Biomedical subjects
Publications and source records attributed to Xiao-Ping Yang.
The use of the Schiff-base ligand N,N'-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine (H2L) and 1,4-benzenedicarboxylate (BDC) enables the construction of the hexanuclear luminescent Zn-Nd complex [Zn4Nd2L4(1,4-BDC)2].[Nd(NO3)5(H2O)].Et2O.2EtOH.3H2O.
Papillary glioneuronal tumor (PGNT) has recently been identified as a new variant of mixed neuronal-glial tumors. We report the clinical and pathological features of PGNT in two Chinese patients. One patient was a 35-year-old man who suffered from intractable seizures for 16 years. Another was a 26-year-old woman who presented with headache for 2 years. In both patients, magnetic resonance imaging showed well demarcated, mixed cystic and solid tumor in the temporal lobe. Histology of the excised tumors revealed a pseudopapillary architecture surrounded by a glial component and intervening areas were occupied by neuronally differentiated cells. No cortical dysplasia was found in the neighboring cortex in one of them. The glial component showed immunoreactivity with glial fibrillary acidic protein and S-100 protein. Neuronally differentiated cells were immunolabeled by antisynaptophysin, NF, NeuN and MAP2 antibodies. Some small cells surrounding the surface of the pseudopapillae and in the compact area were immunopositive for Olig2. The MIB-1 labeling index was < 3%. The tumor did not recur within the follow-up periods of 50 months and 13 months, and the patient with temporal lobe epilepsy became seizure-free after surgery.
Cardiac rupture can be fatal after myocardial infarction (MI). Experiments in animals revealed gender differences in rupture rate; however, patient data are controversial. We found a significantly higher rupture rate in testosterone-treated female mice within 1 wk after MI, whereas castration in males significantly reduced rupture. We hypothesized that testosterone may adversely affect remodeling after MI, exaggerating the inflammatory response and increasing cardiac rupture, whereas estrogen may be cardioprotective, attenuating early remodeling and reducing rupture rate. We studied the effect of gender and hormone manipulation on morphological and histological changes during early remodeling after MI in 4-wk-old male and female C57BL/6J mice and how these events could affect cardiac function. Females were randomly divided into 1) sham ovariectomy + placebo (s-ovx + P), 2) s-ovx + testosterone (T), 3) ovx + P, and 4) ovx + T; males were divided into 1) sham castration + P (s-cas + P), 2) s-cas + 17beta-estradiol (E), 3) cas + P, and 4) cas + E. At 6 wk after gonadectomy and hormone manipulation, MI was induced. Mice were randomly killed 1, 2, 4, 7, and 14 days after MI. The left ventricle was weighed and sectioned for evaluation of MI size, infarct expansion index (IEI), and neutrophil infiltration. Transthoracic echocardiography was performed in conscious mice in the 14-day group before organ harvest. Cardiac rupture rate and IEI were significantly higher in testosterone-treated females and noncastrated males than in controls; these effects were accompanied by enhanced neutrophil infiltration and pronounced deterioration of cardiac function and left ventricular dilatation. Ovariectomy in females and estrogen supplementation in males did not confer significant protection from cardiac rupture, IEI, or neutrophil infiltration. We concluded that, in mice, high testosterone levels enhance acute myocardial inflammation, adversely affecting myocardial healing and early remodeling, as indicated by increased cardiac rupture, and possibly causing deterioration of cardiac function after MI, and, conversely, estrogen seems to have no significant protective effect in the acute phase after MI.
Although NO derived from endothelial NO synthase (eNOS) is thought to be cardioprotective, the role of inducible NO synthase (iNOS) remains controversial. Using mice lacking iNOS (iNOS-/-), we studied (1) whether development of hypertension, cardiac hypertrophy, and dysfunction after deoxycorticosterone acetate (DOCA)-salt would be less severe compared with wild-type controls (WT; C57BL/6J), and (2) whether the cardioprotection attributable to lack of iNOS is mediated by reduced oxidative stress. Mice were uninephrectomized and received either DOCA-salt (30 mg/mouse SC and 1% NaCl+0.2% KCl in drinking water) or vehicle (tap water) for 12 weeks. Systolic blood pressure (SBP) was measured weekly. Left ventricular (LV) ejection fraction (EF) by echocardiography and cardiac response to isoproterenol (50 ng/mouse IV) were studied at the end of the experiment. Expression of eNOS and iNOS as well as the oxidative stress markers 4-hydroxy-2-nonenal (4-HNE, a marker of lipid peroxidation) and nitrotyrosine (a marker for peroxynitrite) were determined by Western blot and immunohistochemical staining, respectively. DOCA-salt increased SBP and LV weight similarly in both strains and decreased EF in WT but not in iNOS-/-. Cardiac contractile and relaxation responses to isoproterenol were greater, 4-HNE and nitrotyrosine levels were lower, and eNOS expression tended to be higher in iNOS-/-. We conclude that lack of iNOS leads to better preservation of cardiac function, which may be mediated by reduced oxidative stress and increased eNOS; however, it does not seem to play a significant role in preventing DOCA-salt-induced hypertension and hypertrophy.
A large number of biochemical and genetic studies have demonstrated the involvement of DNA polymerase beta (Pol beta) in mammalian base excision repair (BER). Pol beta participates in BER sub-pathways by contributing gap filling DNA synthesis and lyase removal of the 5'-deoxyribose phosphate (dRP) group from the cleaved abasic site. To better understand the mechanism of the dRP lyase reaction at an atomic level, we determined a crystal structure of Pol beta complexed with 5'-phosphorylated abasic sugar analogs in nicked DNA. This DNA ligand represents a potential BER intermediate. The crystal structure reveals that the dRP group is bound in a non-catalytic binding site. The catalytic nucleophile in the dRP lyase reaction, Lys72, and all other potential secondary nucleophiles, are too far away to participate in nucleophilic attack on the C1' of the sugar. An approximate model of the dRP group in the expected catalytic binding site suggests that a rotation of 120 degrees about the dRP 3'-phosphate is required to position the epsilon-amino Lys72 close to the dRP C1'. This model also suggests that several other side chains are in position to facilitate the beta-elimination reaction. From results of mutational analysis of key residues in the dRP lyase active site, it appears that the substrate dRP can be stabilized in the observed non-catalytic binding conformation, hindering dRP lyase activity.
Using inducible nitric oxide (NO) synthase (iNOS) knockout mice (iNOS-/-), we tested the hypotheses that 1) lack of iNOS attenuates cardiac remodeling and dysfunction and improves cardiac reserve postmyocardial infarction (MI), an effect that is partially mediated by reduction of oxidative stress due to reduced interaction between NO and reactive oxygen species (ROS); and 2) the cardioprotection afforded by iNOS deletion is eliminated by Nomega-nitro-L-arginine methyl ester (L-NAME) due to inhibition of endothelial NOS (eNOS) and neuronal NOS (nNOS). MI was induced by ligating the left anterior descending coronary artery. Male iNOS-/- mice and wild-type controls (WT, C57BL/6J) were divided into sham MI, MI+vehicle, and MI+l-NAME (100 mg.kg(-1).day(-1) in drinking water for 8 wk). Cardiac function was evaluated by echocardiography. Left ventricular (LV) maximum rate of rise of ventricular pressure divided by pressure at the moment such maximum occurs (dP/dt/instant pressure) in response to isoproterenol (100 ng.kg(-1).min(-1) iv) was measured with a Millar catheter. Collagen deposition, myocyte cross-sectional area, and expression of nitrotyrosine and 4-hydroxy-2-nonenal (4-HNE), markers for ROS, were determined by histopathological and immunohistochemical staining. We found that the MI-induced increase in LV chamber dimension and the decrease in ejection fraction, an index of systolic function, were less severe in iNOS-/- compared with WT mice. L-NAME worsened LV remodeling and dysfunction further, and these detrimental effects were also attenuated in iNOS-/- mice, associated with better preservation of cardiac function. Lack of iNOS also reduced nitrotyrosine and 4-HNE expression after MI, indicating reduced oxidative stress. We conclude that iNOS does not seem to be a pathological mediator of heart failure; however, the lack of iNOS improves cardiac reserve post-MI, particularly when constitutive NOS isoforms are blocked. Decreased oxidative stress and other adaptive mechanisms independent of NOS may be partially responsible for such an effect, which needs to be studied further.
This study was designed to clarify the alpha(1)-adrenoceptor subtypes mediating the vasoconstrictor response to tyramine in isolated and perfused canine splenic artery. It was shown that tyramine potentiated the nerve stimulation-induced second peaked vasoconstriction that was readily suppressed by prazosin treatment. A bolus injection of tyramine (0.01-0.3 micromol) caused a vasoconstriction in a dose-related manner. The tyramine-induced vasoconstriction was inhibited by WB 4101 (10 and 100 nM), an alpha(1A)-and alpha(1D)-adrenoceptor antagonist, in a concentration-related manner. Neither BMY 7378 (100 nM), a selective alpha(1D)-adrenoceptor antagonist, nor chloroethylclonidine (60 microM), an alpha(1B)- and alpha(1D)-adrenoceptor antagonist, affected the tyramine-induced response. The results indicate that the noradrenaline released by tyramine may diffuse to the extrajunctional cleft, and thus it activates the extrajunctional alpha(1A)-adrenoceptors, because nerve stimulation-evoked second peaked vasoconstrictions were markedly inhibited by chloroethylclonidine but not by WB 4101.
Kinins exert cardioprotective effects via 2 G-protein-coupled receptors, B1 and B2. Using B1 kinin receptor gene knockout mice (B1-/-), we tested the hypotheses that the B1 receptor plays an important role in preservation of cardiac function, whereas lack of B1 may accelerate cardiac remodeling and dysfunction after myocardial infarction, and that B2 receptors may compensate for lack of B1, whereas blockade of B2 receptors in B1-/- mice may cause further deterioration of cardiac function and remodeling. Female B1-/- mice and wild-type controls (C57BL/6J, B1+/+) underwent sham surgery or myocardial infarction and were treated with either vehicle or B2-antagonist (icatibant, 500 microg/kg per day, subcutaneous) for 8 weeks. We found that in sham myocardial infarction, B1-/- mice had a larger left ventricular diastolic chamber dimension both initially and at 4 to 8 weeks compared with B1+/+. Left ventricular mass and myocyte size were also larger in B1-/- with sham operation than in B1+/+, although cardiac function did not differ between strains. After myocardial infarction, cardiac remodeling and function were similar in both strains, although B1-/- mice tended to have lower blood pressure. Blockade of B2 receptors tended to worsen cardiac remodeling and dysfunction in B1-/- but not in B1+/+. These results may suggest that B2 receptors play an important role in compensating for lack of B1 receptors in mice with myocardial infarction. Dual blockade of both B1 and B2 eliminates this compensation, leading to further deterioration of cardiac dysfunction and remodeling after myocardial infarction.
UNLABELLED: In failing hearts, although protein phosphatase type 1 (PP1) activity has increased, information about the regulation and status of PP1 inhibitor-1 (INH-1) and inhibitor-2 (INH-2) is limited. In this study, we examined activity and protein expression of PP1, INH-1 and INH-2 and phosphorylation of sarcoplasmic reticulum (SR) phospholamban (PLB), a substrate of PP1 and modulator of SR Ca2+-ATPase activity, in failing and non-failing hearts. These studies were performed in LV myocardium of seven rats with chronic renal hypertension produced by Goldblatt's one-kidney, one-clip procedure and seven age-matched sham-operated normal controls (CTR). Eight weeks after surgery, LV ejection fraction, LV hypertrophy, and pulmonary congestion were determined in all rats. PP1 activity (nmol 32P/min/mg non-collagen protein) was assessed in LV homogenates using 32P-labeled phosphorylase a as substrate. INH-1 and INH-2 activity was determined in the immunoprecipitate of LV homogenates and expressed as percentage inhibitory activity. Using a specific antibody, LV tissue levels of PP1C and calsequestrin (CSQ), a SR calcium binding protein, which is not altered in failing hearts, were also determined. Further, total and phosphorylated PLB, INH-1 and INH-2 protein levels were determined in the LV homogenate and phosphoprotein-enriched fraction, respectively. The band density of each protein was quantified in densitometric units and normalized to CSQ. RESULTS: rats with chronic renal hypertension exhibited significantly reduced LV ejection fraction and increased LV hypertrophy and pulmonary congestion, characteristics of chronic heart failure (CHF). We found that compared to CTR, (1) both INH-1 (10.2+/-2 versus 57.5+/-1; p < 0.05) and INH-2 activity (3.8+/-0.4 versus 36.2+/-4; p < 0.05) were reduced, (2) total and phosphorylated PLB amount reduced, (3) protein level of phosphorylated INH-1 was reduced (2.32+/-0.1 versus 0.73+/-0.04; p < 0.05) whereas that of phosphorylated INH-2 increased (3.05+/-0.3 versus 1.42+/-0.1; p < 0.05), and (4) PP1 activity was increased approximately 2.6-fold in rats with CHF (1.59+/-0.05 versus 0.61+/-0.01; p < 0.05) while protein level of the catalytic subunit of PP1 (PP1C) increased 3.85-fold (0.77+/-0.05 versus 0.20+/-0.02; p < 0.05). These results suggest that reduced inhibitory INH-1 and INH-2 activity, increased PP1C protein level, and reduced PLB phosphorylation are associated with increased PP1 activity in failing hearts.
BACKGROUND: Mitogen-activated protein kinases (MAPKs) have emerged as an important pathophysiologic regulator during the development of heart failure (HF). p38 MAPK activity is elevated in cardiac hypertrophy and HF. We used a mouse model of myocardial infarction (MI) to test the hypotheses that (1) inhibition of p38 MAPK activity may improve cardiac function and remodeling after myocardial infarction (MI) and (2) coadministration of a p38 inhibitor (p38i) and an angiotensin-converting enzyme inhibitor (ACEI) may provide only limited further cardioprotection in this model. METHODS AND RESULTS: MI was induced in C57BL/6J mice by ligating the left anterior descending coronary artery and then either left untreated or treated with a p38i (SC-409, 30 mg/kg/day in chow), ACEI (enalapril, 20 mg/kg in drinking water), or p38i plus ACEI for 12 weeks. Echocardiography was performed and systolic blood pressure measured before MI and weekly thereafter. At the end of the study, interstitial collagen fraction (ICF) and myocyte cross-sectional area (MCSA) were examined histologically. We found that p38i significantly increased left ventricular ejection fraction and cardiac output and decreased left ventricular area at diastole, ICF, and MCSA. ACEi and p38i each had similar beneficial effects in this mouse model of HF produced by a large MI. Coadministration of p38i and ACEi did not provide any additional benefit. CONCLUSION: Our data suggest that inhibition of p38 MAPK provides significant cardioprotection in mice with HF post-MI.
The soft coral Sinularia microclavata collected from the bay of Sanya, Hainan Island, China, yielded a new diterpenoid, microclavatin (1), and a known cembranolide, capillolide (2). The structure of compound 1 was determined on the basis of spectroscopic methods and X-ray single-crystal diffraction analysis. Microclavatin (1) showed cytotoxic activities against tumor cell lines KB and MCF with IC50 values of 5.0 and 20.0 microg/mL, respectively, and capillolide (2) showed potent cytotoxic activity against tumor cell lines (A-549) with an IC50 value of 0.5 microg/mL.
1. The contribution of postjunctional P2X receptors and subtypes of alpha-adrenoceptors to vasoconstrictor responses following periarterial electrical nerve stimulation (PNS, 30 s trains of pulses at a frequency of 2, 4 or 8 Hz) was investigated in human gastroepiploic arteries. 2. The vasoconstrictor response to PNS at a stimulation of 4 or 8 Hz was a two-peaked response, whereas at a frequency of 2 Hz it appeared only as a late peak. All vasoconstrictions evoked by PNS were abolished by phentolamine, a nonselective alpha-adrenoceptor inhibitor, but not by alpha,beta-methylene ATP, a P2X receptor-desensitizing agent. 3. The early peak to PNS at 4 or 8 Hz was abolished by prazosin, an alpha1-adrenoceptor antagonist, while the late one still remained, although it was markedly inhibited. The responses remaining after prazosin were blocked by rauwolscine. The vasoconstrictor response to PNS at 2 Hz was not affected by prazosin (0.1 microM), but was abolished by rauwolscine (0.1 microM), an alpha2-adrenoceptor antagonist. 4. OPC-28326 (10 microM), a newly developed vasodilator, which preferentially exerts its antagonistic actions on the alpha2B- and alpha2C-adrenoceptors, significantly reduced the noradrenaline-induced vasoconstriction in the absence or presence of prazosin. OPC-28326 had a greater inhibitory effect on the late peak evoked by PNS than the early one. The neurogenic responses remaining after OPC-28326 were abolished by prazosin. 5. The present results suggest that sympathetic vasoconstriction of the human gastroepiploic artery is mediated by both alpha1- and alpha2-adrenoceptors postjunctionally, but not by P2X receptors. The alpha2-adrenoceptors may be preferentially activated at a low frequency of stimulation, which induces a constriction more slowly than that by alpha1-adrenoceptors. The existence of alpha2-adrenoceptors may cause an enhancement of alpha1-adrenoceptor-induced responses.
BACKGROUND & OBJECTIVE: Farnesyl-transferase inhibitor manumycin has in vitro and in vivo antitumor effects on pancreatic cancer, colon cancer, and anaplastic thyroid carcinoma. Our previous experiments showed that manumycin could inhibit proliferation pathway and survival pathway in human hepatocellular carcinoma HepG2 cells in vitro. This study was to examine the antitumor and anti-angiogenic effects of manumycin on HepG2 xenografts in nude mice. METHODS: The xenografts derived from HepG2 cells were established in BALB/C nude mice. Inoculated mice were randomly divided into normal saline (NS) group, positive control (cyclophosphamide, CTX, 25 mg/kg) group, negative control (0.1% Me2SO, 20 ml/kg) group, low dose munumycin (2.5 mg/kg) group, and high dose munumycin (5 mg/kg) group. Tumor volume was measured in nude mice bearing xenografts. Microvessel density (MVD) was observed by immunohistochemistry. Protein levels of vascular endothelial growth factor (VEGF) and b-fibroblast growth factor (b-FGF) were determined by Western blot; mRNA level of VEGF was analyzed using reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The mean tumor volume ratio of nude mice xenograft (V/V(0)) was significantly lower in low dose manumycin group and high dose manumycin group than in negative control group (0.68+/-0.09 and 0.59+/-0.04 vs. 1.38+/-0.21, P < 0.01). MVD was significantly lower in manumycin-treated groups than in control group (P < 0.01). Manumycin significantly down-regulated protein level of VEGF in HepG2 cells and HepG2 xenografts, and mRNA level of VEGF in HepG2 xenografts, but didn't affect protein level of b-FGF. CONCLUSIONS: Manumycin could inhibit the growth of human hepatocellular carcinoma HepG2 xenografts in nude mice. The down-regulation of VEGF expression and the inhibition of angiogenesis might play a key role in the anti-neoplastic effect of manumycin.
BACKGROUND & OBJECTIVE: Snake venom phospolipase A2 (PLA(2)), a large family of homologous (14 ku) soluble proteins, exerts diverse pharmacologic activities as well as enzymatic activities. So far, the structure and function of terrestrial snake PLA(2), especially the relationship of its enzymatic and pharmacologic activities have been studied extensively, but the investigation of sea snake PLA(2) are limited. This study was to investigate the in vitro and in vivo antitumor effects of recombinant sea snake basic PLA(2) (rSSBPLA(2)) and its mutants rN48 and rK4 from sea snake Lapemis hardwickii venom, and to explore the influence of 2 residues related with the enzymatic activity on the antitumor effects. METHODS: Site-directed mutagenesis of the 2 conserved residues related with enzymatic activity (His48 mutated to Asn and Asp49 mutated to Lys) was performed. The inhibitory effects of rSSBPLA(2), rN48 and rK49 on proliferation of human myeloid leukemia cell line HL-60, human neuroblastoma cell line SK-N-SH, human gastric cancer cell line MGC-803, and human liver cancer cell line HepG2 were assessed by MTT assay. Their antitumor effects on sarcoma cell line S180 xenograft and EAC ascites cancer model in mice were detected. RESULTS: The relative enzymatic activities of rN48 and rK49 were 0 and 5% of that of rSSBPLA(2). The 50% inhibitory concentration (IC(50)) of rSSBPLA(2) for HL60, SK-N-SH, and MGC-803 cells were (45.28+/-0.09) microg/ml, (57.07+/-0.12) microg/ml, and (69.34+/-0.35) microg/ml, respectively, but it had no inhibitory effect on proliferation of HepG2 cells. rSSBPLA(2) obviously inhibited growth of S180 xenograft in miceû the inhibitory rates were 50.8%, 43.2%, 38.2%, and 55.5%, respectively, under the dose of 2 mg/kg (qd x 10), 2 mg/kg (q2d x 5), 4 mg/kg (qd x 1) and 4 mg/kg (q5d x 2). The inhibitory rate of EAC model was 33.5% under the dose of 4 mg/kg (q5d x 2). The inhibitory rates were significantly higher in test groups than in control groups (P<0.01). rN48 and rK49 had no inhibitory effect on proliferation of the 4 tumor cell lines and on growth of the xenograft tumors. CONCLUSION: The antitumor effect of rSSBPLA(2) may be closely related with its enzymatic activity.
There are conflicting data about gender differences in cardiac function after myocardial infarction (MI), including cardiac rupture and mortality. Using a mouse model of MI, we recently found that the cardiac rupture rate during the first week after MI was significantly lower in females than in males, suggesting that females have attenuated structural remodeling. Thus in this study, we attempted to determine whether: a) females have attenuated remodeling and faster healing during the early phase post-MI, and b) females have better cardiac function and outcome during the chronic phase compared to males. MI was induced in 12-week-old male and female C57BL/6J mice. Signs of early remodeling, including cardiac rupture, infarct expansion, inflammatory response, and collagen deposition, were studied during the first 2 weeks post-MI. Left ventricular remodeling and function were followed for 12 weeks post-MI. We found that males had a higher rate of cardiac rupture, occurring mainly at 3 to 5 days of MI and associated with a higher infarct expansion index. Neutrophil infiltration at the infarct border was more pronounced in males than females during the first days of MI, which were also characterized by increased MMP activity. However, the number of infiltrating macrophages was significantly higher in females at day 4. During the chronic phase post-MI, males had significantly poorer LV function, more prominent dilatation and significant myocyte hypertrophy compared to females. In conclusion, males have delayed myocardial healing, resulting in cardiac rupture, and the survivors have poorer cardiac function and pronounced maladaptive remodeling, whereas females show a better outcome during the development of HF.
N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), a natural inhibitor of pluripotent hematopoietic stem cell proliferation, has been suggested as capable of promoting an angiogenic response. We studied whether Ac-SDKP stimulates endothelial cell proliferation, migration, and tube formation; enhances angiogenic response in the rat cornea after implantation of a tumor spheroid; and increases capillary density in rat hearts with myocardial infarction (MI). In vitro, an immortal BALB/c mouse aortic endothelial 22106 cell line was used to determine the effects of Ac-SDKP on endothelial cell proliferation and migration and tube formation. In vivo, a 9L-gliosarcoma cell spheroid (250-300 microm in diameter) was implanted in the rat cornea and vehicle or Ac-SDKP (800 microg.kg(-1).day(-1) ip) infused via osmotic minipump. Myocardial capillary density was studied in rats with MI given either vehicle or Ac-SDKP. We found that Ac-SDKP 1) stimulated endothelial cell proliferation and migration and tube formation in a dose-dependent manner, 2) enhanced corneal neovascularization, and 3) increased myocardial capillary density. Endothelial cell proliferation and angiogenesis stimulated by Ac-SDKP could be beneficial in cardiovascular diseases such as hypertension and MI. Furthermore, because Ac-SDKP is mainly cleaved by ACE, it may partially mediate the cardioprotective effect of ACE inhibitors.
OBJECTIVES: We studied the role of angiotensin II type 2 (AT(2)) receptors and kinins in the cardioprotective effect of angiotensin II type 1 antagonists (AT(1)-ant) in rats with heart failure (HF) after myocardial infarction. BACKGROUND: The AT(1)-ant is as effective as angiotensin-converting enzyme inhibitors in treating HF, but the mechanisms whereby AT(1)-ant exert their benefits on HF in vivo are more complex than previously understood. METHODS: Brown Norway Katholiek rats (BNK), which are deficient in kinins because of a mutation in the kininogen gene, and their wild-type control (Brown Norway [BN]) underwent myocardial infarction. Two months later, they were treated for two months with: 1) vehicle; 2) AT(1)-ant (L158809, Merck, Rahway, New Jersey); 3) AT(1)-ant + AT(2)-ant (PD-123319, Parke Davis, Ann Arbor, Michigan); or 4) AT(1)-ant + kinin B(2) receptor antagonist (B(2)-ant) (icatibant) (only BN). We measured left ventricular weight (LVW) gravimetrically, myocyte cross-sectional area (MCSA) and interstitial collagen fraction (ICF) histologically, and ejection fraction by ventriculography. RESULTS: Development of HF was comparable in BN and BNK rats. The AT(1)-ant reduced LVW and MCSA and the AT(2)-ant blocked these effects in BN rats, but the B(2)-ant did not. The AT(1)-ant reduced LVW and MCSA in BNK rats, and this effect was reversed by the AT(2)-ant. In BN rats, ICF was reduced and LVEF increased by AT(1)-ant, and both AT(2)-ant and B(2)-ant reversed these effects. In BNK rats, the AT(1)-ant failed to reduce ICF, and its therapeutic effect on LVEF was significantly blunted. CONCLUSIONS: In HF, the AT(2) receptor plays an important role in the therapeutic effects of AT(1)-ant, and this effect may be mediated partly through kinins; however, kinins appear to play a lesser role in the antihypertrophic effect of AT(1)-ant.
N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a ubiquitous tetrapeptide hydrolyzed almost exclusively by angiotensin-converting enzyme (ACE). Chronic treatment with Ac-SDKP decreases cardiac and renal fibrosis and inflammatory cell infiltration in hypertensive rats. However, very little is known about endogenous synthesis of Ac-SDKP, except that thymosin-beta4 may be the most likely precursor. Two enzymes are potentially able to release Ac-SDKP from thymosin-beta4: prolyl oligopeptidase (POP) and endoproteinase asp-N. POP is widely present and active in several tissues and biological fluids, whereas endoproteinase asp-N appears to be lacking in mammals. Therefore, we hypothesized that POP is the main enzyme involved in synthesizing the antifibrotic peptide Ac-SDKP. We investigated in vitro and in vivo production of Ac-SDKP. Using kidney cortex homogenates, we observed that Ac-SDKP was generated in a time-dependent manner in the presence of exogenous thymosin-beta4, and this generation was significantly inhibited by several POP inhibitors (POPi), Z-prolyl-prolinal, Fmoc-prolyl-pyrrolidine-2-nitrile, and S17092. Long-term administration of S17092 in rats significantly decreased endogenous levels of Ac-SDKP in the plasma (from 1.76+/-0.2 to 1.01+/-0.1 nM), heart (from 2.31+/-0.21 to 0.83+/-0.09 pmol/mg protein), and kidneys (from 5.62+/-0.34 to 2.86+/-0.76 pmol/mg protein). As expected, ACE inhibitors significantly increased endogenous levels of Ac-SDKP in the plasma, heart, and kidney, whereas coadministration of POPi prevented this increase. We concluded that POP is the main enzyme responsible for synthesis of the antifibrotic peptide Ac-SDKP.