Assessing the lymphoid tissue bioavailability of antiretrovirals in human primary lymphoid endothelial cells and in mice.

BACKGROUND: The secondary lymphoid tissues (LTs), lymph nodes (LNs) and gut-associated lymphoid tissue (GALT) are considered reservoirs for HIV. Antiretrovirals (ARVs) have lower penetration into LT. In vitro models predictive of ARV LT penetration have not been established. OBJECTIVES: To develop an in vitro model of LT bioavailability using human lymphoid endothelial cells (HLECs) and investigate its predictability with in vivo pharmacokinetic (PK) studies in mice. METHODS: ARV bioavailability in HLECs was evaluated at the maximum plasma concentration (Cmax) observed in HIV-infected patients. ARVs were: abacavir, atazanavir, darunavir, dolutegravir, efavirenz, elvitegravir, emtricitabine, maraviroc, raltegravir, rilpivirine, ritonavir, tenofovir disoproxil fumarate and the PK booster cobicistat. The LT PK of representative drugs showing high (efavirenz), intermediate (dolutegravir) and low (emtricitabine) HLEC bioavailability was investigated in BALB/c mice given 50/10/30 mg/kg efavirenz/dolutegravir/emtricitabine orally, daily for 3 days. The concordance of in vitro and in vivo ARV bioavailability was examined. RESULTS: ARVs showed high (>67th percentile; rilpivirine, efavirenz, elvitegravir and cobicistat), intermediate (67th-33rd percentile; ritonavir, tenofovir disoproxil fumarate, dolutegravir and maraviroc) and low (<33rd percentile; atazanavir, darunavir, raltegravir, emtricitabine and abacavir) HLEC bioavailability. The hierarchy of efavirenz, dolutegravir and emtricitabine bioavailability in LN, gut and brain tissues of mice was: efavirenz>dolutegravir>emtricitabine. CONCLUSIONS: ARVs displayed distinct HLEC penetration patterns. PK studies of representative ARVs in LT of mice were concordant with HLEC bioavailability. These findings support further development of this approach and its translational predictability in humans.

Antifungal liposomes: Lipid saturation and cholesterol concentration impact interaction with fungal and mammalian cells.

Liposomes are lipid-based nanoparticles that have been used to deliver encapsulated drugs for a variety of applications, including treatment of life-threatening fungal infections. By understanding the effect of composition on liposome interactions with both fungal and mammalian cells, new effective antifungal liposomes can be developed. In this study, we investigated the impact of lipid saturation and cholesterol content on fungal and mammalian cell interactions with liposomes. We used three phospholipids with different saturation levels (saturated hydrogenated soy phosphatidylcholine (HSPC), mono-unsaturated 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), and di-unsaturated 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC)) and cholesterol concentrations ranging from 15% to 40% (w/w) in our liposome formulations. Using flow cytometry, >80% of Candida albicans SC5314 cells were found to interact with all liposome formulations developed, while >50% of clinical isolates tested exhibited interaction with these liposomes. In contrast, POPC-containing formulations exhibited low levels of interaction with murine fibroblasts and human umbilical vein endothelial cells (<30%), while HSPC and PLPC formulations had >50% and >80% interaction, respectively. Further, PLPC formulations caused a significant decrease in mammalian cell viability. Formulations that resulted in low levels of mammalian cell interaction, minimal cytotoxicity, and high levels of fungal cell interaction were then used to encapsulate the antifungal drug, amphotericin B. These liposomes eradicated planktonic C. albicans at drug concentrations lower than free drug, potentially due to the high levels of liposome-C. albicans interaction. Overall, this study provides new insights into the design of liposome formulations towards the development of new antifungal therapeutics.

Enhanced external counterpulsation improves systolic blood pressure in patients with refractory angina.

BACKGROUND: Enhanced external counterpulsation (EECP) is a noninvasive treatment of patients with refractory angina. The immediate hemodynamic effects of EECP are similar to intra-aortic balloon pump counterpulsation, but EECP's effects on standard blood pressure measurements during and after treatment are unknown. METHODS: We evaluated systolic blood pressure (SBP) and diastolic blood pressure (DBP) for 108 consecutive patients undergoing EECP. Baseline SBP, DBP, and heart rate were compared for each patient before and after each EECP session, at the end of the course of EECP, and 6 weeks after the final EECP session. RESULTS: One hundred eight patients (mean age 66.4 +/- 11.2 years, 81% male) completed 36.5 +/- 5.1 EECP sessions per patient. Overall, based on 3,586 individual readings, EECP resulted in a decrease in mean SBP of 1.1 +/- 15.3 mm Hg at the end of each EECP session (P < .001), 6.4 +/- 18.2 mm Hg at the end the course of EECP (P < .001), and 3.7 +/- 17.8 mm Hg 6 weeks after the final EECP session (P = .07), with no significant change in DBP or heart rate. Stratifying by baseline SBP, a differential response was demonstrated: SBP increased in the 2 lowest strata (<100 mm Hg and 101-110 mm Hg) and decreased in the remaining strata (P < .001). Stratified differences were sustained after individual EECP sessions, at the end of the course of EECP, and 6 weeks after the final EECP session and were independent of changes in cardiovascular medications. CONCLUSIONS: Enhanced external counterpulsation improved SBP in patients with refractory angina. On average, EECP decreased SBP during treatment and follow-up; but for patients with low baseline SBP (<110 mm Hg), EECP increased SBP. The improvements in SBP may contribute to the clinical benefit of EECP.