Effects of Al on the splenic immune function and NE in rats

Aluminum promotes B1 cells to produce IL-10 and impairs adaptive immune system

Aluminum (Al) is a metal existing in the human body, yet the immunotoxicity of Al remains elusive. To investigate the immunotoxicity of Al, C57BL/6 mice were treated with 200 or 800 ppm Al via drinking water for 3 months, and thereafter the adaptive immune system was evaluated. In addition, mouse splenocytes and human peripheral blood mononuclear cells (PBMC) were treated with Al in vitro to assess the impact of Al in vitro. Treatment with Al reduced the production of IgM and IgG in the serum, and the activation of B cells, CD4 T cells and CD8 T cells in the spleen of mice; treatment with Al in vitro suppressed the production of IgM and IgG, and the activation of B cells, CD4 T cells and CD8 T cells in mouse splenocytes and human PBMC. In vitro co-culture assays suggested that the suppressed adaptive immunity was due to B cells modified by Al. In terms of mechanism, a direct action of Al on B1 cells induced the B1 cells to be IL-10-producing cells and thereby suppressed the adaptive immune system, which was critically dependent on the Jak1/3-STAT signaling. This study reveals that Al suppresses the adaptive immunity via induction of IL-10-producing B1 cells.

Boron Compounds Exhibit Protective Effects against Aluminum-Induced Neurotoxicity and Genotoxicity: In Vitro and In Vivo Study

Genetic, neuropathological and biochemical investigations have revealed meaningful relationships between aluminum (Al) exposure and neurotoxic and hematotoxic damage. Hence, intensive efforts are being made to minimize the harmful effects of Al. Moreover, boron compounds are used in a broad mix of industries, from cosmetics and pharmaceuticals to agriculture. They affect critical biological functions in cellular events and enzymatic reactions, as well as endocrinal and mineral metabolisms. There are limited dose-related data about boric acid (BA) and other boron compounds, including colemanite (Col), ulexite (UX) and borax (BX), which have commercial prominence. In this study, we evaluate boron compounds' genetic, cytological, biochemical and pathological effects against aluminum chloride (AlCl3)-induced hematotoxicity and neurotoxicity on different cell and animal model systems. First, we perform genotoxicity studies on in vivo rat bone marrow cells and peripheric human blood cultures. To analyze DNA and chromosome damage, we use single cell gel electrophoresis (SCGE or comet assay) and micronucleus (MN) and chromosome aberration (CA) assays. The nuclear division index (NDI) is used to monitor cytostasis. Second, we examine the biochemical parameters (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), total antioxidant capacity (TAC) and total oxidative status (TOS)) to determine oxidative changes in blood and brain. Next, we assess the histopathological alterations by using light and electron microscopes. Our results show that Al increases oxidative stress and genetic damage in blood and brain in vivo and in vitro studies. Al also led to severe histopathological and ultrastructural alterations in the brain. However, the boron compounds alone did not cause adverse changes based on the above-studied parameters. Moreover, these compounds exhibit different levels of beneficial effects by removing the harmful impact of Al. The antioxidant, antigenotoxic and cytoprotective effects of boron compounds against Al-induced damage indicate that boron may have a high potential for use in medical purposes in humans. In conclusion, our analysis suggests that boron compounds (especially BA, BX and UX) can be administered to subjects to prevent neurodegenerative and hematological disorders at determined doses.

Melatonin alleviates aluminium chloride-induced immunotoxicity by inhibiting oxidative stress and apoptosis associated with the activation of Nrf2 signaling pathway

The present study aimed to investigate whether melatonin (MT) treatment can attenuate immunotoxicity induced by aluminum chloride (AlCl₃) in rat spleen. Forty-eight healthy male Wistar rats were randomly allocated and treated with AlCl₃ and/or MT. Rats were orally administered with AlCl₃ for 90 days, from 61st days, rats were injected intraperitoneally with MT for 30 days. Firstly, we found that MT relieved the AlCl₃-induced immunosuppression by improving spleen structural damage, CD3⁺ and CD4⁺ T lymphocyte subsets, IL-2 and TNF-α mRNA expressions and decreasing CD8⁺ T lymphocyte subsets. Secondly, MT attenuated the AlCl₃-induced oxidative stress in rat spleen by decreasing the levels of ROS and MDA, while increasing the activities of SOD and CAT. Thirdly, MT relieved the AlCl₃-induced apoptosis in rat spleen by increasing the MMP and Bcl-2 mRNA and protein expressions, while decreasing apoptosis rates, activity of Caspase-3 and pro-apoptotic gene expression. Finally, MT increased Nrf2 nuclear translocation, and Nrf2 target genes (HO-1, NQO1, SOD1 and CAT) mRNA expressions in the spleen of AlCl₃-exposed rat. These results suggest that MT may alleviate AlCl₃-induced immunotoxicity by inhibiting oxidative stress and apoptosis associated with the activation of Nrf2 signaling pathway, which could lay the foundation for the treatment of AlCl₃ immunotoxicity.

Bidirectional Role of β2-Adrenergic Receptor in Autoimmune Diseases

Disorder of the sympathetic nervous system (SNS) is closely related to the pathogenesis of various autoimmune diseases (ADs). Catecholamine triggered beta2-adrenergic receptor (β2-AR) signaling is important in creating a bidirectional response in the progression of ADs due to factors including diverse expression patterns, single nucleotide polymorphisms (SNPs), biased signals, and desensitization of β2-AR, as well as different subtypes of Gα binding to β2-AR. In this review, we summarize the actions of β2-AR signaling in regulating the functions of immunocytes and in the pathogenesis of ADs, and the application of β2-AR agonists or antagonists in treating major types of ADs is also discussed. We suggest that restoring the immune balance via a soft regulation of the expression or activation of β2-AR is one of the promising therapeutic strategies for systematic ADs.

Cytoprotective effect of deferiprone against aluminum chloride-induced oxidative stress and apoptosis in lymphocytes

Aluminum (Al) is a toxic metal, and excessive Al accumulation causes immunosuppression. Deferiprone (DFP) is a well-known chelator and used in dialysis patients for removing Al from tissues. The present study aimed to investigate whether DFP treatment can attenuate immunotoxicity induced by aluminum chloride (AlCl3) in cultured lymphocytes. Lymphocytes were treated with 0 and 0.6 mmol/L AlCl3∙6H2O (pH 7.2) and/or 1.8 mmol/L DFP, respectively. Immune function of lymphocytes was assessed by T and B lymphocytes proliferation rates, T lymphocyte subpopulations and IL-2, IL-6 and TNF-α contents. In addition, lymphocyte damage was assessed by LDH activity, NO and MDA contents, NOS, SOD and GSH-Px activities, lymphocyte apoptosis index. These results showed that AlCl3 exposure reduced T and B lymphocyte proliferation rates, CD3+ and CD4+ T lymphocyte subpopulations, CD4+/CD8+ ratio, IL-2, IL-6 and TNF-α contents, SOD and GSH-Px activities, early and later lymphocyte apoptosis indexes while enhanced CD8+ T lymphocyte subpopulation, NO and MDA contents, LDH activity. DFP treatment attenuated the immunotoxicity of lymphocytes and reduced oxidative stress and lymphocyte apoptosis induced by AlCl3, indicating that DFP could protect lymphocytes against immunosuppression induced by AlCl3 through attenuating oxidative stress and apoptosis.

The immunotoxicity of aluminum trichloride on rat peritoneal macrophages via β2-adrenoceptors/cAMP pathway acted by norepinephrine

The previous research found that norepinephrine (NE) enhanced the immunotoxicity of aluminum trichloride (AlCl3) on rat peritoneal macrophages in vitro through activating the β2-adrenoceptors (β2-AR)/cAMP pathway. On that basis, the experiment in vivo was conducted in this experiment. Eighty Wistar rats were orally exposed to 0 (control group); 0.4 mg/mL (low-dose group); 0.8 mg/mL (mid-dose group) and 1.6 mg/mL (high-dose group) AlCl3 for 120 days, respectively. Aluminum (Al), NE, macrophage migration inhibitory factor (MIF) and tumor necrosis factor-α (TNF-α) contents in serum, cAMP content, β2-AR density, mRNA expressions of TNF-α, MIF and β2-AR in rat peritoneal macrophages were examined. These results showed that AlCl3 increased serum Al and NE contents, peritoneal macrophages cAMP content, the density and mRNA expression of the β2-AR, and decreased serum MIF and TNF-α contents, peritoneal macrophages mRNA expressions of MIF and TNF-α. Serum NE content was negatively correlated with serum TNF-α and MIF contents and peritoneal macrophages mRNA expressions of TNF-α and MIF, but positively correlated with cAMP content, density of β2-AR and mRNA expression of β2-AR of peritoneal macrophages. It indicated that AlCl3 suppresses peritoneal macrophages function of rats through β2-AR/cAMP pathway acted by NE.

NE strengthens the immunosuppression induced by AlCl₃ through β₂-AR/cAMP pathway in cultured rat peritoneal macrophages

To investigate the effect of noradrenaline (NE) on the immunosuppression induced by aluminum trichloride (AlCl3), the peritoneal macrophages were cultured with RPMI-1640 medium containing 0.97 mM AlCl3 (1/10 IC50). NE was added to the medium at the final concentrations of 0 (control group, N-C), 0.1 (low-dose group, N-L), 1 (mid-dose group, N-M), and 10 (high-dose group, N-H) nM, respectively. No addition of both AlCl3 and NE serviced as blank group (D-C). Chemotaxis, adhesion, phagocytosis, tumor necrosis factor α (TNF-α) secretion, cyclic adenosine monophosphate (cAMP) content, β2 adrenergic receptors (β2-AR) density, and messenger RNA (mRNA) expression of macrophages were detected. The results showed that AlCl3 reduced the chemotaxis, adhesion, phagocytosis, and TNF-α secretion and increased the cAMP content, β2-AR density, and mRNA expression of peritoneal macrophages. Meanwhile, the chemotaxis, adhesion, phagocytosis, TNF-α secretion, β2-AR density, and mRNA expression were reduced while the cAMP content was increased in NE-treated groups than those in N-C group. The results indicated that NE strengthens the immunosuppression induced by AlCl3 in cultured rat peritoneal macrophages through the β2-AR/cAMP pathway.

Aluminum chloride- and norepinephrine-induced immunotoxicity on splenic lymphocytes by activating β2-AR/cAMP/PKA/NF-κB signal pathway in rats

We found in our previous research that aluminum (Al) exposure induced immunotoxicity on spleen and increased norepinephrine (NE) content in serum from rats. However, it is unclear how NE is involved in the AlCl3 immunotoxicity on rats. Therefore, this experiment was designed to explore the mechanism of AlCl3 and NE-induced immunotoxicity on the splenic lymphocytes. Eighty male Wistar rats were orally exposed to AlCl3 (0, 64, 128, and 256 mg/kg BW) through drinking water for 120 days. Al contents in brain and spleen; NE contents in serum and in the hypothalamus; β2-AR density; cAMP content; β2-AR, PKA, and NF-κB mRNA expression levels; and protein expressions of PKA and nuclear NF-κB in splenic lymphocytes of AlCl3-treated rats were examined. The results showed that AlCl3 increased NE content in serum, the β2-AR density, the β2-AR and PKA (C-subunits) mRNA expression levels, cAMP content and the PKA (C-subunits) protein expression levels in lymphocytes, whereas, decreased NE content in the hypothalamus, the NF-κB (p65) mRNA expression level and nuclear NF-κB (p65) protein expression level in lymphocytes. These results indicated that the accumulated AlCl3 in spleen and the increased NE in serum induced the immunotoxicity on splenic lymphocytes by activating β2-AR/cAMP/PKA/NF-κB signal pathway in rats.