Low-dose cadmium activates the JNK signaling pathway in human renal podocytes

Hypoxia Inhibits Proliferation of Human Dermal Lymphatic Endothelial Cells via Downregulation of Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 Expression

OBJECTIVE

Lymphatic endothelial cell (LEC) proliferation is essential for lymphangiogenesis. Hypoxia induces lymphangiogenesis, but it directly inhibits LEC proliferation and the underlying mechanisms have not been fully understood. The aim of this study was to investigate the role of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in hypoxia-repressed LEC proliferation.

METHODS

Human dermal lymphatic endothelial cells (HDLECs) were cultured under normoxic or hypoxic conditions, and cell proliferation was determined using MTT or CCK-8 assays. CEACAM1 expression was silenced by siRNA transfection. Activation of mitogen-activated protein kinases (MAPKs) was examined by Western blotting and blocked by specific inhibitors.

RESULTS

Under hypoxia, HDLECs proliferation was suppressed and CEACAM1 expression was downregulated. Silence of CEACAM1 in normoxia inhibited HDLECs proliferation and did not further decrease proliferation in HDLECs in response to hypoxia, suggesting that CEACAM1 may mediate hypoxia-induced inhibition of HDLECs proliferation. In addition, silence of CEACAM1 increased phosphorylation of MAPK molecules: extracellular signal-regulated kinase (ERK), p38 MAPK and Jun N-terminal kinase (JNK) in HDLECs. However, only inhibition of the JNK pathway rescued the reduction of HDLEC proliferation induced by CEACAM1 silence.

CONCLUSION

Our results suggested that hypoxia downregulates CEACAM1 expression by activation of the JNK pathway, leading to inhibition of HDLEC proliferation. These findings may help to understand the mechanisms of LEC-specific response to hypoxia and develop novel therapies for pathological lymphangiogenesis.

Alpha-Linolenic Acid Impedes Cadmium-Induced Oxidative Stress, Neuroinflammation, and Neurodegeneration in Mouse Brain

Alpha-Linolenic acid (ALA), an omega-3 polyunsaturated fatty acid, is extracted from plant sources and has been shown to be one of the anti-inflammatory and antioxidant agents. Herein, we revealed the molecular mechanism underlying the anti-inflammatory and antioxidant potential of (ALA), against cadmium in the adult mouse brain. We evaluated the neuroprotective effect of ALA (60 mg/kg per oral for 6 weeks) against CdCl₂ (5 mg/kg)-induced oxidative stress, neuroinflammation, and neuronal apoptosis. According to our findings, ALA markedly reduced ROS production and nitric oxide synthase 2 (NOS2) and enhanced the expression of nuclear factor-2 erythroid-2 (Nrf-2) and heme oxygenase-1 (HO-1) in mice treated with CdCl₂. Most importantly, the molecular docking study revealed that ALA allosterically decreases the overexpression of c-Jun N-terminal kinase (JNK) activity and inhibited the detrimental effect against CdCl₂. Moreover, ALA suppressed CdCl₂-induced glial fibrillary acidic protein (GFAP), nuclear factor-kappa b (NF-κB), and interleukin-1β (IL-1β) in the mouse brain. Further, we also checked the pro- and anti-apoptotic proteins markers such as Bax, Bcl-2, and caspase-3, which were regulated in the cortex of ALA co-treated mouse brain. Overall, our study suggests that oral administration of ALA can impede oxidative stress, neuroinflammation, and increase neuronal apoptosis in the cortex of Cd-injected mouse brain.

Damage to the Testicular Structure of Rats by Acute Oral Exposure of Cadmium

Cadmium (Cd) is one of the most important heavy metal toxicants, used throughout the world at the industrial level. It affects humans through environmental and occupational exposure and animals through the environment. The most severe effects of oral exposure to Cd on the male reproductive system, particularly spermatogenesis, have not been discussed. In this study, we observed the damage to the testes and heritable DNA caused by oral exposure to Cd. Adult male Sprague–Dawley rats were divided into four groups: a control group and three groups treated with 5, 10, and 15 mg Cd/kg/day for 17 days by oral gavage. Our results revealed that Cd significantly decreases weight gain in 10 and 15 mg/kg groups, whereas the 5 mg/kg groups showed no difference in weight gain. The histopathology showed adverse structural effects on the rat testis by significantly reducing the thickness of the tunica albuginea, the diameter of the tubular lumen, and the interstitial space among seminiferous tubules and increasing the height of the epithelium and the diameter of the seminiferous tubules in Cd treated groups. Comet assay in epididymal sperms demonstrated a significant difference in the lengths of the head and comet in all the 3 Cd treated groups, indicating damage in heritable DNA, although variations in daily sperm production were not significant. Only a slight decrease in sperm count was reported in Cd-treated groups as compared to the control group, whereas the tail length, percentage of DNA in head, and tail showed no significant difference in control and all the experimental groups. Overall, our findings indicate that Cd toxicity must be controlled using natural sources, such as herbal medicine or bioremediation, with non-edible plants, because it could considerably affect heritable DNA and induce damage to the reproductive system.

Manganese exposure induces permeability in renal glomerular endothelial cells via the Smad2/3-Snail-VE-cadherin axis

Manganese (Mn) is an essential micronutrient. However, it is well established that Mn overexposure causes nervous system diseases. In contrast, there are few reports on the effects of Mn exposure on glomerular endothelium. In the present study, the potential effects of Mn exposure on glomerular endothelium were evaluated. Sprague Dawley rats were used as a model of Mn overexposure by intraperitoneal injection of MnCl₂·H₂O at 25 mg/kg body weight. Mn exposure decreased expression of vascular endothelial-cadherin, a key component of adherens junctions, and increased exudate from glomeruli in Sprague Dawley rats. Human renal glomerular endothelial cells were cultured with different concentration of Mn. Exposure to 0.2 mM Mn increased permeability of human renal glomerular endothelial cell monolayers and decreased vascular endothelial-cadherin expression without inducing cytotoxicity. In addition, Mn exposure increased phosphorylation of mothers against decapentaplegic homolog 2/3 and upregulated expression of zinc finger protein SNAI1, a negative transcriptional regulator of vascular endothelial-cadherin. Our data suggest Mn exposure may contribute to development of glomerular diseases by inducing permeability of glomerular endothelium.