Influences of maternal exposure on the tolerance and physiological performance of Daphnia magna under mercury stress

We examined the tolerance development to mercury (Hg) by a population of freshwater zooplankton (Daphnia magna) with different pre-exposure histories to Hg. The growth and reproductive performance of the F1 offspring as affected by the maternal (F0) and offspring (F1) exposures was quantified. The F0 daphnids exposed to 2.5 and 25 nM of Hg for 4 d and followed by 4 d of depuration had elevated levels of Hg and metallothionein-like proteins (MTLPs), as well as higher tolerance to Hg toxicity than the control daphnids. The higher Hg tolerance may be attributed to the higher proportion of Hg partitioned to the MTLPs. Moreover, significant enhancement of Hg tolerance also was found in the F1 offspring originating from the F0 mothers exposed to 25 nM of Hg, but there was no significant induction of MTLPs in these F1 offspring when compared to the offspring from the control mothers. The Hg tissue concentrations in the F1 neonates were approximately 25% of those in the F0 adults. However, there was similar Hg tolerance in the F2 offspring originating from both the control and Hg-exposed F0 mothers, indicating that the Hg tolerance in the daphnids disappeared two generations after Hg contamination. Further exposure of the F1 offspring to different Hg concentrations (1.5 and 15 nM for 28 d) indicated that maternal exposure history did not affect their growth and reproductive performance, which solely were influenced by the offspring exposure. Unexpectedly, the F1 offspring exposed to Hg had significantly higher final wet weights and reproductive rates than the control groups, suggesting the possibility of Hg hormesis. Furthermore, the maternal exposure had no effect on the Hg accumulation and the MTLP concentrations in the F1 offspring. Therefore, we concluded that the Hg tolerance might disappear quickly once the Hg contamination was removed and the maternal exposure history was not important in determining the physiological performance and Hg accumulation of the subsequent generations.     

Modulation by simvastatin of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine coronary artery smooth muscle cells

BACKGROUND AND PURPOSE: Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG CoA) reductase inhibitors) have been demonstrated to reduce cardiovascular mortality. It is unclear how the expression level of HMG CoA reductase in cardiovascular tissues compares with that in cells derived from the liver. We hypothesized that this enzyme exists in different cardiovascular tissues, and simvastatin modulates the vascular iberiotoxin-sensitive Ca2+-activated K(+) (BK(Ca)) channels. EXPERIMENTAL APPROACHES: Expression of HMG CoA reductase in different cardiovascular preparations was measured. Effects of simvastatin on BK(Ca) channel gatings of porcine coronary artery smooth muscle cells were evaluated. KEY RESULTS: Western immunoblots revealed the biochemical existence of HMG CoA reductase in human cardiovascular tissues and porcine coronary artery. In porcine coronary artery smooth muscle cells, extracellular simvastatin (1, 3 and 10 microM) (hydrophobic), but not simvastatin Na+ (hydrophilic), inhibited the BK(Ca) channels with a minimal recovery upon washout. Isopimaric acid (10 microM)-mediated enhancement of the BK(Ca) amplitude was reversed by external simvastatin. Simvastatin Na+ (10 microM, applied internally), markedly attenuated isopimaric acid (10 microM)-induced enhancement of the BK(Ca) amplitude. Reduced glutathione (5 mM; in the pipette solution) abolished simvastatin -elicited inhibition. Mevalonolactone (500 microM) and geranylgeranyl pyrophosphate (20 microM) only prevented simvastatin (1 and 3 microM)-induced responses. simvastatin (10 microM ) caused a rottlerin (1 microM)-sensitive (cycloheximide (10 microM)-insensitive) increase of PKC-delta protein expression. CONCLUSIONS AND IMPLICATIONS: Our results demonstrated the biochemical presence of HMG CoA reductase in different cardiovascular tissues, and that simvastatin inhibited the BK(Ca) channels of the arterial smooth muscle cells through multiple intracellular pathways.     

Integrating multiple programme and policy approaches to hepatitis C prevention and care for injection drug users: a comprehensive approach

BackgroundNew York State is home to an estimated 230,000 individuals chronically infected with hepatitis C virus (HCV) and roughly 171,500 active injection drug users (IDUs). HCV/HIV co-infection is common and models of service delivery that effectively meet IDUs’ needs are required. A HCV strategic plan has stressed integration.MethodsHCV prevention and care are integrated within health and human service settings, including HIV/AIDS organisations and drug treatment programmes. Other measures that support comprehensive HCV services for IDUs include reimbursement, clinical guidelines, training and HCV prevention education. Community and provider collaborations inform programme and policy development.ResultsIDUs access 5 million syringes annually through harm reduction/syringe exchange programmes (SEPs) and a statewide syringe access programme. Declines in HCV prevalence amongst IDUs in New York City coincided with improved syringe availability. New models of care successfully link IDUs at SEPs and in drug treatment to health care. Over 7000 Medicaid recipients with HCV/HIV co-infection had health care encounters related to their HCV in a 12-month period and 10,547 claims for HCV-related medications were paid. The success rate of transitional case management referrals to drug treatment is over 90%. Training and clinical guidelines promote provider knowledge about HCV and contribute to quality HCV care for IDUs. Chart reviews of 2570 patients with HIV in 2004 documented HCV status 97.4% of the time, overall, in various settings. New HCV surveillance systems are operational. Despite this progress, significant challenges remain.DiscussionA comprehensive, public health approach, using multiple strategies across systems and mobilizing multiple sectors, can enhance IDUs access to HCV prevention and care. A holisitic approach with integrated services, including for HCV–HIV co-infected IDUs is needed. Leadership, collaboration and resources are essential.     

Non-prostanoid prostacyclin mimetics as neuronal stimulants in the rat: comparison of vagus nerve and NANC innervation of the colon

The spontaneous activity of the rat isolated colon is suppressed by prostacyclin analogues such as cicaprost (IC(50)=4.0 nM). Activation of prostanoid IP(1)-receptors located on NANC inhibitory neurones is involved. However, several non-prostanoids, which show medium to high IP(1) agonist potency on platelet and vascular preparations, exhibit very weak inhibitory activity on the colon. The aim of the study was to investigate this discrepancy. Firstly, we have demonstrated the very high depolarizing potency of cicaprost on the rat isolated vagus nerve (EC(50)=0.23 nM). Iloprost, taprostene and carbacyclin were 7.9, 66, and 81 fold less potent than cicaprost, indicating the presence of IP(1) as opposed to IP(2)-receptors. Three non-prostanoid prostacyclin mimetics, BMY 45778, BMY 42393 and ONO-1301, although much less potent than cicaprost (195, 990 and 1660 fold respectively), behaved as full agonists on the vagus nerve. On re-investigating the rat colon, we found that BMY 45778 (0.1 - 3 microM), BMY 42393 (3 microM) and ONO-1301 (3 microM) behaved as specific IP(1) partial agonists, but their actions required 30 - 60 min to reach steady-state and only slowly reversed on washing. This profile contrasted sharply with the rapid and readily reversible contractions elicited by a related non-prostanoid ONO-AP-324, which is an EP(3)-receptor agonist. The full versus partial agonism of the non-prostanoid prostacyclin mimetics may be explained by the markedly different IP(1) agonist sensitivities of the two rat neuronal preparations. However, the slow kinetics of the non-prostanoids on the NANC system of the colon remain unexplained, and must be taken into account when characterizing neuronal IP-receptors.     

O6‐methylguanine DNA methyltransferase repairs platinum‐DNA adducts following cisplatin treatment and predicts prognoses of nasopharyngeal carcinoma

Cisplatin (CDDP) is an important anti‐cancer drug commonly used in various human cancers, including nasopharyngeal carcinoma (NPC). How to overcome the drug resistance of CDDP provides opportunities to improve clinical outcomes of NPC. O⁶‐methylguanine–DNA methyltransferase (MGMT) has been well‐characterized to be a therapeutic determinant of O⁶‐alkylguanine alkylating drugs. However, the underlying mechanism and clinical relevance between MGMT and CDDP remain poorly defined in NPC. In this study, we showed that MGMT‐proficient cells were highly resistant to the cytotoxic effects of CDDP as compared to MGMT‐deficient cells. Further studies showed that the platinum level of DNA after CDDP exposure was significantly lower in MGMT‐proficient cells than in MGMT‐deficient cells. Host cell reactivation assay revealed that MGMT protected NPC cells from CDDP‐induced DNA damage by enhancing DNA repair capacity. Importantly, we demonstrated for the first time that MGMT protein directly bound to CDDP‐induced DNA damages. Subsequently, CDDP‐bound MGMT protein became ubiquitinated and was degraded through ubiquitin‐mediated proteasome system. We further analyzed the relationship between MGMT expression and clinical survivals in a cohort of 83 NPC patients. NPC patients who received CDDP‐based concurrent chemoradiotherapy (CCRT), with high MGMT expression level, exhibited shorter progression‐free survival (PFS; p = 0.022) and overall survival (OS; p = 0.015), than patients with low MGMT expression level. Furthermore, high MGMT expression level remained to be an independent prognostic factor for worse PFS (p = 0.01, hazard ratio 2.23) and OS (p = 0.018, hazard ratio 2.14). Our findings suggest that MGMT protein is important to determine the efficacy of CDDP in NPC.     

Multigene targeting of signal transduction pathways for the treatment of breast and prostate tumors

Previous studies have demonstrated that monospecific antisense oligonucleotides (oligos) directed against mRNA encoding proteins associated with tumor growth, death, and survival are efficacious against breast and prostate tumors. Targeted proteins, associated with different signal transduction pathways, have included transforming growth factor-alpha [TGF-α (MR₁)], its binding site the epidermal growth factor receptor [EGFR (MR₂)] sharing sequence homology to the breast cancer prognostic marker Her-2/neu, an apoptosis inhibiting protein [bcl-2 (MR₄)], and the androgen receptor [AR (MR₅)]. In attempts to enhance antisense therapy, recent reports describe how two of the binding sites mentioned above can be sequentially placed within a single complementary (bispecific) strand and administered either in the presence or absence of additional therapeutic agents. When tested against breast and prostate tumor cell lines specific differences were noted: MCF-7 breast cancer cells were more receptive to the inhibitory effects of monospecific oligos, whereas PC-3 and LNCaP prostate cells were particularly responsive to bispecifics. In an effort to identify agents which enhance the activity of oligos and which possess less toxicity than traditionally employed chemotherapeutics, Rapamycin, an immunosuppressive agent known to regulate tumor growth and signal transduction mediated by the mTOR receptor, is compared to paclitaxel in combination therapy employing monospecific or bispecific oligos. Bispecifics were constructed recognizing the binding sites for TGF-α and EGFR mRNA [TGF-α/EGFR (MR₁₂) and EGFR/TGF-α (MR₂₁)]; another pair recognized binding sites for EGFR and bcl-2 [EGFR/bcl-2 (MR₂₄) and bcl-2/EGFR (MR₄₂)]; while a third pair employed only against the LNCaP prostate cell line recognized bcl-2 and the androgen receptor [bcl-2/AR (MR4₄₅) and AR/bcl-2 (MR₅₄)]. Oligo pairs differ in their 5′–3′ linear binding site orientations, and were tested in vitro against MCF-7 breast and PC-3 and LNCaP prostate tumor cell lines. Following cell attachment, incubations were done for 2 days with the agents followed by 2 days in their absence. Five experiments evaluated the effect of monospecific or bispecific antisense oligos in combination with an LD₅₀ dosage of either Rapamycin or paclitaxel and led to the conclusion that although these agents act via different mechanisms, they are comparable in effectiveness.     

Discovery of a potent, selective, and orally available class I phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) kinase inhibitor (GDC-0980) for the treatment of cancer

The discovery of 2 (GDC-0980), a class I PI3K and mTOR kinase inhibitor for oncology indications, is described. mTOR inhibition was added to the class I PI3K inhibitor 1 (GDC-0941) scaffold primarily through the substitution of the indazole in 1 for a 2-aminopyrimidine. This substitution also increased the microsomal stability and the free fraction of compounds as evidenced through a pairwise comparison of molecules that were otherwise identical. Highlighted in detail are analogues of an advanced compound 4 that were designed to improve solubility, resulting in 2. This compound, is potent across PI3K class I isoforms with IC(50)s of 5, 27, 7, and 14 nM for PI3Kα, β, δ, and γ, respectively, inhibits mTOR with a K(i) of 17 nM yet is highly selective versus a large panel of kinases including others in the PIKK family. On the basis of the cell potency, low clearance in mouse, and high free fraction, 2 demonstrated significant efficacy in mouse xenografts when dosed as low as 1 mg/kg orally and is currently in phase I clinical trials for cancer.     

Reduced expression of EphB2 that parallels invasion and metastasis in colorectal tumours

EphB2, a receptor tyrosine kinase regulated by the beta-catenin/Tcf4 complex, is expressed in the proliferative compartment of mouse intestine and regulates bidirectional migration of intestinal precursor cells in the crypt-villus axis through repulsive interaction with Ephrin-B ligands. Recently, it has been shown that reduction of EphB activity accelerates colon tumour progression in the Apc(Min/+) mice. In this study, we examined the expression of EphB2 in normal colon, adenomas, primary colorectal cancers (CRCs), lymph node metastases and liver metastases using immunohistochemistry on tissue microarrays. In addition, EphB2 was overexpressed in SW480 colon cancer cells to study its effect in vitro. We found that EphB2 was expressed in 100% of normal colon crypt base cells, 78% of adenomas, 55.4% of primary CRCs, 37.8% of lymph node metastases and 32.9% of liver metastases (all differences were statistically significant at P < 0.001 compared with primary CRCs). Patients with CRCs that lose EphB2 expression had more advanced tumour stage (P = 0.005), poor differentiation (P < 0.001), poor overall survival (P = 0.005) and disease-free survival (P = 0.001), with the latter being independent of tumour stage. In vitro studies showed that overexpression of EphB2 inhibited colon cancer cell growth in colony formation assay and activation of EphB2 receptor inhibited colon cancer cell adhesion and migration. Our data demonstrated a progressive loss of EphB2 expression in each critical step of colon carcinogenesis, including the onset of invasion, dedifferentiation and metastasis which are paralleled by adverse patient outcome. EphB2 may achieve its tumour suppressor function through regulation of cell survival, adhesion and migration.     

Prevalence and factors related to syringe sharing behaviours among female injecting drug users who are also sex workers in China

Background

Female injecting drug users who are sex workers (IDUFSWs) are at high risk of contracting HIV. They may bridge HIV transmissions from injecting drug users to clients of female sex workers.

Methods

A total of 216 non-institutionalised IDUFSWs were recruited by snowball sampling methods. Anonymous face-to-face interviews were conducted to collect data. Univariate, multivariate and hierarchical logistic regression models were fitted to investigate the associations between background characteristics, cognitive variables, psychological stress and syringe sharing behaviours among IDUFSWs.

Results

Respectively 33.8% and 27.8% of the respondents injected drugs with others’ used syringes and gave used syringes to others for drug injection in the last month. These two syringe sharing behaviours were significantly associated with inconsistent condom use during commercial sex (OR = 5.00 and 1.92, p < 0.05). Over 90% of the respondents reported at least one type(s) of psychological distress included in this study. Adjusting for significant background variables, all variables that are related to the Theory of Planned Behaviour (attitude, norm, perceived control and behavioural intention) and psychological distress (except for depression) were significantly associated with injecting drugs with others’ used syringes (adjusted OR = 2.08-6.25, p < 0.05), whilst variables related to perceived control, behavioural intention and insomnia were significantly associated with providing used syringes to others for injection (adjusted OR = 2.00-3.56, p < 0.05). In two separate summary multivariate models, variables related to the Theory of Planned Behaviours and psychological distress were independently associated with injecting drugs with others’ used syringes (OR = 1.98-4.02, p < 0.05) and giving used syringes to others for injection (OR = 2.06-3.59, p < 0.05).

Conclusions

Syringe sharing behaviours were prevalent among IDUFSWs and were associated with cognitive and psychological factors. Effective integrative intervention programmes targeting IDUFSWs are warranted.