Synthesis, biological evaluation and molecular modeling studies of N6-benzyladenosine analogues as potential anti-toxoplasma agents

Toxoplasma gondii is an opportunistic pathogen responsible for toxoplasmosis. T. gondii is a purine auxotroph incapable of de novo purine biosynthesis and depends on salvage pathways for its purine requirements. Adenosine kinase (EC.2.7.1.20) is the major enzyme in the salvage of purines in these parasites. 6-Benzylthioinosine and analogues were established as "subversive substrates" for the T. gondii, but not for the human adenosine kinase. Therefore, these compounds act as selective anti-toxoplasma agents. In the present study, a series of N(6)-benzyladenosine analogues were synthesized from 6-chloropurine riboside with substituted benzylamines via solution phase parallel synthesis. These N(6)-benzyladenosine analogues were evaluated for their binding affinity to purified T. gondii adenosine kinase. Furthermore, the anti-toxoplasma efficacy and host toxicity of these compounds were tested in cell culture. Certain substituents on the aromatic ring improved binding affinity to T. gondii adenosine kinase when compared to the unsubstituted N(6)-benzyladenosine. Similarly, varying the type and position of the substituents on the aromatic ring led to different degrees of potency and selectivity as anti-toxoplasma agents. Among the synthesized analogues, N(6)-(2,4-dimethoxybenzyl)adenosine exhibited the most favorable anti-toxoplasma activity without host toxicity. The binding mode of the synthesized N(6)-benzyladenosine analogues were characterized to illustrate the role of additional hydrophobic effect and van der Waals interaction within an active site of T. gondii adenosine kinase by induced fit molecular modeling.     

HIV/AIDS and intimate partner violence: intersecting women's health issues in the United States

This article reviews 35 U.S. studies on the intersection of HIV and adult intimate partner violence (IPV). Most studies describe rates of IPV among women at risk or living with HIV/AIDS and identify correlates, using multiple types of convenience samples (e.g., women in methadone treatment, women in shelters or clinics), cross-sectional designs, and self-reported risk behaviors. HIV-positive women appear to experience any IPV at rates comparable to HIV-negative women from the same underlying populations; however, their abuse seems to be more frequent and more severe. The authors found only four relevant interventions and none addressed sexually transmitted HIV and partner violence risk reduction simultaneously. There is a critical need for research on (a) causal pathways and cumulative effects of the syndemic issues of violence, HIV, and substance abuse and (b) interventions that target IPV victims at risk for HIV, as well as HIV-positive women who may be experiencing IPV.     

National standard for health assessment of rail safety workers: the first year

OBJECTIVE: To determine the prevalence of health problems in New South Wales train drivers and the impact of the new national health-assessment standard on train drivers' fitness for work. DESIGN, SETTING AND PARTICIPANTS: Retrospective audit of files of all RailCorp train drivers (743) and train driver recruits (283) who were assessed under the new national standard for health assessment of rail safety workers between February 2004 and February 2005. MAIN OUTCOME MEASURES: Smoking status; prevalence of hypertension, heart disease, diabetes and obstructive sleep apnoea; alcohol use disorders; body mass index (BMI); total cholesterol level; fasting blood glucose level; cardiac risk score; fitness status. RESULTS: 25.2% of drivers and 27.9% of recruits were smokers; 43.8% of drivers and 21.9% of recruits were hypertensive; 34.6% of drivers and 31.4% of recruits had high total cholesterol levels (> 5.5 mmol/L). Median BMI values were 29 kg/m(2) (range, 18-59 kg/m(2)) for drivers and 28 kg/m(2) (range, 19-55 kg/m(2)) for recruits. The prevalence of obesity (BMI > or =30.0 kg/m(2)) was higher in both male drivers and recruits compared with the general male population. At initial assessment, 65.1% of drivers and 88.0% of recruits were certified as unconditionally fit for work; 12.4% of drivers and 7.1% of recruits were assessed as temporarily unfit; and 22.5% of drivers and 4.6% of recruits were considered fit subject to review (after periods ranging from 3 to 12 months). Two per cent of drivers and 2.5% of recruits were subsequently deemed to be permanently unfit, the most common reasons being heart conditions, psychiatric disorders, orthopaedic problems, colour vision impairment and sleep apnoea. CONCLUSIONS: Cardiovascular risk factors and cardiovascular disease are the most significant health issues affecting train drivers' fitness for work. With the more stringent health assessment and regular review required by the new standard, most drivers can continue with their duties, with the added benefits of improved personal health and greater safety to the rail network and the public.     

Weight management practices and their relationship to knowledge, perception and health status of Saudi females attending diet clinics in Riyadh city

The objective of the study was to identify weight management (WM) practices among women attending diet clinics in Riyadh city, assess their impact on knowledge, perceptions, nutritional and health status and define some predictors for weight reduction among these women. The pretest-posttest research design was used. All female clients attending 8 diet clinics for the first visit within 8 months period and fulfilling the study inclusion criteria (212 out of 263) were included. The results show that out of 170 females who had previously tried to lose weight, only 32.4% reported success in reducing weight, meanwhile 61.7% reported weight regain. The mean total score of dietary practices, physical activity score, self efficacy and satisfaction of self-body image were improved significantly at posttest. Analysis of 24 h. dietary recall revealed that total energy and nutrients intake were significantly reduced at posttest. Dieting related problems increased significantly at posttest. Nutritional knowledge was at moderately fair level at both pretest and posttest; however it showed a significant improvement in the posttest. Perceived severity, perceived barriers and negative modeling effect were significantly decreased at the posttest. Over expectation for weight reduction was clearly evident as posttest body mass index (BMI) revealed a wide discrepancy between the expected and final weights. However, as compared to initial and final BMI, there was an increase in women who attained normal weight and a decrease in the percentage of obese and morbid obese women. All anthropometric indices, blood pressure, biochemical investigation showed significant improvement at posttest. Among the five WM modalities studied, moderate hypo-calorie plan diet modality was the longest (chi = 5.6 month) with the least weight loss (7.8%) and the minimum side effects. Both groups under very low calorie diet and protein diet had the highest weight reduction (13.2% &12.3%), at the same time both diets exhibited the highest number of side effects. The study recommends use of the primary approach for achieving weight loss through therapeutic life style change with banning those modalities accompanied with serious health complications.     

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii Isolates in the Gulf Cooperation Council States: Dominance of OXA-23-Type Producers

The molecular epidemiology and mechanisms of resistance of carbapenem-resistant Acinetobacter baumannii (CRAB) were determined in hospitals in the states of the Cooperation Council for the Arab States of the Gulf (Gulf Cooperation Council [GCC]), namely, Saudi Arabia, United Arab Emirates, Oman, Qatar, Bahrain, and Kuwait. Isolates were subjected to PCR-based detection of antibiotic resistance genes and repetitive sequence-based PCR (rep-PCR) assessments of clonality. Selected isolates were subjected to multilocus sequence typing (MLST). We investigated 117 isolates resistant to carbapenem antibiotics (either imipenem or meropenem). All isolates were positive for OXA-51. The most common carbapenemases were the OXA-23-type, found in 107 isolates, followed by OXA-40-type (OXA-24-type), found in 5 isolates; 3 isolates carried the ISAba1 element upstream of bla_OXA-51-type. No OXA-58-type, NDM-type, VIM-type, or IMP-type producers were detected. Multiple clones were detected with 16 clusters of clonally related CRAB. Some clusters involved hospitals in different states. MLST analysis of 15 representative isolates from different clusters identified seven different sequence types (ST195, ST208, ST229, ST436, ST450, ST452, and ST499), as well as three novel STs. The vast majority (84%) of the isolates in this study were associated with health care exposure. Awareness of multidrug-resistant organisms in GCC states has important implications for optimizing infection control practices; establishing antimicrobial stewardship programs within hospital, community, and agricultural settings; and emphasizing the need for establishing regional active surveillance systems. This will help to control the spread of CRAB in the Middle East and in hospitals accommodating transferred patients from this region.     

Factor H dysfunction in patients with atypical hemolytic uremic syndrome contributes to complement deposition on platelets and their activation

Atypical hemolytic uremic syndrome (aHUS) may be associated with mutations in the C-terminal of factor H (FH). FH binds to platelets via the C-terminal as previously shown using a construct consisting of short consensus repeats (SCRs) 15 to 20. A total of 4 FH mutations, in SCR15 (C870R) and SCR20 (V1168E, E1198K, and E1198Stop) in patients with aHUS, were studied regarding their ability to allow complement activation on platelet surfaces. Purified FH-E1198Stop mutant exhibited reduced binding to normal washed platelets compared with normal FH, detected by flow cytometry. Washed platelets taken from the 4 patients with aHUS during remission exhibited C3 and C9 deposition, as well as CD40-ligand (CD40L) expression indicating platelet activation. Combining patient serum/plasma with normal washed platelets led to C3 and C9 deposition, CD40L and CD62P expression, aggregate formation, and generation of tissue factor-expressing microparticles. Complement deposition and platelet activation were reduced when normal FH was preincubated with platelets and were minimal when using normal serum. The purified FH-E1198Stop mutant added to FH-deficient plasma (complemented with C3) allowed considerable C3 deposition on washed platelets, in comparison to normal FH. In summary, mutated FH enables complement activation on the surface of platelets and their activation, which may contribute to the development of thrombocytopenia in aHUS.      

CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308: An inverse relationship between binding affinity and biological potency

Activation of the CB2 receptor is apparently an endogenous protective mechanism. Thus, it restrains inflammation and protects the skeleton against age-related bone loss. However, the endogenous cannabinoids, as well as Δ⁹-tetrahydrocannabinol, the main plant psychoactive constituent, activate both cannabinoid receptors, CB1 and CB2. HU-308 was among the first synthetic, selective CB2 agonists. HU-308 is antiosteoporotic and antiinflammatory. Here we show that the HU-308 enantiomer, designated HU-433, is 3–4 orders of magnitude more potent in osteoblast proliferation and osteoclast differentiation culture systems, as well as in mouse models, for the rescue of ovariectomy-induced bone loss and ear inflammation. HU-433 retains the HU-308 specificity for CB2, as shown by its failure to bind to the CB1 cannabinoid receptor, and has no activity in CB2-deficient cells and animals. Surprisingly, the CB2 binding affinity of HU-433 in terms of [³H]CP55,940 displacement and its effect on [³⁵S]GTPγS accumulation is substantially lower compared with HU-308. A molecular-modeling analysis suggests that HU-433 and -308 have two different binding conformations within CB2, with one of them possibly responsible for the affinity difference, involving [³⁵S]GTPγS and cAMP synthesis. Hence, different ligands may have different orientations relative to the same binding site. This situation questions the usefulness of universal radioligands for comparative binding studies. Moreover, orientation-targeted ligands have promising potential for the pharmacological activation of distinct processes.The CB2 cannabinoid receptor functions as an endogenous protective entity (1). Thus, it is an important regulator of bone mass and inflammation. It represents a therapeutic target that avoids the undesired psychotropic effects caused by CB1 receptor activation. CB2 is expressed in osteoblasts, the bone-forming cells, and in osteoclasts, the bone-resorbing cells (2). Monocytes/macrophages, B cells, certain T-cell subtypes, and mast cells also express CB2 (3–7). In the skeleton, activation of CB2 favors bone formation over resorption, thus protecting the skeleton against age-related bone loss. Inflammatory responses are restrained by CB2 agonists in several instances such as hepatic ischemia-reperfusion injury (8), uveitis (9), and contact dermatitis (10). With their terpene and resorcinol-derived moieties, some synthetic CB2 agonists, such as HU-308 (10), JWH-133 (11), and HU-910 (12), structurally resemble the phytocannabinoids Δ⁹-tetrahydrocannabinol and cannabidiol. Other, non-phytocannabinoid-type agonists have been also reported (13). HU-308 was one of the first fully characterized, highly selective, and highly efficacious cannabinoid type-2 agonist (10). It has three chiral centers, namely, at carbon atoms in positions 3, 4, and 6 (Scheme 1). HU-308 has a 3R, 4S, 6S configuration; that of its enantiomer (HU-433) is 3S, 4R, 6R.Open in a separate windowScheme 1.Structures of HU-433 and -308.In most experiments, the optimal HU-308 mitogenic activity in osteoblasts, as well as its antiosteoclastogenic effect, was obtained by using concentrations in the nanomolar range (2, 14). Surprisingly, testing a new HU-308 batch, we noticed a 3- to 4-magnitude decrease in the dose that triggers optimal proliferative response in osteoblasts, reasoning that this preparation contained a significant amount of the HU-308 enantiomer, presumably responsible for the enhanced activity. We report here that this enantiomer, designated HU-433, was synthesized and compared with HU-308, and indeed showed markedly enhanced bone-anabolic and antiinflammatory activities, but inferior CB2 receptor binding affinity. Although both enantiomers seem to target the same binding pocket, two different orientations relative to the binding site are possible, leading to different behavior of the two enantiomers due to their different occupancy of these orientations. This observation appears to reflect a situation in which relatively small differences in possible binding conformations of the ligands within the receptor—referred to as poses—lead to significant diminution of receptor-binding properties and a marked increase in biological activity.