Intracellular accumulation of efavirenz and nevirapine is independent of P-glycoprotein activity in cultured CD4 T cells and primary human lymphocytes.

BACKGROUND: Interaction of antiretrovirals with drug transporters such as P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), breast cancer resistance protein (BCRP) and solute carrier organic anion transporter (SLCO) may influence the emergence of viral mutants by altering intracellular drug concentrations. Here we characterize the effect of transporter expression in a variety of cell types such as control CEM, CEM(VBL) (P-gp-overexpressing), CEM(E1000) (MRP1-overexpressing), MT4, control MDCKII, MDCKII(MDR1) (P-gp-overexpressing) and peripheral blood mononuclear cells (PBMCs) on the uptake of [(14)C]efavirenz and [(3)H]nevirapine. We also investigated the lipophilicity of [(14)C]efavirenz and [(3)H]nevirapine. METHODS: The expression of P-gp, MRP1, MRP2, SLCO1A2, 1B1, 1B3, 2B1, 3A1 and 4A1 was assessed by PCR. Inhibitors of P-gp (XR9576, GF120918, dipyridamole) and MRP (MK571, frusemide, dipyridamole), and SLCO substrate or inhibitor (estrone-3-sulphate or montelukast, respectively) were used to study the role of drug transporters in the accumulation of [(14)C]efavirenz and [(3)H]nevirapine. Lipophilicity was measured by the octanol/saline partition coefficient. RESULTS: CEM cells, MT4 cells and PBMCs express various SLCO isoforms, with SLCO3A1 detected in all of the cells. XR9576, dipyridamole and GF120918 had no effects on the accumulation of [(14)C]efavirenz, while MK571 and frusemide produced variable effects in the cells. The accumulation of [(14)C]efavirenz was significantly decreased in all the cells by montelukast and estrone-3-sulphate. CONCLUSIONS: P-gp expression had no effect on the accumulation of [(14)C]efavirenz and [(3)H]nevirapine. MRP1/2 expression, lipophilicity and SLCO-like transporters (possibly SLCO3A1) may have greater influence on the accumulation of [(14)C]efavirenz than [(3)H]nevirapine.

Effect of transporter modulation on the emergence of nelfinavir resistance in vitro.

BACKGROUND: HIV drug resistance is of increasing concern and could result from inadequate drug potency, poor therapy adherence and the existence of pharmacological sanctuary sites for viral replication. One contributing factor to the generation of such sites could be drug efflux transporters, which have been shown capable of effluxing HIV protease inhibitors from cells. METHODS: In this 'proof-of-concept' study, the ability of the efflux transport inhibitor verapamil to modulate the intracellular accumulation of radiolabelled nelfinavir (NFV) and the antiviral effect of NFV was assessed in MT4 cells. Wild-type virus was then serially passaged with increasing concentrations of NFV with and without verapamil and resistance mutations monitored by sequencing of the viral protease gene. RESULTS: The cellular accumulation ratio of 3H-NFV was 116.8 +/- 9.7 in controls and was significantly increased to 149.8 +/- 24.5 following incubation with verapamil (P < 0.05, n=4). The EC50 of NFV was decreased in MT4 cells in the presence of verapamil from 8.5 11.3 nM to 4.4 +/- 0.8 nM (P < 0.001, n=6). Of the 24 isolates passaged without verapamil, 21 carried the D30N mutation at detectable levels. Of the 23 passaged with verapamil, 14 carried the mutation (odds ratio = 4.5; P < 0.05). CONCLUSIONS: These results suggest that 'intracellular boosting' of PIs is achievable through inhibition of drug efflux proteins in vitro and that such boosting has the ability to enhance suppression of viral replication, slowing the emergence of resistance mutations.

Survival after an amniotic fluid embolism following the use of sodium bicarbonate.

Amniotic fluid embolism (AFE) is a rare and potentially fatal complication of pregnancy. In this case report, we highlight the successful use of sodium bicarbonate in a patient with an AFE. We present a case of a 38-year-old mother admitted for an elective caesarean section. Following the delivery of her baby, the mother suffered a cardiac arrest. Following a protracted resuscitation, transoesophageal echocardiography demonstrated evidence of acute pulmonary hypertension, with an empty left ventricle and an over-distended right ventricle. In view of these findings and no improvement noted from on-going resuscitation, sodium bicarbonate was infused as a pulmonary vasodilator. Almost instantaneous return of spontaneous circulation was noted, with normalisation of cardiac parameters. We propose that in patients suspected with AFE and who have been unresponsive to advance cardiac life support measures, and where right ventricular failure is present with acidosis and/or hypercarbia, the use of sodium bicarbonate should be considered.