Chronic toxicity of methamphetamine: Oxidative remodeling of pulmonary arteries.

Methamphetamine (MA) has a high uptake in lung, but the precise mechanism of MA-induced lung toxicity remains unclear. The aim of this study is to investigate the role of MA abuse in remodeling of pulmonary arteries and to explore the possible correlation of the association of the remodeling with the redox imbalance in pulmonary arterial smooth muscle cells (PASMCs). Wistar rats were randomly divided into control group and MA group for the experimental study. We employed H&E staining, western blot, immunofluorescence, knockdown, flow in our experimental approach. Our studies shows that chronic exposure to MA led to weight loss, increased pulmonary arterial pressure, hypertrophy of right ventricle and remodeling of pulmonary arterial wall of rats. Our cell culture study with PASMCs indicates that MA significantly induced the imbalance between proliferation and apoptosis by upregulating the level of PCNA, Bcl-2 and reduction in the expression of BAX and Caspase 3. MA markedly prevented the nuclear translocation of Nrf2 to inhibit antioxidation. The knockdown of Nrf2 expression using siRNA significantly elevated the expression of SOD2/GCS and the production of ROS in PASMCs and even scaled up the amount of PASMCs induced by MA. Linear regression analysis showed that knockdown of Nrf2 promoted the positive correlation of relative ROS level with proliferation of PASMCs. Therefore, chronic exposure to MA induces pulmonary arterial remodeling by Nrf2-mediated imbalance of redox system to aggravate oxidative stress, and Nrf2 is a possible target for the treatment of MA-lung toxicity.

Concurrence of autophagy with apoptosis in alveolar epithelial cells contributes to chronic pulmonary toxicity induced by methamphetamine.

OBJECTIVES: Methamphetamine (MA) abuse evokes pulmonary toxicity. The aim of our study is to investigate if autophagy is induced by MA and if autophagy-initiated apoptosis in alveolar epithelial cells is involved in MA-induced chronic pulmonary toxicity. MATERIALS AND METHODS: The rats in Control group and MA group were tested by Doppler and HE staining. The alveolar epithelial cells were treated with MA, following by western blot, RT-PCR and immunofluorescence assay. RESULTS: Chronic exposure to MA resulted in lower growth ratio of weight and in higher heart rate and peak blood flow velocity of the main pulmonary artery of rats. MA induced infiltration of inflammatory cells in lungs, more compact lung parenchyma, thickened alveolar septum and reduction in the number of alveolar sacs. In alveolar epithelial cells, the autophagy marker LC3 and per cent of cells containing LC3-positive autophagosome were significantly increased. MA dose dependently suppressed the phosphorylation of mTOR to inactivate mTOR, elicited autophagy regulatory proteins LC3 and Beclin-1, accelerated the transformation from LC3 I to LC3 II and initiated apoptosis by decreasing Bcl-2 and increasing Bax, Bax/Bcl-2 and cleaved Caspase 3. The above results suggest that sustained autophagy was induced by long-term exposure to MA and that the increased Beclin-1 autophagy initiated apoptosis in alveolar epithelial cells. CONCLUSIONS: Concurrence of autophagy with apoptosis in alveolar epithelial cells contributes to chronic pulmonary toxicity induced by MA.

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.