N-acetyl-L-cysteine protects against cadmium-induced neuronal apoptosis by inhibiting ROS-dependent activation of Akt/mTOR pathway in mouse brain

Medical and Dietary Uses of N-Acetylcysteine

N-acetylcysteine (NAC), a plant antioxidant naturally found in onion, is a precursor to glutathione. It has been used as a drug since the 1960s and is listed on the World Health Organization (WHO) Model List of Essential Medicines as an antidote in poisonings. There are numerous other uses or proposed uses in medicine that are still in preclinical and clinical investigations. NAC is also used in food supplements and cosmetics. Despite its abundant use, there are projections that the NAC global market will grow in the next five years; therefore, the purpose of this work is to provide a balanced view of further uses of NAC as a dietary supplement. Although NAC is considered a safe substance, the results among clinical trials are sometimes controversial or incomplete, like for many other antioxidants. More clinical trials are underway that will improve our understanding of NAC applicability.

Cadmium Exposure Impairs Cognition and Olfactory Memory in Male C57BL/6 Mice

Cadmium (Cd) is a heavy metal of high interest to the superfund initiative. Recent epidemiology studies have suggested a possible association between Cd exposure and cognitive as well as olfactory impairments in humans. However, studies in animal models are needed to establish a direct causal relationship between Cd exposure and impairments in cognition and olfaction. This study aims to investigate the toxic effect of Cd on cognition and olfactory function in mice. One group of 8-week-old C57BL/6 male mice was exposed to 3 mg/l Cd (in the form of CdCl2) through drinking water for 20 weeks for behavior tests and final blood Cd concentration analysis. The behavior tests were conducted before, during, and after Cd exposure to analyze the effects of Cd on cognition and olfactory function. Upon completion of behavior tests, blood was collected to measure final blood Cd concentration. Two additional groups of mice were similarly exposed to Cd for 5 or 13 weeks for peak blood Cd concentration measurement. The peak blood Cd concentration was 2.125-2.25 μg/l whereas the final blood Cd concentration was 0.18 μg/l. At this exposure level, Cd impaired hippocampus-dependent learning and memory in novel object location test, T-maze test, and contextual fear memory test. It also caused deficits in short-term olfactory memory and odor-cued olfactory learning and memory. Results in this study demonstrate a direct relationship between Cd exposure and cognitive as well as olfactory impairments in an animal model.

Endoplasmic reticulum stress induces apoptosis of arginine vasopressin neurons in central diabetes insipidus via PI3K/Akt pathway

Aims

Central diabetes insipidus (CDI), a typical complication caused by pituitary stalk injury, often occurs after surgery, trauma, or tumor compression around hypothalamic structures such as the pituitary stalk and optic chiasma. CDI is linked to decreased arginine vasopressin (AVP) neurons in the hypothalamic supraoptic nucleus and paraventricular nucleus, along with a deficit in circulating AVP and oxytocin. However, little has been elucidated about the changes in AVP neurons in CDI. Hence, our study was designed to understand the role of several pathophysiologic changes such as endoplasmic reticulum (ER) stress and apoptosis of AVP neurons in CDI.

Methods

In a novel pituitary stalk electric lesion (PEL) model to mimic CDI, immunofluorescence and immunoblotting were used to understand the underlying regulatory mechanisms.

Results

We reported that in CDI condition, generated by PEL, ER stress induced apoptosis of AVP neurons via activation of the PI3K/Akt and ERK pathways. Furthermore, application of N‐acetylcysteine protected hypothalamic AVP neurons from ER stress‐induced apoptosis through blocking the PI3K/Akt and ERK pathways.

Conclusion

Our findings showed that AVP neurons underwent apoptosis induced by ER stress, and ER stress might play a vital role in CDI condition through the PI3K/Akt and ERK pathways.

Lanthanum chloride induces autophagy in rat hippocampus through ROS-mediated JNK and AKT/mTOR signaling pathways

Lanthanum (La) can cause central nervous system damage in rats and lead to learning and memory impairment, but the relevant mechanisms have not been fully elucidated.

Cadmium results in accumulation of autophagosomes-dependent apoptosis through activating Akt-impaired autophagic flux in neuronal cells

Environmental exposure to cadmium (Cd) links to neurodegenerative disorders. Autophagy plays an important role in controlling cell survival/death. However, how autophagy contributes to Cd's neurotoxicity remains enigmatic. Here, we show that Cd induced significant increases in autophagosomes with a concomitant elevation of LC3-II and p62 in PC12 cells and primary neurons. Using autophagy inhibitor 3-MA, we demonstrated that Cd-increased autophagosomes contributed to neuronal apoptosis. Impairment of Cd on autophagic flux was evidenced by co-localization of mCherry and GFP tandem-tagged LC3 puncta in the cells. This is further supported by the findings that administration of chloroquine (CQ) potentiated the basic and Cd-elevated LC3-II and p62 levels, autophagosome accumulation and cell apoptosis, whereas rapamycin relieved the effects in the cells in response to Cd. Subsequently, we noticed that Cd evoked the phosphorylation of Akt and BECN1. Silencing BECN1 and especially expression of mutant BECN1 (Ser295A) attenuated Cd-increased autophagosomes and cell death. Of note, inhibition of Akt with Akt inhibitor X, or ectopic expression of dominant negative Akt (dn-Akt), in the presence or absence of 3-MA, significantly alleviated Cd-triggered phosphorylation of Akt and BECN1, autophagosomes, and apoptosis. Importantly, we found that Cd activation of Akt functioned in impairing autophagic flux. Collectively, these results indicate that Cd results in accumulation of autophagosomes-dependent apoptosis through activating Akt-impaired autophagic flux in neuronal cells. Our findings underscore that inhibition of Akt to improve autophagic flux is a promising strategy against Cd-induced neurotoxicity and neurodegeneration.

Maduramicin induces cardiac muscle cell death by the ROS-dependent PTEN/Akt-Erk1/2 signaling pathway

Maduramicin (Mad), a polyether ionophore antibiotic, has been reported to be toxic to animals and humans because of being used at high doses or for long time, resulting in heart failure. However, the toxic mechanism of Mad in cardiac muscle cells is not well understood. Here, we show that Mad induced cell viability reduction and apoptosis in cardiac-derived H9c2, HL-1 cells, primary cardiomyocytes, and murine cardiac muscles, which was because of the inhibition of extracellular-signal-regulated kinase 1/2 (Erk1/2). Expression of constitutively active mitogen-activated protein kinase kinase 1 (MKK1) attenuated Mad-induced cell death in H9c2 cells, whereas silencing Erk1/2 or ectopic expression of dominant negative MKK1 strengthened Mad-induced cell death. Moreover, we found that both phosphatase and tensin homolog on chromosome 10 (PTEN) and protein kinase B (Akt) were implicated in the regulation of Erk1/2 inactivation and apoptosis in the cells and tissues exposed to Mad. Overexpression of dominant negative PTEN and/or constitutively active Akt, or constitutively active Akt and/or constitutively active MKK1 rescued the cells from Mad-induced dephosphorylated-Erk1/2 and cell death. Furthermore, Mad-induced reactive oxygen species (ROS) activated PTEN and inactivated Akt-Erk1/2 contributing to cell death, as N-acetyl- L-cysteine ameliorated the event. Taken together, the results disclose that Mad inhibits Erk1/2 via ROS-dependent activation of PTEN and inactivation of Akt, leading to cell death in cardiac muscle cells. Our findings suggest that manipulation of the ROS-PTEN-Akt-Erk1/2 pathway may be a potential approach to prevent Mad-induced cardiotoxicity.

Protective effects of zinc and N-acetyl-L-cysteine supplementation against cadmium induced erythrocyte cytotoxicity in Arbor Acres broiler chickens (Gallus gallus domesticus)

Cadmium (Cd) is one of the most toxic metals released into the environment. Here, we investigated the protective role of Zn²⁺ and/or N-acetyl-L-cysteine (NAC) against Cd cytotoxicity in the erythrocytes of Arbor Acres (AA) broiler chickens. Four hundred one-day-old AA chickens were divided into 12 groups for in vitro and in vivo studies. Zn²⁺ and/or NAC was given to the Cd exposed AA chickens to assess their protective roles. This was accomplished by investigating nuclear morphological abnormalities, oxidative stress (SOD, CAT, GPx, GSH and T-AOC), cell apoptosis, ROS accumulation and mitochondrial membrane potential (MMP). Results showed that Cd led to dose- and time-dependent cytotoxicity in the erythrocytes of AA chickens characterized by morphological abnormalities, nucleus damage, increased apoptosis rate and antioxidants depletion. Zn²⁺ or NAC significantly decreased the erythrocyte apoptosis, ROS production and mitochondrial membrane depolarization caused by Cd. SOD, CAT, GPx, GSH and T-AOC activities significantly decreased both in serum and erythrocytes of Cd exposed AA chickens. The supplementation with Zn²⁺ or NAC alleviated Cd induced oxidative stress through promoting SOD or GPx/GSH activities respectively. NAC presented a better role in reducing apoptosis, improving antioxidant activities more than Zn²⁺ in vitro. The combined use of Zn²⁺ and NAC enhanced cytoprotection in Cd exposed erythrocytes of AA chickens compared to Zn²⁺ or NAC alone. In conclusion, Zn²⁺ and NAC exerted remarkable protective roles in Cd exposed erythrocytes of AA chickens by inhibiting cell apoptosis and oxidative stress, and this provides a promising approach to antagonize Cd poisoning in poultry.

Copper induces oxidative stress and apoptosis through mitochondria-mediated pathway in chicken hepatocytes

The aim of this study was to investigate the effects of excessive copper (Cu)-induced cytotoxicity on oxidative stress and mitochondrial apoptosis in chicken hepatocytes. Chicken hepatocytes were cultured in medium in the absence and presence of copper sulfate (CuSO₄) (10, 50, 100 μM), in N-acetyl-L-cysteine (NAC) (1 mM), and the combination of CuSO₄ and NAC for 24 h. Morphologic observation and function, reactive oxygen species (ROS) level, antioxidant indices, nitric oxide (NO) content, mitochondrial membrane potential (MMP), and apoptosis-related mRNA and protein levels were determined. These results indicated that excessive Cu could induce release of intracellular lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT); increase levels of ROS, superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), lipid peroxidation (LPO), and NO; decrease glutathione (GSH) content and MMP; upregulated Bak1, Bax, CytC, and Caspase3 mRNA and protein expression, inhibited Bcl2 mRNA and protein expression, and induced cell apoptosis in a dose effect. The Cu-caused changes of all above factors were alleviated by treatment with NAC. These results suggested that excessive Cu could induce oxidative stress and apoptosis via mitochondrial pathway in chicken hepatocytes.

Rutin hydrate ameliorates cadmium chloride-induced spatial memory loss and neural apoptosis in rats by enhancing levels of acetylcholine, inhibiting JNK and ERK1/2 activation and activating mTOR signalling

This study aimed at studying the potential neuroprotective effect of Rutin hydrate (RH) alone or in conjugation with α-tocopherol against cadmium chloride (CdCl₂)-induced neurotoxicity and cognitive impairment in rats and to investigate the mechanisms of action. Rats intoxicated with CdCl₂ were treated with the vehicle, RH, α-tocopherol or combined treatment were examined, and compared to control rats received vehicle or individual doses of either drug. Data confirmed that RH improves spatial memory function by increasing acetylcholine availability, boosting endogenous antioxidant potential, activating cell survival and inhibiting apoptotic pathways, an effect that is more effective when RH was conjugated with α-tocopherol. Mechanism of RH action includes activation of PP2A mediated inhibiting of ERK1/2 and JNK apoptotic pathways and inhibition of PTEN mediated activation of mTOR survival pathway. In conclusion, RH affords a potent neuroprotection against CdCl₂-induced brain damage and memory dysfunction and co-administration of α-tocopherol enhances its activity.

Selenium and zinc: Two key players against cadmium-induced neuronal toxicity

Cadmium (Cd), a worldwide occupational pollutant, is an extremely toxic heavy metal, capable of damaging several organs, including the brain. Its toxicity has been related to neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The neurotoxic potential of Cd has been attributed to the changes induced in the brain enzyme network involved in counteracting oxidative stress. On the other hand, it is also known that trace elements, such as zinc (Zn) and selenium (Se), required for optimal brain functions, appears to have beneficial effects on the prevention of Cd intoxication. Based on this protective effect of Zn and Se, we aimed to investigate whether these elements could protect neuronal cells from Cd-induced excitotoxicity. The experiments, firstly carried out on SH-SY5Y catecholaminergic neuroblastoma cell line, demonstrated that the treatment with 10 μM cadmium chloride (CdCl₂) for 24 h caused significant modifications both in terms of oxidative stress and neuronal sprouting, triggered by endoplasmic reticulum (ER) stress. The evaluation of the effectiveness of 50 μM of zinc chloride (ZnCl₂) and 100 nM sodium selenite (Na₂SeO₃) treatments showed that both elements were able to attenuate the Cd-dependent neurotoxicity. However, considering that following induction with retinoic acid (RA), the neuroblastoma cell line undergoes differentiation into a cholinergic neurons, our second aim was to verify the zinc and selenium efficacy also in this neuronal phenotype. Our data clearly demonstrated that, while zinc played a crucial role on neuroprotection against Cd-induced neurotoxicity independently from the cellular phenotype, selenium is ineffective in differentiated cholinergic cells, supporting the notion that the molecular events occurring in differentiated SH-SY5Y cells are critical for the response to specific stimuli.

The Influence of Heavy Metals and Trace Elements on Comatose Patients with Severe Traumatic Brain Injury in the First Week of Admission

Purpose

The aim of this study is to investigate the possible role of heavy metals (lead and cadmium) and imbalance of trace elements (chromium, iron, zinc, copper, and manganese) in death among patients with severe traumatic brain injury.

Material and Methods

A case-control study was conducted with 64 comatose patients with severe TBI, in the Department of Anesthesiology and Reanimation, Ibn Sina University Hospital and Hospital of Specialties in Rabat, Morocco; 22 healthy volunteers were recruited in Blood Transfusion Center of Rabat. Blood samples were collected from TBI patients, in the first week (3h after admission and each 48h during one week) and from healthy volunteers one time. Concentration of heavy metals and trace elements in serum was determined by electrochemical atomic absorption spectrometry. Statistical analysis was performed using Statistical software (SPSS) and the cases and controls were compared using the Mann–Whitney U test and Student's t-test for cadmium according to gender and final evolution. A P-value <0.05 was considered to be statistically significant.

Results

Our data showed that the difference of heavy metals concentration (lead and cadmium) between patients and healthy subjects was not statistically significant. However, the difference of some trace elements concentration (iron, copper, chromium, and selenium) between patients and healthy subjects was statistically significant. According to the final evolution, the concentration of manganese was higher in dead patients and statistically significant (p = 0.04) for heavy metals; the concentration of lead was not statistically significant while the concentration in cadmium was statistically significant (p = 0.004). By sex, lead and cadmium were statistically significant, respectively p = 0.02, p = 0.001, and cadmium was higher in women, while lead was higher in men.

Conclusion

Among all studied heavy metals (lead and cadmium) and trace elements (iron, zinc, copper, selenium, chromium, and manganese), manganese and cadmium may play a role in the death of patients from severe traumatic brain injury.

Bioengineered intestinal muscularis complexes with long-term spontaneous and periodic contractions

Although critical for studies of gut motility and intestinal regeneration, the in vitro culture of intestinal muscularis with peristaltic function remains a significant challenge. Periodic contractions of intestinal muscularis result from the coordinated activity of smooth muscle cells (SMC), the enteric nervous system (ENS), and interstitial cells of Cajal (ICC). Reproducing this activity requires the preservation of all these cells in one system. Here we report the first serum-free culture methodology that consistently maintains spontaneous and periodic contractions of murine and human intestinal muscularis cells for months. In this system, SMC expressed the mature marker myosin heavy chain, and multipolar/dipolar ICC, uniaxonal/multipolar neurons and glial cells were present. Furthermore, drugs affecting neural signals, ICC or SMC altered the contractions. Combining this method with scaffolds, contracting cell sheets were formed with organized architecture. With the addition of intestinal epithelial cells, this platform enabled up to 11 types of cells from mucosa, muscularis and serosa to coexist and epithelial cells were stretched by the contracting muscularis cells. The method constitutes a powerful tool for mechanistic studies of gut motility disorders and the functional regeneration of the engineered intestine.

N-acetylcysteine attenuates the cuprizone-induced behavioral changes and oligodendrocyte loss in male C57BL/7 mice via its anti-inflammation actions

Previous animal studies have linked white matter damage to certain schizophrenia-like behaviors in cuprizone (CPZ)-exposed mouse. Mitochondrial dysfunction, oxidative stress, neuroinflammation, and oligodendrocyte loss coexist in the brain of such mice. The aim of this study was to examine effects of the antioxidant N-acetylcysteine (NAC) on CPZ-induced behavioral changes and concurrent oligodendrocyte loss, oxidative stress, and neuroinflammation in these animals. Male C57BL/6 mice were given intraperitoneal saline or NAC at doses of 100, 200, and 400 mg/kg/day for 2 weeks; animals were fed a CPZ-containing diet (0.2%, w/w) during days 5-14. During days 15-17, the mice were examined in open-field, social recognition, and Y-maze tests (1 test per day). Six mice in each group were then used for biochemical and enzyme-linked immunosorbent assay analyses, while the remaining animals were used for immunohistochemical and immunofluorescence staining. The mice exposed to CPZ for 10 days showed significantly lower spontaneous alternation in the Y-maze, lower activity of total superoxide dismutase, and glutathione peroxidase, but higher levels of malondialdehyde in the cerebral cortex and hippocampus, elevated concentrations of interleukin-1β and tumor necrosis factor-α in the brain regions mentioned above and caudate putamen, and a decreased number of mature oligodendrocytes, but increased number of microglia in all the brain regions examined. These changes, however, were not seen or effectively alleviated in NAC-treated mice at all three doses. These results demonstrate that NAC protected mature oligodendrocytes against the toxic effects of CPZ, likely via its antioxidant and anti-inflammatory actions.

N-acetylcysteine alleviates cadmium-induced placental endoplasmic reticulum stress and fetal growth restriction in mice

Cadmium (Cd) is a developmental toxicant that induces fetal growth restriction (FGR). Placental endoplasmic reticulum (ER) stress is associated with FGR. This study investigated the effects of N-acetylcysteine (NAC) on Cd-induced placental ER stress and FGR. Pregnant mice were intraperitoneally injected with CdCl₂ daily from gestational day (GD)13 to GD17. As expected, Cd reduced fetal weight and crown-rump length. Cd decreased the internal space of blood vessels in the placental labyrinth layer and inhibited placental cell proliferation. Several genes of growth factors, such as Vegf-a, placental growth factor, Igf1 and Igf1r, and several genes of nutrient transport pumps, such as Glut1, Fatp1 and Snat2, were down-regulated in placenta of Cd-treated mice. Moreover, Cd evoked placental ER stress. Of interest, NAC alleviated Cd-induced FGR. Additional experiment showed that NAC inhibited Cd-induced impairment of placental development and placental ER stress. Therefore, NAC may be exploited for prevention of Cd-induced placental insufficiency and FGR.

A Perfect sTORm: The Role of the Mammalian Target of Rapamycin (mTOR) in Cerebrovascular Dysfunction of Alzheimer's Disease: A Mini-Review

Cerebrovascular dysfunction is detected prior to the onset of cognitive and histopathological changes in Alzheimer's disease (AD). Increasing evidence indicates a critical role of cerebrovascular dysfunction in the initiation and progression of AD. Recent studies identified the mechanistic/mammalian target of rapamycin (mTOR) as a critical effector of cerebrovascular dysfunction in AD. mTOR has a key role in the regulation of metabolism, but some mTOR-dependent mechanisms are uniquely specific to the regulation of cerebrovascular function. These include the regulation of cerebral blood flow, blood-brain barrier integrity and maintenance, neurovascular coupling, and cerebrovascular reactivity. This article examines the available evidence for a role of mTOR-driven cerebrovascular dysfunction in the pathogenesis of AD and of vascular cognitive impairment and dementia (VCID) and highlights the therapeutic potential of targeting mTOR and/or specific downstream effectors for vasculoprotection in AD, VCID, and other age-associated neurological diseases with cerebrovascular etiology.

Molecular signaling cascades involved in nonmelanoma skin carcinogenesis

Nonmelanoma skin cancer (NMSC) is the most common cancer worldwide and the incidence continues to rise, in part due to increasing numbers in high-risk groups such as organ transplant recipients and those taking photosensitizing medications. The most significant risk factor for NMSC is ultraviolet radiation (UVR) from sunlight, specifically UVB, which is the leading cause of DNA damage, photoaging, and malignant transformation in the skin. Activation of apoptosis following UVR exposure allows the elimination of irreversibly damaged cells that may harbor oncogenic mutations. However, UVR also activates signaling cascades that promote the survival of these potentially cancerous cells, resulting in tumor initiation. Thus, the UVR-induced stress response in the skin is multifaceted and requires coordinated activation of numerous pathways controlling DNA damage repair, inflammation, and kinase-mediated signal transduction that lead to either cell survival or cell death. This review focuses on the central signaling mechanisms that respond to UVR and the subsequent cellular changes. Given the prevalence of NMSC and the resulting health care burden, many of these pathways provide promising targets for continued study aimed at both chemoprevention and chemotherapy.

Antagonistic effects of selenium on cadmium-induced apoptosis by restoring the mitochondrial dynamic equilibrium and energy metabolism in chicken spleens

The aim of this study was to investigate the mechanism of cadmium-induced apoptosis in chicken spleens and the antagonistic effects of selenium. We duplicated the selenium-cadmium interaction model and examined the expression of apoptosis-, immune-, mitochondrial dynamics- and energy metabolism-related genes. The results demonstrated that after treatment with cadmium, the frequency of apoptosis was significantly increased, and the morphological characteristics of apoptosis were observed. The expression of pro-apoptotic genes was increased, and that of anti-apoptotic genes was decreased. The mRNA levels of tumor necrosis factor-α and interlenkin-1β were observably increased, but the interlenkin-2 and interferon-γ levels were markedly decreased. Furthermore, the mRNA and protein levels of dynamin-related protein 1 and mitochondrial fission factor were significantly enhanced, whereas mitofusin 1, mitofusin 2, and optic atrophy 1 were markedly decreased. The expression of hexokinase 1, hexokinase 2, aconitase 2, lactate dehydrogenase A, lactate dehydrogenase B, succinatedehydrogenase B, pyruvate kinase and phosphofructokinase were also reduced. Selenium supplements remarkably attenuated cadmium-induced effects (p < 0.05). Based on the above results, conclude that the cadmium treatment promoted a mitochondrial dynamic imbalance and reduced energy metabolism, leading to apoptosis and immune dysfunction in chicken spleens, and selenium had an antagonistic effect on Cd-induced apoptosis.

HSP90 inhibitor 17-DMAG exerts anticancer effects against gastric cancer cells principally by altering oxidant-antioxidant balance

Heat shock protein 90 (HSP90) stabilizes numerous oncoproteins and, therefore, its inhibition has emerged as a promising antineoplastic strategy for diverse malignancies. In this study, we determined the therapeutic effects and mechanisms of action of a specific HSP90 inhibitor, 17-dimethylamino-ethylamino-17-demethoxygeldanamycin (17-DMAG), in gastric cancer cell lines (AGS, SNU-1, and KATO-III), patient-derived tissues, and a mouse xenograft model. 17-DMAG exerted anticancer effects against gastric cancer cells, manifested by significantly decreased proliferation rates (P < 0.05) and increased expression of apoptotic markers. Flow cytometry using dichlorofluorescein (DCF) diacetate revealed that 17-DMAG dose-dependently increases reactive oxygen species (ROS) levels in gastric cancer cells. Inhibition of ROS by N-acetyl-L-cysteine (NAC) abrogated the proapoptotic effects of 17-DMAG, as demonstrated by the decreased expression of proapoptotic proteins. In addition, 17-DMAG dose- and time-dependently reduced the expression of antioxidants such as catalase and glutathione peroxidase (GPx). Moreover, 17-DMAG reduced the expression of nuclear respiratory factor (NRF)-1 and NRF-2, and prevented them from migrating from the cytoplasm to the nucleus dose-dependently. Finally, in a nude mouse xenograft model, the shrinkage of tumors was more prominent in mice treated with 17-DMAG than in control mice (P < 0.05). Taken altogether, our results suggest that 17-DMAG exerts potent antineoplastic activity against gastric cancer cells primarily by promoting ROS generation and suppressing antioxidant enzyme activities.

Celastrol ameliorates Cd-induced neuronal apoptosis by targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway

Celastrol, a plant-derived triterpene, has neuroprotective benefit in the models of neurodegenerative disorders that are characterized by overproduction of reactive oxygen species (ROS). Recently, we have reported that cadmium (Cd) activates c-Jun N-terminal kinase (JNK) pathway leading to neuronal cell death by inducing ROS inactivation of protein phosphatase 5 (PP5), and celastrol prevents Cd-activated JNK pathway against neuronal apoptosis. Therefore, we hypothesized that celastrol could hinder Cd induction of ROS-dependent PP5-JNK signaling pathway from apoptosis in neuronal cells. Here, we show that celastrol attenuated Cd-induced expression of NADPH oxidase 2 (NOX2) and its regulatory proteins (p22^phox , p40^phox , p47^phox , p67^phox , and Rac1), as well as the generation of ROS in PC12 cells and primary neurons. Also, N-acetyl-l-cysteine, a ROS scavenger, potentiated celastrol's inhibition of the events in the cells triggered by Cd, implying neuroprotection by celastrol via blocking Cd-evoked NOX2-derived ROS. Further research revealed that celastrol was involved in the regulation of PP5 inactivation and JNK/c-Jun activation induced by Cd, as celastrol prevented Cd from reducing PP5 expression, and over-expression of wild-type PP5 or dominant negative c-Jun strengthened celastrol's inhibition of Cd-induced phosphorylation of JNK and/or c-Jun, as well as apoptosis in neuronal cells. Of importance, inhibiting NOX2 with apocynin or silencing NOX2 by RNA interference enhanced the inhibitory effects of celastrol on Cd-induced inactivation of PP5, activation of JNK/c-Jun, ROS, and apoptosis in the cells. Furthermore, we noticed that expression of wild-type PP5 or dominant negative c-Jun, or pretreatment with JNK inhibitor SP600125 reinforced celastrol's suppression of Cd-induced NOX2 and its regulatory proteins, and consequential ROS in neuronal cells. These findings indicate that celastrol ameliorates Cd-induced neuronal apoptosis via targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway. Our data highlight a beneficial role of celastrol in the prevention of Cd-induced oxidative stress and neurodegenerative diseases.

Atomization method for verifying size effects of inhalable particles on lung damage of mice

To explore the size effects of inhalable particles on lung damage, aqueous aerosol containing cadmium was studied as a model to design a new type of two-stage atomization device that was composed of two adjustable parts with electronic ultrasonic atomization and pneumatic atomization. The working parameters and effectiveness of this device were tested with H₂O atomization and CdCl₂ inhalation, respectively. By gravimetrically detecting the mass concentrations of PM_2.5 and PM₁₀ and analysing the particle size with a laser sensor, we confirmed the particle size distribution of the aqueous aerosol produced by the new device under different working conditions. Then, we conducted experiments in male Kunming mice that inhaled CdCl₂ to determine the size effects of inhalable particles on lung damage and to confirm the effectiveness of the device. The new device could effectively control the particle size in the aqueous aerosol. The inhaled CdCl₂ entered and injured the lungs of the mice by causing tissue damage, oxidative stress, increasing endoplasmic reticulum stress and triggering an inflammatory response, which might be related to where the particles deposited. The smaller particles in the aqueous aerosol atomized by the new two-stage atomization device deposited deeper into lung causing more damage. This device could provide a new method for animal experiments involving inhalation with water-soluble toxins.

Crosstalk between Ca2+ signaling and mitochondrial H2O2 is required for rotenone inhibition of mTOR signaling pathway leading to neuronal apoptosis

Rotenone, a neurotoxic pesticide, induces loss of dopaminergic neurons related to Parkinson's disease. Previous studies have shown that rotenone induces neuronal apoptosis partly by triggering hydrogen peroxide (H₂O₂)-dependent suppression of mTOR pathway. However, the underlying mechanism is not fully understood. Here, we show that rotenone elevates intracellular free calcium ion ([Ca²⁺]_i) level, and activates CaMKII, resulting in inhibition of mTOR signaling and induction of neuronal apoptosis. Chelating [Ca²⁺]_i with BAPTA/AM, preventing extracellular Ca²⁺ influx using EGTA, inhibiting CaMKII with KN93, or silencing CaMKII significantly attenuated rotenone-induced H₂O₂ production, mTOR inhibition, and cell death. Interestingly, using TTFA, antimycin A, catalase or Mito-TEMPO, we found that rotenone-induced mitochondrial H₂O₂ also in turn elevated [Ca²⁺]_i level, thereby stimulating CaMKII, leading to inhibition of mTOR pathway and induction of neuronal apoptosis. Expression of wild type mTOR or constitutively active S6K1, or silencing 4E-BP1 strengthened the inhibitory effects of catalase, Mito-TEMPO, BAPTA/AM or EGTA on rotenone-induced [Ca²⁺]_i elevation, CaMKII phosphorylation and neuronal apoptosis. Together, the results indicate that the crosstalk between Ca²⁺ signaling and mitochondrial H₂O₂ is required for rotenone inhibition of mTOR-mediated S6K1 and 4E-BP1 pathways. Our findings suggest that how to control over-elevation of intracellular Ca²⁺ and overproduction of mitochondrial H₂O₂ may be a new approach to deal with the neurotoxicity of rotenone.

Celastrol prevents cadmium-induced neuronal cell death by blocking reactive oxygen species-mediated mammalian target of rapamycin pathway

BACKGROUND AND PURPOSE

Increasing evidence has suggested cadmium (Cd), as an inducer of ROS, is a potential pathogenic factor in human neurodegenerative diseases. Thus, it is important to find effective interventions for Cd-induced oxidative stress in the CNS. Here, we have studied the effects of celastrol, a plant-derived triterpene, on ROS production and cell death in neuronal cells, induced by Cd.

EXPERIMENTAL APPROACH

PC12, SH-SY5Y cells and primary murine neurons were used to study celastrol neuroprotection against Cd-poisoning. Cd-induced changes in cell viability, apoptosis, ROS and AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in the cells were analysed by Trypan blue exclusion, DAPI and TUNEL staining, ROS imaging, immunofluorescence staining and Western blotting. Pharmacological and genetic approaches were employed to investigate the mechanisms underlying Cd neurotoxicity.

RESULTS

Celastrol attenuated Cd-induced apoptosis by suppressing Cd activation of mTOR, which was attributed to preventing Cd inactivation of AMPK. Inhibition of AMPK with compound C or expression of dominant negative AMPKα prevented celastrol from hindering Cd-induced dephosphorylation of AMPKα, activation of mTOR and apoptosis. Inhibition of mTOR with rapamycin or knockdown of mTOR potentiated prevention by celastrol, of Cd-induced phosphorylation of p70 S6 kinase 1/eukaryotic initiation factor 4E binding protein 1 and apoptosis. Celastrol attenuated Cd-induced cell death by suppressing induction of mitochondrial ROS.

CONCLUSIONS AND IMPLICATIONS

Celastrol prevented the inactivation of AMPK by mitochondrial ROS, thus attenuating Cd-induced mTOR activation and neuronal apoptosis. Celastrol may be a promising agent for prevention of Cd-induced oxidative stress and neurodegenerative diseases.

l-Theanine attenuates cadmium-induced neurotoxicity through the inhibition of oxidative damage and tau hyperphosphorylation

Cadmium (Cd) has long been known to induce neurological degenerative disorders. We studied effects of l-theanine, one of the major amino acid components in green tea, on Cd-induced brain injury in mice. Male ICR mice were intraperitoneally injected with l-theanine (100 or 200mg/kg/day) or saline and after one hour these mice were orally administrated with CdCl₂ (3.75-6mg/kg). The treatment was conducted for 8 weeks. l-Theanine significantly reduced Cd level in the mouse brain and plasma. Cd-induced neuronal cell death in the mouse cortex and hippocampus were apparently inhibited by l-theanine treatment. l-Theanine also decreased the levels of malondialdehyde (MDA) and ROS, and obviously elevated the levels of glutathione (GSH) and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the mouse brain. Hyperphosphorylation of tau protein is proposed to be an early event for the evolution of tau pathology, and may play an important role in Cd-induced neurodegeneration. Our results showed that l-theanine significantly suppressed Cd-induced tau protein hyperphosphorylation at Ser199, Ser202, and Ser396. Mechanism study showed that l-theanine inhibited the activation of glycogen synthase kinase-3β (GSK-3β) which contributed to the hyperphosphorylation of tau and Cd-induced cytotoxicity. Furthermore, l-theanine reduced Cd-induced cytotoxicity possibly by interfering with the Akt/mTOR signaling pathway. In conclusion, our study indicated that l-theanine protected mice against Cd-induced neurotoxicity through reducing brain Cd level and relieved oxidative damage and tau hyperphosphorylation. Our foundings provide a novel insight into the potential use of l-theanine as prophylactic and therapeutic agents for Cd-induced neurodegenerative diseases.

Sulforaphane protects against rotenone-induced neurotoxicity in vivo: Involvement of the mTOR, Nrf2, and autophagy pathways

Sulforaphane, a naturally occurring compound found in cruciferous vegetables, has been shown to be neuroprotective in several neurological disorders. In this study, we sought to investigate the potential protective effects and associated molecular mechanisms of sulforaphane in an in vivo Parkinson's disease (PD) model, based on rotenone-mediated neurotoxicity. Our results showed that sulforaphane inhibited rotenone-induced locomotor activity deficiency and dopaminergic neuronal loss. Additionally, sulforaphane treatment inhibited the rotenone-induced reactive oxygen species production, malondialdehyde (MDA) accumulation, and resulted in an increased level of total glutathione and reduced glutathione (GSH): oxidized glutathione (GSSG) in the brain. Western blot analysis illustrated that sulforaphane increased the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H quinone oxidoreductase (NQO1), the latter two of which are anti-oxidative enzymes. Moreover, sulforaphane treatment significantly attenuated rotenone-inhibited mTOR-mediated p70S6K and 4E-BP1 signalling pathway, as well as neuronal apoptosis. In addition, sulforaphane rescued rotenone-inhibited autophagy, as detected by LC3-II. Collectively, these findings demonstrated that sulforaphane exert neuroprotective effect involving Nrf2-dependent reductions in oxidative stress, mTOR-dependent inhibition of neuronal apoptosis, and the restoration of normal autophagy. Sulforaphane appears to be a promising compound with neuroprotective properties that may play an important role in preventing PD.

The inhibitory mechanism of Cordyceps sinensis on cigarette smoke extract-induced senescence in human bronchial epithelial cells

OBJECTIVES

Cellular senescence is a state of irreversible growth arrest induced either by telomere shortening (replicative senescence) or stress. The bronchial epithelial cell is often injured by inhaled toxic substances, such as cigarette smoke. In the present study, we investigated whether exposure to cigarette smoke extract (CSE) induces senescence of bronchial epithelial cells; and Cordyceps sinensis mechanism of inhibition of CSE-induced cellular senescence.

METHODS

Human bronchial epithelial cells (16HBE cells) cultured in vitro were treated with CSE and/or C. sinensis. p16, p21, and senescence-associated-galactosidase activity were used to detect cellular senescence with immunofluorescence, quantitative polymerase chain reaction, and Western blotting. Reactive oxygen species (ROS), PI3K/AKT/mTOR and their phosphorylated proteins were examined to testify the activation of signaling pathway by ROS fluorescent staining and Western blotting. Then, inhibitors of ROS and PI3K were used to further confirm the function of this pathway.

RESULTS

Cellular senescence was upregulated by CSE treatment, and C. sinensis can decrease CSE-induced cellular senescence. Activation of ROS/PI3K/AKT/mTOR signaling pathway was enhanced by CSE treatment, and decreased when C. sinensis was added. Blocking ROS/PI3K/AKT/mTOR signaling pathway can attenuate CSE-induced cellular senescence.

CONCLUSION

CSE can induce cellular senescence in human bronchial epithelial cells, and ROS/PI3K/AKT/mTOR signaling pathway may play an important role in this process. C. sinensis can inhibit the CSE-induced senescence.

Rapamycin inhibits Erk1/2-mediated neuronal apoptosis caused by cadmium

Cadmium (Cd), an environmental contaminant, causes neurodegenerative disorders. Recently we have shown that rapamycin prevents Cd-induced neuronal cell death by inhibiting mTOR signaling pathway. Here we found that rapamycin exerted its prevention against Cd-induced neuronal cell death also partially via blocking Erk1/2 pathway. Inhibiting Erk1/2 with PD98059 or silencing Erk1/2 potentiated rapamycin's inhibition of Cd-induced phosphorylation of Erk1/2 and apoptosis in neuronal cells. Both PP2A and PTEN/Akt were involved in the regulation of Erk1/2 activation and cell death triggered by Cd. Inhibition of PP2A with okadaic acid or ectopic expression of dominant negative PP2A attenuated rapamycin's inhibition of Cd-induced phospho-Erk1/2 and apoptosis, whereas over-expression of wild-type PP2A enhanced rapamycin's effects; Over-expression of wild-type PTEN or dominant negative Akt, or inhibition of Akt with Akt inhibitor X strengthened rapamycin's inhibition of Cd-induced phospho-Erk1/2 and cell death. Furthermore, expression of a rapamycin-resistant and kinase-active mTOR (mTOR-T) blocked rapamycin's inhibitory effects on Cd-induced inhibition of PP2A, down-regulation of PTEN, and activation of Akt, leading to Erk1/2 activation and cell death, whereas silencing mTOR mimicked rapamycin's effects. The results uncover that rapamycin inhibits Cd activation of Erk1/2-mediated neuronal apoptosis through intervening mTOR-PP2A/PTEN signaling network.

The involvement of the mitochondrial pathway in manganese-induced apoptosis of chicken splenic lymphocytes

The purpose of this study was to investigate the effect of excess manganese (Mn)-induced cytotoxicity on apoptosis in chicken splenic lymphocytes. Chicken splenic lymphocytes were cultured in medium in the absence and presence of manganese (II) chloride (MnCl2) (2 × 10(-4), 4 × 10(-4), 6 × 10(-4), 8 × 10(-4), 10 × 10(-4), and 12 × 10(-4) mM), in N-acetyl-l-cysteine (NAC) (1 mM), and the combination of MnCl2 and NAC for 12, 24, 36, and 48 h. Tests were performed on morphologic observation, reactive oxygen species (ROS) and malondialdehyde (MDA) content, manganese superoxide dismutase (Mn-SOD) and glutathione peroxidase (GSH-Px) activities, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), p53, and calmodulin (CaM) messenger RNA (mRNA) expression, Caspase-3 mRNA and protein expression, intracellular free Ca(2+) ([Ca(2+)]i), and mitochondrial transmembrane potential (ΔΨm). Our research indicated that excess Mn induced ROS and MDA content, inhibited Mn-SOD and GSH-Px activities, induced Bax and p53 mRNA expression, inhibited Bcl-2 and CaM mRNA expression, induced Caspase-3 mRNA and protein expression, upregulated [Ca(2+)]i, inhibited ΔΨm, and induced apoptosis in a dose effect. NAC relieved excess Mn-caused the changes of all above factors. Mn-induced oxidative injuries were alleviated by treatment with NAC, an ROS scavenger. The above results demonstrated that excess Mn caused oxidative stress and apoptosis via mitochondrial pathway in chicken splenic lymphocytes.

Nickel(II)-induced nasal epithelial toxicity and oxidative mitochondrial damage

In probing the underlying mechanisms of nickel(II)-induced cytotoxicity on nasal epithelium, we investigated the effects of nickel(II) acetate on nasal epithelial RPMI-2650 cells. Nickel(II) elicited apoptosis, as signified by pyknotic and fragmented nuclei, increased caspase-3/7 activity, and an increase in annexin V binding, hypodiploid DNA, and Bax/Bcl-2 protein ratio. Nickel(II)-induced G2/M arrest was associated with up-regulation of p21(WAF1/CIP1) expression, decrease in phosphorylation at Thr(161) of Cdc2, and down-regulation of cyclin B1. Associated with these responses, ROS generation and mitochondrial depolarization increased in a nickel(II) concentration-dependent fashion. Pretreatment with N-acetylcysteine (NAC) attenuated these changes. p53 reporter gene assay and analyses of p53, Puma, Bax, and Bcl-2 protein levels indicated that NAC inhibited nickel(II)-induced activation of p53-mediated mitochondrial apoptotic pathway. Collectively, our study provides evidences that nickel(II) may induce oxidative damage on nasal epithelium in which antioxidant NAC protects cells against nickel(II)-induced apoptosis through the prevention of oxidative stress-mediated mitochondrial damage.

Rapamycin ameliorates cadmium-induced activation of MAPK pathway and neuronal apoptosis by preventing mitochondrial ROS inactivation of PP2A

Cadmium (Cd) is a highly toxic metal that affects the central nervous system. Recently we have demonstrated that inhibition of mTOR by rapamycin rescues neuronal cells from Cd-poisoning. Here we show that rapamycin inhibited Cd-induced mitochondrial ROS-dependent neuronal apoptosis. Intriguingly, rapamycin remarkably blocked phosphorylation of JNK, Erk1/2 and p38 in neuronal cells induced by Cd, which was strengthened by co-treatment with Mito-TEMPO. Inhibition of JNK and Erk1/2 by SP600125 and U0126, respectively, potentiated rapamycin's prevention from Cd-induced apoptosis. Consistently, over-expression of dominant negative c-Jun or MKK1 also potently improved the inhibitory effect of rapamycin on Cd neurotoxicity. Furthermore, pretreatment with SP600125 or U0126, or expression of dominant negative c-Jun or MKK1 enhanced the inhibitory effects of rapamycin or Mito-TEMPO on Cd-induced ROS. Further investigation found that co-treatment with Mito-TEMPO/rapamycin more effectively rescued cells by preventing Cd inactivation of PP2A than treatment with rapamycin or Mito-TEMPO alone. Over-expression of wild-type PP2A reinforced rapamycin or Mito-TEMPO suppression of activated JNK and Erk1/2 pathways, as well as ROS production and apoptosis in neuronal cells in response to Cd. The findings indicate that rapamycin ameliorates Cd-evoked neuronal apoptosis by preventing mitochondrial ROS inactivation of PP2A, thereby suppressing activation of JNK and Erk1/2 pathways. Our results underline that rapamycin may have a potential in preventing Cd-induced oxidative stress and neurodegenerative diseases.

Mevastatin ameliorates sphingosine 1-phosphate-induced COX-2/PGE2-dependent cell migration via FoxO1 and CREB phosphorylation and translocation

BACKGROUND AND PURPOSE

Sphingosine 1-phosphate (S1P), an important inflammatory mediator, has been shown to regulate COX-2 production and promote various cellular responses such as cell migration. Mevastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA), effectively inhibits inflammatory responses. However, the mechanisms underlying S1P-evoked COX-2-dependent cell migration, which is modulated by mevastatin in human tracheal smooth muscle cells (HTSMCs) remain unclear.

EXPERIMENTAL APPROACH

The expression of COX-2 was determined by Western blotting, real time-PCR and promoter analyses. The signalling molecules were investigated by pretreatment with respective pharmacological inhibitors or transfection with siRNAs. The interaction between COX-2 promoter and transcription factors was determined by chromatin immunoprecipitation assay. Finally, the effect of mevastatin on HTSMC migration and leukocyte counts in BAL fluid and COX-2 expression induced by S1P was determined by a cell migration assay, cell counting and Western blot.

KEY RESULTS

S1P stimulated mTOR activation through the Nox2/ROS and PI3K/Akt pathways, which can further stimulate FoxO1 phosphorylation and translocation to the cytosol. We also found that S1P induced CREB activation and translocation via an mTOR-independent signalling pathway. Finally, we showed that pretreatment with mevastatin markedly reduced S1P-induced cell migration and COX-2/PGE2 production via a PPARγ-dependent signalling pathway.

CONCLUSIONS AND IMPLICATIONS

Mevastatin attenuates the S1P-induced increased expression of COX-2 and cell migration via the regulation of FoxO1 and CREB phosphorylation and translocation by PPARγ in HTSMCs. Mevastatin could be beneficial for prevention of airway inflammation in the future.

Rapamycin prevents cadmium-induced neuronal cell death via targeting both mTORC1 and mTORC2 pathways

Cadmium (Cd), a toxic environmental contaminant, contributes to neurodegeneration. Rapamycin, a macrocyclic lactone, has shown preventive effect on Cd-induced neuronal cell death. However, the underlying mechanism is not fully understood. Here, we show that rapamycin prevented Cd-induced apoptotic cell death in neuronal cells. Coincidently, rapamycin markedly blocked Cd-induced phosphorylation of Akt, S6K1 and 4E-BP1 in the cells. Expression of a rapamycin-resistant and kinase-active mTOR (S2035T, mTOR-T), but not a rapamycin-resistant and kinase-dead mTOR (S2035T/D2357E, mTOR-TE), conferred resistance to rapamycin inhibition of Cd-induced cell death, implying that the preventive effect of rapamycin on Cd-induced neurotoxicity is mTOR kinase activity-dependent. It appeared that both mTORC1 and mTORC2 were involved in the inhibitory activity of rapamycin, as silencing raptor, rictor or raptor/rictor enhanced rapamycin's blockage of Cd-induced cell death. Furthermore, downregulation of S6K1, ectopic expression of constitutively hypophosphorylated 4E-BP1 or dominant negative Akt, or co-treatment with Akt inhibitor also potentiated the rapamycin's inhibitory effect. The findings indicate that rapamycin prevents Cd-induced neuronal cell death via suppressing both mTORC1 and mTORC2 pathways. Our results highlight that rapamycin may be exploited for the prevention of Cd-induced neurodegenerative disorders.

Onconase induces autophagy sensitizing pancreatic cancer cells to gemcitabine and activates Akt/mTOR pathway in a ROS-dependent manner

Onconase® (ONC) is a member of the RNase super-family that is secreted in oocytes and early embryos of Rana pipiens. Over the last years, research interest about this small and basic frog RNase, also called ranpirnase, constantly increased because of its high cytotoxicity and anticancer properties. Onconase is currently used in clinical trials for cancer therapy; however, the precise mechanisms determining cytotoxicity in cancer cells have not yet been fully investigated. In the present manuscript, we evaluate the antitumoral property of onconase in pancreatic adenocarcinoma cells and in non-tumorigenic cells as a control. We demonstrate that ONC stimulates a strong antiproliferative and proapoptotic effect in cancer cells by reporting for the first time that ONC triggers Beclin1-mediated autophagic cancer cell death. In addition, ONC inhibits the expression of mitochondrial uncoupling protein 2 (UCP2) and of manganese-dependent superoxide dismutase (MnSOD) triggering mitochondrial superoxide ion production. ONC-induced reactive oxygen species (ROS) are responsible for Akt/mTOR pathway stimulation determining the sensitivity of cancer cells to mTOR inhibitors and lessening autophagic stimulation. This indicates ROS/Akt/mTOR axis as a strategy adopted by cancer cells to reduce ONC-mediated cytotoxic autophagy stimulation. In addition, we demonstrate that ONC can sensitize pancreatic cancer cells to the standard chemotherapeutic agent gemcitabine allowing a reduction of drug concentration when used in combination settings, thus suggesting a lowering of chemotherapy-related side effects. Altogether, our results shed more light on the mechanisms lying at the basis of ONC antiproliferative effect in cancer cells and support its potential use to develop new anticancer strategies.

The environmental pollutant cadmium induces homeostasis alteration in muscle cells in vitro

BACKGROUND

Cadmium (Cd) is a heavy metal widely distributed throughout the environment as a result of contamination from a variety of sources. It exerts toxic effects in many tissues but scarce data are present as yet on potential effects on skeletal muscle tissue.

AIM

To evaluate the potential alteration induced by Cd in skeletal muscle cells.

MATERIALS AND METHODS

C2C12 skeletal muscle cells were treated with Cd at different times of cellular differentiation and gene expression was evaluated.

RESULTS

Exposure to Cd decreased significantly p21 mRNA expression and strongly up-regulated cyclin D1 mRNA expression in committed cells and in differentiated myotubes. Moreover, myogenin, fast MyHC-IIb and slow MyHC-I mRNAs expression were also significantly decreased both in committed cells and in myotubes. Moreover, Cd exposure induced a strong increase of Pax3, Pax7 and Myf5 mRNAs expression and stimulated an up-regulation of IL6 and TNF-α proinflammatory cytokines.

CONCLUSION

These data lead to hypothesize that environmental Cd exposure might trigger an injury-like event in muscle tissue, possibly by an estrogen receptor-mediated mechanism.

Targeting xCT, a cystine-glutamate transporter induces apoptosis and tumor regression for KSHV/HIV-associated lymphoma

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiological agent of primary effusion lymphoma (PEL), which represents a rapidly progressing malignancy arising in HIV-infected patients. Conventional chemotherapy for PEL treatment induces unwanted toxicity and is ineffective — PEL continues to portend nearly 100% mortality within a period of months, which requires novel therapeutic strategies. The amino acid transporter, xCT, is essential for the uptake of cystine required for intracellular glutathione (GSH) synthesis and for maintaining the intracellular redox balance. Inhibition of xCT induces growth arrest in a variety of cancer cells, although its role in virus-associated malignancies including PEL remains unclear. In the current study, we identify that xCT is expressed on the surface of patient-derived KSHV⁺ PEL cells, and targeting xCT induces caspase-dependent cell apoptosis. Further experiments demonstrate the underlying mechanisms including host and viral factors: reducing intracellular GSH while increasing reactive oxygen species (ROS), repressing cell-proliferation-related signaling, and inducing viral lytic genes. Using an immune-deficient xenograft model, we demonstrate that an xCT selective inhibitor, Sulfasalazine (SASP), prevents PEL tumor progression in vivo. Together, our data provide innovative and mechanistic insights into the role of xCT in PEL pathogenesis, and the framework for xCT-focused therapies for AIDS-related lymphoma in future.