Adam L. VanWert

Organic anion transporters: discovery, pharmacology, regulation and roles in pathophysiology.

Our understanding of the mechanisms behind inter- and intra-patient variability in drug response is inadequate. Advances in the cytochrome P450 drug metabolizing enzyme field have been remarkable, but those in the drug transporter field have trailed behind. Currently, however, interest in carrier-mediated disposition of pharmacotherapeutics is on a substantial uprise. This is exemplified by the 2006 FDA guidance statement directed to the pharmaceutical industry. The guidance recommended that industry ascertain whether novel drug entities interact with transporters. This suggestion likely stems from the observation that several novel cloned transporters contribute significantly to the disposition of various approved drugs. Many drugs bear anionic functional groups, and thus interact with organic anion transporters (OATs). Collectively, these transporters are nearly ubiquitously expressed in barrier epithelia. Moreover, several reports indicate that OATs are subject to diverse forms of regulation, much like drug metabolizing enzymes and receptors. Thus, critical to furthering our understanding of patient- and condition-specific responses to pharmacotherapy is the complete characterization of OAT interactions with drugs and regulatory factors. This review provides the reader with a comprehensive account of the function and substrate profile of cloned OATs. In addition, a major focus of this review is on the regulation of OATs including the impact of transcriptional and epigenetic factors, phosphorylation, hormones and gender.

Organic Anion Transporter 3 (Oat3/Slc22a8) Interacts with Carboxyfluoroquinolones and Deletion Increases Systemic Exposure to Ciprofloxacin

Carboxyfluoroquinolones, such as ciprofloxacin, are used for the treatment of numerous infectious diseases. Renal secretion is a major determinant of their systemic and urinary concentration, but the specific transporters involved are virtually unknown. In vivo studies implicate the organic anion transporter (OAT) family as a pivotal component of carboxyfluoroquinolone renal secretion. Therefore, this study identified the specific renal basolateral OAT(s) involved, thereby highlighting potential sources of carboxyfluoroquinolone-drug interactions and variable efficacy. Two heterologous expression systems, Xenopus laevis oocytes and cell monolayers, were used to determine the roles of murine and human renal basolateral mOat1/hOAT1 and mOat3/hOAT3. Ciprofloxacin was transported by mOat3 in both systems (Km value, 70 ± 6 μM) and demonstrated no interaction with mOat1 or hOAT1. Furthermore, ciprofloxacin, norfloxacin, ofloxacin, and gatifloxacin exhibited concentration-dependent inhibition of transport on mOat3 in cells with inhibition constants of 198 ± 39, 558 ± 75, 745 ± 165, and 941 ± 232 μM, respectively. Ciprofloxacin and gatifloxacin also inhibited hOAT3. Thereafter, in vivo elimination of ciprofloxacin was assessed in wild-type and Oat3 null mice [Oat3(-/-)]. Oat3(-/-) mice exhibited significantly elevated plasma levels of ciprofloxacin at clinically relevant concentrations (P < 0.05, male mice; P < 0.01, female mice). Oat3(-/-) mice also demonstrated a reduced volume of distribution (27%, P < 0.01, male mice; 14%, P < 0.01, female mice) and increased area under the concentration-time curve (25%, P < 0.05, male mice; 33%, P < 0.01, female mice). Female Oat3(-/-) mice had a 35% (P < 0.01) reduction in total clearance of ciprofloxacin relative to wild type. In addition, putative ciprofloxacin metabolites were significantly elevated in Oat3(-/-) mice. The present findings indicate that polymorphisms of and drug interactions on hOAT3 may influence carboxyfluoroquinolone efficacy, especially in urinary tract infections.

α-Santalol, a derivative of sandalwood oil, induces apoptosis in human prostate cancer cells by causing caspase-3 activation

The anticancer effects of α-santalol, a major component of sandalwood oil, have been reported against the development of certain cancers such as skin cancer both in vitro and in vivo. The primary objectives of the current study were to investigate the cancer preventive properties of α-santalol on human prostate cancer cells PC-3 (androgen independent and P-53 null) and LNCaP (androgen dependent and P-53 wild-type), and determine the possible mechanisms of its action. The effect of α-santalol on cell viability was determined by trypan blue dye exclusion assay. Apoptosis induction was confirmed by analysis of cytoplasmic histone-associated DNA fragmentation using both an apoptotic ELISA kit and a DAPI fluorescence assay. Caspase-3 activity was determined using caspase-3 (active) ELISA kit. PARP cleavage was analyzed using immunoblotting. α-Santalol at 25-75 μM decreased cell viability in both cell lines in a concentration and time dependent manner. Treatment of prostate cancer cells with α-santalol resulted in induction of apoptosis as evidenced by DNA fragmentation and nuclear staining of apoptotic cells by DAPI. α-Santalol treatment also resulted in activation of caspase-3 activity and PARP cleavage. The α-santalol-induced apoptotic cell death and activation of caspase-3 was significantly attenuated in the presence of pharmacological inhibitors of caspase-8 and caspase-9. In conclusion, the present study reveals the apoptotic effects of α-santalol in inhibiting the growth of human prostate cancer cells.

Organic Anion Transporter 3 Interacts Selectively with Lipophilic β-Lactam Antibiotics

Transporters are major determinants of the disposition of xenobiotics and endogenous chemicals in the body. Organic anion transporter 3 (Oat3) functions in the kidney and brain to remove metabolic waste, toxins, and drugs, and thus transports diverse chemicals. Some β-lactam antibiotics interact with Oat3, and penicillin G exhibits a strong dependence on Oat3 for renal elimination. However, over 80 β-lactams exist, and many have not been assessed for an interaction with Oat3. Moreover, β-lactams continue to receive U.S. Food and Drug Administration approval. This study identified new β-lactam–Oat3 interactions, provided a head-to-head comparison with Oat1, and characterized the physicochemical determinants of affinity for Oat3. Cells expressing mouse Oat3 (mOat3) and Oat1 (mOat1), and human OAT3 (hOAT3) were used to test inhibitors, and high-performance liquid chromatography (HPLC) was used to measure transport. Of 26 β-lactams tested, 12 were clear inhibitors of Oat3, and 14 exhibited poor interactions. Inhibitors exhibited a nearly identical rank-order of potency against mOat3 and hOAT3. Oat1 demonstrated a poor interaction with most β-lactams. The majority of Oat3 inhibitors were substrates, and there were clear physicochemical differences between inhibitors and noninhibitors. That is, inhibitors had nearly 40% fewer hydrogen bond donors (P < 0.001), a lower total polar surface area (P < 0.05), and greater lipophilicity (LogP of inhibitors, +1.41; noninhibitors, −1.54; P < 0.001). Pharmacophore mapping revealed a prohibitive hydrogen bond donor group in noninhibitors adjacent to a hydrophobic moiety that was important for binding to Oat3. These findings indicate that Oat3 recognizes lipophilic β-lactams more readily. Moreover, this study has potential implications for designing β-lactams to avoid renal accumulation or brain efflux via Oat3.

Medicinal properties of alpha-santalol, a naturally occurring constituent of sandalwood oil: review

Abstract Alpha-santalol is a naturally occurring sesquiterpene that is derived from sandalwood oil. Its wide range of health benefits have been attributed to the modulation of various signalling pathways involved in the development of a particular disease. For example, the antitumour and cancer preventive properties of alpha-santalol have been shown to involve cell death induction through apoptosis and cell cycle arrest in various cancer models. A marked decrease in inflammatory markers have also been shown with alpha-santalol administration in skin tissue models. The current review is aimed at bringing the most recent advances of alpha-santalol against various disease-specific models and highlighting its associated mechanistic details.

Alpha-Santalol, a Component of Sandalwood Oil Inhibits Migration of Breast Cancer Cells by Targeting the β-catenin Pathway

Background/Aim: Alpha-santalol, a terpenoid found in sandalwood oil has been shown to inhibit breast cancer cell growth in vitro by inducing apoptosis, but the mechanisms underlying the growth inhibitory effects of alpha-santalol are not fully understood. In this study, we demonstrate that α-santalol treatment targets Wnt/β-catenin pathway to inhibit migration of cultured breast cancer cells. Materials and Methods: Migration assays, immunoblotting and immunofluorescence were used to examine the mechanism of action of a-santalol in breast cancer cells. Results: Exposure of MDA-MB 231 and MCF-7 cells to α-santalol resulted in a significant reduction in their migratory potential and wound healing ability. In addition, α-santalol affected the localization of β-catenin from cytosol to nucleus in MDA-MB 231 cells. Conclusion: Alpha-santalol inhibited migration of breast cancer cells may be mediated, in part, by targeting Wnt//β-catenin pathway. β-catenin represents an important target of α-santalols response for future pre-clinical studies.

The Role of Organosulfur Compounds Derived From Allium Vegetables in Cancer Prevention and Therapy

Organosulfur compounds (OSCs) are a group of small molecules commonly present in Allium vegetables, such as garlic, onions chives, and shallots that have garnered scientific interest for their noted health benefits. OSCs have been evaluated for their potential to prevent or treat major diseases including cancer. Epidemiological evidence of inverse association between increased intake of Allium vegetables and cancer risk is now substantiated by animal studies wherein true causal relationships between OSCs and cancer prevention have been found. This chapter summarizes the chemistry, metabolism, and bioavailability of commonly studied OSCs and the latest developments regarding their anticarcinogenic effects in cell culture and animal models. Data pertinent to clinical trials assessing safety and anticancer efficacy of OSCs are also discussed.

Abstract 4608: Survivin downregulation by α-santalol is not mediated through PI3K-Akt pathway in human breast cancer cells

α-Santalol, a terpenoid found in sandalwood oil, has been shown to inhibit cancer cell growth in vitro by inducing apoptosis. This study was performed to investigate the anticancer properties of α-santalol associated with the induction of apoptosis in cultured MCF-7 (estrogen receptor (ER) positive, and wild type p53) and MDA-MB-231 (ER-negative and mutant p53) breast cancer cells. Expression of major proteins examined in the study were determined using standard Western blot protocol and analyzed by LICOR-Odyssey infra-red scanner. Total protein levels of survivin were confirmed by survivin ELISA kit. Cell viability was assessed by trypan blue dye exclusion assay, and caspase-3 activity was determined by caspase-3 (active) ELISA kit. Treatment of breast cancer cells for 6 and 9 hour time intervals with α-santalol (20, 40 μM) resulted in statistically significant concentration-dependent downregulation of survivin. pAkt levels were found to be slightly upregulated despite the downregulation of survivin. Pharmacological inhibition of the PI3K-Akt pathway did not result in a synergistic/additive increase in cell death or caspase-3 activity caused by α-santalol. The study reveals that survivin downregulation by α-santalol in breast cancer cells is not mediated through the PI3K-Akt pathway. Citation Format: AJAY BOMMAREDDY, KARRYN CRISAMORE, SARAH FILLMAN, SARAH BROZENA, JAMES STEIGERWALT, TERRA LANDIS, ADAM L. VANWERT, CHANDRADHAR DWIVEDI. Survivin downregulation by α-santalol is not mediated through PI3K-Akt pathway in human breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4608.

Pederin, Psymberin and the Structurally Related Mycalamides: Synthetic Aspects and Biological Activities

Pederin, psymberin, and mycalamides are related members of a relatively new family of potent natural antiviral and antitumor compounds originally isolated from marine sponges in 1988. This natural family of chemicals is of great interest to medicinal chemists and biologists, stemming from its extremely low abundance in source organisms and strikingly potent biological activity. They have clearly emerged as promising new synthetic targets, and are the focus of quite an interdisciplinary approach to molecular characterization. In this chapter we review diverse synthetic approaches to this family of natural products that has been demonstrating remarkable biological activity. We discuss relevant history, biological origins with the latest information on source organisms and their hosts, in-depth synthetic approaches, and biological data supporting their potential as therapeutic compounds.

Sodium Oxybate for Narcolepsy Explaining Untoward Effects and Recommending New Approaches in Light of Prevailing Receptor Pharmacology

Objective: Gamma-hydroxybutyrate (GHB) has been an abused and illicit substance for decades, but the antinarcoleptic medication Xyrem (sodium oxybate), the sodium salt of GHB, was approved just in 2002 for increasing wakefulness. We present a case of coma induced by co-ingestion of prescription GHB and ethanol and describe the response to naloxone treatment, by first responders, without evidence of opiate exposure. The purpose of this report is to bridge updated knowledge on GHB and ethanol pharmacology with the clinical sequence of events in a patient co-ingesting these compounds and to theorize on a potentially better pharmacological approach to narcolepsy. Case Summary: The patient was a 25-year-old woman with a history of narcolepsy. She suddenly collapsed at home but became transiently responsive after being administered naloxone in the ambulance. She presented to the emergency department with apnea, poor responsiveness with a Glasgow Coma Score of 7, and urinary incontinence. While undergoing intubation, the patient spontaneously and abruptly awoke. Labs were unremarkable except a blood alcohol concentration of 0.123%. The dosage of, and adherence to, GHB was unknown in this case. Discussion: The case is described in light of the most recent pharmacological advancements on these co-ingestants. A conceptual dose–response curve is shown to facilitate understanding of the complex pharmacology of GHB. Conclusions: Approved and potential alternatives to GHB, for achieving wakefulness, are discussed. Potential new strategies should bear low to no risk of coma with accidental overdose or co-ingestion of ethanol. In addition, promising antidotes for future consideration are discussed.