Enhanced anticancer efficacy of histone deacetyl inhibitor, suberoylanilide hydroxamic acid, in combination with a phosphodiesterase inhibitor, pentoxifylline, in human cancer cell lines and in-vivo tumor xenografts.

Vorinostat [suberoylanilide hydroxamic acid (SAHA)], a histone deacetylase inhibitor, shows limited clinical activity against solid tumors when used alone. The methyl xanthine drug, pentoxifylline (PENT), has been described to have antitumor properties. The aim of this study was to look for the enhanced anticancer activities of both agents when used in combination at doses lower than their respective efficacy dose when used alone. We investigated the antitumor potential of this novel combination in vitro and in vivo. The combination index was assessed for these two drugs to look for synergistic antiproliferative activity against a broad spectrum of human cancer cell lines. Consistent additive to synergistic interactions were observed in HCT116 cells when PENT was combined with SAHA at all drug tested concentrations. The combination of SAHA and PENT induces chromatin condensation and apoptosis downstream of the pan histone deacetylase inhibition and phosphodiesterase regulation, leading to subsequent cell cycle arrest at their lower tested concentrations. Further, the ability of this combination to inhibit angiogenesis, both in vitro and in vivo, was examined and a significant inhibition in tube formation in HUVEC cells and neovascularization of Matrigel plug was observed. A significant inhibition in tumor growth was observed in severe combined immunodeficient mice bearing HCT116 (colon) and PC3 (prostate) human xenografts treated with SAHA (30 mg/kg, intraperitoneal) in combination with PENT (60 mg/kg, intraperitoneal), with no loss in body weight and 100% survival. In conclusion, these findings indicate the enhanced anticancer activity of SAHA in combination with PENT both in vitro and in vivo.

Pregnancy influences the plasma pharmacokinetics but not the cerebrospinal fluid pharmacokinetics of raltegravir: a preclinical investigation.

Alterations in antiretroviral pharmacokinetics during pregnancy must be understood for the drugs to be used safely and effectively. Present study is an attempt to understand the potential changes in raltegravir plasma and cerebrospinal fluid pharmacokinetics during pregnancy in late pregnant and non-pregnant rats. In vitro plasma protein binding, metabolic stability, intravenous blood-brain barrier (BBB) permeability and oral pharmacokinetic studies were performed. Raltegravir concentrations in different matrices were measured using LC-MS/MS. Raltegravir plasma protein binding remained similar in both groups, whereas, metabolic stability was significantly lower in pregnant rats than the non-pregnant rats liver microsomes. In oral pharmacokinetic study, peak plasma concentrations and systemic exposures were significantly lower (∼37%) and clearance was significantly higher (∼61%) in late pregnant rats compared to non-pregnant rats. However, unlike plasma pharmacokinetics, CSF pharmacokinetic profile of raltegravir was similar in both pregnant and non-pregnant rats. Following intravenous administration, raltegravir showed higher BBB permeability in pregnant rats compared to non-pregnant rats. But the mean CSF-to-plasma ratio was significantly higher in pregnant rats compared to non-pregnant rats suggesting higher brain penetration in pregnant rats. In conclusion, pregnancy significantly affected the plasma pharmacokinetics, whereas cerebrospinal fluid pharmacokinetics remained fairly similar in pregnant and non-pregnant rats. Although current plasma pharmacokinetic data is in contradiction to the reported human data, pregnancy-specific pharmacokinetic changes observed in the current study emphasize the need for close therapeutic monitoring while treating the pregnant population and also warrants the need for additional clinical data with larger group of patients.

Modulation of the cyclooxygenase pathway via inhibition of nitric oxide production contributes to the anti-inflammatory activity of kaempferol.

Kaempferol has been reported to inhibit nitric oxide synthase and cyclooxygenase enzymes in animal models. The present study was designed to investigate whether kaempferol modulates the cyclooxygenase pathway via inhibition of nitric oxide production, which in turn contributes to its anti-inflammatory activity. Investigations were performed using carrageenan induced rat air pouch model. Inflammation was assessed by measurement of nitrites (nitrite, a breakdown product of nitric oxide), prostaglandin-E(2) levels and cellular infiltration in the pouch fluid exudates. To assess the anti-inflammatory effect of the extract, rat air pouch linings were examined histologically. The levels of nitrite and prostaglandin-E(2) in pouch fluid were measured by using Griess assay and ELISA respectively. Cell counts and differential counts were performed using a Coulter counter and Wright-Giemsa stain respectively. Kaempferol when administered orally at 50 and 100mg/kg dose showed significant inhibition of carrageenan induced production of nitrite (40.12 and 59.74%, respectively) and prostaglandin-E(2) generation (64.23 and 78.55%, respectively). Infiltration of the cells into the rat granuloma air pouch was also significantly inhibited by kaempferol. Modulation of cyclooxygenase pathway via inhibition of nitric oxide synthesis significantly contributes to kaempferol's anti-inflammatory activity. The present study characterizes the effects and mechanisms of naturally occurring phenolic flavonoid kaempferol, on inducible nitric oxide synthase expression and nitric oxide production. These results partially explain the pharmacological efficacy of flavonoids in general and kaempferol in particular as anti-inflammatory compounds.