A mammalian embryo can successfully implant in the uterus only after it has become a blastocyst. This consists of a small cluster of cells called the inner cell mass, which eventually develops into the fetus, and a thin layer of outer cells called trophectoderm, which gives rise to the placenta . When cells in the trophectoderm become ready to implant, their metabolic rate increases and they develop a repertoire of surface molecules that allows them to adhere to the uterine epithelium. But for this interaction to occur, the uterus must first mature to a receptive state. The process of synchronization between blastocyst and uterus involves a complex network of membrane-associated molecules and soluble signals, including steroid hormones, growth factors and lipid media tors. In a series of landmark studies, Dey and colleagues have established that cannabinoid receptors and their endoge nous activator, anandamide, are integral components of this network. Before it becomes receptive, the uterus contains exceedingly high levels of anandamide—higher, in fact, than anywhere else in the body. As the tissue progresses into receptivity, anandamide concentra tions drop, suggesting that a lower cannabinoid tone creates a friendlier environment for implantation. In keeping with this idea, activation of cannabinoid recep tors on the trophectoderm inhibits blasto cyst development and implantation. This simple scenario does not explain all the available data, however. If the only role of the endogenous cannabinoid system were to prevent implantation, mutant mice that do not express cannabinoid receptors should be more fertile than wild-type animals. Yet the opposite is true: mutant ani mals actually have 40% fewer pregnancies than do wild-type ones. Another inconsistency is that anandamide improves implan tation when administered at very low doses,vertical farming system lower than those needed to impair it. How can these seemingly opposite effects be explained?
Dey and coworkers addressed this question using either freshly isolated mouse blastocysts or, when they needed larger quantities of tissue, trophectoderm cells in culture. The researchers found that anandamide activates cannabinoid receptors in the trophectoderm to initiate two distinct signaling cascades in a dose-dependent manner. At a low concentration , anandamide stimulated the extracellular signal–regulated protein kinase ; at a higher concentration , anan damide reduced calcium entry by closing voltage-operated N-type calcium channels. These events had opposite functional con sequences, such that blastocysts treated with 7 nM anandamide became competent for implantation, whereas those treated with 28 nM anandamide did not. Thus, the uterus may be able to titrate its anandamide production to either promote or arrest embryo implantation . These results confirm and extend the regulatory function of the endogenous cannabinoid system in female fertility. At the same time, they raise two potentially serious public health issues. The first derives from clinical reports that link defects in anandamide breakdown to increased risk of spontaneous abortion. These studies found that expression of fatty acid amide hydrolase, the enzyme that catalyzes the intracellular degradation of anandamide, was reduced in lymphocytes obtained from women who had had mis carriages, compared with those who had not. It is unclear, however, whether the mechanism underlying these miscarriages is related to the ability of anandamide to stop implantation . The second issue stems from the fact that a large number of women of childbearing age—4.9%, according to a recent survey10—regularly smoke marijuana. How might this drug affect their fertility? If the same signaling system described in mice were present in humans, one might expect fertility problems among heavy marijuana users. Although there is no clear indication at present that marijuana impairs fertility, this possibility should certainly be revisited in the light of the current animal data.The first infectious human retrovirus to be identified, before we even imagined the devastation of HIV, was human T-lymphotropic virus type 1 1. HTLV-1 causes disease—mainly adult T-cell lymphoma or leukemia or HTLV-1-associated myelopa thy—in only small fraction of infected individuals.
The virus, however, cuts a wide swath, infecting about 10–20 million people worldwide by spreading from person to per son through infected cells in semen, blood and breast milk. Despite years of effort, the identity of the receptor that facilitates the spread of HTLV-1 has remained elusive. In a recent issue of Cell, Manel et al. provide evidence that GLUT-1, a ubiquitous glucose transport protein, is a receptor for HTLV-1 . Most retroviral receptors have been cloned by transferring a library of sequences from a cell line that is permissive for entry, and therefore expresses the receptor, into one that is nonpermissive. A marked version of the virus can then be used to specifically select cells with the receptor gene from cells that acquired irrelevant cellular sequences. HTLV-1 infects most cell lines but is found primarily in lymphocytes, including lymphoma cells, in infected patients. The paucity of nonpermissive cell lines, as well as difficulties in making high titers of marked virus, has foiled attempts at conventional receptor cloning strategies. For these reasons, Manel et al. used a clever deductive approach that relied on several clues to identify a receptor candidate. The first clue was that cells expressing the HTLV-1 envelope protein, which binds the receptor and initiates entry, showed perturbations in lactate and glucose metabolism— namely, delayed acidification of the cell culture medium. This observation implicated a receptor involved in lactate or glucose transport. Because many known retroviral receptor proteins are transporters, a trans port protein has always been a strong con tender for the HTLV-1 receptor. Another crucial clue came from HTLV-1 envelope binding studies, which suggested that the receptor was expressed very early after lymphocyte activation, and that its temporal pattern of expression was distinct from that of many other activation markers. Together, these clues led the authors to GLUT-1, a member of a family of glucose transport proteins. The tactic of finding a receptor to meet the authors’ criteria, rather than letting the virus select the receptor in a functional screen, carries with it a considerable burden of proof. The authors used several lines of evidence to support their case. Binding studies demonstrated a direct interaction between the HTLV-1 envelope and GLUT-1, but not other related transport proteins. Down modulating GLUT-1 led to reduced HTLV-1 binding and infection, whereas increasing GLUT-1 expression restored these outcomes.
Finally, the authors provided data that GLUT-1 is a receptor for a related, relatively avirulent retrovirus, HTLV-2, fulfilling predictions from previous studies. Collectively, the results pro vide a compelling case for GLUT-1 as an HTLV-1 receptor .Cambodia has the highest HIV prevalence of any Asian country, and over the last decade has experienced the most serious HIV/AIDS epidemic in Southeast Asia. Heterosexual contact is the major route of HIV trans mission, and female sex workers remain the group at highest risk. Although crucial progress has been made in reducing risky sexual behavior, including widespread condom use and promotion of reduced number of sexual partners, HIV prevalence among FSW remains high, ranging from 11% to 26%. Poverty, low literacy, a high prevalence of sexually transmitted infections,cannabis vertical farming and a highly mobile work force are contributing factors to the epidemic. Recent research has also identified drug use and, in particular, amphetamine-type stimulant use as a serious emerging problem associated with HIV risk among FSW, which threatens to reverse downward trends in HIV infection rates in the region. Amphetamine-type stimulants include a range of syn the ticpsycho stimulants, including methamphetamine, amphetamine, and ecstasy, which can be injected, smoked, or taken orally. Effects of these drugs include euphoria, alertness, arousal, increased libido, increased sympathetic nervous responses,and perceived increases in confidence, energy and physical strength. In Cambodia, a pill form of methamphetamine known as “yama” is widely produced, trafficked, and used. The tablets generally contain about 25% methamphetamine. “Crystal” is generally about 85% metham phetamine and more addictive. Although yama pills are swallowed, both forms are usually melted and the vapors inhaled, resulting in rapid neurologic effects. Use of ATS has been associated with elevated HIV risk behavior in many countries and in several population sub groups. The United Nations Office on Drugs and Crime reports that use of these drugs is widespread in Asia and increasing rapidly in Cambodia. In Cambodia, ATS are highly available both in pill and crystalline form and are generally ingested or smoked; injection use is uncommon. The Cambodia National Authority for Combating Drug Abuse estimated that 70% of all drug users in Cambodia use ATS. The drug accounts for the majority of all drug seizures by authorities, and, in pill form, has been ranked as the leading drug of abuse for the past nine years with consistent increases since 2006, at which time it was estimated that 30,000 tablets of yama were consumed orally or smoked there daily. Use is particularly high among vulnerable populations, including FSW, men who have sex with men , and street children.Self-reported measures of drug use have the advantage of being noninvasive and permit evaluation over longer time periods compared with bio chemical assessments. However, study participants may misrepresent drug use due to social desirability bias, stigma, poor recall, poorly worded questions, or poorly worded response categories in surveys and interviews, all of which could result in mis-classification of measured exposures. Although studies have shown that the use of Audio Computer-Assisted Self Interview increases reporting of sensitive and stigmatized behaviors, research suggests that the validity of self-reported drug use varies by population, race/ ethnicity, mental health, and drug treatment status, although not by gender.
Accuracy has varied in studies of arrestee populations but have been reported as higher in groups sampled in emergency department and STI clinics. Those that report more frequent drug use, compared to infrequent use, are more likely to self-report recent drug use. Urine toxicology assessments provide sensitive and valid measures of many drug types; but some, like ATS, are restricted to a short time frame due to rapid metabolization. The detection window may also depend on the physical condition of the individual , route of drug ingestion , frequency of use, and drug-related factors such as purity. To explore the validity of self-reported ATS use among young FSW in Phnom Penh, Cambodia, we com pared self-reported ATS use with results from concurrently collected urine toxicology tests. We also examine whether sociodemographic, sex-work venue, and HIV status were associated with validity of self-reported ATS use.The Young Women’s Health Study was a prospective study of HIV and ATS use among 15–29 year-old women engaged in sex work in a diversity of settings in Phnom Penh, Cambodia. Data for this cross-sectional validity assessment was collected at the second quarterly study visit women attended. Both self-reported measures and urine toxicology testing for ATS were assessed. The YWHS-2 was led by HIV-research and HIV-prevention specialists from the Cambodian National Center for HIV, AIDS, Dermatology, and STDs , the Cambodian Women’s Development Association , the University of California San Francisco in the United States, and the Kirby Center at the University of New South Wales in Australia.Young women at high risk of HIV infection were the target study population. Inclusion criteria were age 15–29 years, understanding of spoken Khmer, Cambodian ethnicity, reporting of at least two different sexual partners in the last month or engaging in transactional sex within the last three months, plans to stay in the Phnom Penh area for 12 months, being biologically female, and being able to provide voluntary informed consent. Study methods have been described previously. In brief, trained field assistants from the CWDA recruited women from community locations, provided study information, and obtained group informed consent. Women who consented were then seen by appointment at the YWHS-2 clinic site; free transportation was provided. Participants received US $5 and condoms at each study visit. Contact information was collected to facilitate participant tracking and maximize follow-up. Women were asked to enroll for a one-year study with quarterly study visits. Data collection for this validity assessment occurred in November 2009 at the second study visit . All study visits included administration of a structured questionnaire in Khmer by trained inter viewers who queried participants about sociodemo graphic characteristics, health care, occupational and sexual risk exposures, alcohol and self-reported ATS use as well as testing for HIV and ATS using blood and urine samples, respectively. The second visit was used for this cross-sectional analysis because questions about past 48-hour drug use were added to the questionnaire starting with that visit; thus, it was the first available time point for comparison and validation of self-reported use and urine testing.