A new compound from an endophytic fungus Bambusicola massarinia.

One new chromone, rel-(1S,2S,3S)-2,8-dihydroxy-6-methoxy-1,3-dimethyl-3,4-dihydro-1H-xanthen-9(2H)-one (1), together with one known compound wentiquinone A (2), were isolated from solid culture of endophytic fungus strain Bambusicola massarinia. The structures of all compounds were determined mainly by analysis of their NMR spectroscopic data. The relative configuration of compound 1 was determined by the single-crystal X-ray diffraction analyses.

Cell-free DNA testing for early hepatocellular carcinoma surveillance.

BACKGROUND: Liver cirrhosis (LC) is the highest risk factor for hepatocellular carcinoma (HCC) development worldwide. The efficacy of the guideline-recommended surveillance methods for patients with LC remains unpromising. METHODS: A total of 4367 LCs not previously known to have HCC and 510 HCCs from 16 hospitals across 11 provinces of China were recruited in this multi-center, large-scale, cross-sectional study. Participants were divided into Stage Ⅰ cohort (510 HCCs and 2074 LCs) and Stage Ⅱ cohort (2293 LCs) according to their enrollment time and underwent Tri-phasic CT/enhanced MRI, US, AFP, and cell-free DNA (cfDNA). A screening model called PreCar Score was established based on five features of cfDNA using Stage Ⅰ cohort. Surveillance performance of PreCar Score alone or in combination with US/AFP was evaluated in Stage Ⅱ cohort. FINDINGS: PreCar Score showed a significantly higher sensitivity for the detection of early/very early HCC (Barcelona stage A/0) in contrast to US (sensitivity of 51.32% [95% CI: 39.66%-62.84%] at 95.53% [95% CI: 94.62%-96.38%] specificity for PreCar Score; sensitivity of 23.68% [95% CI: 14.99%-35.07%] at 99.37% [95% CI: 98.91%-99.64%] specificity for US) (P < 0.01, Fisher's exact test). PreCar Score plus US further achieved a higher sensitivity of 60.53% at 95.08% specificity for early/very early HCC screening. INTERPRETATION: Our study developed and validated a cfDNA-based screening tool (PreCar Score) for HCC in cohorts at high risk. The combination of PreCar Score and US can serve as a promising and practical strategy for routine HCC care. FUNDING: A full list of funding bodies that contributed to this study can be found in Acknowledgments section.

Calorie restriction remodels gut microbiota and suppresses tumorigenesis of colorectal cancer in mice.

Colorectal cancer (CRC) is one of the most common cancers worldwide and the consumption of a high-calorie diet is one of its risk factors. Calorie restriction (CR) slows tumor growth in a variety of cancers, including colorectal cancer; however, the mechanism behind this remains unknown. In the present study, CR effectively reduced the tumor volume and weight in a xenograft BALB/c male nude mouse model. In addition, tumor immunohistochemistry revealed that the CR group had significantly higher expression of Bax (P<0.001) and significantly lower levels of Bcl2 (P<0.0001) and Ki67 (P<0.001) compared with control group. Furthermore, data from 16S ribosomal (r)RNA sequencing implied that CR was able to reprogram the microbiota structure, characterized by increased Lactobacillus constituent ratio (P<0.05), with amelioration of microbial dysbiosis caused by CRC. Further receiver operating characteristic curves demonstrated that the bacteria Bacteroides [area under the curve (AUC)=0.800], Lactobacillus (AUC=0.760) and Roseburia (AUC=0.720) served key roles in suppression of CRC in the mouse model. The functional prediction of intestinal flora indicated 'cyanoamino acid metabolism' (P<0.01), 'replication initiation protein REP (rolling circle plasmid replication)' (P<0.01), 'tRNA G10 N-methylase Trm11' (P<0.01) and 'uncharacterized protein with cyclophilin fold, contains DUF369 domain' (P<0.05) were downregulated in CR group. These findings implied that CR suppressed CRC in mice and altered the gut microbiota.

Identification of thrombotic biomarkers in orthopedic surgery patients by plasma proteomics.

BACKGROUND: Due to the poor specificity of D-dimer, more accurate thrombus biomarkers are clinically needed to improve the diagnostic power of VTE. METHODS: The plasma samples were classified into low-risk group (n = 6) and high-risk group (n = 6) according to the Caprini Thrombosis Risk Assessment Scale score. Data-independent acquisition mass spectrometry (DIA-MS) was performed to identify the proteins in the 12 plasma samples. Bioinformatics analysis including volcano plot, heatmap, KEGG pathways and chord diagram analysis were drawn to analyze the significantly differentially expressed proteins (DEPs) between the two groups. Then, another 26 plasma samples were collected to verify the key proteins as potential biomarkers of VTE in orthopedic surgery patients. RESULTS: A total of 371 proteins were identified by DIA-MS in 12 plasma samples. Volcano plotting showed that there were 30 DEPs. KEGG pathway enrichment analysis revealed that the DEPs were majorly involved in the blood coagulation pathway. The chord diagram analysis demonstrated that proteins SAA1, VWF, FLNA, ACTB, VINC, F13B, F13A and IPSP in the DEPs were significantly related to blood coagulation. VWF and F13B were selected for validation experiments. ELISA test showed that, as compared with those in the low-risk group, the level of VWF in the high-risk sera was significantly increased. CONCLUSIONS: The level of VWF in the high-risk group of thrombosis after orthopedic surgery was significantly higher than that in the low-risk group of preoperative thrombosis, suggesting that VWF may be used as a potential thrombus biomarker in orthopedic surgery patients.

The development of a cSMART-based integrated model for hepatocellular carcinoma diagnosis.

BACKGROUND: Hepatocellular carcinoma (HCC) generally arises from a background of liver cirrhosis (LC). Patients with cirrhosis and suspected HCC are recommended to undergo serum biomarker tests and imaging diagnostic evaluation. However, the performance of routine diagnostic methods in detecting early HCC remains unpromising. METHODS: Here, we conducted a large-scale, multicenter study of 1675 participants including 490 healthy controls, 577 LC patients, and 608 HCC patients from nine clinical centers across nine provinces of China, profiled gene mutation signatures of cell-free DNA (cfDNA) using Circulating Single-Molecule Amplification and Resequencing Technology (cSMART) through detecting 931 mutation sites across 21 genes. RESULTS: An integrated diagnostic model called "Combined method" was developed by combining three mutation sites and three serum biomarkers. Combined method outperformed AFP in the diagnosis of HCC, especially early HCC, with sensitivities of 81.25% for all stages and 66.67% for early HCC, respectively. Importantly, the integrated model exhibited high accuracy in differentiating AFP-negative, AFP-L3-negative, and PIVKA-II-negative HCCs from LCs.

Development of a novel 7 immune-related genes prognostic model for oral cancer: A study based on TCGA database.

Oral squamous cell carcinoma (OSCC) is an aggressive tumor whose prognosis has little improvement in the last three decades. Various immune-related genes have been suggested as significant roles in the development and progression of malignant cancers. In this study, we acquired and integrated differentially expressed genes of OSCC patients, including immune-related genes and transcription factors (TFs), from The Cancer Genome Atlas (TCGA) database. TF-mediated network was established to exploring the regulatory mechanisms of prognostic immune-related genes. A 7 immune-related genes prognostic model for OSCC was obtained, including CGB8, CTLA4, TNFRSF19, CCL26, NRG1, TPM2 and PLAU, which was further proved to be an independent prognostic indicator after adjusting for other clinical factors. The immune-related genes prognostic index was significantly negatively correlated to the infiltration abundances of B cells (P < 0.05) and CD8+ T cells (P < 0.05). The novel proposed immune-based prognostic model not only provided a promising biomarker and a way to monitor the long-term treatment of OSCC, but also gave a new insight into a potential immunotherapy strategy.

The Landscape of Cell-Free HBV Integrations and Mutations in Cirrhosis and Hepatocellular Carcinoma Patients.

PURPOSE: Intratumoral hepatitis B virus (HBV) integrations and mutations are related to hepatocellular carcinoma (HCC) progression. Circulating cell-free DNA (cfDNA) has shown itself as a powerful noninvasive biomarker for cancer. However, the HBV integration and mutation landscape on cfDNA remains unclear. EXPERIMENTAL DESIGN: A cSMART (Circulating Single-Molecule Amplification and Resequencing Technology)-based method (SIM) was developed to simultaneously investigate HBV integration and mutation landscapes on cfDNA with HBV-specific primers covering the whole HBV genome. Patients with HCC (n = 481) and liver cirrhosis (LC; n = 517) were recruited in the study. RESULTS: A total of 6,861 integration breakpoints including TERT and KMT2B were discovered in HCC cfDNA, more than in LC. The concentration of circulating tumor DNA (ctDNA) was positively correlated with the detection rate of these integration hotspots and total HBV integration events in cfDNA. To track the origin of HBV integrations in cfDNA, whole-genome sequencing (WGS) was performed on their paired tumor tissues. The paired comparison of WGS data from tumor tissues and SIM data from cfDNA confirmed most recurrent integration events in cfDNA originated from tumor tissue. The mutational landscape across the whole HBV genome was first generated for both HBV genotype C and B. A region from nt1100 to nt1500 containing multiple HCC risk mutation sites (OR > 1) was identified as a potential HCC-related mutational hot zone. CONCLUSIONS: Our study provides an in-depth delineation of HBV integration/mutation landscapes at cfDNA level and did a comparative analysis with their paired tissues. These findings shed light on the possibilities of noninvasive detection of virus insertion/mutation.

Effects of hyperglycemia on the modulation of vascular function by perivascular adipose tissue.

OBJECTIVE: To study the acute and chronic effect of hyperglycemia on perivascular adipose tissue (PVAT) function in rat aorta. METHOD: Alterations in PVAT function in rat aorta incubated with 22 mmol/l D-glucose for 30 min and in aorta from streptozotocin (STZ)-induced diabetic rats were studied. RESULTS: Incubation with D-glucose caused an attenuation of contraction in response to phenylephrine, both in the presence and absence of endothelium, whereas removal of PVAT eliminated this attenuation effect. The presence of PVAT did not affect concentration-related relaxation response of the aorta to carbamylcholine in STZ rats. There was also no difference in the relaxation response of the aorta to carbamylcholine between STZ and control rats. The presence of PVAT, however, caused a higher attenuation of the concentration-dependent contraction to phenylephrine in aorta from STZ rats with intact endothelium as compared with that from control rats. Incubation of the aorta from control rats with Nomega-nitro-L-arginine or carboxy-2-phenyl-4,4,5,5-tetra-methyl-imidazoline-1-oxyl-3-oxide potentiated the contraction of the vessels to phenylephrine, and this potentiation effect was higher in the vessels from STZ rats than control rats when N-nitro-L-arginine was used. Removal of PVAT reduced this potentiation effect and eliminated the difference between the vessels from control and STZ rats. CONCLUSION: Under both acute and chronic conditions, hyperglycemia enhanced the relaxation response of the vessels mediated by PVAT. These new findings provide important information on the mechanism underlying the postprandial effect of hyperglycemia on blood pressure control and the presence of hypotension under chronic hyperglycemia in a type-1 model of diabetes.

Alteration of perivascular adipose tissue function in angiotensin II-induced hypertension.

We studied the role of perivascular adipose tissue (PVAT) in the control of vascular function in an in vivo experimental model of hypertension produced by angiotensin II infusion by osmotic minipump in adult male Wistar rats. Two weeks after infusion with angiotensin II, blood pressure in treated rats was significantly elevated but heart rate was reduced compared with control rats infused with physiological saline. Contraction of aorta from the 2 groups of rats in response to phenylephrine or serotonin was significantly attenuated by the presence of PVAT in both the presence and absence of endothelium. This attenuation effect on contraction to phenylephrine was higher, however, in vessels from control rats than in vessels from hypertensive rats in the absence of endothelium. In the mesenteric resistance arteries, lumen diameter was larger in both hypertensive and control vessels with intact PVAT than in vessels with PVAT removed. The medial wall was thicker in arteries from hypertensive rats. The presence of PVAT potentiated the contraction induced by KCl in mesenteric arteries from control rats, but not in hypertensive rats. PVAT also attenuated the contraction of mesenteric arteries in response to phenylephrine or serotonin in both hypertensive and control groups. Mesenteric arteries from hypertensive rats were more responsive to stimulation by serotonin than those from control rats. We conclude that the increased blood pressure of Wistar rats that occurred after infusion with angiotensin II was associated with changes in the functions of PVAT in the aorta and mesenteric arteries and in the structure and function of resistance arteries.

Do cardiac and perivascular adipose tissue play a role in atherosclerosis?

Recent evidence suggests that epicardial and perivascular adipose tissue could mechanically and functionally affect the heart and vasculature, thereby possibly playing a role in adiposity-related atherosclerosis. Experimental and clinical observations suggest both favorable and unfavorable effects of epicardial and perivascular fat. The double role of epicardial and perivascular adipose tissue in the development of cardiovascular pathology and/or in protecting the heart and arteries warrants further studies.

Superoxide anion mediates angiotensin II-induced potentiation of contractile response to sympathetic stimulation.

Angiotensin II is known to potentiate vasoconstriction induced by electrical field stimulation (EFS), but the underlying mechanisms for this potentiation are not fully understood. This study was designed to investigate the role of superoxide anion in the potentiation effects of angiotensin II. Contraction of rat mesenteric arterial segments was induced by perivascular nerve stimulation with EFS, and superoxide production was measured with lucigenin-enhanced chemiluminescence. Extracellular signal-regulated kinase (ERK) phosphorylation was determined in cultured smooth muscle cells with Western blot. Angiotensin II concentration dependently potentiated the contraction of rat mesenteric arteries to EFS, which is frequency-dependent. This potentiation was blunted by an angiotensin AT(1) receptor antagonist (2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylic acid, CV-11974), NAD(P)H oxidase inhibitor (apocynin), superoxide dismutase (SOD) and its mimetic tiron, but not affected by angiotensin AT(2) receptor antagonist and inhibitors of xanthine oxidase, cytochrome P450, and cyclooxygenase. Angiotensin II increased superoxide production by mesenteric arteries, which was blunted by angiotensin AT(1) receptor antagonist CV-11974, and NAD(P)H oxidase inhibitor apocynin. Superoxide generating compound pyrogallol mimicked the effects of angiotensin II. Tyrosine kinase inhibitor (tyrphostin A25) and mitogen-activated protein kinase (MAPK)/ERK inhibitors (1,4-diamino-2,3-dicyano-1,4-bis [2-aminophenylthio]butadiene (U 0126)) inhibited angiotensin II- and pyrogallol-induced potentiation of EFS-induced contraction, while inactive forms of these inhibitors did not show any inhibitory effects. In cultured smooth muscle cells from mesenteric arteries, angiotensin II and superoxide similarly induced ERK phosphorylation. These results showed that superoxide mediated angiotensin II-induced potentiation of contractile response to EFS and tyrosine kinase-MAPK/ERK activation was involved.

Effects of fetal and neonatal exposure to nicotine on blood pressure and perivascular adipose tissue function in adult life.

In Wistar rats, maternal exposure to nicotine was shown to impair the inhibitory function of perivascular adipose tissue on vascular contractility in the aorta of the offspring. It is not known whether an impairment of perivascular adipose tissue function occurs in smaller arteries, and whether the control of blood pressure is affected. Here we studied the blood pressure effects and the alteration of perivascular adipose tissue function in mesenteric arteries of the offspring born to Wistar-Kyoto rat (WKY) dams exposed to nicotine. Nulliparous female WKY rats were given either nicotine bitartrate (1 mg/kg/day) or saline (vehicle) by subcutaneous injection 2 weeks prior to mating, during pregnancy and until weaning. Blood pressure of the offspring and functional studies with mesenteric arteries were conducted. Tissue samples (thoracic aorta, mesenteric arteries, and kidneys) were collected for morphological and immunohistochemical examinations. Blood pressure increased from 14 weeks of age onwards in the offspring born to nicotine-exposed dams. Nicotine-exposed offspring showed a significant increase in the number of brown adipocytes in aortic perivascular adipose tissue relative to control offspring. In mesenteric arteries from control offspring, contractile responses induced by phenylephrine, serotonin, and 9,11-dideoxy-11alpha, 9alpha-epoxymethanoprostaglandin F(2)alpha (U44619) were significantly attenuated in the presence of perivascular adipose tissue, an effect not observed in the nicotine-exposed tissues. Endothelium-dependent relaxation responses to carbachol, kidney weight, the total number of nephrons and glomerulus' size were comparable in nicotine and saline groups. We conclude that fetal and neonatal exposure to nicotine caused blood pressure elevation. Alterations in perivascular adipose tissue composition and modulatory function are some of the mechanisms associated with this blood pressure increase.

[A case-control study on risk factors for tuberculosis in Yinchuan city].

OBJECTIVE: To study the risk factors of tuberculosis in Yinchuan city and lay a basis for its prevention and control. METHODS: A matched case-control (119:179) study for the risk factors was carried out. Data were analyzed with single-variable analysis and multiple factor logistic regression analysis. RESULTS: Single-variable analysis showed that the education background (chi2 = 2.363, P = 0.018), family economic income (chi2 = 3.040, P = 0.002), smoking (chi2 = 2.500, P = 0.012), physical activities (chi2 = 2.330, P = 0.020), bacille Calmette-Guerin (BCG) vaccination history (chi2 = 22.151, P = 0.000), history of exposure to tuberculosis (chi2 = 15.740, P = 0.000) and so on had significant effects on tuberculosis. Multiple logistic regression analysis showed that family monthly income, smoking, physical activity, BCG vaccination history, history of exposure to tuberculosis entered the final regression model (chi2 = 5.880, 7.368, 3.891, 21.127, 14.536; OR = 0.529, 1.571, 0.774, 0.264, 3.978; P < 0.05). CONCLUSION: History of exposure to tuberculosis and smoking should be the risk factors of tuberculosis in Yinchuan. Having much income, physical activities, and BCG vaccination history should be the preventive factors.

Perivascular adipose tissue promotes vasoconstriction: the role of superoxide anion.

OBJECTIVES: Recent studies have demonstrated that perivascular adipose tissue (PVAT) releases vascular relaxation factor(s). In this study, we examined if PVAT releases other vasoactive factors in response to perivascular nerve activation by electrical field stimulation (EFS). METHODS AND RESULTS: In Wistar-Kyoto rats, rings of superior mesenteric artery (MA) with intact PVAT (PVAT (+)) showed a greater contractile response to EFS than rings with PVAT removed (PVAT (-)). Superoxide dismutase (SOD) reduced the contractile response to EFS more in PVAT (+) MA than in PVAT (-) MA. Inhibitors of NAD(P)H oxidase and cyclooxygenase exerted a greater inhibition on EFS-induced contraction in PVAT (+) MA than in PVAT (-) MA. Inhibitors of tyrosine kinase (tyrphostin A25) and MAPK/ERK (U 0126) attenuated EFS-induced contraction in PVAT (+) MA in a concentration-related manner, while inactive forms of these inhibitors (tyrphostin A1 and U 0124) did not inhibit the response. Exogenous superoxide augmented the contractile response to EFS and to phenylephrine in PVAT (-) MA, and this augmentation was blunted by inhibition of tyrosine kinase and MAPK/ERK. EFS increased superoxide generation in isolated PVAT and PVAT (+)/(-) MA, which was attenuated by NAD(P)H oxidase inhibition. RT-PCR showed the mRNA expression of p(67phox) subunit of NAD(P)H oxidase and immunohistochemical staining confirmed its localization in the adipocytes of PVAT. CONCLUSION: These results show that PVAT enhances the arterial contractile response to perivascular nerve stimulation through the production of superoxide mediated by NAD(P)H oxidase, and that this enhancement involves activation of tyrosine kinase and MAPK/ERK pathway.

Hydrogen peroxide is an endothelium-dependent contracting factor in rat renal artery.

In addition to endothelium-derived relaxing factor and hyperpolarizing factor, vascular endothelium also modulates smooth muscle tone by releasing endothelium-derived contracting factor(s) (EDCF), but the identity of EDCF remains obscure. We studied here the involvement of hydrogen peroxide (H2O2) in endothelium-dependent contraction (EDC) of rat renal artery to acetylcholine (ACh). ACh (10(-6), 10(-5), and 10(-4) M) induced a transient contraction of rat renal artery with intact endothelium in a concentration-related manner, but not in the artery with endothelium removed. In phenylephrine-precontracted renal arteries, ACh induced an endothelium-dependent relaxation response at lower concentrations (10(-8)-10(-6) M), and a relaxation followed by a contraction at higher concentrations (10(-5) M). Inhibition of nitric oxide synthase by N(omega)-nitro-L-arginine (10(-4) M) enhanced the EDC to ACh. Catalase (1000 U ml(-1)) reduced the EDC to ACh. H2O2 (10(-6), 10(-5), and 10(-4) M) induced a similar transient contraction of the renal arteries as ACh, but in an endothelium-independent manner. Inhibition of NAD(P)H oxidase and cyclooxygenase by diphenylliodonium chloride and diclofenac greatly attenuated ACh-induced EDC, while inhibition of xanthine oxidase (allopurinol) and cytochrome P450 monooxygenase (17-octadecynoic acid) did not affect the contraction. Antagonist of thromboxane A2 and prostaglandin H2 receptors (SQ 29548) and thromboxane A2 synthase inhibitor (furegrelate) attenuated the contraction to ACh and to H2O2. In isolated endothelial cells, ACh (10(-5) M) induced a transient H2O2 production detected with a fluorescence dye sensitive to H2O2 (2',7'-dichlorofluorescein diacetate). The peak concentration of H2O2 was 5.1 x 10(-4) M at 3 min and was prevented by catalase. Taken together, these results show that ACh triggers H2O2 production through NAD(P)H oxidase activation in the endothelial cells, and that ACh and H2O2 share the same signaling pathway in causing smooth muscle contraction. Therefore, H2O2 is most likely the EDCF in rat renal artery in response to ACh stimulation.

The effects of quinapril and atorvastatin on artery structure and function in adult spontaneously hypertensive rats.

We studied the combined treatment effects of quinapril and atorvastatin on blood pressure and structure and function of resistance arteries from adult spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY rats). Apoptotic cells were identified by in situ end labeling using the terminal deoxynucleotide transferase-mediated dUTP nick end labeling method. Vascular structure was measured using a morphometric protocol and confocal microscopy and a pressurized artery system was used to study vascular functions. We found that a combined treatment with quinapril and atorvastatin lowered systolic blood pressure in both adult SHR and WKY rats and decreased medial thickness and volume and the number of smooth muscle cell layers in mesenteric arteries, as well as media-to-lumen ratio in the interlobular arteries from SHR but not in those from WKY rats. The number of apoptotic smooth muscle cells was higher in the mesenteric arteries from control WKY rats than control SHR and treatment increased the number of apoptotic smooth muscle cells in the arteries from both SHR and WKY rats. Treatment with quinapril and atorvastatin reduced ventricular weight in SHR and normalized the augmented contractile responses to norepinephrine but did not alter the contraction to electric field stimulation. Relaxation responses to acetylcholine and sodium nitroprusside were not affected by the treatment. We conclude that a combined treatment with quinapril and atorvastatin lowered blood pressure and improved cardiac and vessel hypertrophy and vessel function. An increase in apoptotic smooth muscle cells may be one of the mechanisms underlying the structural improvement.

Alteration of arterial smooth muscle potassium channel composition and BKCa current modulation in hypertension.

We investigated K+ currents and their regulation by the sarcoplasmic reticulum in mesenteric arterial smooth muscle cells of the spontaneously hypertensive rat (SHR). Using perforated patch-clamp technique, we found the overall K+ current density was significantly lower in adult SHR compared to adult Wistar-Kyoto rats (WKY). The K+ currents were almost exclusively of large-conductance Ca2+-dependent (BK(Ca)) variety in SHR, but largely of voltage-gated (Kv) variety in WKY. Western blot assay showed parallel findings. These differences were not observed in pre-hypertensive rats. Depleting the intracellular Ca2+ store inhibited the K+ currents in adult SHR. Ryanodine augmented the K+ current at 1 microM, but suppressed it at 10 microM; 2-aminoethoxydiphenyl borate demonstrated concentration-dependent inhibition. We conclude that an alteration of membrane K+ channel composition has resulted in lower overall K+ current density. The changes in K+ current type may indicate an underlying defect in Ca2+-handling that predisposes smooth muscle cells to the hypertensive phenotype.

Vascular relaxation response to hydrogen peroxide is impaired in hypertension.

1. In phenylephrine (1 microm)-precontracted rat superior mesenteric arteries (MA), hydrogen peroxide (H(2)O(2), 0.3 and 1 mm) caused a biphasic response: a transient contraction followed by a relaxation. In the presence of thromboxane A(2)/prostaglandin H(2) (TP) receptor antagonist (SQ 29548), the contractile component of the biphasic response was abolished. The relaxation response to H(2)O(2) was smaller in spontaneously hypertensive rats (SHR) when compared with normotensive Wistar-Kyoto rats (WKY). 2. The mechanisms for the attenuated relaxation to H(2)O(2) in the SHR were studied. KCl (40 mm) prevented the relaxation response. Calcium-dependent K(+) channel (K(Ca)) blockers (tetraethylammonium chloride, TEA; iberiotoxin, and charybdotoxin) showed a greater inhibition of H(2)O(2) relaxation in SHR than in WKY, whereas voltage-dependent K(+)-channel (K(v)) blocker 4-aminopyridine was more effective in inhibiting the relaxation in WKY than in SHR. 3. H(2)O(2) (1 mm) greatly enhanced the frequency and intensity of the spontaneous transient outward K(+) currents in SHR MA, and the effects of H(2)O(2) were inhibited by iberiotoxin, while in WKY MA the K(+) currents induced by H(2)O(2) were mainly of the K(v) type. The consequence of the activation of different types of K(+) channel was that the net increase in mean outward K(+) current density in response to H(2)O(2) was smaller in SHR than in WKY, which may account for the attenuated relaxation response to H(2)O(2) in the SHR. 4. The contractile responses of MA to TEA, iberiotoxin, and charybdotoxin were greater in SHR than in WKY. 5. In summary, an attenuated relaxation response to H(2)O(2) was found in SHR MA when compared to WKY. In contrast to the activation of K(v) channels in WKY, H(2)O(2) markedly enhanced K(Ca) activity in SHR, resulting in an attenuation of the increase in mean outward K(+) current density in response to H(2)O(2). These results suggest that alteration in K(+) channel activation by reactive oxygen species may play a role in the development of hypertension in SHR.

Mechanisms of hydrogen-peroxide-induced biphasic response in rat mesenteric artery.

1. In phenylephrine (PHE) (1 micro M)-precontracted superior mesenteric arteries from adult rats, low concentration of hydrogen peroxide (H(2)O(2), 10-100 micro M) caused only contraction, while high concentration of H(2)O(2) (0.3-1 mM) caused a biphasic response: a transient contraction followed by a relaxation response. 2. Endothelium removal did not affect the biphasic response. 7,7-Dimethyl-(5Z,8Z)-eicosadienoic acid, diclofenac, furegrelate, or SQ 29548 greatly inhibited the contraction but did not affect the relaxation. 17-Octadecynoic acid, eicosatriynoic acid, ICI 198615, SQ 22536, or ODQ did not inhibit the biphasic response. 3. KCl at 40 mM inhibited the relaxation response to H(2)O(2) by 98+/-24%. 4-Aminopyridine (4-AP) inhibited while tetraethylammonium chloride (TEA), charybdotoxin, or glibenclamide attenuated the relaxation response. A combination of 4-AP, TEA and glibenclamide mimicked the effects of 40 mM KCl. Iberiotoxin, apamin, or barium chloride did not inhibit the relaxation response. 4. H(2)O(2) at 1 mM hyperpolarized membrane potential and reversibly augmented K(+) current in smooth muscle cells of mesenteric artery. These effects of H(2)O(2) were attenuated significantly by 4-AP. 5. In summary, in PHE-precontracted rat mesenteric artery: (1) the response to H(2)O(2) shifted qualitatively from contraction to a biphasic response as H(2)O(2) increased to 0.3 mM or higher; (2) the relaxation response is caused by the activation of K(+) channels, with voltage-dependent K(+) channels playing a primary role; and the contraction is likely to be mediated by thromboxane A(2); (3) the K(+) channel activation by H(2)O(2) is independent of phospholipase A(2), cyclooxygenase, lipoxygenase, cytochrome P450 monooxygenase, adenylate or guanylate cyclase.

Detrimental effects of papaverine on the human internal thoracic artery.

OBJECTIVE: We sought to determine the effects of papaverine on human and canine internal thoracic artery function and structure. METHODS: Vascular function was assessed with wire myography, and apoptosis was examined with confocal microscopy in arteries stained with ApopTag. RESULTS: Acetylcholine-induced endothelium-dependent relaxation in phenylephrine-precontracted arteries was significantly impaired by papaverine treatment in both human and canine internal thoracic arteries (maximal relaxation: 68.35% +/- 7.13% vs 47.5% +/- 9.32% in human arteries and 74.8% +/- 5.5% vs 34.3% +/- 8.5% in canine arteries) but not by incubation with acidified saline solution (pH 3.9, which is equivalent to the pH of 10(-2) mol/L papaverine solution) in canine internal thoracic arteries. Contraction of human internal thoracic arteries to phenylephrine or to U46619 was not significantly affected by papaverine treatment and neither was the contraction of canine internal thoracic arteries to phenylephrine. Total apoptotic endothelial and smooth muscle cells were significantly greater in papaverine-treated human and canine internal thoracic arteries. CONCLUSIONS: Papaverine impairs endothelial function and triggers apoptosis of endothelial and smooth muscle cells of human and canine internal thoracic arteries. The long-term consequence of this impairment on vascular function is not known. Until this question is answered, it will be prudent to use other vasodilators that are less damaging to the internal thoracic artery for cardiac surgery.