Several agonists of the peroxisome proliferator-activated receptors (PPARs) are currently used for the treatment of metabolic disorders including diabetes. We have recently shown that one of them, Rosiglitazone, inhibits the vascular ATP-sensitive K+ (KATP) channel and compromises the coronary vasodilation by the β-adrenoceptor agonist. Here, we show evidence for the channel inhibition by various PPAR agonists, information that may be useful for finding new therapeutical agents with less cardiovascular side-effects and more selective KATP channel blockers targeting at the Kir6.1 subunit. Structural comparison of these PPAR agonists may shed insight into the critical chemical groups for the channel inhibition.
Kir6.1/SUR2B channel was expressed in HEK293 cells and studied in whole-cell voltage clamp. The Kir6.1/SUR2B channel was strongly inhibited by several PPARγ agonists with potencies similar to, or higher than, that of Rosiglitazone, while other PPARγ agonists barely inhibited the channel. The Kir6.1/SUR2B channel was also inhibited by PPARα and PPARβ/δ agonists with intermediate potencies. The structure necessary for the channel inhibition appears to include the thiazole linked to an aromatic or furan ring. Additions of side groups such as small aliphatic chain increased the potency for channel inhibition, while additions of aromatic rings reduced it. These results indicate that the PPARγ agonists with weak KATP channel inhibition may be potential candidates as therapeutical agents, and those with strong channel inhibition may be used as selective KATP channel blockers. The structural information of the PPAR agonists may be useful for the development of new therapeutical modalities with less cardiovascular side-effects.
PPAR; thiazolidinedione; Type-2 diabetes mellitus; potassium channel; vascular tones; cardiovascular
Preeclampsia (PE) is an extremely serious condition in pregnant women and the leading cause of maternal and fetal morbidity and mortality. Despite active research, the etiological factors of this disorder remain elusive. The increased release of 15-hydroxyeicosatetraenoic acid (15-HETE) in the placenta of preeclamptic patients has been studied, but its exact role in PE pathogenesis remains unknown. Mounting evidence shows that PE is associated with placental hypoxia, impaired placental angiogenesis, and endothelial dysfunction. In this study, we confirmed the upregulated expression of hypoxia-inducible factor 1α (HIF-1α) and 15-lipoxygenase-1/2 (15-LO-1/2) in patients with PE. Production of the arachidonic acid metabolite, 15-HETE, also increased in the preeclamptic placenta, which suggests enhanced activation of the HIF-1α–15-LO–15-HETE axis. Furthermore, this study is the first to show that the umbilical cord of preeclamptic women contains significantly higher serum concentrations of 15-HETE than that of healthy pregnant women. The results also show that expression of 15-LO-1/2 is upregulated in both human umbilical vein endothelial cells (HUVECs) collected from preeclamptic women and in those cultured under hypoxic conditions. Exogenous 15-HETE promotes the migration of HUVECs and in vitro tube formation and promotes cell cycle progression from the G0/G1 phase to the G2/M + S phase, whereas the 15-LO inhibitor, NDGA, suppresses these effects. The HIF-1α/15-LO/15-HETE pathway is therefore significantly associated within the pathology of PE.
Pulmonary hypertension (PH) is characterized with pulmonary vasoconstriction and vascular remodeling mediated by 15-lipoxygenase (15-LO)/15-hydroxyeicosatetraenoic acid (15-HETE) according to our previous studies. Meanwhile, telomerase reverse transcriptase (TERT) activity is highly correlated with vascular injury and remodeling, suggesting that TERT may be an essential determinant in the development of PH. The aim of this study was to determine the contribution and molecular mechanisms of TERT in the pathogenesis of PH.
Approach and Results
We measured the right ventricular systolic pressure (RVSP) and ventricular weight, analyzed morphometric change of the pulmonary vessels in the hypoxia or monocrotaline treated rats. Bromodeoxyuridine incorporation, transwell assay and flow cytometry in pulmonary smooth muscle cells were performed to investigate the roles and relationship of TERT and 15-LO/15-HETE in PH. We revealed that the expression of TERT was increased in pulmonary vasculature of patients with PH and in the monocrotaline or hypoxia rat model of PH. The up-regulation of TERT was associated with experimental elevated RVSP and pulmonary vascular remodeling. Coimmunoprecipitation experiments identified TERT as a novel interacting partner of 15-LO-2. TERT and 15-LO-2 augmented protein expression of each other. In addition, the proliferation, migration and cell-cycle transition from G0/G1 phase to S phase induced by hypoxia were inhibited by TERT knockdown, which were rescued by 15-HETE addition.
These results demonstrate that TERT regulates pulmonary vascular remodeling. TERT and 15-LO-2 form a positive feedback loop and together promote proliferation and migration of pulmonary artery smooth muscle cells, creating a self-amplifying circuit which propels pulmonary hypertension.
To elucidate the influence of recreational physical activity, body mass index (BMI), and waist circumference on the risk of specific types of urinary incontinence.
We conducted a population-based cross-sectional survey in Gansu, China among 2603 women aged 20 years or older.
The study found that BMI was positively associated with urinary incontinence (P for trend = 0.008) and the association was mainly observed for stress urinary incontinence (OR = 1.4, 95% CI: 1.1, 1.9 for BMI = 24.0–27.9 kg/m2; OR = 2.3, 95% CI: 1.5, 3.6 for BMI ≥ 28.0 kg/m2; P for trend = 0.0005). A positive association between stress incontinence (OR = 1.7, 95% CI: 1.2, 2.5) and waist circumference was observed for women who had waist circumference between 70 cm and 75 cm compared to waist circumference less than 70 cm. Recreational physical activity was inversely associated with overall and mixed urinary incontinence (P for trend <0.0001 for both). A significant interaction between physical activity and waist circumference was found for overall (P = 0.0007) and stress incontinence (P = 0.001).
The findings that physical activity inversely associated with urinary incontinence and its interaction with waist circumference warrant further investigation, particularly in prospective studies.
Recreational physical activity; Body mass index; Waist circumference; Female urinary incontinence
To assess effects of a localized anastomosis between the aorta and left lower lobe pulmonary artery (LLLPA) on flows through central vessels, and on vascular reactivity of small PAs distal or contralateral to the shunt.
Flow rates in major vessels and tensions from small PAs from left and right lower lobes were determined 48 hours after creation of an end-to-side anastomosis of the LLLPA to the aorta.
Anastomoses increased flow through the LLLPA from 194 ± 6 to 452 ± 18 ml/min immediately after anastomosis and to 756 ± 19 ml/min by the time of harvest (n=88, p<0.05). Flow rates in main PAs from hosts with anastomoses were lower (557 ± 26 versus1033 ± 244 ml/min) while aortic root flows were not different from controls (1370 ± 53 compared to 1120 ± 111 ml/min; p = 0.07). Wet-to-dry weights of the both lungs and aortic flow rates were proportional to shunt flow rates. PA rings harvested from the right (unshunted) lobe of high flow hosts exhibited increased reactivity to the thromboxane agonist U46619 and phenylephrine relative to those of left PAs from the same animal or those of control hosts.
Our studies are the first to identify enhanced reactivity of PAs in a lung contralateral to a localized high output shunt between an aorta and pulmonary artery. These observations suggest that patients with localized systemic-to-pulmonary shunt could exhibit modified vascular tone in remote pulmonary arteries.
pulmonary vascular resistance; arteriovenous shunt; phenylephrine; U46619
Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA) catalyzed by cytochrome P450 (CYP), have many essential biologic roles in the cardiovascular system including inhibition of apoptosis in cardiomyocytes. In the present study, we tested the potential of 8,9-EET and derivatives to protect pulmonary artery smooth muscle cells (PASMCs) from starvation induced apoptosis. We found 8,9-epoxy-eicos-11(Z)-enoic acid (8,9-EET analog(214)), but not 8,9-EET, increased cell viability, decreased activation of caspase-3 and caspase-9, and decreased TUNEL-positive cells or nuclear condensation induced by serum deprivation (SD) in PASMCs. These effects were reversed after blocking the Rho-kinase (ROCK) pathway with Y-27632 or HA-1077. Therefore, 8,9-EET analog(214) protects PASMC from serum deprivation-induced apoptosis, mediated at least in part via the ROCK pathway. Serum deprivation of PASMCs resulted in mitochondrial membrane depolarization, decreased expression of Bcl-2 and enhanced expression of Bax, all effects were reversed by 8,9-EET analog(214) in a ROCK dependent manner. Because 8,9-EET and not the 8,9-EET analog(214) protects pulmonary artery endothelial cells (PAECs), these observations suggest the potential to differentially promote apoptosis or survival with 8,9-EET or analogs in pulmonary arteries.
8,9-EET; PASMCs; Rho-kinase; apoptosis; 8,9-EET analog
Photobiomodulation with near infrared light (NIR) provides cellular protection in various disease models. Previously, infrared light emitted by a low-energy laser has been shown to significantly improve recovery from ischemic injury of the canine heart. The goal of this investigation was to test the hypothesis that NIR (670 nm) from light emitting diodes produces cellular protection against hypoxia and reoxygenation-induced cardiomyocyte injury. Additionally, nitric oxide (NO) was investigated as a potential cellular mediator of NIR. Our results demonstrate that exposure to NIR at the time of reoxygenation protects neonatal rat cardiomyocytes and HL-1 cells from injury, as assessed by lactate dehydrogenase release and MTT assay. Similarly, indices of apoptosis, including caspase 3 activity, annexin binding and the release of cytochrome c from mitochondria into the cytosol, were decreased after NIR treatment. NIR increased NO in cardiomyocytes, and the protective effect of NIR was completely reversed by the NO scavengers carboxy-PTIO and oxyhemoglobin, but only partially blocked by the NO synthase (NOS) inhibitor L-NMMA. Mitochondrial metabolism, measured by ATP synthase activity, was increased by NIR, and NO-induced inhibition of oxygen consumption with substrates for complex I or complex IV was reversed by exposure to NIR. Taken together these data provide evidence for protection against hypoxia and reoxygenation injury in cardiomyocytes by NIR in a manner that is dependent upon NO derived from NOS and non-NOS sources.
To characterize structural and functional injuries following a single dose of whole-thorax irradiation that might be survivable after a nuclear attack/accident.
Rats were exposed to 5 or 10 Gy of X-rays to the whole thorax with other organs shielded. Non-invasive measurements of breathing rate and arterial oxygen saturation, and invasive evaluations of bronchoalveolar lavage fluid, (for total protein, Clara cell secretory protein), vascular reactivity and histology were conducted for at least 6 time points up to 52 wks after irradiation.
Irradiation with 10 Gy resulted in increased breathing rate, a reduction in oxygen saturation, an increase in bronchoalveolar lavage fluid protein and attenuation of vascular reactivity between 4–12 wks after irradiation. These changes were not observed with the lower dose of 5 Gy. Histological examination revealed perivascular edema at 4–8 wks after exposure to both doses, and mild fibrosis beyond 20 wks after 10 Gy.
Single-dose exposure of rat thorax to 10 but not 5 Gy X-irradiation resulted in a decrease in oxygen uptake and vasoreactivity and an increase in respiratory rate, which paralleled early pulmonary vascular pathology. Vascular edema resolved and was replaced by mild fibrosis beyond 20 wks after exposure, while lung function recovered.
Radiation injury; non invasive assays; lung injury markers; vascular reactivity
Vasoactive intestinal polypeptide (VIP) is a potent vasodilator, and has been successfully used to alleviate hypertension. Consistently, disruption of VIP gene in mice leads to hypertension. However, its downstream targets in the vascular regulation are still not well demonstrated. To test the hypothesis that the vascular smooth muscle isoform of KATP channels is a downstream target of the VIP signaling, we performed the studies on the Kir6.1/SUR2B channel expressed in HEK293 cells. We found that the channel was strongly activated by VIP. Through endogenous VIP receptors, the channel activation was reversible and dependent on VIP concentrations with the midpoint-activation concentration ∼10 nM. The channel activation was voltage-independent and could be blocked by KATP channel blocker glibenclamide. In cell-attached patches, VIP augmented the channel open-state probability with modest suppression of the single channel conductance. The VIP-induced Kir6.1/SUR2B channel activation was blocked by PKA inhibitor RP-cAMP. Forskolin, an adenylyl cyclase activator, activated the channel similarly as VIP. The effect of VIP was further evident in the native tissues. In acutely dissociated mesenteric vascular smooth myocytes, VIP activated the KATP currents in a similar manner as in HEK293 cells. In endothelium-free mesenteric artery rings, VIP produced concentration-dependent vasorelaxation that was attenuated by glibenclamide. These results therefore indicate that the vascular isoform (Kir6.1/SUR2B) of KATP channels is a target of VIP. The channel activation relies on the PKA pathway and produces mesenteric arterial relaxation.
VIP; K+ channel; antagonist; second messenger; vascular tones
Rationale: Airway hyperresponsiveness is a critical feature of asthma. Substantial epidemiologic evidence supports a role for female sex hormones in modulating lung function and airway hyperresponsiveness in humans.
Objectives: To examine the role of estrogen receptors in modulating lung function and airway responsiveness using estrogen receptor–deficient mice.
Methods: Lung function was assessed by a combination of whole-body barometric plethysmography, invasive measurement of airway resistance, and isometric force measurements in isolated bronchial rings. M2 muscarinic receptor expression was assessed by Western blotting, and function was assessed by electrical field stimulation of tracheas in the presence/absence of gallamine. Allergic airway disease was examined after ovalbumin sensitization and exposure.
Measurements and Main Results: Estrogen receptor-α knockout mice exhibit a variety of lung function abnormalities and have enhanced airway responsiveness to inhaled methacholine and serotonin under basal conditions. This is associated with reduced M2 muscarinic receptor expression and function in the lungs. Absence of estrogen receptor-α also leads to increased airway responsiveness without increased inflammation after allergen sensitization and challenge.
Conclusions: These data suggest that estrogen receptor-α is a critical regulator of airway hyperresponsiveness in mice.
lung function; asthma; hyperreactivity; M2 muscarinic receptor; estrogen receptor
Airway hyperresponsiveness is a critical feature of asthma. Substantial epidemiologic evidence supports a role for female sex hormones in modulating lung function and airway hyperresponsiveness in humans.
To examine the role of estrogen receptors in modulating lung function and airway responsiveness using estrogen receptor–deficient mice.
Lung function was assessed by a combination of whole-body barometric plethysmography, invasive measurement of airway resistance, and isometric force measurements in isolated bronchial rings. M2 muscarinic receptor expression was assessed by Western blotting, and function was assessed by electrical field stimulation of tracheas in the presence/absence of gallamine. Allergic airway disease was examined after ovalbumin sensitization and exposure.
Measurements and Main Results
Estrogen receptor-α knockout mice exhibit a variety of lung function abnormalities and have enhanced airway responsiveness to inhaled methacholine and serotonin under basal conditions. This is associated with reduced M2 muscarinic receptor expression and function in the lungs. Absence of estrogen receptor-α also leads to increased airway responsiveness without increased inflammation after allergen sensitization and challenge.
These data suggest that estrogen receptor-α is a critical regulator of airway hyperresponsiveness in mice.
lung function; asthma; hyperreactivity; M2 muscarinic receptor; estrogen receptor