The role of ovarian hormone-derived neurosteroids on the regulation of GABAA receptors in affective disorders

Rationale

Neuroactive derivatives of steroid hormones, neurosteroids, can act on GABA_A receptors (GABA_ARs) to potentiate the effects of GABA on these receptors. Neurosteroids become elevated to physiologically relevant levels under conditions characterized by increased steroid hormones. There is considerable evidence for plasticity of GABA_ARs associated with altered levels of neurosteroids which may counteract the fluctuations in the levels of these allosteric modulators.

Objectives

The objective of this review is to summarize the current literature on GABA_AR plasticity under conditions characterized by alterations in neurosteroid levels, such as over the estrous cycle, during puberty, and throughout pregnancy and the postpartum period.

Results

The expression of specific GABA_AR subunits is altered over the estrous cycle, at puberty, and throughout pregnancy and the postpartum period. Inability to regulate δ subunit-containing GABA_ARs throughout pregnancy and the postpartum period is associated with depression-like behavior restricted to the postpartum period.

Conclusions

GABA_AR plasticity associated with alterations in neurosteroid levels represents a homeostatic compensatory mechanism to maintain an ideal level of inhibition to offset the potentiating effects of neurosteroids on GABAergic inhibition. Failure to properly regulate GABA_ARs under conditions of altered neurosteroid levels may increase vulnerability to mood disorders, such as premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD), and postpartum depression.     

Phosphatidylinositol 4,5-bisphosphate depletion fails to affect neurosteroid modulation of GABAA receptor function

Rationale

Neurosteroids and likely other lipid modulators access transmembrane sites on the GABA_A receptor (GABA_AR) by partitioning into and diffusing through the plasma membrane. Therefore, specific components of the plasma membrane may affect the potency or efficacy of neurosteroid-like modulators. Here, we tested a possible role for phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that governs activity of many channels and transporters, in modulation or function of GABA_ARs.

Objectives

In these studies, we sought to deplete plasma-membrane PIP2 and probe for a change in the strength of potentiation by submaximal concentrations of the neurosteroid allopregnanolone (3α5αP) and other anesthetics, including propofol, pentobarbital, and ethanol. We also tested for a change in the behavior of negative allosteric modulators pregnenolone sulfate and dipicrylamine.

Methods

We used Xenopus oocytes expressing the ascidian voltage-sensitive phosphatase (Ci-VSP) to deplete PIP2. Voltage pulses to positive membrane potentials were used to deplete PIP2 in Ci-VSP-expressing cells. GABA_ARs composed of α1β2γ2L and α4β2δ subunits were challenged with GABA and 3α5αP or other modulators before and after PIP2 depletion. KV7.1 channels and NMDA receptors (NMDARs) were used as positive controls to verify PIP2 depletion.

Results

We found no evidence that PIP2 depletion affected modulation of GABA_ARs by positive or negative allosteric modulators. By contrast, Ci-VSP-induced PIP2 depletion depressed KV7.1 activation and NMDAR activity.

Conclusions

We conclude that despite a role for PIP2 in modulation of a wide variety of ion channels, PIP2 does not affect modulation of GABA_ARs by neurosteroids or related compounds.     

11-trifluoromethyl-phenyldiazirinyl neurosteroid analogues: potent general anesthetics and photolabeling reagents for GABAA receptors

Rationale

While neurosteroids are well-described positive allosteric modulators of gamma-aminobutyric acid type A (GABA_A) receptors, the binding sites that mediate these actions have not been definitively identified.

Objectives

This study was conducted to synthesize neurosteroid analogue photolabeling reagents that closely mimic the biological effects of endogenous neurosteroids and have photochemical properties that will facilitate their use as tools for identifying the binding sites for neurosteroids on GABA_A receptors.

Results

Two neurosteroid analogues containing a trifluromethyl-phenyldiazirine group linked to the steroid C11 position were synthesized. These reagents, CW12 and CW14, are analogues of allopregnanolone (5α-reduced steroid) and pregnanolone (5β-reduced steroid), respectively. Both reagents were shown to have favorable photochemical properties with efficient insertion into the C–H bonds of cyclohexane. They also effectively replicated the actions of allopregnanolone and pregnanolone on GABA_A receptor functions: they potentiated GABA-induced currents in Xenopus laevis oocytes transfected with α₁β₂γ_2L subunits, modulated [³⁵S]t-butylbicyclophosphorothionate binding in rat brain membranes, and were effective anesthetics in Xenopus tadpoles. Studies using [³H]CW12 and [³H]CW14 showed that these reagents covalently label GABA_A receptors in both rat brain membranes and in a transformed human embryonal kidney (TSA) cells expressing either α₁ and β₂ subunits or β₃ subunits of the GABA_A receptor. Photolabeling of rat brain GABA_A receptors was shown to be both concentration-dependent and stereospecific.

Conclusions

CW12 and CW14 have the appropriate photochemical and pharmacological properties for use as photolabeling reagents to identify specific neurosteroid-binding sites on GABA_A receptors.     

Quantification of ten neuroactive steroids in plasma in Withdrawal Seizure-Prone and -Resistant mice during chronic ethanol withdrawal

Rationale

The rapid membrane actions of neuroactive steroids, particularly via an enhancement of γ-aminobutyric acid_A receptors (GABA_ARs), participate in the regulation of central nervous system excitability. Prior evidence suggests an inverse relationship between endogenous GABAergic neuroactive steroid levels and behavioral changes in excitability during ethanol withdrawal.

Objectives

Previously, we found that ethanol withdrawal significantly decreased plasma allopregnanolone (ALLO) levels, a potent GABAergic neuroactive steroid, and decreased GABA_AR sensitivity to ALLO in Withdrawal Seizure-Prone (WSP) but not in Withdrawal Seizure-Resistant (WSR) mice. However, the effect of ethanol withdrawal on levels of other endogenous GABA_AR-active steroids is not known.

Methods

After validation of a gas chromatography-mass spectrometry method for the simultaneous quantification of ten neuroactive steroids, we analyzed plasma from control male WSP-1 and WSR-1 mice and during ethanol withdrawal.

Results

We quantified levels of nine neuroactive steroids in WSP-1 and WSR-1 plasma; levels of pregnanolone were not detectable. Basal levels of five neuroactive steroids were higher in WSR-1 versus WSP-1 mice. Ethanol withdrawal significantly suppressed five neuroactive steroids in WSP-1 and WSR-1 mice, including ALLO.

Conclusions

Due to lower basal levels of some GABA_AR-active steroids in WSP-1 mice, a withdrawal-induced decrease in WSP-1 mice may have a greater physiological consequence than a similar decrease in WSR-1 mice. Because WSP-1 mice also exhibit a reduction in GABA_AR sensitivity to neuroactive steroids during withdrawal, it is possible that the combined decrease in neuroactive steroids and GABA_AR sensitivity during ethanol withdrawal in WSP-1 mice represents a neurochemical substrate for severe ethanol withdrawal.     

Allopregnanolone modulation of HPA axis function in the adult rat

Rationale

GABAergic neuronal circuits regulate neuroendocrine stress response, and the most potent positive endogenous modulator of GABA_A receptor function is allopregnanolone. This neurosteroid acts in a nongenomic manner to selectively increase the inhibitory signal meditated by GABA_A receptors; in addition, it also induces long-lasting changes in the expression of specific GABA_A receptor subunits in various brain regions, with consequent changes in receptor function.

Objective

The objective of this review is to summarize our findings on emotional state and stress responsiveness in three animal models in which basal brain concentrations of allopregnanolone differ. It is postulated that individual differences in allopregnanolone levels can influence general resilience.

Results

The results showed that there is an apparent correlation between endogenous levels of brain allopregnanolone and basal and stress-stimulated HPA axis activity.

Conclusion

The relationship between endogenous brain levels of allopregnanolone and HPA axis activity and function sustains the therapeutic potential of this neurosteroid for the treatment of stress-associated disorders.     

Proof-of-concept randomized controlled trial of pregnenolone in schizophrenia

Rationale

Preclinical and clinical data suggest that pregnenolone may be a promising therapeutic in schizophrenia. Pregnenolone is neuroprotective and enhances learning and memory, myelination, and microtubule polymerization. Treatment with pregnenolone elevates allopregnanolone (a neurosteroid that enhances GABA_A receptor responses) and pregnenolone sulfate (a positive NMDA receptor modulator). Pregnenolone could thus potentially mitigate GABA dysregulation and/or NMDA receptor hypofunction in schizophrenia via metabolism to other neurosteroids.

Objective

The objective of this study is to conduct a randomized controlled trial of adjunctive pregnenolone in schizophrenia.

Methods

Following a placebo lead-in, 120 participants were randomized to pregnenolone or placebo for 8 weeks (Institute for Mental Health, Singapore). Primary endpoints were changes in MATRICS Consensus Cognitive Battery (MCCB) composite scores (cognitive symptoms), UCSD Performance-based Skills Assessment—Brief (UPSA-B) composite scores (functional capacity), and Scale for Assessment of Negative Symptoms (SANS) total scores (negative symptoms). A modified intent-to-treat analysis approach was utilized.

Results

No significant changes compared to placebo were demonstrated in composite MCCB scores. In contrast, participants randomized to pregnenolone (n?=?56) demonstrated greater improvements in functional capacity (UPSA-B composite changes) compared to placebo (n?=?55), p?=?0.03. Pregnenolone was also superior to placebo in the communication subscale of the UPSA-B (p?r _s?=?0.497, p?n?=?17) but not in males. Mean total SANS scores were very low at baseline and did not improve further post-treatment. Pregnenolone was well-tolerated.

Conclusions

Pregnenolone improved functional capacity in participants with schizophrenia, but did not improve cognitive symptoms over an 8-week treatment period. Neurosteroid changes correlated with functional improvements in female participants. Neurosteroid interventions may exhibit promise as new therapeutic leads for schizophrenia.     

Pharmacological profile of a 17β-heteroaryl-substituted neuroactive steroid

Rationale

In order to improve upon the pharmacological properties of the neuroactive steroid ganaxolone, it was used as the starting point in the design of novel neurosteroids that replace the 17β-acetyl side chain with an isoxazole bioisostere.

Objectives

UCI-50027 (3-[3α-hydroxy-3β-methyl-5α-androstan-17β-yl]-5-(hydroxymethyl)isoxazole) was designed as an orally active neuroactive steroid specifically targeted at the gamma-aminobutyric acid(A) receptor (GABA_AR).

Methods

UCI-50027 was tested in vitro in Xenopus oocytes expressing human GABA_ARs and in vivo as an anticonvulsant, for ataxic effects and for anxiolytic activity.

Results

In vitro, UCI-50027 dose-dependently enhanced the activity of GABA at human α₁β₂γ_2L, α₂β₁γ_2L, and α₄β₃δ GABA_ARs. Consistent with its action as a positive allosteric modulator (PAM), it had no direct activity in the absence of GABA. UCI-50027 protected against acute pentylenetetrazol (PTZ)-induced convulsions with an ED₅₀ of 6 mg/kg p.o. In the rotarod (RR) paradigm in mice, the AD₅₀ (the ataxic dose where half of the animals fail the RR test) was found to be 38 mg/kg p.o., giving a therapeutic index (TI = RR AD₅₀/PTZ ED₅₀)～6 versus 2.8 for ganaxolone. In the mouse-elevated plus maze (EPM) model for anxiety, UCI-50027 showed a minimum effective dose (MED) ≤0.3 mg/kg p.o. Thus, the TI (TI = RR AD₅₀/EPM MED) for the compound as an anxiolytic is ≥127 versus 3.3 for ganaxolone.

Conclusions

UCI-50027 is an orally active neuroactive steroid with pharmacological activity consistent with a GABA_AR PAM that has an improved separation between anticonvulsant/anxiolytic and rotarod effects, potent activity as an anticonvulsant and anxiolytic when compared to ganaxolone.     

Characterization of neurosteroid effects on hyperpolarizing current at α4β2δ GABAA receptors

Rationale

The neurosteroid 3α,5β-THP (3α-OH-5β-pregnan-20-one, pregnanolone) is a modulator of the GABA_A receptor (GABAR), with α4β2δ GABARs the most sensitive. However, the effects of 3α,5β-THP at α4β2δ are polarity-dependent: 3α,5β-THP potentiates depolarizing current, as has been widely reported, but decreases hyperpolarizing current by accelerating desensitization.

Objectives

The present study further characterized 3α,5β-THP inhibition of hyperpolarizing current at this receptor and compared effects of other related steroids at α4β2δ GABARs.

Methods

α4β2δ GABARs were expressed in HEK-293 cells, and agonist-gated current recorded with whole cell voltage-clamp techniques using a theta tube to rapidly apply agonist before and after application of neurosteroids.

Results

The GABA-modulatory steroids (30 nM) 3α,5α-THP (3α-OH-5α-pregnan-20-one, allopregnanolone) and THDOC (3α,21-dihydroxy-5α-pregnan-20-one) inhibited hyperpolarizing GABA (10 μM)-gated current at α4β2δ GABARs similar to 3α,5β-THP, while the inactive 3β,5β-THP isomer had no effect. Greater inhibition was seen for current gated by the high efficacy agonist gaboxadol (THIP, 100 μM) than for GABA (0.1–1000 μM), consistent with an effect of 3α,5β-THP on desensitization. Inhibitory effects of the steroid were not seen under low [Cl^?] conditions or in the presence of calphostin C (500 nM), an inhibitor of protein kinase C. Chimeras swapping the IL (intracellular loop) of α4 with α1, when expressed with β2 and δ, produced receptors (α[414]β2δ) which were not inhibited by 3α,5β-THP when GABA-gated current was hyperpolarizing, while α[141]β2δ exhibited steroid-induced polarity-dependent modulation.

Conclusions

These findings suggest that numerous neurosteroids exhibit polarity-dependent effects at α4β2δ GABARs, which are dependent upon protein kinase C and the IL of α4.     

TCDD-induced chick cardiotoxicity is abolished by a selective cyclooxygenase-2 (COX-2) inhibitor NS398

Halogenated aromatic hydrocarbons, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are known to cause severe heart defects in avian species. However, the mechanism of TCDD-induced chick cardiovascular toxicity is unclear. In this study, we investigated cyclooxygenase-2 (COX-2) as a possible mechanism of TCDD-induced cardiotoxicity. Fertile chicken eggs were injected with TCDD and a COX-2 selective inhibitor, NS398, and we investigated chick heart failure on day 10. We found that the chick heart to body weight ratio and atrial natriuretic factor mRNA expression were increased, but this increase was abolished with treatment of NS398. In addition, the morphological abnormality of an enlarged ventricle resulting from TCDD exposure was also abolished with co-treatment of TCDD and NS398. Our results suggested that TCDD-induced chick heart defects are mediated via the nongenomic pathway and that they do not require the genomic pathway.     

Sex differences in neurosteroid and hormonal responses to metyrapone in posttraumatic stress disorder

Rationale

Mechanisms contributing to sex differences in the regulation of acute stress responsivity and their effect on the increased incidence of posttraumatic stress disorder (PTSD) in women are poorly understood. The reproductive hormone, progesterone, through conversion to allopregnanolone (ALLO), suppresses the hypothalamic pituitary adrenal (HPA) axis and has potent anxiolytic effects. The potential that progesterone and allopregnanolone reactivity modulate HPA axis responses and account for sex differences in PTSD has not been previously examined.

Objective

The present study examined the effects of sex and PTSD on adrenocorticotropic hormone (ACTH), progesterone, and allopregnanolone responses to metyrapone and whether progesterone and allopregnanolone reactivity could affect the ACTH response in PTSD.

Methods

Healthy medication-free male and premenopausal follicular phase female participants with chronic PTSD (n?=?43; 49 % female) and controls (n?=?42; 50 % female) completed an overnight metyrapone challenge and ACTH, progesterone, and allopregnanolone were obtained by repeated blood sampling.

Results

The increase in ACTH response to metyrapone was higher in PTSD subjects compared to controls and in women compared to men. Contrary to our initial prediction of an inverse relationship, progesterone and allopregnanolone were positively associated with ACTH. Progesterone and allopregnanolone partially mediated the relationship between PTSD and ACTH.

Conclusions

Our findings of increased ACTH to metyrapone in PTSD and in women may reflect heightened hypothalamic CRF hypersecretion. Progesterone and allopregnanolone partially mediated the ACTH response in PTSD. Further characterizing sex differences in these processes will advance our understanding of the pathophysiology of PTSD, and may ultimately lead to better-targeted, more effective treatment.     

Modulation of the human ρ1 GABAA receptor by inhibitory steroids

Rationale

Modulators of the ρ1 GABA_A receptor may be useful in the treatment of visual, sleep, and cognitive disorders. Neuroactive steroids and analogues have been shown to modulate ρ1 receptor function, but the molecular mechanisms are poorly understood.

Objectives

We employed electrophysiology and voltage-clamp fluorometry to compare the actions of several neuroactive steroids and analogues on the human ρ1 GABA_A receptor.

Results

Results confirmed that P294S and T298F mutations affect modulation by steroids. The P294S mutation abolished inhibition by (3α,5β)-3-hydroxypregnan-20-one (3α5βP) while the T298F mutation eliminated inhibition by 17β-estradiol. Voltage-clamp fluorometry demonstrated that steroids differing in the presence of a charged group on C3 or nature of substituent on C17 uniquely modified fluorescence changes elicited by GABA in the extracellular domain. The I307Q mutation reversed the inhibitory effect of 3α5βP but was without effect on modulation by (3α,5β)-3-hydroxypregnan-20-one sulfate or 17β-estradiol. The effect of 3α5βP on the fluorescence change generated at Y241C was dependent on whether the steroid acted as an inhibitor or a potentiator. Further, the effect was limited to uncharged 5β-reduced steroids containing an acetyl group on C17.

Conclusions

The data demonstrate that steroids and analogues differ with respect to conformational changes elicited by these drugs as well as sensitivity to the effects of mutations. Steroids and analogues could be provisionally divided into three major groups based on their actions on the ρ1 GABA_A receptor: 5β-reduced uncharged steroids, sulfated and carboxylated steroids, and 17β-estradiol. Further division among 5β-reduced uncharged steroids was based on substituent at position C17.     

Ginsenoside metabolite compound K stimulates glucagon-like peptide-1 secretion in NCI-H716 cells via bile acid receptor activation

Compound K (CK) is a major metabolite of ginsenosides that is absorbed. CK has antidiabetic effects, although the mechanisms underlying the effects of CK have not fully been known. To elucidate the mechanisms underlying the antidiabetic effects of CK, we studied the effects of CK on GLP-1 secretion from NCI-H716 cells, and explored the mechanisms underlying CK-induced GLP-1 secretion. Treatment of NCI-H716 cells with 10, 50, and 100 μM CK significantly increased GLP-1 secretion, and intracellular Ca²⁺ and cAMP levels in a dose-dependent manner. Transfection of NCI-H716 cells with siRNA specific to α-gustducin and siRNA specific to TAS1R3 had no effect on CK-induced GLP-1 secretion and Ca²⁺ increase. However, transfection of NCI-H716 cells with TGR5-specific siRNA significantly inhibited CK-induced GLP-1 secretion and the increase in Ca²⁺ and cAMP levels. Moreover, CK showed human TGR5 agonist activity in CHO-K1 cells transiently transfected with human TGR5. Our data provide a novel mechanism of CK for antidiabetic effects. Moreover, the findings might suggest that CK is a potential agent that has multiple biological functions in the body via GLP-1 secretion and TGR5 activation.     

Zinc Protoporphyrin Polymeric Nanoparticles: Potent Heme Oxygenase Inhibitor for Cancer Therapy

Purpose

Oxidation therapy is an antitumor strategy in which, apoptosis or necrosis is caused by either excess delivery of reactive oxygen species (ROS) as an oxidant or anti-oxidant inhibition. Heme oxygenase (HO) is an anti-oxidant enzyme that plays an important role in cell growth and proliferation. The purpose of this study was to prepare poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) loaded with zinc protoporphyrin (ZnPP) to deliver the HO inhibitor into tumor.

Methods

PLGA NPs were prepared using nanoprecipitation technique and their characteristics were optimized by Box-Behnken experimental design. Scanning electron microscopy and in vitro studies consisting of drug release, HO inhibitory effect, cytotoxicity and cellular uptake followed by in vivo biodistribution and blood cytotoxicity were carried out. Internalization of coumerin-6 loaded NPs by PC3 cells was visualized by confocal laser scanning microscopy beside quantitatively analysis.

Results

NPs average size, entrapment efficiency and drug loading were 100.12?±?5.345 nm, 55.6%?±?2.49 and 7.98%?±?0.341 respectively. Equal HO inhibitory effect of NPs compared to free ZnPP was observed. The IC₅₀ value of ZnPP-NPs for PC3 human prostate cancer cells was found to be 2.14?±?0.083 μM.

Conclusion

In conclusion, ZnPP loaded PLGA NPs could exhibit enough HO inhibitory effect against cancer cells to be considered as a promising candidate for cancer treatment investigation.     

The Ca2+-calmodulin-Ca2+/calmodulin-dependent protein kinase II signaling pathway is involved in oxidative stress-induced mitochondrial permeability transition and apoptosis in isolated rat hepatocytes

Oxidative stress (OS) is a common event in most hepatopathies, leading to mitochondrial permeability transition pore (MPTP) formation and further exacerbation of both OS from mitochondrial origin and cell death. Intracellular Ca²⁺ increase plays a permissive role in these events, but the underlying mechanisms are poorly known. We examined in primary cultured rat hepatocytes whether the Ca²⁺/calmodulin (CaM)-dependent protein kinase II (CaMKII) signaling pathway is involved in this process, by using tert-butyl hydroperoxide (tBOOH) as a pro-oxidant, model compound. tBOOH (500 μM, 15 min) induced MPTP formation, as assessed by measuring mitochondrial membrane depolarization as a surrogate marker, and increased lipid peroxidation in a cyclosporin A (CsA)-sensitive manner, revealing the involvement of MPTPs in tBOOH-induced radical oxygen species (ROS) formation. Intracellular Ca²⁺ sequestration with BAPTA/AM, CaM blockage with W7 or trifluoperazine, and CaMKII inhibition with KN-62 all fully prevented tBOOH-induced MPTP opening and reduced tBOOH-induced lipid peroxidation to a similar extent to CsA, suggesting that Ca²⁺/CaM/CaMKII signaling pathway fully mediates MPTP-mediated mitochondrial ROS generation. tBOOH-induced apoptosis, as shown by flow cytometry of annexin V/propidium iodide, mitochondrial release of cytochrome c, activation of caspase-3 and increase in the Bax-to-Bcl-xL ratio, and the Ca²⁺/CaM/CaMKII signaling antagonists fully prevented these effects. Intramitochondrial CaM and CaMKII were partially involved in tBOOH-induced MPTP formation, since W7 and KN-62 both attenuated the tBOOH-induced, MPTP-mediated swelling of isolated mitochondria. We concluded that Ca²⁺/CaM/CaMKII signaling pathway is a key mediator of OS-induced MPTP formation and the subsequent exacerbation of OS from mitochondrial origin and apoptotic cell death.     

Enhanced alcohol-seeking behavior by nicotine in the posterior ventral tegmental area of female alcohol-preferring (P) rats: modulation by serotonin-3 and nicotinic cholinergic receptors

Rationale

Alcohol and nicotine co-use can reciprocally promote self-administration and drug-craving/drug-seeking behaviors. To date, the neurocircuitry in which nicotine influences ethanol (EtOH) seeking has not been elucidated. Clinical and preclinical research has suggested that the activation of the mesolimbic dopamine system is involved in the promotion of drug seeking. Alcohol, nicotine, and serotonin-3 (5-HT₃) receptors interact within the posterior ventral tegmental area (pVTA) to regulate drug reward. Recently, our laboratory has reported that systemic administration of nicotine can promote context-induced EtOH seeking.

Objectives

The goals of the current study were to (1) determine if microinjections of pharmacologically relevant levels of nicotine into the pVTA would enhance EtOH seeking, (2) determine if coadministration of nicotinic cholinergic receptor antagonist (nACh) or 5-HT₃ receptor antagonists would block the ability of nicotine microinjected into the pVTA to promote EtOH seeking, and (3) determine if 5-HT₃ receptors in the pVTA can modulate EtOH seeking.

Results

Nicotine (100 and 200 μM) microinjected into the pVTA enhanced EtOH seeking. Coinfusion with 200 μM mecamylamine (nACh antagonist) or 100 and 200 μM zacopride (5-HT₃ receptor antagonist) blocked the observed nicotine enhancement of EtOH seeking. The data also indicated that microinjection of 1 μM CPBG (5-HT₃ receptor agonist) promotes context-induced EtOH seeking; conversely, microinjection of 100 and 200 μM zacopride alone reduced context-induced EtOH seeking.

Conclusions

Overall, the results show that nicotine-enhanced EtOH-seeking behavior is modulated by 5-HT₃ and nACh receptors within the pVTA and that the 5-HT₃ receptor system within pVTA may be a potential pharmacological target to inhibit EtOH-seeking behaviors.     

Potential role of nitric oxide synthase isoforms in pathophysiology of neuropathic pain

Neuropathic pain triggers a cascade of events in the sensory neurons. It is the main complication of diabetes after cardiovascular disease. Nitric oxide (NO) produced from nitric oxide synthases (NOS) is an important signaling molecule which is crucial for many physiological processes such as synaptic plasticity, neuronal survival, vasodilation, vascular homeostasis, immune regulation. Overproduction of NO due to changes in NOS isoforms level involves pathological processes such as neurotoxicity, septic shock and neuropathic pain. All three isoforms of NOS as well as their end product, NO have modulatory effect on neuropathic pain. Overactivation of the N-Methyl-d-Aspartate receptor and peroxynitrite formation results in high levels of neuronal NOS (nNOS) and endothelial NOS (eNOS) which suggest that nNOS and eNOS are critical for pain hypersensitivity. Inducible NOS induced in glia by inflammation due to activation of Tumor Necrosis Factor α, Calcitonin Gene Regulating Peptide, Mitogen Activated Protein Kinases, Extracellular signal Regulated Kinase, c-Jun N-terminal kinases can induce neuronal death. This review focuses on different nitric oxide synthases and their role in pathophysiology of neuropathic pain considering NOS as an important therapeutic target.     

Targeting EGFR mutants with non-cognate kinase inhibitors in non-small cell lung cancer

Considering that the human protein kinase family members share high conservation in both primary sequence and advanced structure, and a large number of small-molecule inhibitors have already been developed to target these different members, we herein are interested in whether certain existing inhibitors that were originally designed for other (cognate) kinases can also bind efficiently to (non-cognate) epidermal growth factor receptor (EGFR) mutants and simultaneously lie low affinity to wild-type EGFR. To explore this notion, a structure-based quantitative structure–activity relationship model was derived from 77 crystal structure-solved, affinity-known kinase–inhibitor complexes. We employed this model to profile a systematic interaction map of 2 cognate and 11 non-cognate kinase inhibitors with wild-type EGFR and its several important NSCLC-related mutants. As might be expected, the cognate inhibitors exhibited generally high affinity to both wild-type and mutant EGFR, while most non-cognate inhibitors have low binding potency for EGFR. However, few combinations of non-cognate inhibitors and EGFR mutants, such as TAE684 and T790M, SKI606 and L858R, and R406 and T790M, show a favorable interaction as compared to the same inhibitors with wild-type EGFR. A further kinase assay was performed to determine the inhibitory activities of compound TAE684, originally developed as a ALK kinase inhibitor, against wild-type and T790M mutant EGFR; it is revealed that the TAE684 inhibited the mutant with ~tenfold higher potency than the wild-type enzyme. This work would help to establish a new strategy for the new use of an old drug.     

MDMA effects consistent across laboratories

Rationale

Several laboratories have conducted placebo-controlled drug challenge studies with 3,4-methylenedioxymethamphetamine (MDMA), providing a unique source of data to examine the reliability of the acute effects of the drug across subject samples and settings. We examined the subjective and physiological responses to the drug across three different laboratories and investigated the influence of prior MDMA use.

Methods

Overall, 220 healthy volunteers with varying levels of previous MDMA experience participated in laboratory-based studies in which they received placebo or MDMA orally (1.5 mg/kg or 125-mg fixed dose) under double-blind conditions. Cardiovascular and subjective effects were assessed before and repeatedly after drug administration. The studies were conducted independently by investigators in Basel, San Francisco, and Chicago.

Results

Despite methodological differences between the studies and differences in the subjects’ drug use histories, MDMA produced very similar cardiovascular and subjective effects across the sites. The participants’ prior use of MDMA was inversely related to feeling “Any Drug Effect” only at sites testing more experienced users.

Conclusions

These data indicate that the pharmacological effects of MDMA are robust and highly reproducible across settings. There was also modest evidence for tolerance to the effects of MDMA in regular users.