Involvement of serotonin mechanism in methamphetamine-induced chronic pulmonary toxicity in rats

Modulation of pulmonary oxidative status in methamphetamine-withdrawn rats, comparing the effects of continuous training and NBS superfood supplementation

OBJECTIVE

This study aimed to investigate the effects of six weeks of continuous training and Nutrition Bio-shield (NBS) Superfood Supplementation on the state of oxidative stress by the expression of Nrf2, NOX4, superoxide dismutase, and malondialdehyde genes in the lungs of rats after methamphetamine withdrawal.

METHODS

Forty male Wistar rats were randomly divided into five groups (n = 8, per group), undergoing methamphetamine administration (six weeks, 5 mg/kg ip, and once per day) followed by a 21-day withdrawal period. The rats were supplemented NBS superfood at a dosage of 25 g/kg per day for six weeks. The training protocol was 30 minutes of daily continuous training (treadmill running), five days a week for six weeks. The regimen escalated from a pace of 3 m/min for the initial 5 minutes, to 5 m/min for the following 5 minutes, culminating at 8 m/min for the remainder of the session, all at a 0° incline. A one-way analysis of variance was performed to analyze the gene expression of Nrf2, NOX4, MDA, and SOD in the lungs tissue of rats.

RESULTS

The results indicated that, in the experimental groups which underwent continuous training and NBS Superfood supplementation, the expression of the Nrf2 gene exhibited a significant elevation compared to the control group (P < 0.05), while the NOX4, MDA, and SOD genes expression exhibited a significant decline in comparison to the control group (P < 0.05).

CONCLUSION

In general, both exercise interventions and NBS superfood supplementation, when employed separately or in combination after methamphetamine withdrawal, can enhance the state of oxidative stress in the lung.

Overview of Methamphetamine-Associated Pulmonary Arterial Hypertension

TOPIC IMPORTANCE

The global surge in methamphetamine use is a critical public health concern, particularly due to its robust correlation with methamphetamine-associated pulmonary arterial hypertension (MA-PAH). This association raises urgent alarms about the potential escalation of MA-PAH incidence, posing a significant and imminent challenge to global public health.

REVIEW FINDINGS

This comprehensive review meticulously explores MA-PAH, offering insights into its epidemiology, pathophysiology, clinical presentation, diagnostic intricacies, and management strategies. The pathogenesis, yet to be fully described, involves complex molecular interactions, including alterations in serotonin signaling, reduced activity of carboxylesterase 1, oxidative stress, and dysregulation of pulmonary vasoconstrictors and vasodilators. These processes culminate in the structural remodeling of the pulmonary vasculature, resulting in pulmonary arterial hypertension. MA-PAH exhibits a more severe clinical profile in functional class and hemodynamics compared with idiopathic pulmonary arterial hypertension. Management involves a multifaceted approach, integrating pulmonary vasodilators, cessation of methamphetamine use, and implementing social and rehabilitation programs. These measures aim to enhance patient outcomes and detect potential relapses for timely intervention.

SUMMARY

This review consolidates our understanding of MA-PAH, pinpointing knowledge gaps for future studies. Addressing these gaps is crucial for advancing diagnostic accuracy, unraveling mechanisms, and optimizing treatment for MA-PAH, thereby addressing the evolving landscape of this complex health concern.

Methamphetamine-associated pulmonary arterial hypertension: data from the national biological sample and data repository for pulmonary arterial hypertension (PAH Biobank)

OBJECTIVE

This study compares the clinical and haemodynamic severity of methamphetamine-associated pulmonary arterial hypertension (MA-PAH) with idiopathic pulmonary arterial hypertension (IPAH) and connective tissue-associated pulmonary arterial hypertension (CTD-PAH). It also examines sex differences in clinical and physiological parameters among those with MA-PAH.

DESIGN

This is a cross-sectional study using clinically derived data from the National Biological Sample and Data Repository for Pulmonary Arterial Hypertension (PAH biobank), a US-based registry, to compare clinical and physiological characteristics between males and females with MA-PAH.

POPULATION

The analysis included 1830 patients enrolled in the PAH biobank, with a diagnosis of MA-PAH (n=42), IPAH (n=1073), or CTD-PAH (n=715).

MAIN OUTCOME MEASURES

The study assessed and compared the clinical and haemodynamic parameters of patients with MA-PAH, IPAH and CTD-PAH.

RESULTS

Among the patients analysed, 42 had MA-PAH, with 69.1% being female. There were no statistically significant differences in functional class among patients with MA-PAH, IPAH and CTD-PAH. The per cent predicted 6-min walk distance (6MWD) was comparable between the three groups. Patients with MA-PAH had similar mean pulmonary artery pressure and pulmonary vascular resistance to patients with IPAH but higher compared with patients with CTD-PAH. Male patients with MA-PAH exhibited a worse functional class and lower per cent predicted 6MWD, but no significant differences in haemodynamic findings were observed between the sexes.

CONCLUSION

There were no differences in haemodynamic between MA-PAH and IPAH but we found that MA-PAH differed from CTD-PAH. The study did not find evidence of sex differences in MA-PAH. Further research is necessary to identify risk factors and underlying mechanisms of MA-PAH, particularly considering the increasing prevalence of methamphetamine use. Such investigations will contribute to the development of effective prevention and treatment strategies for this condition.

Associations and relative risks of pulmonary hypertension and lung diseases in individuals with methamphetamine use disorder

OBJECTIVE

Methamphetamine causes considerable short- and long-term adverse health effects. Our aim was to assess the effects of methamphetamine use on pulmonary hypertension and lung diseases at the population level.

METHODS

This population-based retrospective study used data from the Taiwan National Health Insurance Research Database between 2000 and 2018 that included 18,118 individuals with methamphetamine use disorder (MUD) and 90,590 matched participants of the same age and sex without substance use disorder as the non-exposed group. A conditional logistic regression model was used to estimate associations of methamphetamine use with pulmonary hypertension and lung diseases such as lung abscess, empyema, pneumonia, emphysema, pleurisy, pneumothorax, or pulmonary hemorrhage. Incidence rate ratios (IRRs) of pulmonary hypertension and hospitalization due to lung diseases were determined between the methamphetamine group and non-methamphetamine group using negative binomial regression models.

RESULTS

During an 8-year observation period, 32 (0.2%) individuals with MUD and 66 (0.1%) non-methamphetamine participants suffered from pulmonary hypertension, and 2652 (14.6%) individuals with MUD and 6157 (6.8%) non-methamphetamine participants suffered from lung diseases. After adjusting for demographic characteristics and comorbidities, individuals with MUD were 1.78 times (95% confidence interval (CI) = 1.07-2.95) more likely to have pulmonary hypertension and 1.98 times (95% CI = 1.88-2.08) more likely to have a lung disease, especially emphysema, lung abscess, and pneumonia in descending order. Furthermore, compared to the non-methamphetamine group, the methamphetamine group was associated with higher risks of hospitalization caused by pulmonary hypertension and lung diseases. The respective IRRs were 2.79 and 1.67. Individuals with polysubstance use disorder were associated with higher risks of empyema, lung abscess, and pneumonia compared to individuals with MUD alone, with respective adjusted odds ratios of 2.96, 2.21, and 1.67. However, pulmonary hypertension and emphysema did not differ significantly between MUD individuals with or without polysubstance use disorder.

CONCLUSIONS

Individuals with MUD were associated with higher risks of pulmonary hypertension and lung diseases. Clinicians need to ensure that a methamphetamine exposure history is obtained as part of the workup for these pulmonary diseases and provide timely management for this contributing factor.

Investigation of Genes and Proteins Expression Associating Serotonin Signaling Pathway in Lung and Pulmonary Artery Tissues of Dogs with Pulmonary Hypertension Secondary to Degenerative Mitral Valve Disease: The Preliminary Study

Simple Summary

Pulmonary hypertension is an unusual elevation of the blood pressure in pulmonary circulation. In dogs, pulmonary hypertension is commonly occurred as a complication of progressive degenerative mitral valve disease especially in senior small-breed dogs. Previous studies revealed that the serotonin signaling pathway is associated with the pathogenesis of pulmonary hypertension. However, research in dogs was scarce. Therefore, the present study aimed to illustrate the understanding of this point by assessing the expression of the targeted genes and proteins related to the serotonin pathway in lung tissues and pulmonary arteries of dogs. Our results showed that the pattern of gene and protein expression was different in canine lung and pulmonary arteries. The targeted proteins in pulmonary artery tissues of the degenerative mitral valve disease dogs with and without pulmonary hypertension tended to be upregulated. In addition, the expression of these protein was increased in the pneumocytes of the alveolar walls, pulmonary alveolar macrophages, and bronchial epithelial cells. A correlation between the targeted gene and protein expression and the echocardiographic data was also founded. Overall results pointed out that the serotonin pathway in lung and pulmonary artery tissues might have different roles in degenerative mitral disease with and without pulmonary hypertension.

Abstract

Pulmonary hypertension (PH) is defined as an increase in pulmonary vascular pressure. It is one of the most common complications that occur as a result of degenerative mitral valve disease (DMVD) in dogs. Serotonin (5-HT) can trigger the development of PH. Accordingly, this study investigated the changes in the expression of genes and proteins associated with local 5-HT signaling in the lungs and pulmonary arteries (PA) of dogs with PH secondary to DMVD. Lung and PA tissue samples were collected from the cadavers of fourteen small-breed dogs and divided into normal (n = 4), DMVD (n = 5) and DMVD with PH (n = 5) groups. Gene expression (tph1, slc6a4 and htr2a) was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The expression of proteins (TPH-1, SERT, 5-HTR2A, ERK1/2 and pERK1/2) was examined by Western blot analysis and immunohistochemical staining. The results showed that the expression of genes and proteins evaluated by qRT-PCR and Western blot analysis in lung and PA tissues did not differ among groups. However, the expression of proteins related to 5-HT signaling tended to be upregulated in PA tissues from DMVD dogs with and without PH. Immunohistochemical examination revealed the overexpression of these proteins in the DMVD and DMVD with PH groups in lung tissue. These findings suggest a local effect of 5-HT signaling in DMVD dogs with and without PH.

Sex-dependent right ventricular hypertrophic gene changes after methamphetamine treatment in mice

Methamphetamine (MA) abuse is associated with the development of pulmonary arterial hypertension (PAH) and subsequent right ventricular failure. A recent clinical study demonstrated that female sex is a major risk factor for MA-induced PAH. The mechanisms associated with increased prevalence and severity of MA-induced PAH in females are still unclear. We hypothesized that MA may promote changes in gene expression in the right ventricle contributing to the development and/or worsening of PAH in females. Male and female C57BL/6 mice were treated with either MA or vehicle. Right and left ventricular systolic pressures (RVSP and LVSP, respectively) were assessed and tissue samples were collected for gene expression and histology. LVSP and RVSP were not affected by MA in either males or females. Right ventricular hypertrophy was significantly increased by MA in females but it was not affected by MA in males. In the female mice, MA-induced right ventricular hypertrophy was associated with increased expression of brain natriuretic peptide gene and members of the TGF-β receptor signaling pathway such as TGF-β receptor-1, smad3 and smad7. In male mice, there were no changes in right ventricular gene expression. Our results suggest that MA caused right ventricular hypertrophy in female mice, but not in males and that this was associated with an increase in hypertrophic genes. The right ventricular hypertrophy was not dependent on increased RVSP suggesting a direct effect of MA on the right ventricle. If this translates to PAH patients, it might explain the poor outcome observed in MA-associated female PAH patients.

TBHQ Attenuates Neurotoxicity Induced by Methamphetamine in the VTA through the Nrf2/HO-1 and PI3K/AKT Signaling Pathways

Methamphetamine (METH) leads to nervous system toxicity. Long-term exposure to METH results in damage to dopamine neurons in the ventral tegmental area (VTA), and depression-like behavior is a clinical symptom of this toxicity. The current study was designed to investigate whether the antioxidant tertiary butylhydroquinone (TBHQ) can alleviate neurotoxicity through both antioxidative stress and antiapoptotic signaling pathways in the VTA. Rats were randomly divided into a control group, a METH-treated group (METH group), and a METH+TBHQ-treated group (METH+TBHQ group). Intraperitoneal injections of METH at a dose of 10 mg/kg were administered to the rats in the METH and METH+TBHQ groups for one week, and METH was then administered at a dose that increased by 1 mg/kg per week until the sixth week, when the daily dosage reached 15 mg/kg. The rats in the METH+TBHQ group received 12.5 mg/kg TBHQ intragastrically. Chronic exposure to METH resulted in increased immobility times in the forced swimming test (FST) and tail suspension test (TST) and led to depression-like behavior. The production of reactive oxygen species (ROS) and apoptosis levels were increased in the VTA of animals in the METH-treated group. METH downregulated Nrf2, HO-1, PI3K, and AKT, key factors of oxidative stress, and the apoptosis signaling pathway. Moreover, METH increased the caspase-3 immunocontent. These changes were reversed by treatment with the antioxidant TBHQ. The results indicate that TBHQ can enhance Nrf2-induced antioxidative stress and PI3K-induced antiapoptotic effects, which can alleviate METH-induced ROS and apoptosis, and that the crosstalk between Nrf2 and PI3K/AKT is likely the key factor involved in the protective effect of TBHQ against METH-induced chronic nervous system toxicity.

Molecular pathogenesis and current pathology of pulmonary hypertension

Following its initial description over a century ago, pulmonary arterial hypertension (PAH) continues to challenge researchers committed to understanding its pathobiology and finding a cure. The last two decades have seen major developments in our understanding of the genetics and molecular basis of PAH that drive cells within the pulmonary vascular wall to produce obstructive vascular lesions; presently, the field of PAH research has taken numerous approaches to dissect the complex amalgam of genetic, molecular and inflammatory pathways that interact to initiate and drive disease progression. In this review, we discuss the current understanding of PAH pathology and the role that genetic factors and environmental influences share in the development of vascular lesions and abnormal cell function. We also discuss how animal models can assist in elucidating gene function and the study of novel therapeutics, while at the same time addressing the limitations of the most commonly used rodent models. Novel experimental approaches based on application of next generation sequencing, bioinformatics and epigenetics research are also discussed as these are now being actively used to facilitate the discovery of novel gene mutations and mechanisms that regulate gene expression in PAH. Finally, we touch on recent discoveries concerning the role of inflammation and immunity in PAH pathobiology and how they are being targeted with immunomodulatory agents. We conclude that the field of PAH research is actively expanding and the major challenge in the coming years is to develop a unified theory that incorporates genetic and mechanistic data to address viable areas for disease modifying drugs that can target key processes that regulate the evolution of vascular pathology of PAH.

Drug-induced pulmonary arterial hypertension: a primer for clinicians and scientists

Drug-induced pulmonary arterial hypertension (D-PAH) is a form of World Health Organization Group 1 pulmonary hypertension (PH) defined by severe small vessel loss and obstructive vasculopathy, which leads to progressive right heart failure and death. To date, 16 different compounds have been associated with D-PAH, including anorexigens, recreational stimulants, and more recently, several Food and Drug Administration-approved medications. Although the clinical manifestation, pathology, and hemodynamic profile of D-PAH are indistinguishable from other forms of pulmonary arterial hypertension, its clinical course can be unpredictable and to some degree dependent on removal of the offending agent. Because only a subset of individuals develop D-PAH, it is probable that genetic susceptibilities play a role in the pathogenesis, but the characterization of the genetic factors responsible for these susceptibilities remains rudimentary. Besides aggressive treatment with PH-specific therapies, the major challenge in the management of D-PAH remains the early identification of compounds capable of injuring the pulmonary circulation in susceptible individuals. The implementation of pharmacovigilance, precision medicine strategies, and global warning systems will help facilitate the identification of high-risk drugs and incentivize regulatory strategies to prevent further outbreaks of D-PAH. The goal for this review is to inform clinicians and scientists of the prevalence of D-PAH and to highlight the growing number of common drugs that have been associated with the disease.

Suppression of nuclear factor erythroid‑2‑related factor 2‑mediated antioxidative defense in the lung injury induced by chronic exposure to methamphetamine in rats

The imbalance between oxidative stress and antioxidant defense is important in the pathogenesis of lung diseases. Nuclear factor erythroid‑2‑related factor 2 (Nrf2) is a key transcriptional factor that regulates the antioxidant response. The purpose of the present study was to investigate whether Nrf2‑mediated antioxidative defense is involved in methamphetamine (MA)‑induced lung injury in rats. Following establishment of chronic MA toxicity in rats, Doppler ultrasonic detection was used to measure the changes of physiological indexes, followed by hematoxylin and eosin staining, ELISA and western blot analysis. MA was demonstrated to increase the heart rate and peak blood flow velocity of pulmonary arterial valves and to decrease the survival rate of rats, and resulted in lung injury characterized by perivascular exudates, airspace edema, slight hemorrhage and inflammatory cell infiltration. MA significantly inhibited the expression of nuclear Nrf2 protein and its target genes (glutamate‑cysteine ligase catalytic subunit C and heme oxygenase‑1), and dose‑dependently reduced glutathione (GSH) levels and the ratio of GSH/oxidized glutathione, accompanied by increases in reactive oxygen species (ROS) levels in rat lungs. Linear regression analysis revealed that there was a positive correlation between lung ROS level and lung injury indexes. These findings suggested that chronic exposure to MA led to lung injury by suppression of Nrf2‑mediated antioxidative defense, suggesting that Nrf2 may be an important therapeutic target for MA‑induced chronic lung toxicity.

TBHQ Alleviated Endoplasmic Reticulum Stress-Apoptosis and Oxidative Stress by PERK-Nrf2 Crosstalk in Methamphetamine-Induced Chronic Pulmonary Toxicity

Methamphetamine (MA) leads to cardiac and pulmonary toxicity expressed as increases in inflammatory responses and oxidative stress. However, some interactions may exist between oxidative stress and endoplasmic reticulum stress (ERS). The current study is designed to investigate if both oxidative stress and ERS are involved in MA-induced chronic pulmonary toxicity and if antioxidant tertiary butylhydroquinone (TBHQ) alleviated ERS-apoptosis and oxidative stress by PERK-Nrf2 crosstalk. In this study, the rats were randomly divided into control group, MA-treated group (MA), and MA plus TBHQ-treated group (MA + TBHQ). Chronic exposure to MA resulted in slower growth of weight and pulmonary toxicity of the rats by increasing the pulmonary arterial pressure, promoting the hypertrophy of right ventricle and the remodeling of pulmonary arteries. MA inhibited the Nrf2-mediated antioxidative stress by downregulation of Nrf2, GCS, and HO-1 and upregulation of SOD2. MA increased GRP78 to induce ERS. Overexpression and phosphorylation of PERK rapidly phosphorylated eIF2α, increased ATF4, CHOP, bax, caspase 3, and caspase 12, and decreased bcl-2. These changes can be reversed by antioxidant TBHQ through upregulating expression of Nrf2. The above results indicated that TBHQ can alleviate MA-induced oxidative stress which can accelerate ERS to initiate PERK-dependent apoptosis and that PERK/Nrf2 is likely to be the key crosstalk between oxidative stress and ERS in MA-induced chronic pulmonary toxicity.

Amphetamines promote mitochondrial dysfunction and DNA damage in pulmonary hypertension

Amphetamine (AMPH) or methamphetamine (METH) abuse can cause oxidative damage and is a risk factor for diseases including pulmonary arterial hypertension (PAH). Pulmonary artery endothelial cells (PAECs) from AMPH-associated-PAH patients show DNA damage as judged by γH2AX foci and DNA comet tails. We therefore hypothesized that AMPH induces DNA damage and vascular pathology by interfering with normal adaptation to an environmental perturbation causing oxidative stress. Consistent with this, we found that AMPH alone does not cause DNA damage in normoxic PAECs, but greatly amplifies DNA damage in hypoxic PAECs. The mechanism involves AMPH activation of protein phosphatase 2A, which potentiates inhibition of Akt. This increases sirtuin 1, causing deacetylation and degradation of HIF1α, thereby impairing its transcriptional activity, resulting in a reduction in pyruvate dehydrogenase kinase 1 and impaired cytochrome c oxidase 4 isoform switch. Mitochondrial oxidative phosphorylation is inappropriately enhanced and, as a result of impaired electron transport and mitochondrial ROS increase, caspase-3 is activated and DNA damage is induced. In mice given binge doses of METH followed by hypoxia, HIF1α is suppressed and pulmonary artery DNA damage foci are associated with worse pulmonary vascular remodeling. Thus, chronic AMPH/METH can induce DNA damage associated with vascular disease by subverting the adaptive responses to oxidative stress.

Fluoxetine protects against methamphetamine‑induced lung inflammation by suppressing oxidative stress through the SERT/p38 MAPK/Nrf2 pathway in rats

Methamphetamine (MA) abuse is a major public health and safety concern throughout the world and a growing burden on healthcare costs. The purpose of the present study was to investigate the protective effect of fluoxetine against MA‑induced chronic pulmonary inflammation and to evaluate the potential role of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidative stress. Wistar rats were divided into control, MA and two fluoxetine‑treated groups. Rats in the MA and the two fluoxetine‑treated groups were treated daily with intraperitoneal injection of 10 mg/kg MA twice daily. Rats in the two fluoxetine‑treated groups were injected intragastrically with fluoxetine (2 and 10 mg/kg) once daily, respectively. After 5 weeks, the rats were euthanized and hematoxylin and eosin staining, immunohistochemistry, western blot analysis and redox assay were performed. It was demonstrated that chronic exposure to MA can induce pulmonary inflammation in rats, with the symptoms of inflammatory cell infiltration, crowded lung parenchyma, thickened septum and a reduced number of alveolar sacs. Fluoxetine attenuated pulmonary inflammation and the expression of interleukin‑6 and tumor necrosis factor‑α in rat lungs. Fluoxetine inhibited MA‑induced increases in the expression levels of serotonin transporter (SERT) and p‑p38 mitogen‑activated protein kinase (MAPK), and reversed the MA‑induced decrease in nuclear Nrf2 and human heme oxygenase‑1 in lungs. Fluoxetine at 10 mg/kg significantly reversed the reduced glutathione (GSH) level, the ratio of GSH/oxidized glutathione, and the reactive oxygen species level in rat lungs from the MA group. These findings suggested that fluoxetine, a SERT inhibitor, has a protective effect against MA‑induced lung inflammation by suppressing oxidative stress through the SERT/p38 MAPK/Nrf2 pathway in rats.

High-mesembrine Sceletium extract (Trimesemine™) is a monoamine releasing agent, rather than only a selective serotonin reuptake inhibitor

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts from and alkaloids contained in plants in the genus Sceletium have been reported to inhibit ligand binding to serotonin transporter. From this, the conclusion was made that Sceletium products act as selective serotonin-reuptake inhibitors. However, other mechanisms which may similarly result in the anxiolytic or anti-depressant effect ascribed to Sceletium, such as monoamine release, have not been investigated.

AIMS OF THE STUDY

The current study investigated simultaneously and at two consecutive time points, the effect of high-mesembrine Sceletium extract on both monoamine release and serotonin reuptake into both human astrocytes and mouse hippocampal neurons, as well as potential inhibitory effects on relevant enzyme activities.

MATERIALS AND METHODS

Human astrocytes and mouse hippocampal cells were treated with citalopram or Sceletium extract for 15 and 30min, after which protein expression levels of serotonin transporter (SERT) and vesicular monoamine transporter-2 (VAMT-2) was assessed using fluorescent immunocytochemistry and digital image analysis. Efficacy of inhibition of acetylcholinesterase (AChE) and monoamine oxidate-A (MAO-A) activity were assessed using the Ellman and Olsen methods (and appropriate controls) respectively.

RESULTS

We report the first investigation of mechanism of action of Sceletium extract in the context of serotonin transport, release and reuptake in a cellular model. Cell viability was not affected by Sceletium treatment. High-mesembrine Sceletium extract down-regulated SERT expression similarly to citalopram. In addition, VMAT-2 was upregulated significantly in response to Sceletium treatment. The extract showed only relatively mild inhibition of AChE and MAO-A.

CONCLUSIONS

We conclude that the serotonin reuptake inhibition activity ascribed to the Sceletium plant, is a secondary function to the monoamine-releasing activity of high-mesembrine Sceletium extract (Trimesemine(TM)).

Perioperative management in the patient with substance abuse

Drug and alcohol use is a pervasive problem in the general population and in those requiring anesthesia for an operation. History and screening can help delineate those who may be acutely intoxicated or chronic drug and alcohol users. Both acute intoxication and chronic abuse of these substances present challenges for anesthetic management during and after an operation. The clinician should be aware of problems that may be encountered during any part of anesthesia or postoperative care.