Suppression of methylmercury-induced IL-6 and MCP-1 expressions by N-acetylcysteine in U-87MG human astrocytoma cells

Human-induced pluripotent stem cell-derived neural stem cell exosomes improve blood-brain barrier function after intracerebral hemorrhage by activating astrocytes via PI3K/AKT/MCP-1 axis

JOURNAL/nrgr/04.03/01300535-202502000-00029/figure1/v/2024-05-28T214302Z/r/image-tiff Cerebral edema caused by blood-brain barrier injury after intracerebral hemorrhage is an important factor leading to poor prognosis. Human-induced pluripotent stem cell-derived neural stem cell exosomes (hiPSC-NSC-Exos) have shown potential for brain injury repair in central nervous system diseases. In this study, we explored the impact of hiPSC-NSC-Exos on blood-brain barrier preservation and the underlying mechanism. Our results indicated that intranasal delivery of hiPSC-NSC-Exos mitigated neurological deficits, enhanced blood-brain barrier integrity, and reduced leukocyte infiltration in a mouse model of intracerebral hemorrhage. Additionally, hiPSC-NSC-Exos decreased immune cell infiltration, activated astrocytes, and decreased the secretion of inflammatory cytokines like monocyte chemoattractant protein-1, macrophage inflammatory protein-1α, and tumor necrosis factor-α post-intracerebral hemorrhage, thereby improving the inflammatory microenvironment. RNA sequencing indicated that hiPSC-NSC-Exo activated the PI3K/AKT signaling pathway in astrocytes and decreased monocyte chemoattractant protein-1 secretion, thereby improving blood-brain barrier integrity. Treatment with the PI3K/AKT inhibitor LY294002 or the monocyte chemoattractant protein-1 neutralizing agent C1142 abolished these effects. In summary, our findings suggest that hiPSC-NSC-Exos maintains blood-brain barrier integrity, in part by downregulating monocyte chemoattractant protein-1 secretion through activation of the PI3K/AKT signaling pathway in astrocytes.

Mercury and cadmium-induced inflammatory cytokines activation and its effect on the risk of preeclampsia: a review

During the last decade, there has been an increase in exposure to heavy metals that can affect human health and the environment, especially mercury (Hg) and cadmium (Cd). These exposures can pollute the rivers or oceans, then contaminating marine organisms. Humans as the last consumer of this food chain cycle can be a place for the bioaccumulation of Hg and Cd, especially for people living in coastal areas, including pregnant women. Exposure to heavy metals Hg and Cd can have a high risk of triggering blood vessel disorders, penetrating the blood-brain barrier (BBB) and the placental barrier, one of which can increase the risk of preeclampsia. Several immunological biomarkers such as some cytokines associated with Hg and Cd exposure are also involved in the pathophysiology of preeclampsia, which are the placental implantation process and endothelial dysfunction in pregnant women. Therefore, countries that have a high incidence of preeclampsia should be aware of the environmental factors, especially heavy metal pollution such as Hg and Cd.

Mitochondrial impairment and downregulation of Drp1 phosphorylation underlie the antiproliferative and proapoptotic effects of alantolactone on oral squamous cell carcinoma cells

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most prevalent and fatal oral cancers. Mitochondria-targeting therapies represent promising strategies against various cancers, but their applications in treating OSCC are limited. Alantolactone (ALT) possesses anticancer properties and also regulates mitochondrial events. In this study, we explored the effects of ALT on OSCC and the related mechanisms.

METHODS

The OSCC cells were treated with varying concentrations and duration of ALT and N-Acetyl-L-cysteine (NAC). The cell viability and colony formation were assessed. The apoptotic rate was evaluated by flow cytometry with Annexin V-FITC/PI double staining. We used DCFH-DA and flow cytometry to detect reactive oxygen species (ROS) production and DAF-FM DA to investigate reactive nitrogen species (RNS) level. Mitochondrial function was reflected by mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP levels. KEGG enrichment analyses determined the mitochondrial-related hub genes involved in OSCC progression. Dynamin-related protein 1 (Drp1) overexpression plasmids were further transfected into the cells to analyze the role of Drp1 in OSCC progression. Immunohistochemistry staining and western blot verified the expression of the protein.

RESULTS

ALT exerted anti-proliferative and pro-apoptosis effects on OSCC cells. Mechanistically, ALT elicited cell injury by promoting ROS production, mitochondrial membrane depolarization, and ATP depletion, which were reversed by NAC. Bioinformatics analysis showed that Drp1 played a crucial role in OSCC progression. OSCC patients with low Drp1 expression had a higher survival rate. The OSCC cancer tissues presented higher phosphorylated-Drp1 and Drp1 levels than the normal tissues. The results further showed that ALT suppressed Drp1 phosphorylation in OSCC cells. Moreover, Drp1 overexpression abolished the reduced Drp1 phosphorylation by ALT and promoted the cell viability of ALT-treated cells. Drp1 overexpression also reversed the mitochondrial dysfunction induced by ALT, with decreased ROS production, and increased mitochondrial membrane potential and ATP level.

CONCLUSIONS

ALT inhibited proliferation and promoted apoptosis of oral squamous cell carcinoma cells via impairment of mitochondrial homeostasis and regulation of Drp1. The results provide a solid basis for ALT as a therapeutic candidate for treating OSCC, with Drp1 being a novel therapeutic target in treating OSCC.

An exploratory review of Potential Adjunct Therapies for the Treatment of Coronavirus Infections

Objective

The purpose of this exploratory review c, including vitamin D, zinc, vitamin A, elderberry (S nigra), garlic (A sativum), licorice (G glabra), stinging nettle (U dioica), N-acetylcysteine, quercetin and selenium as potential adjunct therapies for the treatment of coronavirus infections.

Methods

A search of PubMed was performed for articles published from 2005 to 2021. Key words searched were zinc, vitamin A, vitamin D, Sambucus nigra, Allium sativum, Glycyrrhiza glabra, Urtica dioica, N-Acetylcysteine, quercetin, selenium and coronavirus.

Results

There were 47 articles selected for this review. Findings included that vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra, U dioica, N-acetylcysteine, quercetin and selenium have been shown to produce anti-inflammatory, immunostimulatory or antiviral effects that may enhance the actions of standard therapeutics for the treatment of CoV infections. We found only research articles related to the effects of vitamin D, zinc, G glabra, quercetin and selenium against COVID-19.

Conclusion

We identified non-pharmaceutical supplements (Vitamin D, zinc, vitamin A, S nigra, A sativum, G glabra and U dioica) which may have potential to provide support for those with coronavirus infections. However, rigorous clinical studies need to be performed before any clinical recommendations can be made at this time.

Methylmercury-induced pro-inflammatory cytokines activation and its preventive strategy using anti-inflammation N-acetyl-l-cysteine: a mini-review

The exposure of methylmercury (MeHg) has become a public health concern because of its neurotoxic effect. Various neurological symptoms were detected in Minamata disease patients, who got intoxicated by MeHg, including paresthesia, ataxia, gait disturbance, sensory disturbances, tremors, visual, and hearing impairments, indicating that MeHg could pass the blood-brain barrier (BBB) and cause impairment of neurons and other brain cells. Previous studies have reported some expected mechanisms of MeHg-induced neurotoxicity including the neuroinflammation pathway. It was characterized by the up-regulation of numerous pro-inflammatory cytokines expression. Therefore, the use of anti-inflammatories such as N-acetyl-l-cysteine (NAC) may act as a preventive compound to protect the brain from MeHg harmful effects. This mini-review will explain detailed information on MeHg-induced pro-inflammatory cytokines activation as well as possible preventive strategies using anti-inflammation NAC to protect brain cells, particularly in in vivo and in vitro studies.

Regulation of lymphatic function and injury by nitrosative stress in obese mice

Objective

Obesity results in lymphatic dysfunction, but the cellular mechanisms that mediate this effect remain largely unknown. Previous studies in obese mice have shown that inducible nitric oxide synthase-expressing (iNOS⁺) inflammatory cells accumulate around lymphatic vessels. In the current study, we therefore tested the hypothesis that increased expression of iNOS results in nitrosative stress and injury to the lymphatic endothelial cells (LECs). In addition, we tested the hypothesis that lymphatic injury, independent of obesity, can modulate glucose and lipid metabolism.

Methods

We compared the metabolic changes and lymphatic function of wild-type and iNOS knockout mice fed a normal chow or high-fat diet for 16 weeks. To corroborate our in vivo findings, we analyzed the effects of reactive nitrogen species on isolated LECs. Finally, using a genetically engineered mouse model that allows partial ablation of the lymphatic system, we studied the effects of acute lymphatic injury on glucose and lipid metabolism in lean mice.

Results

The mesenteric lymphatic vessels of obese wild-type animals were dilated, leaky, and surrounded by iNOS⁺ inflammatory cells with resulting increased accumulation of reactive nitrogen species when compared with lean wild-type or obese iNOS knockout animals. These changes in obese wild-type mice were associated with systemic glucose and lipid abnormalities, as well as decreased mesenteric LEC expression of lymphatic-specific genes, including vascular endothelial growth factor receptor 3 (VEGFR-3) and antioxidant genes as compared with lean wild-type or obese iNOS knockout animals. In vitro experiments demonstrated that isolated LECs were more sensitive to reactive nitrogen species than blood endothelial cells, and that this sensitivity was ameliorated by antioxidant therapies. Finally, using mice in which the lymphatics were specifically ablated using diphtheria toxin, we found that the interaction between metabolic abnormalities caused by obesity and lymphatic dysfunction is bidirectional. Targeted partial ablation of mesenteric lymphatic channels of lean mice resulted in increased accumulation of iNOS⁺ inflammatory cells and increased reactive nitrogen species. Lymphatic ablation also caused marked abnormalities in insulin sensitivity, serum glucose and insulin concentrations, expression of insulin-sensitive genes, lipid metabolism, and significantly increased systemic and mesenteric white adipose tissue (M-WAT) inflammatory responses.

Conclusions

Our studies suggest that increased iNOS production in obese animals plays a key role in regulating lymphatic injury by increasing nitrosative stress. In addition, our studies suggest that obesity-induced lymphatic injury may amplify metabolic abnormalities by increasing systemic and local inflammatory responses and regulating insulin sensitivity. These findings suggest that manipulation of the lymphatic system may represent a novel means of treating metabolic abnormalities associated with obesity.

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Increased iNOS+ cells around mesenteric lymphatics of high fat diet-induced obese mice.

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iNOS knockout mice are protected from obesity-induced lymphatic dysfunction.

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Lymphatic endothelial cells are highly sensitive to nitrosative stress.

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Nitrosative stress causes lymphatic gene regulation.

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Lymphatic injury alone enhances iNOS+ cells and causes insulin resistance and dyslipidemia.

Sulfhydryl groups as targets of mercury toxicity

The present study addresses existing data on the affinity and conjugation of sulfhydryl (thiol; -SH) groups of low- and high-molecular-weight biological ligands with mercury (Hg). The consequences of these interactions with special emphasis on pathways of Hg toxicity are highlighted. Cysteine (Cys) is considered the primary target of Hg, and link its sensitivity with thiol groups and cellular damage. In vivo, Hg complexes play a key role in Hg metabolism. Due to the increased affinity of Hg to SH groups in Cys residues, glutathione (GSH) is reactive. The geometry of Hg(II) glutathionates is less understood than that with Cys. Both Cys and GSH Hg-conjugates are important in Hg transport. The binding of Hg to Cys mediates multiple toxic effects of Hg, especially inhibitory effects on enzymes and other proteins that contain free Cys residues. In blood plasma, albumin is the main Hg-binding (Hg2+, CH3Hg+, C2H5Hg+, C6H5Hg+) protein. At the Cys34 residue, Hg2+ binds to albumin, whereas other metals likely are bound at the N-terminal site and multi-metal binding sites. In addition to albumin, Hg binds to multiple Cys-containing enzymes (including manganese-superoxide dismutase (Mn-SOD), arginase I, sorbitol dehydrogenase, and δ-aminolevulinate dehydratase, etc.) involved in multiple processes. The affinity of Hg for thiol groups may also underlie the pathways of Hg toxicity. In particular, Hg-SH may contribute to apoptosis modulation by interfering with Akt/CREB, Keap1/Nrf2, NF-κB, and mitochondrial pathways. Mercury-induced oxidative stress may ensue from Cys-Hg binding and inhibition of Mn-SOD (Cys196), thioredoxin reductase (TrxR) (Cys497) activity, as well as limiting GSH (GS-HgCH3) and Trx (Cys32, 35, 62, 65, 73) availability. Moreover, Hg-thiol interaction also is crucial in the neurotoxicity of Hg by modulating the cytoskeleton and neuronal receptors, to name a few. However, existing data on the role of Hg-SH binding in the Hg toxicity remains poorly defined. Therefore, more research is needed to understand better the role of Hg-thiol binding in the molecular pathways of Hg toxicology and the critical role of thiols to counteract negative effects of Hg overload.

Activation of MIP-2 and MCP-5 Expression in Methylmercury-Exposed Mice and Their Suppression by N-Acetyl-L-Cysteine

Methylmercury (MeHg) is a well-known neurotoxin of the central nervous system (CNS). Neuroinflammation is one of the main pathways of MeHg-induced CNS impairment. This study aims to investigate the expressions of IL-6, MIP-2, and MCP-5, as biomarkers in relation with MeHg-induced CNS impairment and N-acetyl-L-cysteine (NAC) treatment in mice, as well as histopathological changes of brain tissue and clinical symptom such as ataxia. Twenty male Balb/c mice, aged 8-9 weeks, were divided into 4 groups and treated with saline (control), NAC [150 mg/kg body weight (BW) day], MeHg (4 mg Hg/kg BW), or a combination of MeHg and NAC for 17 days. MeHg induced the expression of IL-6, MIP-2, and MCP-5 in the serum, with median values (those in controls) of 55.06 (9.44), 15.94 (9.30), and 458.91 (239.91) mg/dl, respectively, and a statistical significance was observed only in IL-6 expression (p < 0.05). MIP-2 and MCP-5 expressions tended to increase in the cerebrum of MeHg-treated group compared with controls; however, the difference was not statistically significant. MeHg treatment also increased IL-6 expression in the cerebellum (7.73 and 4.81 mg/dl in MeHg-treated group and controls, respectively), with a marginal significance. NAC significantly suppressed MeHg-induced IL-6 and MIP-2 expressions in the serum (p < 0.05 for both), and slightly reduced MCP-5 expression in the cerebrum. Ataxia was observed in all MeHg-treated mice after 9-day exposure as well as the decrease of intact Purkinje cells in brain tissue (p < 0.05). These findings suggest that MeHg induced neurotoxicity by elevating the expression of IL-6, MIP-2, and MCP-5 and causing ataxia symptoms, and NAC reduced MeHg-mediated effects on the CNS.

Inorganic mercury-induced MIP-2 expression is suppressed by N-acetyl-L-cysteine in RAW264.7 macrophages

Macrophages play an important role in neurotoxicity caused by methylmercury exposure through inflammatory responses. Methylmercury is known to demethylate to inorganic mercury in the brain, and macrophages are likely to be involved in this process. However, the inflammatory responses of macrophages against exposure to inorganic mercury are unclear. In the present study, inflammatory cytokine expression profiles were examined in the presence of non-toxic doses of inorganic mercury (Hg²⁺) using RAW264.7 macrophages, focusing on the expression of C-X-C motif chemokine 2 (MIP-2)/platelet-derived growth factor-inducible protein KC (KC) and C-C motif chemokine 12 (MCP-5). Furthermore, the suppressive effect of N-acetyl-L-cysteine (NAC) on inorganic mercury-induced MIP-2 expression was also examined. Inorganic mercury-induced mRNA expression was measured using reverse transcription-quantitative PCR. The mRNA expression of MIP-2 and MCP-5 was significantly upregulated by exposure to 20 µM Hg²⁺ (non-toxic levels), but not that of KC. The suppressive effect of NAC on these cytokine expression levels was examined by its addition to the culture medium together with Hg²⁺ (co-treatment), and pre- and post-treatments in which the cells were treated with NAC before and after Hg²⁺ exposure, respectively. Hg²⁺-upregulated MIP-2 expression was suppressed by NAC regardless of the time sequence of the treatment, suggesting that the suppressive role of NAC in Hg²⁺-induced inflammation manifests as a possible chelator and antioxidant/reactive oxygen species scavenger.

Associations of maternal immune response with MeHg exposure at 28 weeks' gestation in the Seychelles Child Development Study

PROBLEM

Maternal methylmercury (MeHg) exposure may be associated with immune response during pregnancy.

METHOD OF STUDY

In the high fish-eating Seychelles Child Development Study Nutrition Cohort 2, we examined the association between maternal MeHg, polyunsaturated fatty acids (PUFA), and immune markers (Th1:Th2; TNF-α, IL-1β, IFN-γ, IL-2, IL-4, IL-5, IL-10, MCP-1, TARC, sFlt-1, VEGF-D, CRP and IL-6) at 28 weeks' gestation. Linear regression examined associations between MeHg exposure and immune markers with and without adjustment for PUFA.

RESULTS

In all models, as MeHg concentrations increased, the Th1:Th2 ratio, total Th1 and individual Th1 (IL-1β, IL-2, TNF-α) concentrations decreased. MeHg was not associated with total Th2 cytokines but was associated with a decrease in IL-4 and IL-10. MeHg was positively associated with TARC and VEGF-D and negatively associated with CRP. There was a significant interaction between MeHg and the n-6:n-3 ratio, with MeHg associated with a larger decrease in Th1:Th2 at higher n-6:n-3 PUFA ratios. The n-3 PUFA were associated with lower CRP, IL-4 and higher IFN-γ. The n-6 PUFA were associated with higher IL-1β, IL-2, TNF-α, IL-4, IL-10, CRP and IL-6.

CONCLUSION

Maternal MeHg was associated with markers of immune function at 28 weeks' gestation. A significant interaction between MeHg and the n-6:n-3 ratio on the Th1:Th2 ratio suggests that the n-3 PUFA may mitigate any immunosuppressive associations of MeHg. The n-3 and n-6 PUFA were associated with suppressive and stimulatory immune responses, respectively. Overall, the associations were of small magnitude, and further research is required to determine the clinical significance.

Curcumin Inhibits Monocyte Chemoattractant Protein-1 Expression in TNF-α induced Astrocytes Through AMPK Pathway

Curcumin, a phenolic pigment, plays an inhibitory role in astrocytes activation, a key step for neuropathic pain (NP). The present study aimed to investigate the mechanism behind the therapeutic effect of Curcumin on NP in vitro. Specifically, we investigated the inhibitory effect of Curcumin on tumor necrosis factor-α (TNF-α)-induced astrocyte migration. We also studied the effects of Curcumin on monocyte chemoattractant protein-1(MCP-1) expression and activity, as well as super oxide dismutase-2 (SOD2) expression and activity in TNF-α-induced astrocytes. Additionally, we investigated whether the adenosine-monophosphate-activated protein kinase signaling (AMPK) pathway was involved in this process. Our data demonstrated that Curcumin inhibited TNF-α-induced astrocytes migration, decreased MCP-1 expression, and up-regulated SOD2 expression in TNF-α-induced astrocytes in vitro. Our study also indicated that this process was mediated through the AMPK signaling pathway, as addition of Curcumin significantly increased the level of phosphorylated AMPK protein. Furthermore, the specific AMPK activator AICAR (5-aminoimidazole-4-carboxamide 1-D-ribofuranoside) mimicked the effects of Curcumin, whereas a selective AMPK inhibitor Compound C (also called dorsomorphin) partially blocked its function. These results could shed light on understanding of the molecular basis for the inhibition of Curcumin on MCP-1 expression during the process of astrocyte activation, and provide a molecular mechanism for using Curcumin in neuropathic pain.

Suppression of methylmercury-induced MIP-2 expression by N-acetyl-L-cysteine in murine RAW264.7 macrophage cell line

Background

The aim of this study is to examine the inflammatory-cytokine expressions in the presence of non-cytotoxic dose of methylmercury (MeHg) in murine macrophages, which is suspected to play an important role in brain damage caused by MeHg exposure. We focused on murine macrophage inflammatory protein-2 (MIP-2), keratinocyte chemoattractant (KC), and monocyte chemoattractant protein-5 (MCP-5). MIP-2 and KC are murine functional homologues of human IL-8 and MCP-5 for human MCP-1. Furthermore, we examined the suppressive effect of N-acetyl-l-cysteine (NAC) on the MeHg-induced inflammatory cytokines.

Methods

In a murine RAW264.7 macrophage cell line, MeHg-induced cytokine expressions were measured using real-time PCR. The suppressive effect of NAC was examined by putting it into the culture medium together with MeHg (co-treatment). In addition, pre- and post-treatment experiments were conducted, in which the cells were treated with NAC before and after MeHg exposure, respectively.

Results

Exposure to a non-cytotoxic dose of MeHg up-regulated the mRNA expression of MIP-2 and MCP-5. On the other hand, KC expression was not induced in the presence of MeHg. Effect of MeHg on MIP-2 expressions was suppressed by pre-, co-, and post-treatment with NAC. However, the suppressive effect of pre-treatment was less than the post-treatment, which was as effective as co-treatment.

Conclusion

In functional homologues of human IL-8, only MIP-2 expression, not KC, was activated in the presence of non-cytotoxic dose of MeHg in murine RAW264.7 macrophage cell line. The more evident inhibitory effect of NAC observed in post-treatment experiments suggests a possible involvement of intracellular activities such as antioxidant effects.

Effect of acrylamide-induced neurotoxicity in a primary astrocytes/microglial co-culture model

Acrylamide (AA), is a common food contaminant generated by heat processing. Astrocytes and microglia are the two major glial cell types in the brain that play pivotal but different roles in maintaining optimal brain function. The objective of this study is to investigate the neurotoxicity of AA, using a primary astrocytes/microglia co-culture model. Co-cultural cells obtained from Balb/c mice were cultured and treated with 0-1.0mM AA for 24-96h. Cell viability, reactive oxygen species (ROS) generation, oxidative end produces formation and glutathione (GSH) levels were measured. The expression of nuclear-E2-related factor 2(Nrf2), and nuclear factor kappa-beta (NF-κB) and selected down-stream genes were measured. Results showed that AA treatment led toa dose-dependent toxicity. Oxidative stress was induced as indicated by an increase of ROS, a decrease of GSH levels, and an increase in the formation of 4-hydroxynonenal-adduct and 8-hydroxy-2-deoxyguanosine-adduct. Both Nrf2 and NF-κB pathway contributed to the initiation of oxidative stress but the timing of two factors was different. Nrf2 and its related downstream genes were activated earlier than that in NF-κB pathway. In conclusion, AA-induced neurotoxicity attribute to oxidative stress via Nrf2 and NF-κB pathway. Moreover, the co-culture cell model was proven to be a viable model to study AA neurotoxicity.

Diphenylarsinic Acid Induced Activation of Cultured Rat Cerebellar Astrocytes: Phosphorylation of Mitogen-Activated Protein Kinases, Upregulation of Transcription Factors, and Release of Brain-Active Cytokines

Diphenylarsinic acid (DPAA) was detected as the primary compound responsible for the arsenic poisoning that occurred in Kamisu, Ibaraki, Japan, where people using water from a well that was contaminated with a high level of arsenic developed neurological (mostly cerebellar) symptoms and dysregulation of regional cerebral blood flow. To understand the underlying molecular mechanism of DPAA-induced cerebellar symptoms, we focused on astrocytes, which have a brain-protective function. Incubation with 10 µM DPAA for 96 h promoted cell proliferation, increased the expression of antioxidative stress proteins (heme oxygenase-1 and heat shock protein 70), and induced the release of cytokines (MCP-1, adrenomedullin, FGF2, CXCL1, and IL-6). Furthermore, DPAA overpoweringly increased the phosphorylation of three major mitogen-activated protein kinases (MAPKs) (ERK1/2, p38MAPK, and SAPK/JNK), which indicated MAPK activation, and subsequently induced expression and/or phosphorylation of transcription factors (Nrf2, CREB, c-Jun, and c-Fos) in cultured rat cerebellar astrocytes. Structure-activity relationship analyses of DPAA and other related pentavalent organic arsenicals revealed that DPAA at 10 µM activated astrocytes most effective among organic arsenicals tested at the same dose. These results suggest that in a cerebellum exposed to DPAA, abnormal activation of the MAPK-transcription factor pathway and irregular secretion of these neuroactive, glioactive, and/or vasoactive cytokines in astrocytes can be the direct/indirect cause of functional abnormalities in surrounding neurons, glial cells, and vascular cells: This in turn might lead to the onset of cerebellar symptoms and disruption of cerebral blood flow.