist and hypoxia primarily via inhibiting Ca2+ influx and release in normal and hypoxic pulmonary hypertension rats.

The present study was designed to investigate the vascular effects and underlying mechanisms of tanshinone IIA on isolated rat pulmonary artery. Isometric tension was recorded in the arteries from normal and hypoxic pulmonary hypertension rats under normoxia or hypoxia condition. The results showed that tanshinone IIA exerted a biphasic effect on rat pulmonary artery. The constriction was attenuated by endothelium-denudation but was enhanced by inhibition of nitric oxide synthase. Pretreatment with tetraethylammonium (Ca2+-activated K+ channel inhibitor) upward shifted the concentration-response curve without affecting the maximum dilatation. Pretreatment with zinc protoporphyrin IX (heme oxygenase-1 inhibitor), 4-aminopyridine (KV channel inhibitor), glibenclamide (KATP channel inhibitor) or BaCl2 (inwardly rectifying K+ channel inhibitor) did not affect the vasoreactivity. Meanwhile, tanshinone IIA almost abolished vasoconstriction induced by extracellular Ca2+. Under hypoxia condition, tanshinone IIA eliminated acute hypoxia-induced initial contraction, potentiated following vasorelaxation, attenuated and reversed sustained contraction to relaxation in pulmonary artery from normal rats, and reversed phenylephrine-induced sustained constriction to sustained relaxation in remodeled pulmonary artery from hypoxic pulmonary hypertension rats. We concluded that the mild constrictive effect induced by tanshinone IIA was affected by integrity of endothelium and production of nitric oxide, while the potent dilative effect was endothelium-independent and produced primarily by inhibiting extracellular Ca2+ influx and partially by inhibiting intracellular Ca2+ release, as well as activating Ca2+-activated K+ channels. The modulation of tanshinone IIA on pulmonary vasoreactivity under both acute and chronic hypoxia condition may provide a new insight for curing hypoxic pulmonary hypertension.