PEER REVIEWED JOURNAL ARTICLES = 17
17. Switchable on-demand release of nanocarrier from a segmented reservoir type intravaginal ring filled with a pH-responsive supramolecular polyurethane hydrogel.
Kim S, Traore YL, Chen Y
, Ho EA, Liu S. ACS Applied Bio Materials. 2018 Aug 14. 1, 3, 652-662
To achieve pH-responsive switchable on-demand release of nanoparticles (NPs) from intravaginal rings (IVR), new pH-sensitive polyurethane (PU) bearing dimethylolpropionic acid (PEG-DMPA-HDI-PG) was synthesized to encapsulate NPs as a physically crosslinked hydrogel within a segmented reservoir-IVR. New PEGylated poly(aspartic acid)-based copolymer conjugated with the fluorescent dye orange II (PASP-PEG-Ph-Orange) was synthesized to self-assemble in aqueous solution into NPs (251-283 nm) for the release study. Chemical structures of the PEG-DMPA-HDI-PG and PASP-PEG-Ph-Orange were confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) and 1H-nuclear magnetic resonance (1H-NMR) spectroscopy. PASP-PEG-Ph-Orange NPs showed the highest fluorescent emission at 570 nm for tracking, and PEG-DMPA-HDI-PG became a pH-responsive supramolecular hydrogel in distilled water at 20 wt%. PASP-PEG-Ph-Orange NPs were blended with the PEG-DMPA-HDI-PG hydrogel to form an inclusion complex and then filled into segmented reservoir-IVRs containing two 1/32" diameter holes. The segmented IVR filled with the NP encapsulated hydrogel showed continuous release of the NPs at pH 7.0 but close-to-zero release at pH 4.2 for 12 h, and moreover, demonstrated pH-responsive switchable on-demand NPs release. The PASP-PEG-Ph-Orange and PEG-DMPA-HDI-PG showed no and low cytotoxicity toward human vaginal epithelial cell line VK2/E6E7, respectively. Overall, the segmented IVR filled with PEG-DMPA-HDI-PG hydrogel demonstrated its potential use for switchable on-demand intravaginal release of nanocarriers.
16. Current State of Microbicide Development.
Traore YL, Chen Y
, Ho EA. Clin Pharmacol Ther. 2018 Aug 14. doi: 10.1002/cpt.1212. (IF=6.544)
Efforts in developing an effective vaccine for HIV has been challenging as HIV strains are highly variable and exhibit extraordinary mutability. Despite condom usage and pre-exposure prophylaxis as excellent prevention strategies, lack of accessibility in some developing countries and low adherence due to socio-cultural factors continue to act as barriers in reducing the HIV epidemic. Microbicides are topical therapies developed to prevent HIV and other sexually transmitted infections during intercourse. Microbicides applied vaginally or rectally are intended to prevent HIV infection at the site of transmission by either inhibiting its entry into immune cells or prevent viral replication. This review will summarize some of the current state-of-the-art microbicide formulations that are in pre-clinical and clinical stages of development and discuss some of the challenges associated with microbicide development.
15. Using safe, affordable and accessible non-steroidal anti-inflammatory drugs to reduce the number of HIV target cells in the blood and at the female genital tract.
Lajoie J, Birse K, Mwangi L, Chen Y
, Cheruiyot J, Akolo M, Mungai J, Boily-Larouche G, Romas L, Mutch S, Kimani M, Oyugi J, Ho EA, Burgener A, Kimani J, Fowke KR. J Int AIDS Soc. 2018 Jul;21(7):e25150. (IF=5.131)
At its basic level, HIV infection requires a replication-competent virus and a susceptible target cell. Elevated levels of vaginal inflammation has been associated with the increased risk of HIV infection as it brings highly activated HIV target cells (CCR5+CD4+ T cells; CCR5+CD4+CD161+ Th17 T cells) to the female genital tract (FGT) where they interact with HIV. Decreased HIV risk has been associated with a phenotype of decreased immune activation, called immune quiescence, described among Kenyan female sex workers who were intensely exposed to HIV yet remain uninfected. Current prevention approaches focus on limiting viral access. We took the novel HIV prevention approach of trying to limit the number of HIV target cells in the genital tract by reducing inflammation using safe, affordable and globally accessible anti-inflammatory drugs.
We hypothesized that the daily administration of low doses of acetylsalicylic acid (ASA 81 mg) or hydroxychloroquine (HCQ 200 mg) would reduce inflammation thereby decreasing HIV target cells at the FGT. Low-risk HIV seronegative women from Nairobi, Kenya were randomized for six weeks therapy of ASA (n = 37) or HCQ (n = 39) and tested to determine the impact on their systemic and mucosal immune environment.
The results showed that HCQ use was associated with a significant reduction in the proportion of systemic T cells that were CCR5+CD4+ (p = 0.01) and Th17 (p = 0.01). In the ASA arm, there was a 35% and 28% decrease in the proportion of genital T cells that were CD4+CCR5+ (p = 0.017) and Th17 (p = 0.04) respectively. Proteomic analyses of the cervical lavage showed ASA use was associated with significantly reduced amount of proteins involved in the inflammatory response and cell recruitment at the mucosa, although none of the individual proteins passed multiple comparison correction. These changes were more apparent in women with Lactobacillus dominant microbiomes.
Together, these data indicate that taking low-dose ASA daily was associated with significant reduction in HIV target cells at the FGT. This study provides proof-of-concept for a novel HIV-prevention approach that reducing inflammation using safe, affordable and globally accessible non-steroidal anti-inflammatory agents is associated with significant reduction in the proportion of HIV-target cells at the FGT.
14. Implant delivering hydroxychloroquine attenuates vaginal T lymphocyte activation and inflammation.
, Traore YL, Yang S, Lajoie J, Fowke KR, Rickey DW, Ho EA. J Control Release. 2018 May 10;277:102-113. (Selected as Cover Story, IF=7.877)
Evidence suggests that women who are naturally resistant to HIV infection exhibit low baseline immune activation at the female genital tract (FGT). This "immune quiescent" state is associated with lower expression of T-cell activation markers, reduced levels of gene transcription and pro-inflammatory cytokine or chemokine production involved in HIV infection while maintaining an intact immune response against pathogens. Therefore, if this unique immune quiescent state can be pharmacologically induced locally, it will provide an excellent women-oriented strategy against HIV infection To our knowledge, this is the first research article evaluating in vivo, an innovative trackable implant that can provide controlled delivery of hydroxychloroquine (HCQ) to successfully attenuate vaginal T lymphocyte activation and inflammation in a rabbit model as a potential strategy to induce an "immune quiescent" state within the FGT for the prevention of HIV infection. This biocompatible implant can deliver HCQ above therapeutic concentrations in a controlled manner, reduce submucosal immune cell recruitment, improve mucosal epithelium integrity, decrease protein and gene expression of T-cell activation markers, and attenuate the induction of key pro-inflammatory mediators. Our results suggest that microbicides designed to maintain a low level of immune activation at the FGT may offer a promising new strategy for reducing HIV infection.
13. Disposition, metabolism and histone deacetylase and acetyltransferase inhibition activity of tetrahydrocurcumin and other curcuminoids.
Novaes JT, Lillico R, Sayre CL, Nagabushnam K, Majeed M, Chen Y
,Ho EA, Oliveira ALP, Martinez SE, Alrushaid S, Davies NM, Lakowski TM. Pharmaceutics. 2017 Oct 12;9(4). (IF=3.746)
Tetrahydrocurcumin (THC), curcumin and calebin-A are curcuminoids found in turmeric (Curcuma longa). Curcuminoids have been established to have a variety of pharmacological activities and are used as natural health supplements. The purpose of this study was to identify the metabolism, excretion, antioxidant, anti-inflammatory and anticancer properties of these curcuminoids and to determine disposition of THC in rats after oral administration. We developed a UHPLC-MS/MS assay for THC in rat serum and urine. THC shows multiple redistribution phases with corresponding increases in urinary excretion rate. In-vitro antioxidant activity, histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity and anti-inflammatory inhibitory activity were examined using commercial assay kits. Anticancer activity was determined in Sup-T1 lymphoma cells. Our results indicate THC was poorly absorbed after oral administration and primarily excreted via non-renal routes. All curcuminoids exhibited multiple pharmacological effects in vitro, including potent antioxidant activity as well as inhibition of CYP2C9, CYP3A4 and lipoxygenase activity without affecting the release of TNF-α. Unlike curcumin and calebin-A, THC did not inhibit HDAC1 and PCAF and displayed a weaker growth inhibition activity against Sup-T1 cells. We show evidence for the first time that curcumin and calebin-A inhibit HAT and PCAF, possibly through a Michael-addition mechanism.
12. Clofibrate attenuates ROS production by lipid overload in cultured rat hepatoma cells.
, Li W, Wang GQ, Burczynski FJ. J Pharm Pharm Sci. 2017;20(0):239-251. (IF=2.333)
To investigate the effect of clofibrate on inducing liver fatty acid binding protein (FABP1) following a high-fat load in a hepatocyte cell culture model.
METHODS: Rat hepatoma cells (CRL-1548) were treated with a fatty acid (FA) mixture consisting of oleate:palmitate (2:1) in the presence of 3% albumin. Cells were treated with 0, 0.5, 1, 2, or 3 mM FA for 24 and 48 hr, or further treated with 500 µM clofibrate (CLO) to induce FABP1 levels. Cytotoxicity was determined using the WST-1 assay. Intracellular lipid droplets were quantitated following staining with Nile Red. Dichlorofluorescein (DCF) was used to assess the extent of intracellular reactive oxygen species (ROS).
RESULTS: Cell viability decreased (p < 0.01) with an increase in lipid concentration. Intracellular lipid droplets accumulated significantly (p < 0.001) with an increase in long-chain fatty acid load, which was associated with a statistical increase (p < 0.05) in ROS levels. Early clofibrate treatment showed significant increases in intracellular FABP1 levels with significant decreases in ROS levels (p < 0.05). Silencing FABP1 expression using siRNA revealed that FABP1 was the main contributor for the observed intracellular ROS clearance.
CONCLUSIONS: Characteristic cellular damage resulted from released ROS following a high fat load to hepatoma cells. The damage was attenuated through early treatment with clofibrate, which may act as a hepatoprotectant by inducing FABP1 expression and in this manner, suppress intracellular ROS levels.
11. Reversibly pH-responsive polyurethane membranes for on-demand intravaginal drug delivery.
, Chen Y†
, Ho EA, Liu S. Acta Biomater. 2017 Jan 1;47:100-112. (IF=6.383)
† equal contribution
To provide better protection for women against sexually transmitted infections, on-demand intravaginal drug delivery was attempted by synthesizing reversibly pH-sensitive polyether-polyurethane copolymers using poly(ethylene glycol) (PEG) and 1,4-bis(2-hydroxyethyl)piperazine (HEP). Chemical structure and thermo-characteristics of the synthesized polyurethanes were confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 1H-nuclear magnetic resonance (1H-NMR), and melting point testing. Membranes were cast by solvent evaporation method using the prepared pH-sensitive polyurethanes. The impact of varying pH on membrane swelling and surface morphology was evaluated via swelling ratio change and scanning electron microscopy (SEM). The prepared pH-responsive membranes showed two times higher swelling ratio at pH 4 than pH 7 and pH-triggered switchable surface morphology change. The anionic anti-inflammatory drug diclofenac sodium (NaDF) was used as a model compound for release studies. The prepared pH-responsive polyurethane membranes allowed continuous NaDF release for 24h and around 20% release of total NaDF within 3h at pH 7 but little-to-no drug release at pH 4.5. NaDF permeation across the prepared membranes demonstrated a reversible pH-responsiveness. The pH-responsive polyurethane membranes did not show any noticeable negative impact on vaginal epithelial cell viability or induction of pro-inflammatory cytokine production compared to controls. Overall, the non-cytotoxic HEP-based pH-responsive polyurethane demonstrated its potential to be used in membrane-based implants such as intravaginal rings to achieve on-demand "on-and-off" intravaginal drug delivery.
STATEMENT OF SIGNIFICANCE:
A reversible and sharp switch between "off" and "on" drug release is achieved for the first time through new pH-sensitive polyurethane membranes, which can serve as window membranes in reservoir-type intravaginal rings for on-demand drug delivery to prevent sexually transmitted infections (STIs). Close to zero drug release occurs at the normal vaginal pH (4.5) for minimal side effects. Drug release is only triggered by elevation of pH to 7 during heterosexual intercourse. The reversibly sharp and fast "on-and-off" switch arises from the creative incorporation of a pH-sensitive monomer in the soft segment of polyurethane. This polyurethane biomaterial holds great potential to better protect women who are generally at higher risk and are more vulnerable to STIs.
10. Impact of hydroxychloroquine-loaded polyurethane intravaginal rings on lactobacilli.
Traore YL, Chen Y
, Bernier AM, Ho EA. Antimicrob Agents Chemother. 2015 Dec;59(12):7680-6. (IF=4.255)
The use of polymeric devices for controlled sustained delivery of drugs is a promising approach for the prevention of HIV-1 infection. Unfortunately, certain microbicides, when topically applied vaginally, may be cytotoxic to vaginal epithelial cells and the protective microflora present within the female genital tract. In this study, we evaluated the impact of hydroxychloroquine (HCQ)-loaded, reservoir-type, polyurethane intravaginal rings (IVRs) on the growth of Lactobacillus crispatus and Lactobacillus jensenii and on the viability of vaginal and ectocervical epithelial cells. The IVRs were fabricated using hot-melt injection molding and were capable of providing controlled release of HCQ for 24 days, with mean daily release rates of 17.01 ± 3.6 μg/ml in sodium acetate buffer (pH 4) and 29.45 ± 4.84 μg/ml in MRS broth (pH 6.2). Drug-free IVRs and the released HCQ had no significant effects on bacterial growth or the viability of vaginal or ectocervical epithelial cells. Furthermore, there was no significant impact on the integrity of vaginal epithelial cell monolayers, in comparison with controls, as measured by transepithelial electrical resistance. Overall, this is the first study to evaluate the effects of HCQ-loaded IVRs on the growth of vaginal flora and the integrity of vaginal epithelial cell monolayers.
9. Pharmacological effects of a C-phycocyanin-based multicomponent nutraceutical in an in-vitro canine chondrocyte model of osteoarthritis.
Martinez SE, Chen Y
, Ho EA, Martinez SA, Davies NM. Can J Vet Res. 2015 Jul;79(3):241-9.
Multicomponent nutraceuticals are becoming increasingly popular treatments or adjunctive therapies for osteoarthritis in veterinary medicine despite lack of evidence of efficacy for many products. The objective of this study was to evaluate the anti-inflammatory and antioxidant activities of a commercially available C-phycocyanin-based nutraceutical and select constituent ingredients in an in-vitro model of canine osteoarthritis. Normal canine articular chondrocytes were used in an in-vitro model of osteoarthritis. Inflammatory conditions were induced using interleukin-1β. The nutraceutical preparation as a whole, its individual constituents, as well as carprofen were evaluated at concentrations of 0 to 250 μg/mL for reduction of the following inflammatory mediators and indicators of catabolism of the extracellular matrix: prostaglandin E2 (PGE2), tumor necrosis factor-α (TFN-α), interleukin-6 (IL-6), metalloproteinase-3 (MMP-3), nitric oxide, and sulfated glycosaminoglycans (sGAGs). Validated, commercially available assay kits were used for quantitation of inflammatory mediators. The antioxidant capacities, as well as cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and lipoxygenase (LOX) inhibitory activities of the whole nutraceutical preparation and select constituents, were also assessed using validated commercially available assay kits. The antioxidant capacity of the nutraceutical and constituents was concentration-dependent. The nutraceutical and constituents appear to display anti-inflammatory activity primarily through the inhibition of COX-2. The nutraceutical displayed similar strength to carprofen in reducing TNF-α, IL-6, MMP-3, nitric oxide, and sGAGs at select concentration ranges. The C-phycocyanin (CPC)-based nutraceutical and constituents may be able to mediate 3 primary pathogenic mechanisms of osteoarthritis: inflammation, chondral degeneration, and oxidative stress in vitro. The nutraceutical may be clinically useful in veterinary medicine and its efficacy should be further investigated in vivo.
8. Development of an Analytical Method for the Rapid Quantitation of Peptides Used in Microbicide Formulations.
, Yang S, Ho EA. Chromatographia. 2014;77(23-24):1713-1720. (IF=1.401)
Recently, a growing number of macromolecules such as peptides and proteins have been formulated into various microbicide formulations for the prevention of sexually transmitted infections. However, a fast and reliable high-throughput method for quantitating peptide/protein in polymer-based microbicide formulations is still lacking. As a result, we developed and validated a reversed-phase high-performance liquid chromatography method for the quantitation of gp120 fragment and LL-37 simultaneously in various microbicide gel formulations. This method was capable of detecting a limit of linearity (regression coefficient of 0.999) for gp120 fragment and LL-37 within a range of 0.625-80 and 1.25-80 µg mL-1, respectively. The lower limit of quantification for gp120 fragment and LL-37 was 1.14 and 0.31 µg mL-1, respectively. Method validation demonstrated acceptable intra- and inter-day RSD % (<5 %) and accuracy (95.67-100.5 %). Formulating both peptides into polymeric pharmaceutical gel formulations showed high extraction efficiency (in the range of 95.90 ± 3.03 to 111.45 ± 2.51 %). Using this method, we were able to separate and identify the forced degraded products from both peptides simultaneously without affecting the quantitation of both peptides in the polymeric dosage forms. Furthermore, this method was able to detect and separate degradants that were unable to be revealed using gel eletrophoresis.
7. Development of polyether urethane intravaginal rings for the sustained delivery of hydroxychloroquine.
, Traore YL, Li A, Fowke KR, Ho EA. Drug Des Devel Ther. 2014 Oct 9;8:1801-15. (IF=2.935)
Hydroxychloroquine (HCQ) has been shown to demonstrate anti-inflammatory properties and direct anti-HIV activity. In this study, we describe for the first time the fabrication and in vitro evaluation of two types of intravaginal ring (IVR) devices (a surfaced-modified matrix IVR and a reservoir segmental IVR) for achieving sustained delivery (>14 days) of HCQ as a strategy for preventing male-to-female transmission of HIV. Both IVRs were fabricated by hot-melt injection molding. Surface-modified matrix IVRs with polyvinylpyrrolidone or poly(vinyl alcohol) coatings exhibited significantly reduced burst release on the first day (6.45% and 15.72% reduction, respectively). Reservoir IVR segments designed to release lower amounts of HCQ displayed near-zero-order release kinetics with an average release rate of 28.38 μg/mL per day for IVRs loaded with aqueous HCQ and 32.23 μg/mL per day for IVRs loaded with HCQ mixed with a rate-controlling excipient. Stability studies demonstrated that HCQ was stable in coated or noncoated IVRs for 30 days. The IVR segments had no significant effect on cell viability, pro-inflammatory cytokine production, or colony formation of vaginal and ectocervical epithelial cells. Both IVR systems may be suitable for the prevention of HIV transmission and other sexually transmitted infections.
6. Hepatoprotective role of liver fatty acid binding protein in acetaminophen induced toxicity.
Gong Y, Wang G, Gong Y, Yan J, Chen Y
, Burczynski FJ. BMC Gastroenterol. 2014 Mar 10;14:44. (IF=2.731)
FABP1 has been reported to possess strong antioxidant properties. Upon successful transfection of the Chang cell line, which has undetectable FABP1 mRNA levels, with human FABP1 cDNA, the Chang cells were shown to express FABP1. Using the transfected and control (normal) Chang cells and subjecting them to oxidative stress, transfected cells were reported to be associated with enhanced cell viability. This study extends those observations by investigating the effect of FABP1 on acetaminophen (AAP)-induced hepatotoxicity. We hypothesized that presence of FABP1 would enhance cell viability compared to control cells (vector transfected cells).
Following AAP treatment of Chang FABP1 transfected and control cells, cell viability, oxidative stress, and apoptosis were evaluated using lactate dehydrogenase (LDH) release, the fluorescent probe DCF, and Bax expression, respectively.
FABP1 cDNA transfected cells showed greater resistance against AAP toxicity than vector transfected cells. Significantly lower LDH levels (p < 0.05) were observed as were lower DCF fluorescence intensity (p < 0.05) in FABP1 cDNA transfected cells compared to vector transfected cells. FABP1 expression also attenuated the expression of Bax following AAP induced toxicity.
FABP1 attenuated AAP-induced toxicity and may be considered a cytoprotective agent in this in vitro model of drug induced oxidative stress.
5. Novel intravaginal nanomedicine for the targeted delivery of saquinavir to CD4+ immune cells.
Yang S, Chen Y
, Gu K, Dash A, Sayre CL, Davies NM, Ho EA. Int J Nanomedicine. 2013;8:2847-58. (IF=4.370)
The goal of this study was to develop and characterize an intravaginal nanomedicine for the active targeted delivery of saquinavir (SQV) to CD4(+) immune cells as a potential strategy to prevent or reduce HIV infection. The nanomedicine was formulated into a vaginal gel to provide ease in self-administration and to enhance retention within the vaginal tract. SQV-encapsulated nanoparticles (SQV-NPs) were prepared from poly(lactic-co-glycolic acid) (PLGA) and conjugated to antihuman anti-CD4 antibody. Antibody-conjugated SQV-NPs (Ab-SQV-NPs) had an encapsulation efficiency (EE%) of 74.4% + 3.7% and an antibody conjugation efficiency (ACE%) of 80.95% + 1.10%. Over 50% of total loaded SQV was released from NPs over 3 days. NPs were rapidly taken up by Sup-T1 cells, with more than a twofold increase in the intracellular levels of SQV when delivered by Ab-SQV-NPs in comparison to controls 1 hour post-treatment. No cytotoxicity was observed when vaginal epithelial cells were treated for 24 hours with drug-free Ab-NPs (1,000 μg/mL), 1% HEC placebo gel (200 mg/mL), or 1% HEC gel loaded with drug-free Ab-NPs (5 mg NPs/g gel, 200 mg/mL of gel mixture). Overall, we described an intravaginal nanomedicine that is nontoxic and can specifically deliver SQV into CD4(+) immune cells. This platform may demonstrate potential utility in its application as postexposure prophylaxis for the treatment or reduction of HIV infection, but further studies are required.
4. Advancements in the field of intravaginal siRNA delivery.
Yang S, Chen Y
, Ahmadie R, Ho EA. J Control Release. 2013 Apr 10;167(1):29-39. (IF=7.877)
The vaginal tract is a suitable site for the administration of both local and systemic acting drugs. There are numerous vaginal products on the market such as those approved for contraception, treatment of yeast infection, hormonal replacement therapy, and feminine hygiene. Despite the potential in drug delivery, the vagina is a complex and dynamic organ that requires greater understanding. The recent discovery that injections of double stranded RNA (dsRNA) in Caenorhabditis elegans (C. elegans) results in potent gene specific silencing, was a major scientific revolution. This phenomenon known as RNA interference (RNAi), is believed to protect host genome against invasion by mobile genetic elements such as transposons and viruses. Gene silencing or RNAi has opened new potential opportunities to study the function of a gene in an organism. Furthermore, its therapeutic potential is being investigated in the field of sexually transmitted infections such as human immunodeficiency virus (HIV) and other diseases such as age-related macular degeneration (AMD), diabetes, hypercholesterolemia, respiratory disease, and cancer. This review will focus on the therapeutic potential of siRNA for the treatment and/or prevention of infectious diseases such as HIV, HPV, and HSV within the vaginal tract. Specifically, formulation design parameters to improve siRNA stability and therapeutic efficacy in the vaginal tract will be discussed along with challenges, advancements, and future directions of the field.
3. Metabolic disposition of the insect repellent DEET and the sunscreen oxybenzone following intravenous and skin administration in rats.
Fediuk DJ, Wang T, Chen Y
, Parkinson FE, Namaka MP, Simons KJ, Burczynski FJ, Gu X. Int J Toxicol. 2012 Sep-Oct;31(5):467-76. (IF=1.504)
Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone have shown a synergistic percutaneous enhancement when applied concurrently. Both compounds are extensively metabolized in vivo into a series of potentially toxic metabolites: 2 metabolites of DEET, N,N-diethyl-m-hydroxymethylbenzamide (DHMB) and N-ethyl-m-toluamide (ET), and 3 metabolites of oxybenzone, 2,4-dihydroxybenzophenone (DHB), 2,2-dihydroxy-4-methoxybenzophenone (DMB), and 2,3,4-trihydroxybenzophenone (THB). In this study, the metabolites were extensively distributed following intravenous and topical skin administration of DEET and oxybenzone in rats. Combined application enhanced the disposition of all DEET metabolites in the liver but did not consistently affect the distribution of oxybenzone metabolites. The DHMB appeared to be the major metabolite for DEET, while THB and its precursor DHB were the main metabolites for oxybenzone. Repeated once-daily topical application for 30 days led to higher concentrations of DEET metabolites in the liver. Hepatoma cell studies revealed a decrease in cellular proliferation from all metabolites as single and combined treatments, most notably at 72 hours. Increased accumulation of DHMB and ET in the liver together with an ability to reduce cellular proliferation at achievable plasma concentrations indicated that simultaneous exposure to DEET and oxybenzone might have the potential to precipitate adverse effects in a rat animal model.
2. Silymarin and hepatoprotection.
Burczynski FJ, Wang G, Nguyen D, Chen Y
, Smith HJ, Gong Y. Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2012 Jan;37(1):6-10.
To determine the hepatoprotective effect of silymarin with Chang cell cultures. Specifically, to investigate the antioxidant properties of silymarin and its protective function in reducing pro-apoptotic markers.
Intracellular free radical levels were assessed with dichlorofluorescein (DCF) fluorescence after exposing cells to an oxidative stress of 400 μmol/L H2O2 for 20 min. Levels of cellular ATP and bax expression were examined to evaluate the protective effects of silymarin.
Silymarin significantly reduced the DCF fluorescence signal. Cell viability, assessed by the MTT assay, showed that silymarin enhanced the cell growth. Drug treatment was also associated with enhanced ATP levels, and reduced Bax and protein mRNA levels.
Silymarin can function as a hepatoprotectant against free radical damage due to oxidative stress. The protective nature extends to reducing levels of pro-apoptotic Bax protein. Silymarin may be a useful adjuvant for the treatment of specific liver diseases.
1. Tissue disposition of the insect repellent DEET and the sunscreen oxybenzone following intravenous and topical administration in rats.
Fediuk DJ, Wang T, Chen Y
, Parkinson FE, Namaka MP, Simons KJ, Burczynski FJ, Gu X. Biopharm Drug Dispos. 2011 Oct;32(7):369-79. (IF=1.677)
The insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone (OBZ) have been shown to produce synergistic permeation enhancement when applied concurrently in vitro and in vivo. The disposition of both compounds following intravenous administration (2 mg/kg of DEET or OBZ) and topical skin application (100 mg/kg of DEET and 40 mg/kg of OBZ) was determined in male Sprague-Dawley rats. Pharmacokinetic analysis was also conducted using compartmental and non-compartmental methods. A two-compartment model was deemed the best fit for intravenous administration. The DEET and oxybenzone permeated across the skin to accumulate in blood, liver and kidney following topical skin application. Combined use of DEET and oxybenzone accelerated the disappearance of both compounds from the application site, increased their distribution in the liver and significantly decreased the apparent elimination half-lives of both compounds (p < 0.05). Hepatoma cell studies revealed toxicity from exposure to all treatment concentrations, most notably at 72 h. Although DEET and oxybenzone were capable of mutually enhancing their percutaneous permeation and systemic distribution from topical skin application, there was no evidence of increased hepatotoxic deficits from concurrent application.