Heme oxygenase-1 mediates the protective effects of ischemic preconditioning on mitigating lung injury induced by lower limb ischemia-reperfusion in rats.

BACKGROUND: Lower limb ischemia-reperfusion (I/R) imposes oxidative stress, elicits inflammatory response, and subsequently induces acute lung injury. Ischemic preconditioning (IP), a process of transient I/R, mitigates the acute lung injury induced by I/R. We sought to elucidate whether the protective effects of IP involve heme oxygenase-1 (HO-1). METHODS: Adult male rats were randomized to receive I/R, I/R plus IP, I/R plus IP plus the HO-1 inhibitor tin protoporphyrin (SnPP) (n = 12 in each group). Control groups were run simultaneously. I/R was induced by applying rubber band tourniquet high around each thigh for 3 h followed by reperfusion for 3 h. To achieve IP, three cycles of bilateral lower limb I/R (i.e., ischemia for 10 min followed by reperfusion for 10 min) were performed. IP was performed immediately before I/R. After sacrifice, degree of lung injury was determined. RESULTS: Histologic findings, together with assays of leukocyte infiltration (polymorphonuclear leukocytes/alveoli ratio and myeloperoxidase activity) and lung water content (wet/dry weight ratio), confirmed that I/R induced acute lung injury. I/R also caused significant inflammatory response (increases in chemokine, cytokine, and prostaglandin E(2) concentrations), imposed significant oxidative stress (increases in nitric oxide and malondialdehyde concentrations), and up-regulated HO-1 expression in lung tissues. IP significantly enhanced HO-1 up-regulation and, in turn, mitigated oxidative stress, inflammatory response, and acute lung injury induced by I/R. In addition, the protective effects of IP were counteracted by SnPP. CONCLUSIONS: The protective effects of IP on mitigating acute lung injury induced by lower limb I/R are mediated by HO-1.

L-type calcium channels and µ-opioid receptors are involved in mediating the anti-inflammatory effects of naloxone.

BACKGROUND: We sought to elucidate the effects of naloxone on regulating the up-regulation of inflammatory molecules and activation of the transcription factor nuclear factor-kappaB (NF-κB) induced by endotoxin. Possible roles of the µ-opioid receptors and L-type calcium channels in mediating the effects of naloxone in this regard were also investigated. MATERIALS AND METHODS: RAW264.7 cells were treated with phosphate buffered saline, naloxone, lipopolysaccharide (LPS), LPS plus naloxone, LPS plus naloxone plus morphine (i.e., the nonselective opioid receptors agonist), LPS plus naloxone plus fentanyl (i.e., the µ-opioid receptors agonist), or LPS plus naloxone plus BAY-K8644 (i.e., the L-type calcium channel activator). After harvesting, production of inflammatory molecules and expression NF-κB were evaluated. RESULTS: The effects of LPS on inducing the up-regulation of macrophage inflammatory protein-2, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1ß, IL-6, nitric oxide/inducible nitric oxide synthase, and prostaglandin E(2)/cyclooxygenase 2 were inhibited by naloxone. Naloxone also inhibited the effects of LPS on inducing NF-κB activation, including inhibitor-κB (I-κB) degradation, NF-κB nuclear translocation, and NF-κB-DNA binding. The effects of naloxone on inhibiting IL-1ß up-regulation and NF-κB activation were enhanced by morphine. In contrast, the effects of naloxone on inhibiting IL-1ß up-regulation and I-κB degradation were counteracted by fentanyl. Moreover, except for TNF-α, the effects of naloxone on inhibiting inflammatory molecules up-regulation and NF-κB activation were significantly counteracted by BAY-K8644. CONCLUSIONS: Naloxone significantly inhibited endotoxin-induced up-regulation of inflammatory molecules and NF-κB activation. The mechanisms may involve antagonizing the L-type calcium channels and, to a lesser extent, the µ-opioid receptors.

Magnesium sulfate mitigates lung injury induced by bilateral lower limb ischemia-reperfusion in rats.

BACKGROUND: Lower limb ischemia-reperfusion (I/R) elicits oxidative stress and causes inflammation in lung tissues that may lead to lung injury. Magnesium sulfate (MgSO(4)) possesses potent anti-oxidation and anti-inflammation capacity. We sought to elucidate whether MgSO(4) could mitigate I/R-induced lung injury. As MgSO(4) is an L-type calcium channel inhibitor, the role of the L-type calcium channels was elucidated. MATERIALS AND METHODS: Adult male rats were allocated to receive I/R, I/R plus MgSO(4) (10, 50, or 100 mg/kg), or I/R plus MgSO(4) (100 mg/kg) plus the L-type calcium channels activator BAY-K8644 (20 µg/kg) (n = 12 in each group). Control groups were run simultaneously. I/R was induced by applying rubber band tourniquets high around each thigh for 3 h followed by reperfusion for 3 h. After euthanization, degrees of lung injury, oxidative stress, and inflammation were determined. RESULTS: Arterial blood gas and histologic assays, including histopathology, leukocyte infiltration (polymorphonuclear leukocytes/alveoli ratio and myeloperoxidase activity), and lung water content, confirmed that I/R caused significant lung injury. Significant increases in inflammatory molecules (chemokine, cytokine, and prostaglandin E(2) concentrations) and lipid peroxidation (malondialdehyde concentration) confirmed that I/R caused significant inflammation and oxidative stress in rat lungs. MgSO(4), at the dosages of 50 and 100 mg/kg but not 10 mg/kg, attenuated the oxidative stress, inflammation, and lung injury induced by I/R. Moreover, BAY-K8644 reversed the protective effects of MgSO(4). CONCLUSIONS: MgSO(4) mitigates lung injury induced by bilateral lower limb I/R in rats. The mechanisms may involve inhibiting the L-type calcium channels.

Magnesium sulfate mitigates acute lung injury in endotoxemia rats.

BACKGROUND: Magnesium sulfate (MgSO4) possesses potent anti-inflammation capacity. We sought to elucidate the effects of MgSO4 on mitigating acute lung injury induced by endotoxemia. MgSO4 is an antagonist of the L-type calcium channels and the N-methyl-D-aspartate (NMDA) receptor. The roles of the L-type calcium channels and NMDA receptor in this regard were also elucidated. METHODS: Ninety-six adult male rats were randomized to receive normal saline, MgSO4 (100 mg/kg), lipopolysaccharide (LPS), LPS plus MgSO4 (10, 50, or 100 mg/kg), LPS plus MgSO4 (100 mg/kg) plus the L-type calcium channel activator BAY-K8644, or LPS plus MgSO4 (100 mg/kg) plus exogenous NMDA (n=12 in each group). Between-group differences in lung injury were evaluated. RESULTS: Histologic findings, in concert with assays of leukocyte infiltration (polymorphonuclear leukocytes/alveoli ratio and myeloperoxidase activity) and lung water content (wet/dry weight ratio), confirmed that LPS induced acute lung injury. LPS also caused significant inflammatory response (increases in chemokine, cytokine, and prostaglandin E2 concentrations) and imposed significant oxidative stress (increases in nitric oxide and malondialdehyde concentrations) in rat lungs. MgSO4 at the dosages of 50 mg/kg and 100 mg/kg, but not at 10 mg/kg, significantly mitigated the acute lung injury, lung inflammatory response, and oxidative stress caused by endotoxemia. Moreover, the protective effects of MgSO4 were counteracted by BAY-K8644 and exogenous NMDA. CONCLUSIONS: MgSO4 mitigates lung inflammatory response, oxidative stress, and acute lung injury in endotoxemia rats in a dose-dependent manner. The mechanisms may involve antagonizing the L-type calcium channels and the NMDA receptor.

Optimised nano-formulation on the bioavailability of hydrophobic polyphenol, curcumin, in freely-moving rats.

This study has optimised the poly lactic-co-glycolic acid (PLGA) nano-formulation of curcumin to prolong its retention time in the body and improve bioavailability. High-pressure emulsification-solvent-evaporation was designed to obtain curcumin-loaded PLGA nanoparticles (C-NPs) prepared with 2% of PVA containing 20% sucrose as aqueous phase and dichloromethane as oil phase. The size and entrapment efficiency of C-NPs was 158±10nm and 46.6±13.5%, respectively. The stable storage time of C-NPs was one month at 4°C. When curcumin was formulated, a significant increase of curcumin exposure in rat plasma was revealed from the intravenous study (AUC/Dose raised 55%) and the oral study (AUC/Dose increased 21-fold). The oral bioavailability of curcumin at C-NPs was 22-fold higher than conventional curcumin. Excretion results support oral study that absorption of curcumin was significantly increased by nano-formulation. These findings demonstrate that PLGA nano-formulation could potentially be applied to increase bioavailability of hydrophobic polyphenols.

The First 100 Days: Establishment and Effectiveness of Campus Protection Measures at a College during the COVID-19 Pandemic.

To prevent transmission of the coronavirus, we established the campus protection measures for coronavirus disease 2019 (COVID-19) (CPMCV-19) and analyzed the effectiveness and cost in practice. This project was set in Taiwan. We organized an anti-epidemic task force team from multidisciplinary co-workers to establish the CPMCV-19. The essential components were as follows: no close contact communication, sterilization, temperature control, social distancing, activity restrictions, personal hygiene control, and situational awareness. During 100 days of operation, the mean time spent for frontal temperature measuring was 2.7 ± 0.3 s per person. The mean on-duty time for individual personnel to control the gate and measure temperature was 3.5 h per day. In total, 31 persons with loss of taste/smell or fever were detected on campus and sent to hospital for screening within 1 h. A total of 6 persons were instructed to observe self-health management due to possible contact or travel history, and none were diagnosed with COVID-19 infection. A total budget of USD 27,100 was used for CMPCV-19 in this period. The established campus protection measures for COVID-19 were practical and might be effective. They can be used as reference for schools in a pandemic, such as COVID-19.

Phosphoinositide 3-Kinase Is Involved in Mediating the Anti-inflammation Effects of Vasopressin.

Vasopressin possesses potent anti-inflammatory capacity. Phosphoinositide 3-kinase (PI3K) and its downstream activator Akt contribute to endogenous anti-inflammation capacity. We sought to elucidate whether PI3K is involved in mediating the anti-inflammation effects of vasopressin. Macrophages (RAW264.7 cells) were randomized to receive endotoxin, endotoxin plus vasopressin, or endotoxin plus vasopressin plus the nonselective PI3K inhibitor (LY294002) or the selective isoform inhibitor of PI3Kα (PIK-75), PI3Kß (TGX-221), PI3Kδ (IC-87114), or PI3Kγ (AS-252424). Compared to macrophages treated with endotoxin, the concentrations of cytokines (tumor necrosis factor-α, interleukin-6) and chemokine (macrophage inflammatory protein-2) in macrophages treated with endotoxin plus vasopressin were significantly lower (all P < 0.05). The concentrations of phosphorylated nuclear factor-κB p65 (p-NF-κB p65) in nuclear extracts and phosphorylated inhibitor-κBα (p-I-κBα) in cytosolic extracts as well as NF-κB-DNA binding activity were also lower (all P < 0.05). Of note, except for macrophages treated with endotoxin plus vasopressin plus PIK-75, the concentrations of cytokines, chemokine, p-NF-κB p65, and p-I-κBα as well as NF-κB-DNA binding activity in macrophages treated with endotoxin plus vasopressin plus LY294002, TGX-221, IC-87114, or AS-252424 were significantly higher than those in macrophages treated with endotoxin plus vasopressin (all P < 0.05). In contrast, the phosphorylated Akt concentration in macrophages treated with endotoxin plus vasopressin was significantly higher than that in macrophages treated with endotoxin or in macrophages treated with endotoxin plus vasopressin plus LY294002, TGX-221, IC-87114, or AS-252424, but not PIK-75. These data confirmed that PI3K, especially the isoforms of PI3Kß, PI3Kδ, and PI3Kγ, is involved in mediating the anti-inflammatory effects of vasopressin.

Molecular pathways associated with transcriptional alterations in hyperparathyroidism.

Hyperparathyroidism is characterized by the oversecretion of parathyroid hormone biochemically and increased cell proliferation histologically. Primary and secondary hyperparathyroidism exhibit distinct pathophysiology but share certain common microscopic features. The present study performed the first genome-wide expression analysis directly comparing the expression profile of primary and secondary hyperparathyroidism. Microarray gene expression analyses were performed in parathyroid tissues from 2 primary hyperparathyroidism patients and 3 secondary hyperparathyroidism patients. Unsupervised hierarchical clustering analysis identified two natural subgroups containing different types of hyperparathyroidism. Combined with additional data extracted from a publicly available database, a meta-signature was constructed to represent an intersection of two sets of differential expression profile. Multiple pathways were identified that are aberrantly regulated in hyperparathyroidism. In primary hyperparathyroidism, dysregulated pathways included cell adhesion molecules, peroxisome proliferator-activated receptor signaling pathway, and neuroactive ligand-receptor interaction. Pathways implicated in secondary hyperparathyroidism included tryptophan metabolism, tight junctions, renin-angiotensin system, steroid hormone biosynthesis, and O-glycan biosynthesis. The present study demonstrates that different pathophysiology is associated with differential gene profiling in hyperparathyroidism. Several pathways are involved in parathyroid dysregulation and may be future targets for therapeutic intervention.

1,6-Bis[4-(4-amino-3-hydroxyphenoxy)phenyl] diamantane potentiates in vitro and in vivo antitumor effects of irinotecan on human colorectal cancer cells.

1,6-Bis[4-(4-amino-3-hydroxyphenoxy)phenyl] diamantane (DPD), a diamantane derivative, was previously noted as an anticancer compound through anticancer drug screening with NCI-60 human tumor cells. Irinotecan (CPT-11), a semisynthetic derivative of camptothecin, is clinically active in the treatment of colorectal cancer, with no cross-resistance. The current study conducted a pharmacokinetic evaluation of DPD, an essential component of drug discovery. Subsequent pathway analysis of microarray gene expression data indicated that the anticancer mechanisms of DPD were associated with cell cycle progression and apoptosis. The combined effect of DPD and CPT-11 with regard to the mechanisms of apoptosis-related pathways in COLO 205 cells, and the antitumor effects in colon cancer xenograft mice, were investigated. The plasma concentration and pharmacokinetic parameters of DPD in male albino rats were analyzed following a single dose of DPD by injection. The protein expression of active caspase-3, procaspase-3 and poly ADP-ribose polymerase (PARP) in COLO 205 cells treated with DPD and CPT-11, alone or combined, was evaluated by western blotting. A trypan blue dye exclusion assay revealed that, whilst DPD alone demonstrated good antitumor effects, this effect was potentiated when combined with CPT-11. Combined treatment with DPD and CPT-11 upregulated the expression of cleaved PARP, procaspase-3, caspase-3 and active caspase-3 in COLO 205 cells. In the colon cancer xenograft model, compared with the control (vehicle-treated) mice, the sizes of the tumors were significantly lower in mice treated with DPD and CPT-11, alone or in combination. Thus, DPD may be a potential therapeutic agent for the treatment of colorectal cancer via upregulating apoptosis-related pathways.

Identification of the microsomal oxidation metabolites of rutaecarpine, a main active alkaloid of the medicinal herb Evodia rutaecarpa.

Rutaecarpine is a quinazolinocarboline alkaloid of the medicinal herb Evodia rutaecarpa and shows a variety of pharmacological effects. Four oxidation metabolites of rutaecarpine were prepared from 3-methylcholanthrene-treated rat liver microsomes. These metabolites had an [M + H]+ ion at m/z 304. The structures of metabolites were identified by comparison of their liquid chromatograms and mass, absorbance, and 1H NMR spectra with those of synthetic standards. Rutaecarpine was metabolized by microsomal enzymes to form 3-, 10-, 11-, and 12-hydroxyrutaecarpine. The formation of 10-hydroxyrutaecarpine was highly induced by a cytochrome P450 1A inducer, 3-methylcholanthrene.

Herb-drug interaction of Evodia rutaecarpa extract on the pharmacokinetics of theophylline in rats.

The extract of Evodia rutaecarpa fruit and its preparation were used for the treatment of gastrointestinal disorders and headache. To assess the possible herb-drug interaction, the ethanol extract of Evodia rutaecarpa fruit (1 and 2 g/kg/day, p.o.) and the herbal preparation Wu-Chu-Yu-Tang (1 and 5 g/kg/day) were given to rats daily for three consecutive days and on the fourth day theophylline was administered (2 mg/kg, i.v.). Theophylline concentration in blood was measured by a microdialysis coupled to a liquid chromatographic system. Pharmacokinetic data were calculated by noncompartmental model. The results indicate that the theophylline level was significantly decreased by the pretreatment with the extract of Evodia rutaecarpa and herbal preparation Wu-Chu-Yu-Tang with dose-related manner. It is suggested that the herb-drug interaction may occur through the induction of the metabolism of theophylline.

Anticolorectal cancer effects and pharmacokinetic application of 2, 2-Bis [4-(4-amino-3-hydroxyphenoxy) phenyl] adamantane.

2, 2-Bis (4-(4-amino-3-hydroxyphenoxy) phenyl) adamantane (DPA) induced growth inhibition in human cancer cells using the national cancer institute (NCI) anticancer drug screen. In our previous study, we demonstrated that DPA exerted growth inhibitory activities in the three human colon cancer cell lines (Colo 205, HT-29, and HCT-15). To identify the detailed mechanism, we examined the functional importance of p21 and p53 in DPA-induced anticancer effect. We used three isogenic colon cancer cell lines, HCT-116, HCT-116 p53(-/-), and HCT-116 p21(-/-), to evaluate the roles of p21 and p53 in the in vitro anticancer effects of DPA. DPA dose-dependently inhibited cell growth, cell migration and increased cell cycle at the G0/G1 phase in HCT116 cells but not in p21(-/-) and p53(-/-) isogenic HCT-116 cells. Additionally, Western blot showed that DPA treatment induced the p21, p53, and cyclin-E protein expressions in HCT-116 cells. The p21 associated cell cycle regulatory protein such as cyclin D, CDK4, and pRb were decreased after DPA treatment in HCT-116 cells. DPA decreased cell migration in HCT-116 and HCT-116 p53(-/-) but not in HCT-116 p21(-/-) cells. We observed the up-regulation of E-cadherin, p-p38, and p-Erk in DPA-treated HCT-116 group but not in HCT-116 p21(-/-) and HCT-116 p53(-/-) groups. We assumed that p21 was required for DPA-induced anti-colon cancer effect through the Erk and p38 pathway leading to cell cycle arrest and inhibition of cell motility. Mean (± SE) pharmacokinetic parameters of the DPA were as follows: AUC = 64.44 ± 8.41, Cmax = 1.56 ± 0.48 and t1/2 = 113.92 ± 58.19. The pharmacokinetic data suggest DPA can be applied to further clinical study. This is the first pharmacokinetic study of DPA, and indicated that anti-proliferation and the cell mobility inhibition effects of DPA in HCT116 WT cells may result from the induction of p21 through activation of ERK and p38 pathway.

Limb ischemic preconditioning mitigates lung injury induced by haemorrhagic shock/resuscitation in rats.

AIM OF THE STUDY: Haemorrhagic shock and subsequent resuscitation induce acute lung injury. We elucidated whether bilateral lower limb ischemic pre-conditioning (IP) could mitigate lung injury in haemorrhagic shock/resuscitation rats. The role of heme oxygenase-1 (HO-1) was also elucidated. METHOD: Adult male rats were randomized to receive haemorrhagic shock/resuscitation (HS), HS plus IP, or HS plus IP plus the HO-1 inhibitor tin protoporphyrin (SnPP) (n = 12 in each group). Sham groups were employed simultaneously. For pre-conditioning, 3 cycles of limb IP (10 min ischemia followed by 10 min reperfusion) were performed immediately before haemorrhagic shock. Haemorrhagic shock (mean arterial pressure: 40-45 mmHg) was induced by blood drawing and maintained for 120 min. SnPP was injected 5 min before resuscitation. Shed blood/saline mixtures were re-infused to achieve resuscitation. After monitoring for another 8h, rats were sacrificed. Arterial blood gas and alveolar-arterial oxygen difference (lung function index), histology, polymorphonuclear leukocytes/alveoli ratio (leukocyte infiltration index), wet/dry weight ratio (water content index), inflammatory molecules (e.g., chemokine, cytokine, prostaglandin E(2)), and malondialdehyde (lipid peroxidation index) assays were preformed. RESULTS: Haemorrhagic shock/resuscitation induced significant lung function alterations and significant increases in leukocyte infiltration, water content, inflammation, and lipid peroxidation in lungs. Histological analysis confirmed that haemorrhagic shock/resuscitation caused marked lung injury. Limb IP significantly mitigated the adverse effects of haemorrhagic shock/resuscitation. Moreover, the protective effects of limb IP were reversed by SnPP. CONCLUSIONS: Limb IP mitigates lung injury in haemorrhagic shock/resuscitation rats. The mechanisms may involve HO-1.

Elimination of rutaecarpine and its metabolites in rat feces and urine measured by liquid chromatography.

Rutaecarpine is an alkaloid isolated from the medicinal herb Evodia rutaecarpa. This study was to evaluate the elimination pathway of rutaecarpine in rat feces and urine. Rutaecarpine and its metabolites (3-, 10-, 11- and 12-hydroxyrutaecarpine) in urine were measured after incubation with beta-glucuronidase. After the rutaecarpine was administered (25 and 100 mg/kg) orally to rats, the urine and fecal samples were collected using a metabolic cage for five consecutive days. For determining rutaecarpine, the mobile phase consisted of acetontrile-10 mM NaH(2)PO(4) (60:40, v/v, pH 4.2 adjusted with orthophosphoric acid) with a flow rate of 1 mL/min. The calibration curve was linear in concentrations of 0.05-50 microg/mL in fecal and urine sample. The results indicated that more than 42% of the rutaecarpine was excreted by feces after oral administration (25 and 100 mg/kg), but only a small amount of rutaecarpine was detected in urine at a higher dose of rutaecarpine (100 mg/kg). After incubation with beta-glucuronidase, the hydroxyrutaecarpine in urine was eluted using methanol-acetonitrile-0.04% formic acid (6:30:64, v/v) with a flow rate of 1.2 mL/min. We conclude that the metabolic pathway of rutaecarpine went through phase I hydroxylation and phase II conjugation, and the major metabolite is 10-hydroxyrutaecarpine eliminated from urine of the rat.

Oxidative metabolism of the alkaloid rutaecarpine by human cytochrome P450.

Rutaecarpine is the main active alkaloid of the herbal medicine, Evodia rutaecarpa. To identify the major human cytochrome P450 (P450) participating in rutaecarpine oxidative metabolism, human liver microsomes and bacteria-expressed recombinant human P450 were studied. In liver microsomes, rutaecarpine was oxidized to 10-, 11-, 12-, and 3-hydroxyrutaecarpine. Microsomal 10- and 3-hydroxylation activities were strongly inhibited by ketoconazole. The 11- and 12-hydroxylation activities were inhibited by alpha-naphthoflavone, quinidine, and ketoconazole. These results indicated that multiple hepatic P450s including CYP1A2, CYP2D6, and CYP3A4 participate in rutaecarpine hydroxylations. Among recombinant P450s, CYP1A1 had the highest rutaecarpine hydroxylation activity. Decreased metabolite formation at high substrate concentration indicated that there was substrate inhibition of CYP1A1- and CYP1A2-catalyzed hydroxylations. CYP1A1-catalyzed rutaecarpine hydroxylations had V(max) values of 1,388 to approximately 1,893 pmol/min/nmol P450, K(m) values of 4.1 to approximately 9.5 microM, and K(i) values of 45 to approximately 103 microM. These results indicated that more than one molecule of rutaecarpine is accessible to the CYP1A active site. The major metabolite 10-hydroxyrutaecarpine decreased CYP1A1, CYP1A2, and CYP1B1 activities with respective IC(50) values of 2.56 +/- 0.04, 2.57 +/- 0.11, and 0.09 +/- 0.01 microM, suggesting that product inhibition might occur during rutaecarpine hydroxylation. The metabolite profile and kinetic properties of rutaecarpine hydroxylation by human P450s provide important information relevant to the clinical application of rutaecarpine and E. rutaecarpa.

The alkaloid rutaecarpine is a selective inhibitor of cytochrome P450 1A in mouse and human liver microsomes.

Rutaecarpine, evodiamine, and dehydroevodiamine are quinazolinocarboline alkaloids isolated from a traditional Chinese medicine, Evodia rutaecarpa. The in vitro effects of these alkaloids on cytochrome P450 (P450)-catalyzed oxidations were studied using mouse and human liver microsomes. Among these alkaloids, rutaecarpine showed the most potent and selective inhibitory effect on CYP1A-catalyzed 7-methoxyresorufin O-demethylation (MROD) and 7-ethoxyresorufin O-deethylation (EROD) activities in untreated mouse liver microsomes. The IC(50) ratio of EROD to MROD was 6. For MROD activity, rutaecarpine was a noncompetitive inhibitor with a K(i) value of 39 +/- 2 nM. In contrast, rutaecarpine had no effects on benzo[a]pyrene hydroxylation (AHH), aniline hydroxylation, and nifedipine oxidation (NFO) activities. In human liver microsomes, 1 microM rutaecarpine caused 98, 91, and 77% decreases of EROD, MROD, and phenacetin O-deethylation activities, respectively. In contrast, less than 15% inhibition of AHH, tolbutamide hydroxylation, chlorzoxazone hydroxylation, and NFO activities were observed in the presence of 1 microM rutaecarpine. To understand the selectivity of inhibition of CYP1A1 and CYP1A2, inhibitory effects of rutaecarpine were studied using liver microsomes of 3-methylcholanthrene (3-MC)-treated mice and Escherichia coli membrane expressing bicistronic human CYP1A1 and CYP1A2. Similar to the CYP1A2 inhibitor furafylline, rutaecarpine preferentially inhibited MROD more than EROD and had no effect on AHH in 3-MC-treated mouse liver microsomes. For bicistronic human P450s, the IC(50) value of rutaecarpine for EROD activity of CYP1A1 was 15 times higher than the value of CYP1A2. These results indicated that rutaecarpine was a potent inhibitor of CYP1A2 in both mouse and human liver microsomes.

Diterpene quinone tanshinone IIA selectively inhibits mouse and human cytochrome p4501A2.

1. Tanshinone IIA is the main active diterpene quinone in the herbal medicine Salvia miltiorrhiza. In untreated mouse liver microsomes, tanshinone IIA selectively inhibited 7-ethoxyresorufin O-deethylation (EROD) and 7-methoxyresorufin O-demethylation (MROD) activities without affecting the oxidation of benzo(a)pyrene, tolbutamide, N-nitrosodimethylamine and nifedipine. Tanshinone IIA was a competitive inhibitor of MROD activity with a K(i) of 7.2 +/- 0.7 nM. 2. In 3-methylcholanthrene-treated mouse liver microsomes, tanshinone IIA and two minor tanshinones, tanshinone I and cryptotanshinone, inhibited liver microsomal MROD activity without affecting EROD and benzo(a)pyrene hydroxylation activities at the concentrations up to 1 microM. Tanshinone IIA induced a type I binding spectrum with a spectral dissociation constant K(s) of 2.3 +/-0.8 microM without cooperativity. 3. In human liver microsomes, tanshinone IIA decreased EROD and MROD activities without affecting the oxidation of benzo(a)pyrene, tolbutamide, chlorzoxazone and nifedipine. 4. In Escherichia coli membranes expressing bicistronic human CYP1A enzymes, tanshinone IIA inhibited EROD activity of CYP1A1 with an IC(50) 48 times higher than that for CYP1A2. Tanshinone I and cryptotanshinone had the same IC(50) ratio (1A1/1A2) of 4. 5. The results indicate that tanshinone represents a new group of CYP1A inhibitors, and tanshinone IIA had the highest selectivity in inhibition of CYP1A2.