兔耳病理性瘢痕皮回植术后组织中基质金属蛋白酶－1及金属蛋白酶组织抑制剂－1表达的变化

目的通过建立兔耳模型观察基质金属蛋白酶－1（matrixmetalloproteinase－1,MMP－1）及金属蛋白酶组织抑制剂－1（tissueinh｜bitorofmetalloproteinase1,TIMP1）在病理性瘢痕皮回植术后组织中表达的变化,探讨瘢痕皮回植治疗病理性瘢痕的机制。方法建立兔耳病理性瘢痕模型。共分为3组：正常皮肤组（对照组,A组）、病理性瘢痕组（B组）及瘢痕皮回植组（c组）。切取标本行HE染色和Masson特殊组织化学染色及免疫组织化学染色,观察各组标本MMP－1、TIMP－1的表达情况。结果病理性瘢痕经瘢痕皮回植术后,MMP－1及TIMP－l均较A组明显升高（P〈O．01）．MMP一1的表达较TIMP一1明显增强（P〈O．01）。结论瘢痕皮回植术治疗瘢痕的机制与瘢痕组织内MMP一1和TIMP一1相互作用的失衡有关。     

SGLT2 inhibitor lowers serum uric acid through alteration of uric acid transport activity in renal tubule by increased glycosuria

Sodium glucose cotransporter 2 (SGLT2) inhibitors have been reported to lower the serum uric acid (SUA) level. To elucidate the mechanism responsible for this reduction, SUA and the urinary excretion rate of uric acid (UE_UA) were analysed after the oral administration of luseogliflozin, a SGLT2 inhibitor, to healthy subjects. After dosing, SUA decreased, and a negative correlation was observed between the SUA level and the UE_UA, suggesting that SUA decreased as a result of the increase in the UE_UA. The increase in UE_UA was correlated with an increase in urinary d ‐glucose excretion, but not with the plasma luseogliflozin concentration. Additionally, in vitro transport experiments showed that luseogliflozin had no direct effect on the transporters involved in renal UA reabsorption. To explain that the increase in UE_UA is likely due to glycosuria, the study focused on the facilitative glucose transporter 9 isoform 2 (GLUT9ΔN, SLC2A9b), which is expressed at the apical membrane of the kidney tubular cells and transports both UA and d ‐glucose. It was observed that the efflux of [¹⁴C]UA in Xenopus oocytes expressing the GLUT9 isoform 2 was trans‐stimulated by 10 mm d ‐glucose, a high concentration of glucose that existed under SGLT2 inhibition. On the other hand, the uptake of [¹⁴C]UA by oocytes was cis‐inhibited by 100 mm d ‐glucose, a concentration assumed to exist in collecting ducts. In conclusion, it was demonstrated that the UE_UA could potentially be increased by luseogliflozin‐induced glycosuria, with alterations of UA transport activity because of urinary glucose. © 2014 The Authors. Biopharmaceutics & Drug Disposition. Published by John Wiley & Sons Ltd.     

Isolation,synthesis and characterization of ω-TRTX-Cc1a,a novel tarantula venom peptide that selectively targets L-type CaV channels

Spider venoms are replete with peptidic ion channel modulators, often with novel subtype selectivity, making them a rich source of pharmacological tools and drug leads. In a search for subtype-selective blockers of voltage-gated calcium (Ca_V) channels, we isolated and characterized a novel 39-residue peptide, ω-TRTX-Cc1a (Cc1a), from the venom of the tarantula Citharischius crawshayi (now Pelinobius muticus). Cc1a is 67% identical to the spider toxin ω-TRTX-Hg1a, an inhibitor of Ca_V2.3 channels. We assembled Cc1a using a combination of Boc solid-phase peptide synthesis and native chemical ligation. Oxidative folding yielded two stable, slowly interconverting isomers. Cc1a preferentially inhibited Ba²⁺ currents (I_Ba) mediated by L-type (Ca_V1.2 and Ca_V1.3) Ca_V channels heterologously expressed in Xenopus oocytes, with half-maximal inhibitory concentration (IC₅₀) values of 825 nM and 2.24 μM, respectively. In rat dorsal root ganglion neurons, Cc1a inhibited I_Ba mediated by high voltage-activated Ca_V channels but did not affect low voltage-activated T-type Ca_V channels. Cc1a exhibited weak activity at Na_V1.5 and Na_V1.7 voltage-gated sodium (Na_V) channels stably expressed in mammalian HEK or CHO cells, respectively. Experiments with modified Cc1a peptides, truncated at the N-terminus (ΔG1–E5) or C-terminus (ΔW35–V39), demonstrated that the N- and C-termini are important for voltage-gated ion channel modulation. We conclude that Cc1a represents a novel pharmacological tool for probing the structure and function of L-type Ca_V channels.     

Targeting PI3K/AKT/mTOR pathway in non small cell lung cancer

While PI3K/AKT/mTOR pathway is altered in a variety of cancers including non small cell lung cancer, abnormalities in this pathway are more common in squamous cell lung carcinoma than in adenocarcinoma of the lung. Moreover, aberrant activation of PI3K/AKT/mTOR pathway is one of the mechanisms of acquired resistance to EGFR-TK inhibitors in patients with adenocarcinoma carrying EGFR activating mutations.     

Population pharmacokinetic analysis of axitinib in healthy volunteers

AIMS

Axitinib is a potent and selective second generation inhibitor of vascular endothelial growth factor receptors 1, 2 and 3 approved for second line treatment of advanced renal cell carcinoma. The objectives of this analysis were to assess plasma pharmacokinetics and identify covariates that may explain variability in axitinib disposition following single dose administration in healthy volunteers.

METHODS

Plasma concentration–time data from 337 healthy volunteers in 10 phase I studies were analyzed, using non-linear mixed effects modelling (nonmem) to estimate population pharmacokinetic parameters and evaluate relationships between parameters and food, formulation, demographic factors, measures of renal and hepatic function and metabolic genotypes (UGT1A1*28 and CYP2C19).

RESULTS

A two compartment structural model with first order absorption and lag time best described axitinib pharmacokinetics. Population estimates for systemic clearance (CL), central volume of distribution (V_c), absorption rate constant (k_a) and absolute bioavailability (F) were 17.0 l h⁻¹, 45.3 l, 0.523 h⁻¹ and 46.5%, respectively. With axitinib Form IV, k_a and F increased in the fasted state by 207% and 33.8%, respectively. For Form XLI (marketed formulation), F was 15% lower compared with Form IV. CL was not significantly influenced by any of the covariates studied. Body weight significantly affected V_c, but the effect was within the estimated interindividual variability for V_c.

CONCLUSIONS

The analysis established a model that adequately characterizes axitinib pharmacokinetics in healthy volunteers. V_c was found to increase with body weight. However, no change in plasma exposures is expected with change in body weight; hence no dose adjustment is warranted.     

Citalopram and escitalopram plasma drug and metabolite concentrations: genome-wide associations

Aims

Citalopram (CT) and escitalopram (S-CT) are among the most widely prescribed selective serotonin reuptake inhibitors used to treat major depressive disorder (MDD). We applied a genome-wide association study to identify genetic factors that contribute to variation in plasma concentrations of CT or S-CT and their metabolites in MDD patients treated with CT or S-CT.

Methods

Our genome-wide association study was performed using samples from 435 MDD patients. Linear mixed models were used to account for within-subject correlations of longitudinal measures of plasma drug/metabolite concentrations (4 and 8 weeks after the initiation of drug therapy), and single-nucleotide polymorphisms (SNPs) were modelled as additive allelic effects.

Results

Genome-wide significant associations were observed for S-CT concentration with SNPs in or near the CYP2C19 gene on chromosome 10 (rs1074145, P = 4.1 × 10⁻⁹) and with S-didesmethylcitalopram concentration for SNPs near the CYP2D6 locus on chromosome 22 (rs1065852, P = 2.0 × 10⁻¹⁶), supporting the important role of these cytochrome P450 (CYP) enzymes in biotransformation of citalopram. After adjustment for the effect of CYP2C19 functional alleles, the analyses also identified novel loci that will require future replication and functional validation.

Conclusions

In vitro and in vivo studies have suggested that the biotransformation of CT to monodesmethylcitalopram and didesmethylcitalopram is mediated by CYP isozymes. The results of our genome-wide association study performed in MDD patients treated with CT or S-CT have confirmed those observations but also identified novel genomic loci that might play a role in variation in plasma levels of CT or its metabolites during the treatment of MDD patients with these selective serotonin reuptake inhibitors.