Tetrahydropalmatine protects against methamphetamine-induced spatial learning and memory impairment in mice

Gut Microbiota Taxon-Dependent Transformation of Microglial M1/M2 Phenotypes Underlying Mechanisms of Spatial Learning and Memory Impairment after Chronic Methamphetamine Exposure

Methamphetamine (METH) exposure may lead to cognitive impairment. Currently, evidence suggests that METH exposure alters the configuration of the gut microbiota. However, the role and mechanism of the gut microbiota in cognitive impairment after METH exposure are still largely unknown. Here, we investigated the impact of the gut microbiota on the phenotype status of microglia (microglial phenotypes M1 and microglial M2) and their secreting factors, the subsequent hippocampal neural processes, and the resulting influence on spatial learning and memory of chronically METH-exposed mice. We determined that gut microbiota perturbation triggered the transformation of microglial M2 to M1 and a subsequent change of pro-brain-derived neurotrophic factor (proBDNF)-p75NTR-mature BDNF (mBDNF)-TrkB signaling, which caused reduction of hippocampal neurogenesis and synaptic plasticity-related proteins (SYN, PSD95, and MAP2) and, consequently, deteriorated spatial learning and memory. More specifically, we found that Clostridia, Bacteroides, Lactobacillus, and Muribaculaceae might dramatically affect the homeostasis of microglial M1/M2 phenotypes and eventually contribute to spatial learning and memory decline after chronic METH exposure. Finally, we found that fecal microbial transplantation could protect against spatial learning and memory decline by restoring the microglial M1/M2 phenotype status and the subsequent proBDNF-p75NTR/mBDNF-TrkB signaling in the hippocampi of chronically METH-exposed mice. IMPORTANCE Our study indicated that the gut microbiota contributes to spatial learning and memory dysfunction after chronic METH exposure, in which microglial phenotype status plays an intermediary role. The elucidated "specific microbiota taxa-microglial M1/M2 phenotypes-spatial learning and memory impairment" pathway would provide a novel mechanism and elucidate potential gut microbiota taxon targets for the no-drug treatment of cognitive deterioration after chronic METH exposure.

Corydalis decumbens Can Exert Analgesic Effects in a Mouse Neuropathic Pain Model by Modulating MAPK Signaling

Objectives

This study is aimed at investigating the analgesic effect of the administration of Corydalis decumbens (CD) in a mouse model of postherpetic neuralgia (PHN) and at elucidating its mechanism of analgesic action.

Methods

Adult Kunming (KM) mice were randomly divided into control, CD, and vehicle-treated groups. Neuropathic pain was induced with a single intraperitoneal injection of resiniferatoxin (RTX). Thermal hyperalgesia was assessed with a hot/cold plate test, and mechanical allodynia was evaluated using von Frey filaments. The activation states of astrocytes, microglia, and the mitogen-activated protein kinase (MAPK) pathway in the spinal cord were determined by immunofluorescence staining and Western blot analysis of Iba-1, GFAP, phospho-p38, and phospho-Jun N-terminal kinase (JNK).

Results

RTX diminished thermal sensitivity and gradually increased sensitivity to tactile stimulation. The expression of Iba-1, GFAP, phospho-p38 MAPK, and phospho-JNK was upregulated in the RTX-induced postherpetic neuralgia mouse model. Systemic treatment with CD significantly ameliorated thermal sensitivity and mechanical hyperalgesia and was accompanied by a reduction in the expression of Iba-1 and GFAP and reduced phosphorylation of p38 and JNK.

Conclusions

This study suggests that CD is effective at ameliorating mechanical hyperalgesia in PHN mice and that its mechanism of action may involve modulation of MAPK phosphorylation and glial cell activation. Thus, CD may be a promising alternative therapy for PHN.

A Comprehensive Review on the Chemical Properties, Plant Sources, Pharmacological Activities, Pharmacokinetic and Toxicological Characteristics of Tetrahydropalmatine

Tetrahydropalmatine (THP), a tetrahydroproberine isoquinoline alkaloid, is widely present in some botanical drugs, such as Stephania epigaea H.S. Lo (Menispermaceae; Radix stephaniae epigaeae), Corydalis yanhusuo (Y.H.Chou & Chun C.Hsu) W.T. Wang ex Z.Y. Su and C.Y. Wu (Papaveraceae; Corydalis rhizoma), and Phellodendron chinense C.K.Schneid (Berberidaceae; Phellodendri chinensis cortex). THP has attracted considerable attention because of its diverse pharmacological activities. In this review, the chemical properties, plant sources, pharmacological activities, pharmacokinetic and toxicological characteristics of THP were systematically summarized for the first time. The results indicated that THP mainly existed in Papaveraceae and Menispermaceae families. Its pharmacological activities include anti-addiction, anti-inflammatory, analgesic, neuroprotective, and antitumor effects. Pharmacokinetic studies showed that THP was inadequately absorbed in the intestine and had rapid clearance and low bioavailability in vivo, as well as self-microemulsifying drug delivery systems, which could increase the absorption level and absorption rate of THP and improve its bioavailability. In addition, THP may have potential cardiac and neurological toxicity, but toxicity studies of THP are limited, especially its long-duration and acute toxicity tests. In summary, THP, as a natural alkaloid, has application prospects and potential development value, which is promising to be a novel drug for the treatment of pain, inflammation, and other related diseases. Further research on its potential target, molecular mechanism, toxicity, and oral utilization should need to be strengthened in the future.

Effects of Buprenorphine on the Memory and Learning Deficit Induced by Methamphetamine Administration in Male Rats

Little is known about the effects of methamphetamine (Meth) and buprenorphine (Bup) on memory and learning in rats. The aim of this investigation was to examine the impact of Meth and Bup on memory and learning. Fourteen male Wistar rats weighing 250–300 g were assigned to four groups: Sham, Meth, Bup, and Meth + Bup and were treated for 1 week. Spatial learning and memory, avoidance learning, and locomotion were assessed using the Morris water maze, passive avoidance learning, and open field tests, respectively. Meth and Bup impaired spatial learning and memory in rats. Co-administration of Meth + Bup did not increase the time spent in the target quadrant compared to Meth alone in the MWM. The Bup and Meh + Bup groups were found with an increase in step-through latency (STLr) and a decrease in the time spent in the dark compartment (TDC). Meth and Bup had no effects on locomotor activity in the open field test. Bup showed a beneficial effect on aversive memory. Since Bup demonstrates fewer side effects than other opioid drugs, it may be preferable for the treatment of avoidance memory deficits in patients with Meth addiction.

Attenuative Effects of Fluoxetine and Triticum aestivum against Aluminum-Induced Alzheimer's Disease in Rats: The Possible Consequences on Hepatotoxicity and Nephrotoxicity

BACKGROUND

Alzheimer's disease (AD) is a chronic neurological illness that causes considerable cognitive impairment. Hepatic and renal dysfunction may worsen AD by disrupting β-amyloid homeostasis at the periphery and by causing metabolic dysfunction. Wheatgrass (Triticum aestivum) has been shown to have antioxidant and anti-inflammatory properties. This work aims to study the effect of aluminum on neuronal cells, its consequences on the liver and kidneys, and the possible role of fluoxetine and wheatgrass juice in attenuating these pathological conditions.

METHOD

Rats were divided into five groups. Control, AD (AlCl₃), Fluoxetine (Fluoxetine and AlCl₃), Wheatgrass (Wheatgrass and AlCl₃), and combination group (fluoxetine, wheatgrass, and AlCl₃). All groups were assigned daily to different treatments for five weeks.

CONCLUSIONS

AlCl₃ elevated liver and kidney enzymes, over-production of oxidative stress, and inflammatory markers. Besides, accumulation of tau protein and Aβ, the elevation of ACHE and GSK-3β, down-regulation of BDNF, and β-catenin expression in the brain. Histopathological examinations of the liver, kidney, and brain confirmed this toxicity, while treating AD groups with fluoxetine, wheatgrass, or a combination alleviates toxic insults.

CONCLUSION

Fluoxetine and wheatgrass combination demonstrated a more significant neuroprotective impact in treating AD than fluoxetine alone and has protective effects on liver and kidney tissues.

Tetrahydropalmatine Regulates BDNF through TrkB/CAM Interaction to Alleviate the Neurotoxicity Induced by Methamphetamine

Tetrahydropalmatine (THP) has analgesic, hypnotic, sedative, and other pharmacological effects. Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal plasticity, growth, and development. However, their mechanism of action in methamphetamine (MA)-induced neurotoxicity remains unclear. This study aims to explore the important role of BDNF in MA neurotoxicity and whether THP can regulate BDNF through the interaction between tyrosine kinase receptor B (TrkB)/calmodulin (CAM) to alleviate the neurotoxicity induced by MA. SD rats were randomly divided into control, MA, and MA + THP groups. Stereotyped behavior test, captive rejection test, open field test (OFT), and Morris water maze (MWM) were used to evaluate the anxiety, aggression, cognition, learning, and memory. Extracted hippocampus and mesencephalon tissue were detected by Western blot, HE staining, and immunohistochemistry. TUNEL staining was used to detect apoptosis. MOE was used for bioinformatics prediction, and coimmunoprecipitation was used to confirm protein interactions. Long-term abuse of MA resulted in lower weight gain ratio and nerve cell damage and caused various neurotoxicity-related behavioral abnormalities: anxiety, aggression, cognitive motor disorders, and learning and memory disorders. MA-induced neurotoxicity is related to the down-regulation of BDNF and apoptosis. THP attenuated the MA-induced neurotoxicity by decreasing CAM, increasing TrkB, phosphorylating Akt, up-regulating NF-κB and BDNF, and inhibiting cell apoptosis. MA can induce neurotoxicity in rats. BDNF may play a vital role in MA-induced neurotoxicity. THP regulates BDNF through TrkB/CAM interaction to alleviate the neurotoxicity induced by MA. THP may be a potential therapeutic drug for the neurotoxic and neurodegenerative diseases related to MA.

Neuroprotective Effect for Cerebral Ischemia by Natural Products: A Review

Natural products have a significant role in the prevention of disease and boosting of health in humans and animals. Stroke is a disease with high prevalence and incidence, the pathogenesis is a complex cascade reaction. In recent years, it’s reported that a vast number of natural products have demonstrated beneficial effects on stroke worldwide. Natural products have been discovered to modulate activities with multiple targets and signaling pathways to exert neuroprotection via direct or indirect effects on enzymes, such as kinases, regulatory receptors, and proteins. This review provides a comprehensive summary of the established pharmacological effects and multiple target mechanisms of natural products for cerebral ischemic injury in vitro and in vivo preclinical models, and their potential neuro-therapeutic applications. In addition, the biological activity of natural products is closely related to their structure, and the structure-activity relationship of most natural products in neuroprotection is lacking, which should be further explored in future. Overall, we stress on natural products for their role in neuroprotection, and this wide band of pharmacological or biological activities has made them suitable candidates for the treatment of stroke.

Role of natural products in mitigation of toxic effects of methamphetamine: A review of in vitro and in vivo studies

OBJECTIVE

Methamphetamine (METH) increases dopamine, norepinephrine and serotonin concentrations in the synaptic cleft, and induces hyperactivity. The current management of acute METH poisoning relies on supportive care and no specific antidote is available for treatment. The main objective of this review was to present the evidence for effectiveness of the herbal medicine in alleviating the adverse effects of METH abuse.

MATERIALS AND METHODS

Literature search was performed using the following electronic databases: MEDLINE, Scopus, PubMed and EMBASE.

RESULTS

Plant-derived natural products ginseng and sauchinone reduced METH-induced hyperactivity, conditioned place preference and neurological disorder. Garcinia kola decreased METH-induced hepatotoxicity, raised METH lethal dose, and restored the METH-impaired cognitive function. Repeated administration of baicalein resulted in attenuation of acute binge METH-induced amnesia via dopamine receptors. Activation of extracellular-regulated kinase in the hypothalamus by levo-tetrahydropalmatine facilitated the extinction of METH-induced conditioned place preference and reduced the hyperactivity. Other herbal medicine from various parts of the world were also discussed including hispidulin, silymarin, limonene, resveratrol, chlorogenic acid and barakol.

CONCLUSION

Based on the current study, some natural products such as ginseng and levo-tetrahydropalmatine are promising candidates to treat METH abuse and poisoning. However, clinical trials are needed to confirm these finding.

Cognition and Related Neural Findings on Methamphetamine Use Disorder: Insights and Treatment Implications From Schizophrenia Research

Despite the prevalence of methamphetamine (meth) use disorder, research on meth is disproportionately scarce compared to research on other illicit drugs. Existing evidence highlights cognitive deficits as an impediment against daily function and treatment of chronic meth use. Similar deficits are also observed in schizophrenia, and this review therefore draws on schizophrenia research by examining similarities and differences between the two disorders on cognition and related neural findings. While meth use disorder and schizophrenia are two distinct disorders, they are highly co-morbid and share impairments in similar cognitive domains and altered brain structure/function. This narrative review specifically identifies overlapping features such as deficits in learning and memory, social cognition, working memory and inhibitory/impulse control. We report that while working memory deficits are a core feature of schizophrenia, such deficits are inconsistently observed following chronic meth use. Similar structural and functional abnormalities are also observed in cortical and limbic regions between the two disorders, except for cingulate activity where differences are observed. There is growing evidence that targeting cognitive symptoms may improve functional outcome in schizophrenia, with evidence of normalized abnormal brain activity in regions associated with cognition. Considering the overlap between meth use disorder and schizophrenia, targeting cognitive symptoms in people with meth use disorder may also improve treatment outcome and daily function.

Methamphetamine-associated cognitive decline is attenuated by neutralizing IL-1 signaling

Methamphetamine (METH) abusers are prone to develop a variety of comorbidities, including cognitive disabilities, and the immunological responses have been recognized as an important component involved in the toxicity of this drug. Cytokines are among the key mediators between systemic inflammatory status and tissue responses. One of these, interleukin 1 (IL-1), has been hypothesized to be involved in cognitive functions and also appears to play a pivotal role among inflammatory molecules. In the present study, we demonstrate that exposure of mice to METH markedly increased the protein level of IL-1β in hippocampal tissue. Additionally, METH administration induced a decline in spatial learning as determined by the Morris water maze test. We next evaluated the hypothesis that blocking IL-1β signaling can protect against METH-induced loss of cognitive functioning. The results indicated that METH-induced impaired spatial learning abilities were attenuated by co-administration of mouse IL-1 Trap, a dimeric fusion protein that incorporates the extracellular domains of both of the IL-1 receptor components required for IL-1 signaling (IL-1 receptor type 1 and IL-1 receptor accessory protein), linked to the Fc portion of murine IgG2a. This effect was associated with a decrease in hippocampal IL-1β level. The current study indicates for the first time that the loss of METH-related cognitive decline can be attenuated by neutralizing IL-1 signaling. Our findings suggest a potential new therapeutic pathway for treatment of altered cognitive abilities that occur in METH abusing individuals.

The Neuroprotective Effect of L-Stepholidine on Methamphetamine-Induced Memory Deficits in Mice

Repeated methamphetamine (METH) exposure can cause severe neurotoxicity to the central nervous system, and lead to memory deficits. L-Stepholidine (L-SPD) is a structurally identified alkaloid extract of the Chinese herb Stephania intermedia, which elicits dopamine (DA) D1-type receptors partial agonistic activity and D2-type receptors antagonistic activity. In this study, we investigated the effect of L-SPD on METH-induced memory deficits in mice and its underlying mechanisms. We found that repeated exposure to METH (10 mg/kg, i.p., once per day for 7 consecutive days) impaired memory functions in the novel object recognition experiment. Pretreatment of L-SPD (10 mg/kg, i.p.) significantly improved METH-induced memory deficits in mice. Meanwhile, the protein expression of dopaminergic D2 receptors in hippocampus area was significantly increased by repeated METH exposure, while the protein expression of dopamine transporter (DAT) was significantly reduced. Additionally, the protein expression of phospho-protein kinase A (p-PKA) was significantly increased by repeated METH exposure. The hyperpolarization-activated cyclic-nucleotide-gated non-selective cation 1 (HCN1) channel, which was a key regulator of memory functions and could be regulated by p-PKA, was also significantly increased by repeated METH exposure. These changes caused by METH could be prevented by L-SPD pretreatment. Therefore, our data firstly showed that pretreatment of L-SPD exhibited the protective effect against METH-induced memory deficits, possibly through reducing METH-induced upregulation of dopaminergic pathway and HCN1 channels.

Downregulation of HCN1 channels in hippocampus and prefrontal cortex in methamphetamine re-exposed mice with enhanced working memory

The hyperpolarization-activated cyclic-nucleotide-gated non-selective cation (HCN) channels play a potential role in the neurological basis underlying drug addiction. However, little is known about the role of HCN channels in methamphetamine (METH) abuse. In the present study, we examined the changes in working memory functions of METH re-exposed mice through Morris water maze test, and investigated the protein expression of HCN1 channels and potential mechanisms underlying the modulation of HCN channels by Western blotting analysis. Mice were injected with METH (1 mg/kg, i.p.) once per day for 6 consecutive days. After 5 days without METH, mice were re-exposed to METH at the same concentration. We found that METH re-exposure caused an enhancement of working memory, and a decrease in the HCN1 channels protein expression in both hippocampus and prefrontal cortex. The phosphorylated extracellular regulated protein kinase 1/2 (p-ERK1/2), an important regulator of HCN channels, was also obviously reduced in hippocampus and prefrontal cortex of mice with METH re-exposure. Meanwhile, acute METH exposure did not affect the working memory function and the protein expressions of HCN1 channels and p-ERK1/2. Overall, our data firstly showed the aberrant protein expression of HCN1 channels in METH re-exposed mice with enhanced working memory, which was probably related to the down-regulation of p-ERK1/2 protein expression.

Tetrahydropalmatine Prevents High-Fat Diet-Induced Hyperlipidemia in Golden Hamsters (Mesocricetus Auratus)

Background

Hyperlipidemia is a major cause of atherosclerotic cardiovascular disease. Tetrahydropalmatine (THP) can exhibit hepatoprotective, anti-arrhythmic, and anti-inflammatory activities. The mechanism of THP on the hyperlipidemia remains unknown; therefore, the present study explored the role of THP in hyperlipidemia.

Material/Methods

We established an animal model of hyperlipidemia by high-fat diet (HFD) feeding. Blood samples were obtained for determination of serum cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), pro-inflammatory cytokines, and CYP7A1 expression. Histology was performed and inflammation was detected in the liver using hematoxylin-eosin (HE) staining and enzyme-linked immunosorbent assay (ELISA), respectively. The mRNA and protein levels of TLR4 and TRAF-6 were determined by quantitative real-time PCR (qPCR) and Western blot, respectively.

Results

THP suppressed hepatic lipid accumulation and reduced serum levels of TC, TG, LDL-c, and HDL-c in HFD-fed golden hamsters. THP increased cholesterol 7 α-hydroxylase (CYP7A1) expression and prevented inflammation by the limited reduction in interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) expressions in serum and liver. THP slightly increased the ratio of the body/liver weight. THP inhibited the mRNA and protein levels of Toll-like receptor 4 (TLR4) and TNF-receptor associated factor-6 (TRAF-6).

Conclusions

These results suggest that THP attenuates hyperlipidemia by multiple effects, including hepatoprotective and anti-inflammatory effects. Moreover, THP also suppressed the expressions of TLR4 and TRAF-6 in golden hamsters.

Sex Differences in Neuropathology and Cognitive Behavior in APP/PS1/tau Triple-Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia among the elderly, characterized by amyloid plaques, neurofibrillary tangles, and neuroinflammation in the brain, as well as impaired cognitive behaviors. A sex difference in the prevalence of AD has been noted, while sex differences in the cerebral pathology and relevant molecular mechanisms are not well clarified. In the present study, we systematically investigated the sex differences in pathological characteristics and cognitive behavior in 12-month-old male and female APP/PS1/tau triple-transgenic AD mice (3×Tg-AD mice) and examined the molecular mechanisms. We found that female 3×Tg-AD mice displayed more prominent amyloid plaques, neurofibrillary tangles, neuroinflammation, and spatial cognitive deficits than male 3×Tg-AD mice. Furthermore, the expression levels of hippocampal protein kinase A-cAMP response element-binding protein (PKA-CREB) and p38-mitogen-activated protein kinases (MAPK) also showed sex difference in the AD mice, with a significant increase in the levels of p-PKA/p-CREB and a decrease in the p-p38 in female, but not male, 3×Tg-AD mice. We suggest that an estrogen deficiency-induced PKA-CREB-MAPK signaling disorder in 12-month-old female 3×Tg-AD mice might be involved in the serious pathological and cognitive damage in these mice. Therefore, sex differences should be taken into account in investigating AD biomarkers and related target molecules, and estrogen supplementation or PKA-CREB-MAPK stabilization could be beneficial in relieving the pathological damage in AD and improving the cognitive behavior of reproductively-senescent females.

The effects of methamphetamine and buprenorphine, and their interaction on anxiety-like behavior and locomotion in male rats

Methamphetamine (Meth) abuse and dependence are major global problems. Most of previous studies showed that Meth is anxiogenic. While buprenorphine (Bup) is used to treat anxiety-related behaviors, the effects of Meth in combination with Bup on anxiety-like behavior are unclear. In this study, we examined the effects of these drugs on anxiety-like behavior with the elevated plus maze (EPM) and open field (OF) tests, which are widely used to assess anxiety-like behavior in small rodents. Forty male Wistar rats were divided into four groups: sham, Meth, Bup, and Bup+Meth. The groups were administered their assigned treatments for 7days. The time spent in the open arms, and number of total entries into the arms (total activity) in the EPM were recorded. In addition, locomotor activity and number of entrances into the center area in the OF were recorded. The 7-day administration of Meth or Bup increased open arm exploration in the EPM. In contrast, the combined administration of Bup and Meth had the opposite effects. In addition, Meth and Bup had no effects on total and locomotor activity. Furthermore, the rats in the Meth and Bup groups spent more time in the center of the OF, while the group given both Bup and Meth spent less time in the center of the OF. The administration of Meth and Bup alone was anxiolytic in rats, whereas the coadministration of Bup and Meth was anxiogenic.

Inhibition of histone deacetylase reduces transcription of NADPH oxidases and ROS production and ameliorates pulmonary arterial hypertension

Excessive levels of reactive oxygen species (ROS) and increased expression of NADPH oxidases (Nox) have been proposed to contribute to pulmonary artery hypertension (PAH) and other cardiovascular diseases (CVD). Nox enzymes are major sources of ROS but the mechanisms regulating changes in Nox expression in disease states remain poorly understood. Epigenetics encompasses a number of mechanisms that cells employ to regulate the ability to read and transcribe DNA. Histone acetylation is a prominent example of an epigenetic mechanism regulating the expression of numerous genes by altering chromatin accessibility. The goal of this study was to determine whether inhibition of histone deacetylases (HDAC) affects the expression of Nox isoforms and reduces pulmonary hypertension. In immune cells, we found that multiple HDAC inhibitors robustly decreased Nox2 mRNA and protein expression in a dose-dependent manner concomitant with reduced superoxide production. This effect was not restricted to Nox2 as expression of Nox1, Nox4 and Nox5 was also reduced by HDAC inhibition. Surprisingly, Nox promoter-luciferase activity was unchanged in the presence of HDAC inhibitors. In macrophages and lung fibroblasts, ChIP experiments revealed that HDAC inhibitors block the binding of RNA polymerase II and the histone acetyltransferase p300 to the Nox2, Nox4 and Nox5 promoter regions and decrease histones activation marks (H3K4me3 and H3K9ac) at these promoter sites. We further show that the ability of CRISPR-ON to drive transcription of Nox1, Nox2, Nox4 and Nox5 genes is blocked by HDAC inhibitors. In a monocrotaline (MCT) rat model of PAH, multiple HDAC isoforms are upregulated in isolated pulmonary arteries, and HDAC inhibitors attenuate Nox expression in isolated pulmonary arteries and reduce indices of PAH. In conclusion, HDAC inhibitors potently suppress Nox gene expression both in vitro and in vivo via epigenetically regulating chromatin accessibility.

Molecular Mechanism: ERK Signaling, Drug Addiction, and Behavioral Effects

Addiction to psychostimulants has been considered as a chronic psychiatric disorder characterized by craving and compulsive drug seeking and use. Over the past two decades, accumulating evidence has demonstrated that repeated drug exposure causes long-lasting neurochemical and cellular changes that result in enduring neuroadaptation in brain circuitry and underlie compulsive drug consumption and relapse. Through intercellular signaling cascades, drugs of abuse induce remodeling in the rewarding circuitry that contributes to the neuroplasticity of learning and memory associated with addiction. Here, we review the role of the extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase, and its related intracellular signaling pathways in drug-induced neuroadaptive changes that are associated with drug-mediated psychomotor activity, rewarding properties and relapse of drug seeking behaviors. We also discuss the neurobiological and behavioral effects of pharmacological and genetic interferences with ERK-associated molecular cascades in response to abused substances. Understanding the dynamic modulation of ERK signaling in response to drugs may provide novel molecular targets for therapeutic strategies to drug addiction.

Antihypertensive and vasorelaxant effects of Rhizoma corydalis and its active component tetrahydropalmatine via NO/cGMP pathway and calcium channel blockade in isolated rat thoracic aorta

The vasorelaxant effects of RC and THPviathe NO/cGMP pathway and calcium channel blockade in isolated rat thoracic aorta are explored.

Cognitive deficits associated with combined HIV gp120 expression and chronic methamphetamine exposure in mice

Methamphetamine abuse is common among individuals infected by human immunodeficiency virus (HIV). Neurocognitive outcomes tend to be worse in methamphetamine users with HIV. However, it is unclear whether discrete cognitive domains are susceptible to impairment after combined HIV infection and methamphetamine abuse. The expression of HIV/gp120 protein induces neuropathology in mice similar to HIV-induced pathology in humans. We investigated the separate and combined effects of methamphetamine exposure and gp120 expression on cognitive function in transgenic (gp120-tg) and control mice. The mice underwent an escalating methamphetamine binge regimen and were tested in novel object/location recognition, object-in-place recognition, and Barnes maze tests. gp120 expression disrupted performance in the object-in-place test (i.e. similar time spent with all objects, regardless of location), indicating deficits in associative recognition memory. gp120 expression also altered reversal learning in the Barnes maze, suggesting impairments in executive function. Methamphetamine exposure impaired spatial strategy in the Barnes maze, indicating deficits in spatial learning. Methamphetamine-exposed gp120-tg mice had the lowest spatial strategy scores in the final acquisition trials in the Barnes maze, suggesting greater deficits in spatial learning than all of the other groups. Although HIV infection involves interactions between multiple proteins and processes, in addition to gp120, our findings in gp120-tg mice suggest that humans with the dual insult of HIV infection and methamphetamine abuse may exhibit a broader spectrum of cognitive deficits than those with either factor alone. Depending on the cognitive domain, the combination of both insults may exacerbate deficits in cognitive performance compared with each individual insult.

Caveolin-1 is a negative regulator of NADPH oxidase-derived reactive oxygen species

Changes in the expression and function of caveolin-1 (Cav-1) have been proposed as a pathogenic mechanism underlying many cardiovascular diseases. Cav-1 binds to and regulates the activity of numerous signaling proteins via interactions with its scaffolding domain. In endothelial cells, Cav-1 has been shown to reduce reactive oxygen species (ROS) production, but whether Cav-1 regulates the activity of NADPH oxidases (Noxes), a major source of cellular ROS, has not yet been shown. Herein, we show that Cav-1 is primarily expressed in the endothelium and adventitia of pulmonary arteries (PAs) and that Cav-1 expression is reduced in isolated PAs from multiple models of pulmonary artery hypertension (PH). Reduced Cav-1 expression correlates with increased ROS production in the adventitia of hypertensive PA. In vitro experiments revealed a significant ability of Cav-1 and its scaffolding domain to inhibit Nox1-5 activity and it was also found that Cav-1 binds to Nox5 and Nox2 but not Nox4. In addition to posttranslational actions, in primary cells, Cav-1 represses the mRNA and protein expression of Nox2 and Nox4 through inhibition of the NF-κB pathway. Last, in a mouse hypoxia model, the genetic ablation of Cav-1 increased the expression of Nox2 and Nox4 and exacerbated PH. Together, these results suggest that Cav-1 is a negative regulator of Nox function via two distinct mechanisms, acutely through direct binding and chronically through alteration of expression levels. Accordingly, the loss of Cav-1 expression in cardiovascular diseases such as PH may account for the increased Nox activity and greater production of ROS.

Regulation of NADPH oxidase 5 by protein kinase C isoforms

NADPH oxidase5 (Nox5) is a novel Nox isoform which has recently been recognized as having important roles in the pathogenesis of coronary artery disease, acute myocardial infarction, fetal ventricular septal defect and cancer. The activity of Nox5 and production of reactive oxygen species is regulated by intracellular calcium levels and phosphorylation. However, the kinases that phosphorylate Nox5 remain poorly understood. Previous studies have shown that the phosphorylation of Nox5 is PKC dependent, but this contention was based on the use of pharmacological inhibitors and the isoforms of PKC involved remain unknown. Thus, the major goals of this study were to determine whether PKC can directly regulate Nox5 phosphorylation and activity, to identify which isoforms are involved in the process, and to understand the functional significance of this pathway in disease. We found that a relatively specific PKCα inhibitor, Ro-32-0432, dose-dependently inhibited PMA-induced superoxide production from Nox5. PMA-stimulated Nox5 activity was significantly reduced in cells with genetic silencing of PKCα and PKCε, enhanced by loss of PKCδ and the silencing of PKCθ expression was without effect. A constitutively active form of PKCα robustly increased basal and PMA-stimulated Nox5 activity and promoted the phosphorylation of Nox5 on Ser490, Thr494, and Ser498. In contrast, constitutively active PKCε potently inhibited both basal and PMA-dependent Nox5 activity. Co-IP and in vitro kinase assay experiments demonstrated that PKCα directly binds to Nox5 and modifies Nox5 phosphorylation and activity. Exposure of endothelial cells to high glucose significantly increased PKCα activation, and enhanced Nox5 derived superoxide in a manner that was in prevented by a PKCα inhibitor, Go 6976. In summary, our study reveals that PKCα is the primary isoform mediating the activation of Nox5 and this maybe of significance in our understanding of the vascular complications of diabetes and other diseases with increased ROS production.

Methamphetamine and Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder predominantly affecting the elderly. The aetiology of the disease is not known, but age and environmental factors play an important role. Although more than a dozen gene mutations associated with familial forms of Parkinson's disease have been described, fewer than 10% of all cases can be explained by genetic abnormalities. The molecular basis of Parkinson's disease is the loss of dopamine in the basal ganglia (caudate/putamen) due to the degeneration of dopaminergic neurons in the substantia nigra, which leads to the motor impairment characteristic of the disease. Methamphetamine is the second most widely used illicit drug in the world. In rodents, methamphetamine exposure damages dopaminergic neurons in the substantia nigra, resulting in a significant loss of dopamine in the striatum. Biochemical and neuroimaging studies in human methamphetamine users have shown decreased levels of dopamine and dopamine transporter as well as prominent microglial activation in the striatum and other areas of the brain, changes similar to those observed in PD patients. Consistent with these similarities, recent epidemiological studies have shown that methamphetamine users are almost twice as likely as non-users to develop PD, despite the fact that methamphetamine abuse and PD have distinct symptomatic profiles.