Impact of the ß-1 adrenergic receptor polymorphism on tolerability and efficacy of bisoprolol therapy in Korean heart failure patients: association between ß adrenergic receptor polymorphism and bisoprolol therapy in heart failure (ABBA) study.

BACKGROUND/AIMS: We evaluated the association between coding region variants of adrenergic receptor genes and therapeutic effect in patients with congestive heart failure (CHF). METHODS: One hundred patients with stable CHF (left ventricular ejection fraction [LVEF] < 45%) were enrolled. Enrolled patients started 1.25 mg bisoprolol treatment once daily, then up-titrated to the maximally tolerable dose, at which they were treated for 1 year. RESULTS: Genotypic analysis was carried out, but the results were blinded to the investigators throughout the study period. At position 389 of the ß-1 adrenergic receptor gene (ADRB1), the observed minor Gly allele frequency (Gly389Arg + Gly389Gly) was 0.21, and no deviation from Hardy-Weinberg equilibrium was observed in the genotypic distribution of Arg389Gly (p = 0.75). Heart rate was reduced from 80.8 ± 14.3 to 70.0 ± 15.0 beats per minute (p < 0.0001). There was no significant difference in final heart rate across genotypes. However, the Arg389Arg genotype group required significantly more bisoprolol compared to the Gly389X (Gly389Arg + Gly389Gly) group (5.26 ± 2.62 mg vs. 3.96 ± 2.05 mg, p = 0.022). There were no significant differences in LVEF changes or remodeling between two groups. Also, changes in exercise capacity and brain natriuretic peptide level were not significant. However, interestingly, there was a two-fold higher rate of readmission (21.2% vs. 10.0%, p = 0.162) and one CHF-related death in the Arg389Arg group. CONCLUSIONS: The ADRB1 Gly389X genotype showed greater response to bisoprolol than the Arg389Arg genotype, suggesting the potential of individually tailoring ß-blocker therapy according to genotype.

Chitin from Cuttlebone Activates Inflammatory Cells to Enhance the Cell Migration.

Our previous report showed that the extract from cuttlebone (CB) had wound healing effect in burned lesion of rat and the extract was identified as chitin by HPLS analysis. We herein investigated the morphology in CB extract using scanning electron microscope (SEM). Chitin was used as a control. There is no difference in morphology between CB extract and chitin. We also assessed the role of CB extract on the production of inflammatory mediators using murine macrophages and the migration of inflammatory cells. The extract induced the production of nitric oxide (NO) in macrophages. While the extract of CB itself stimulated macrophages to increase the expression of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6, CB extract suppressed the production of those cytokines by LPS. CB extract also induced the production of mouse IL-8 which is related to the cell migration, and treatment with CB enhanced fibroblast migration and invasion. Therefore, our results suggest that CB activates inflammatory cells to enhance the cell migration.

Short-term use of telmisartan attenuates oxidation and improves Prdx2 expression more than antioxidant ß-blockers in the cardiovascular systems of spontaneously hypertensive rats.

Reactive oxygen species (ROS) and antioxidant enzymes are required to maintain homeostasis. The loss of this balance can cause excessive ROS production and damage to the cardiovascular tissues. Angiotensin II receptor blockers (ARBs) and ß-blockers with antioxidant effects may inhibit ROS in the cardiovascular system. In this study, we directly compared the effects of ARBs and ß-blockers with antioxidant properties on cardiovascular protection and the regulation of endothelial progenitor cell (EPC) numbers in the setting of oxidative stress in hypertensive rats. To compare the effects of the drugs, animals were divided into the following groups: Wistar-Kyoto rats (WKY), untreated spontaneously hypertensive rats (SHR) and SHR treated with tempol (TEMP, 5 mg kg(-1) per day), trichlorothiazide (TCTZ, 1.6 mg kg(-1) per day), atenolol (25 mg kg(-1) per day), nebivolol (NEBL, 5 mg kg(-1) per day), carvedilol (CVDL, 30 mg kg(-1) per day) or telmisartan (TERT, 5 mg kg(-1) per day). Following 2 weeks of treatment, blood pressures (BPs) and aortic wall thicknesses were similarly reduced in each antihypertensive drug-treated group. Superoxide anion and malondialdehyde levels were significantly reduced following treatment with NEBL, CVDL and TERT. Additionally, the expression levels of NADPH oxidase subunits were also reduced in the TERT-, CVDL- and NEBL-treated groups. Furthermore, these drugs improved both EPC numbers and the expression levels of peroxiredoxin 2 (Prdx2), an antioxidant enzyme, in the heart and kidneys but not the aorta. Cardiac Prdx2 expression, in particular, was markedly improved by TERT, NEBL and CVDL treatment, and renal Prdx2 expression was enhanced by TEMP. Our data indicate that short-term treatment with TERT may have more beneficial effects on cardiovascular protection, EPC number improvements and Prdx2 expression compared with CVDL and NEBL. In conclusion, TERT may positively modulate the balance between oxidative stress and antioxidant properties and demonstrate capabilities beyond its BP-lowering effects.

Chitin from the Extract of Cuttlebone Induces Acute Inflammation and Enhances MMP1 Expression.

We previously reported that the extract from cuttlebone (CB) has wound healing effect in burned lesion of rat. In present study, the main component of CB extract was analyzed and its wound healing activity was evaluated by using in vitro acute inflammation model. The extract of CB stimulated macrophages to increase the production of TNF-α. The extract also enhanced the production of TGF-ß and VEGF, which were involved in angiogenesis and fibroblast activation. The treatment with CB extract enhanced proliferation of murine fibroblast. CB extract also induced the activation of fibroblast to increase the secretion of matrix metalloproteases 1 (MMP1). The constituent of CB extract which has wound healing activity was identified as chitin by HPLC analysis. The mechanism that the CB extract helps to promote healing of burned lesion is associated with that chitin in CB extracts stimulated wound skins to induce acute inflammation and to promoted cell proliferation and MMP expression in fibroblast. Our results suggest that CB or chitin can be a new candidate material for the treatment of skin wound such as ulcer and burn.

Interrelation between Expression of ADAM 10 and MMP 9 and Synthesis of Peroxynitrite in Doxorubicin Induced Cardiomyopathy.

Doxorubicin is still main drug in chemotherapy with limitation of use due to adverse drug reaction. Increased oxidative stress and alteration of nitric oxide control have been involved in cardiotoxicity of doxorubicin (DOX). A Disintegrin And Metalloproteinase (ADAMs) are transmembrane ectoproteases to regulate cell-cell and cell-matrix interactions, but role in cardiac disease is unclear. The aim of this study was to determine whether DOX activates peroxynitrite and ADAM 10 and thus ADAM and matrix metalloproteinase (MMP) induce cardiac remodeling in DOX-induced cardiomyopathy. Adult male Sprague-Dawley rats were subjected to cardiomyopathy by DOX (6 times of 2.5 mg/kg DOX over 2-weeks), and were randomized as four groups. Then followed by 3, 5, 7, and 14 days after cessation of DOX injection. DOX-injected animals significantly decreased left ventricular fractional shortening compared with control by M-mode echocardiography. The expressions of cardiac nitrotyrosine by immunohistochemistry were significant increased, and persisted for 2 weeks following the last injection. The expression of eNOS was increased by 1.9 times (p<0.05), and iNOS was marked increased in DOX-heart compared with control (p<0.001). Compared to control rats, cardiac ADAM10- and MMP 9- protein expressions increased by 20 times, and active/total MMP 9 proteolytic activity showed increase tendency at day 14 after cessation of DOX injection (n=10, each group). DOX-treated H9C2 cell showed increased ADAM10 protein expression with dose-dependency (p<0.01) and morphometric changes showed the increase of ventricular interstitial, nonvascular collagen deposition. These data suggest that activation of cardiac peroxynitrite with increased iNOS expression and ADAM 10-dependent MMP 9 expression may be a molecular mechanism that contributes to left ventricular remodeling in DOXinduced cardiomyopathy.

Investigation of metabolite alteration in dimethylnitrosamine-induced liver fibrosis by GC-MS.

BACKGROUND: A metabolomic study of biomarkers associated with dimethylnitrosamine (DMN)-induced hepatic fibrosis in Sprague-Dawley rats was performed using GC-MS. The clinical chemistry of the collected blood and the histopathology of excised liver samples were examined, and urine samples were prepared by solvent extraction. RESULTS: Through pattern analysis, the DMN-treated group was divided into two subgroups based on the aspartate aminotransferase (AST) levels compared with the control, a moderately higher group (DMN subgroup A) and a significantly higher group (DMN subgroup B). Uric acid, orotic acid, N-phenylacetylglycine and glutaric acid were biomarkers for DMN subgroup A, aminomalonic acid was a biomarker for DMN subgroup B, and arabitol level distinguished control versus DMN treatment regardless of AST level. CONCLUSION: This study suggests that the identification and profiling of AST level-related metabolites may be useful as a diagnostic tool and for the study of the mechanism of liver fibrosis induced by DMN.

Comparative evaluation for the use of oral ibuprofen and intravenous indomethacin in Korean infants with patent ductus.

Ductus arteriosus is a normal connecting blood vessel between the pulmonary artery and aorta in the fetus. However, if the ductus arteriosus is not closed and maintained as the open state even after 72 h of the birth, this is called a patent ductus arteriosus (PDA). Intravenous indomethacin is the conventional treatment for PDA in immature infants, but remains controversial in mature infants. The purpose of this study was to compare intravenous indomethacin and oral ibuprofen with regard to efficacy and safety for treatment of PDA. 78 neonates treated for PDA were included and classified into immature (n = 49) and mature (n = 29) groups. Ductal closure occurred in immature infants treated with indomethacin (74.1%) and ibuprofen (90.9%). Ductal closure occurred in mature infants treated with indomethacin (66.7%) and ibuprofen (92.9%). Platelet counts were increased in immature infants treated with ibuprofen (p = 0.027). Hyponatremia occurred in immature infants treated with ibuprofen (p = 0.002) and in both groups of mature infants (p = 0.001 for both groups). Serum creatinine values were lowered in mature infants treated with ibuprofen (p = 0.032). Bleeding occurred in 5 immature infants treated with indomethacin. Administration of furosemide for urine output was more frequent in the mature groups than in the immature group. In conclusion, oral ibuprofen was as effective as intravenous indomethacin in the immature groups and more effective in the mature groups. Adverse effects of oral ibuprofen were less severe than intravenous indomethacin.

Modulatory effects of sesamin on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of sesamin on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Sesamin at concentration ranges of 20-75 µM exhibited a significant increase in intracellular dopamine levels at 24 h: 50 µM sesamin increased dopamine levels to 133% and tyrosine hydroxylase (TH) activity to 128.2% of control levels. Sesamin at 20-100 µM rapidly increased the intracellular levels of cyclic AMP (cAMP) to 158.3%-270.3% of control levels at 30 min. At 50 µM, sesamin combined with L-DOPA (50, 100 and 200 µM) further increased the intracellular dopamine levels for 24 h compared to L-DOPA alone. In the absence or presence of L-DOPA (100 and 200 µM), sesamin (50 µM) increased the phosphorylation of TH, cAMP-dependent protein kinase (PKA), and cAMP-response element-binding protein (CREB), as well as the mRNA levels of TH and CREB for 24 h, an effect which was reduced by L-DOPA (100 and 200 µM). In addition, 50 µM sesamin exhibited a protective effect against L-DOPA (100 and 200 µM)-induced cytotoxicity via the inhibition of reactive oxygen species (ROS) production and superoxide dismutase reduction, induction of extracellular signal-regulated kinase (ERK)1/2 and BadSer112 phosphorylation and Bcl-2 expression, and inhibition of cleaved-caspase-3 formation. These results suggested that sesamin enhanced dopamine biosynthesis and L-DOPA-induced increase in dopamine levels by inducing TH activity and TH gene expression, which was mediated by cAMP-PKA-CREB systems. Sesamin also protected against L-DOPA (100-200 µM)-induced cytotoxicity through the suppression of ROS activity via the modulation of ERK1/2, BadSer112, Bcl-2, and caspase-3 pathways in PC12 cells. Therefore, sesamin might serve as an adjuvant phytonutrient for neurodegenerative diseases.

Effects of myricetin, an anticancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its main metabolite, 4-hydroxytamoxifen, in rats.

This study examined the effect of myricetin, an anticancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, in rats. The effect of myricetin on P-glycoprotein (P-gp), cytochrome P450 (CYP)3A4 and 2C9 activity was evaluated. Myricetin inhibited CYP3A4 and 2C9 activity with IC(50) values of 7.81 and 13.5 µM, respectively, and significantly inhibited P-gp activity in a concentration-dependent manner. Pharmacokinetic parameters of tamoxifen and 4-hydroxytamoxifen were determined in rats after oral (10 mg/kg) and intravenous (2 mg/kg) administration of tamoxifen in the presence and absence of myricetin (0.4, 2, and 8 mg/kg). Compared with the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve (AUC(0-∞)) and the peak plasma concentration (C (max)) of tamoxifen were significantly (P < 0.05, 2 mg/kg; P < 0.01, 8 mg/kg) increased by 41.8-74.4 and 48.4-81.7%, respectively. Consequently, the absolute bioavailability (AB) of tamoxifen with myricetin (2 and 8 mg/kg) was 29.0-35.7%, which was significantly enhanced (P < 0.05 for 2 mg/kg, P < 0.01 for 8 mg/kg) compared with the oral control group (20.4%). Moreover, the relative bioavailability (RB) of tamoxifen was 1.14- to 1.74-fold greater than that of the control group. The metabolite-parent AUC ratio (MR) was significantly reduced (P < 0.05, 8 mg/kg), implying that the formation of 4-hydroxytamoxifen was considerably affected by myricetin. The enhanced bioavailability of tamoxifen might be mainly due to inhibition of the CYP3A4- and CYP2C9-mediated metabolism of tamoxifen in the small intestine and/or in the liver, and inhibition of P-gp efflux pump in the small intestine by myricetin.

Effects of berberine on 6-hydroxydopamine-induced neurotoxicity in PC12 cells and a rat model of Parkinson's disease.

Protoberberine isoquinoline alkaloids including berberine inhibit dopamine biosynthesis and aggravate l-DOPA-induced cytotoxicity in PC12 cells. In this study, the effects of berberine on 6-hydroxydopamine (6-OHDA)-induced cytotoxicity in PC12 cells and on unilateral 6-OHDA-lesioned rats were investigated. In PC12 cells, berberine at 10 and 30µM associated with 6-OHDA (10, 20, and 50µM) enhanced cytotoxicity at 48h compared to 6-OHDA alone, indicated by an increase in apoptotic cell death. In addition, treatment with berberine (5 and 30mg/kg, i.p.) for 21 days in 6-OHDA-lesioned rats markedly depleted tyrosine hydroxylase-immunopositive cells in the substantia nigra as compared to berberine-untreated rats. Further, the levels of dopamine and norepinephrine were also significantly decreased by berberine administration (5 and 30mg/kg) in the striatal regions of 6-OHDA-lesioned rats. These results suggested that berberine aggravated 6-OHDA-induced cytotoxicity in PC12 cells, and led to the degeneration of dopaminergic neuronal cells in the substantia nigra of 6-OHDA-lesioned rats. It is, therefore, suggested that the use of long-term l-DOPA therapy with isoquinoline derivatives including berberine may need to be examined for the presence of adverse symptoms.

Effects of scoparone on dopamine release in PC12 cells.

The effects of scoparone on dopamine release in PC12 cells were investigated. Scoparone at 50-200 microM increased dopamine release into the culture medium. However, the released levels of dopamine by scoparone were not altered in the absence of extracellular Ca(2+) and by adenylyl cyclase inhibitor MDL-12,330A. Scoparone increased phosphorylation of PKA, CaMK II and synapsin I. Scoparone also enhanced K(+)-induced levels of dopamine release by CaMK II phosphorylation. These results suggest that scoparone increases dopamine release by synapsin I phosphorylation via activation of PKA and CaMK II, which are mediated by cyclic AMP levels and Ca(2+) influx.

Effects of scoparone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of scoparone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. PC12 cells treated with scoparone at concentrations of 100-200 microM showed a 128-136% increase in dopamine levels over the course of 24 hr. Scoparone significantly increased the secretion of dopamine into the culture medium. Under the same conditions, the activities of tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) were enhanced by treatment with 200 microM scoparone for 6-48 hr, but the activity of TH was regulated for a longer period than that of AADC. The intracellular levels of cyclic AMP and Ca(2+) were increased by treatment with 200 microM scoparone. The levels of TH mRNA and the phosphorylation of cyclic AMP-response element-binding protein (CREB) were also significantly increased by treatment with 200 microM scoparone. In addition, scoparone at a concentration of 200 microM stimulated the activities of cyclic AMP-dependent protein kinase (PKA), protein kinase C (PKC), and Ca(2+)/calmodulin kinase II (CaMK II). Finally, pretreatment with 200 microM scoparone reduced the cytotoxicity induced by L-DOPA (20-100 microM) at 24 hr. These results suggest that scoparone enhances dopamine biosynthesis by regulating TH activity and TH gene expression, which is mediated by the PKA, CREB, PKC, and CaMK II pathways, and protects cells from L-DOPA-induced cytotoxicity by inducing cyclic AMP-PKA systems in PC12 cells.

Catalponol enhances dopamine biosynthesis and protects against L-DOPA-induced cytotoxicity in PC12 cells.

The effects of catalponol (1) on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Catalponol at concentration ranges of 1-5 microM increased the intracellular levels of dopamine at 12-48 h. Catalponol at concentrations of up to 10 microM did not alter cell viability. Tyrosine hydroxylase (TH) activity was enhanced by 1 at 3 microM in a time-dependent manner, but aromatic L-amino acid decarboxylase activity was not. Catalponol also increased the intracellular levels of cyclic AMP and TH phosphorylation. In addition, catalponol at 3 microM associated with L-DOPA (20-50 microM) further enhanced the increases in dopamine levels induced by L-DOPA (50-100 microM) at 24 h. Catalponol at 2-5 microM inhibited L-DOPA (100-200 microM)-induced cytotoxicity at 48 h. These results suggest that 1 enhanced dopamine biosynthesis by inducing TH activity and protected against L-DOPA-induced cytotoxicity in PC12 cells, which was mediated by the increased levels of cyclic AMP.

Effects of asimilobine on dopamine biosynthesis and l-DOPA-induced cytotoxicity in PC12 cells.

The effects of asimilobine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Asimilobine at concentration ranges of 0.05-0.2 microM showed a significant inhibition of intracellular dopamine levels for 24 h in a concentration-dependent manner with an IC50 value of 0.13 microM. Asimilobine at 0.15 microM inhibited tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) activities at 24 h (73.2% inhibition of TH activity): the inhibition of TH activity was stronger and longer than that of AADC activity. Asimilobine also decreased TH mRNA levels and intracellular cyclic AMP levels, but not the basal Ca2+ concentrations. In addition, asimilobine at 0.05-5.0 microM, but not 10 microM, did not alter cell viability toward PC12 cells. A non-cytotoxic asimilobine (0.15 microM) associated with l-DOPA (20, 50, and 100 microM) for 24 h inhibited L-DOPA-induced increases in dopamine levels and enhanced L-DOPA-induced cell death when compared with L-DOPA alone. These results suggest that asimilobine inhibits dopamine biosynthesis by mainly reducing the TH activity and TH mRNA expression, and enhances L-DOPA-induced cytotoxicity in PC12 cells.

Induction of dopamine biosynthesis by l-DOPA in PC12 cells: implications of L-DOPA influx and cyclic AMP.

The effects of 3,4-dihydroxyphenylalanine (l-DOPA) on dopamine biosynthesis and cytotoxicity were investigated in PC12 cells. l-DOPA treatment (20-200 microM) increased the levels of dopamine by 226%-504% after 3-6 h of treatment and enhanced the activities of tyrosine hydroxylase (TH) and aromatic l-amino acid decarboxylase (AADC). l-DOPA (20-200 muM) treatment led to a 562%-937% increase in l-DOPA influx at 1 h, which inhibited the activity of TH, but not AADC, during the same period. The extracellular releases of dopamine were also increased by 231%-570% after treatment with 20 and 200 microM l-DOPA for 0.5-3 h. l-DOPA at a concentration of 100-200 microM, but not 20 microM, exerted apoptotic cytotoxicity towards PC12 cells for 24-48 h. l-DOPA (20-200 microM) increased the intracellular cyclic AMP levels by 318%-557% after 0.5-1 h in a concentration-dependent manner. However, the elevated cyclic AMP levels by l-DOPA could not protect against l-DOPA (100-200 microM)-induced cytotoxicity after 24-48 h. In addition, l-DOPA (20-200 microM)-induced increases in cyclic AMP and dopamine were significantly reduced by treatment with SCH23390 (dopamine D(1) receptor antagonist). The increased levels of dopamine by l-DOPA were also reduced by H89 (protein kinase A, PKA, inhibitor) and GF109203X (protein kinase C inhibitor); however, the reduction by GF109203X was not significant. l-DOPA at 20-200 microM stimulated the phosphorylation of PKA and cyclic AMP-response element binding protein and induced the biosynthesis of the TH protein. These results indicate that 20-200 microM l-DOPA induces dopamine biosynthesis by two pathways. One pathway involves l-DOPA directly entering the cells to convert dopamine through AADC activity (l-DOPA decarboxylation). The other pathway involves l-DOPA and/or released dopamine activating TH to enhance dopamine biosynthesis by the dopamine D(1) receptor-cyclic AMP-PKA signaling system (dopamine biosynthesis by TH).

Effect of scoparone on neurite outgrowth in PC12 cells.

The neurite outgrowth-promoting effects of scoparone isolated from the stem bark of Liriodendron tulipifera were investigated in PC12 cells. At a concentration of 200 microM, scoparone markedly induced neurite outgrowth from PC12 cells. Scoparone at 200 microM also enhanced the outgrowth of neurites from cells in the presence of nerve growth factor (NGF, 2 ng/ml). The levels of intracellular cyclic AMP and concentration of Ca2+ were also increased by 200 microM scoparone. In addition, scoparone at 200 microM increased the activities of extracellular signal-regulated protein kinase (ERK), cyclic AMP-dependent protein kinase (PKA), protein kinase C (PKC) and Ca2+/calmodulin kinase II (CaMK II). However, scoparone-induced neurite outgrowth was blocked by a mitogen-activated protein kinase inhibitor (U0126), a PKA inhibitor (H89), a PKC inhibitor (GF109203X) and a CaMK II inhibitor (KN62). These kinase inhibitors also reduced the scoparone-induced neurite outgrowth associated with NGF. These results suggest that scoparone can induce neurite outgrowth by stimulating the upstream steps of ERK, PKA, PKC and CaMK II in PC12 cells.

Effects of harman and norharman on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of harman and norharman on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Harman and norharman at a concentration of 20 microM and 100 microM showed 49.4% and 49.5% inhibition of dopamine content for 48 h, respectively. The IC50 values of harman and norharman were 21.2 microM and 103.3 microM. Dopamine content, tyrosine hydroxylase (TH) activity and TH mRNA levels were decreased during the first 6 h, maintained for up to 48 h and then gradually recovered at 72 h after exposure to 20 microM harman and 100 microM norharman. Under the same conditions, the intracellular cyclic AMP levels and Ca2+ concentrations were also decreased by harman and norharman. In addition, harman and norharman at concentrations higher than 80 microM and 150 microM caused cytotoxicity at 48 h in PC12 cells. Non-cytotoxic ranges of 10-30 microM harman and 50-150 microM norharman inhibited L-DOPA (20-50 microM)-induced increases in dopamine content at 48 h. Harman at 20-150 microM and norharman at 100-300 microM also enhanced L-DOPA (20-100 microM)-induced cytotoxicity at 48 h with an apoptotic process. These results suggest that harman and norharman inhibit dopamine biosynthesis by reducing TH activity and enhance L-DOPA-induced cytotoxicity in PC12 cells.

Effects of anonaine on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of anonaine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Anonaine at concentration ranges of 0.01-0.2 microM showed a significant inhibition of dopamine content at 24 h, with an IC(50) value of 0.05 microM. Anonaine at 0.05 microM inhibited tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) activities to 38.4-40.2% and 78.4-90.2% of control levels at 12-24 h and 3-6 h, respectively. TH activity was more influenced than AADC activity. Anonaine also decreased intracellular cyclic AMP levels, but not intracellular Ca(2+) concentrations. In addition, anonaine (0.05 microM) reduced L-DOPA (50 microM and 100 microM)-induced increases in dopamine content at 24 h. However, anonaine (0.05 microM) did not enhance L-DOPA (50 microM and 100 microM)-induced cell death after 24 h. These results suggest that anonaine inhibits dopamine biosynthesis by mainly reducing TH activity without aggravating L-DOPA-induced cytotoxicity in PC12 cells.

Effects of catalpalactone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of catalpalactone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Catalpalactone at 5-30µM decreased intracellular dopamine content with the IC(50) value of 22.1µM. Catalpalactone at 5-20µM, but not 30µM, did not alter cell viability. Catalpalactone at 20µM inhibited tyrosine hydroxylase (TH) and aromatic-l-amino acid decarboxylase (AADC) activities. Catalpalactone also decreased cyclic AMP levels and inhibited TH phosphorylation. In addition, catalpalactone at 20µM reduced the increases in dopamine levels induced by L-DOPA (20-50µM). Catalpalactone (5-30µM) associated with L-DOPA (50-100µM) enhanced L-DOPA-induced cytotoxicity at 48h, which was prevented by N-acetyl-l-cysteine. These results suggest that catalpalactone inhibited dopamine biosynthesis by reducing TH and AADC activities and enhanced L-DOPA-induced cytotoxiciy in PC12 cells.

Effects of tributyltin acetate on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of tributyltin acetate (TBTA) on dopamine biosynthesis and L-3,4-dihydroxyphenylalanine (L-DOPA)-induced cytotoxicity in PC12 cells were examined. TBTA at concentrations of 0.1-0.2 microM inhibited dopamine biosynthesis by reducing tyrosine hydroxylase (TH) activity and TH gene expression in PC12 cells. TBTA at 0.1-0.4 microM also reduced L-DOPA (20-50 microM)-induced increases in dopamine content for 24 h in PC12 cells. TBTA at concentrations up to 0.3 microM did not affect cell viability. However, TBTA at concentrations higher than 0.4 microM caused apoptotic cytotoxicity. Exposure of PC12 cells to non-cytotoxic (0.1 and 0.2 microM) or cytotoxic (0.4 microM) concentrations of TBTA with L-DOPA (20, 50 and 100 microM) significantly increased the cell loss and the percentage of apoptotic cells after 24 or 48 h compared with TBTA or L-DOPA alone. These data suggest that TBTA inhibits dopamine biosynthesis and enhances L-DOPA-induced cytotoxicity in PC12 cells.