A Preliminary Study On Mechanism Of Occupational Contact Dermatitis Caused By Nickel

ObjectiveOccupational contact dermatitis（OCD）caused by nickel（Ni）is a common occupational skin disease which is also a problem that needs attention in our country’s occupational health field.OCD will bring inconvenience in life and work to patients.At present,the pathogenesis of this disease has been studied but it is not yet clear,so it is difficult to provide effective prevention and treatment for patients.This article attempts to explore the possible mechanisms of nickel-induced OCD through the coculture of two immune related cells.The viability of HaCaT cells,the level of ROS in THP-1 cells and the expression of surface markers CD54 and CD86,and the secretion of inflammatory cytokines IL-18,IL-1β,and IL-8 were detected and analyzed.A preliminary exploration of the possible mechanism of OCD induced by nickel was made.Method1.Effects of nickel compounds on HaCaT cells:Different concentrations of NiCl₂·6H₂O and NiSO₄·6H₂O solutions were prepared,and the cytotoxicity of the two compounds against HaCaT cells in vitro was detected by MTT.3.Effect of nickel compounds on THP-1 cells:Different concentrations of NiCl₂·6H₂O and NiSO₄·6H₂O solutions were prepared,to detect change of intracellular ROS levels and cell surface markers（CD54,CD86）of THP-1 at the cell viability was greater than 50%.3.Use HaCaT cells and THP-1 cells to establish a coculture system:Then exposed to different concentrations of NiCl₂·6H₂O and NiSO₄·6H₂O solutions to detect the expression of surface markers（CD54,CD86）on THP-1 cells and the secretion of inflammatory cytokines（IL-18,IL-1β,IL-8）in culture medium.The data was analyzed to compare the differences between the coculture system and the single cell system.A preliminary exploration of the interactive relationship between this two kinds of cells in the process of nickel induced OCD.Results1.Under this experimental conditions,two kinds of nickel compounds can produce toxic effects on HaCaT cells,the IC₅₀ of NiCl₂·6H₂O is273.44μg/mL and the CV75 is 113.30μg/mL;the IC₅₀ and CV75 of NiSO₄·6H₂O is 392.71μg/mL and 191.65μg/mL,respectively.The mechanism of nickel induced OCD may be related to its damage to epidermal cells.2.As a result of the effect of two kinds of nickel compounds on THP-1cells,under the experimentally designed concentration range,NiCl₂·6H₂O failed to induce the change of ROS level in THP-1 cell and the expression of cell surface markers（CD54,CD86）;NiSO₄·6H₂O can not cause the ROS level changes in THP-1 cell,but it can make THP-1 cell surface markers CD54,CD86 rise,indicating that the sensitization mechanism of this two kinds nickel compounds will not cause the ROS level changes in THP-1 cell.NiCl₂·6H₂O does not directly affect THP-1 cells during sensitization,while NiSO₄·6H₂O can directly activate THP-1 cells,causing rise of cell surface markers,indicating that the acid ions(Cl^-,SO₄^2-)bind with nickel compounds may have some influence on its sensitization mechanism.3.Under the experimental conditions,the results of the coculture method using HaCaT cells and THP-1 cells showed that:under the coculture system,the surface markers CD54 and CD86 of THP-1 cells were still not observed by NiCl₂·6H₂O;but can enhance the effect on the surface markers by NiSO₄·6H₂O.Comparing the secretion of inflammatory factors by HaCaT cells and THP-1 cells by two kinds of nickel compounds,it was found that the two nickel compounds did not increase the secretion of IL-8 in HaCaT cells at all concentrations,but increased the secretion of IL-1βand have dose-efect relationship,and the IL-18 secretion was increased at 125μg/mL and 250μg/mL but no effect was observed at 31.25μg/mL and 62.50μg/mL;this two kinds of nickel compounds can increase the secretion of IL-8 and IL-1βin THP-1,but have no effect on IL-18.When use coculture system,its effect on IL-18 is not affected when the concentration is lower than 125μg/mL,at the concentration of 250μg/mL can increase the secretion of IL-18,but significantly lower than that of HaCaT cells.There was no significant difference in the secretion of IL-8 compared with THP-1 cells,and IL-1βsecretion was significantly higher than the sum of he concentrations of two single cell groups.It is suggested that the IL-18 produced by HaCaT cells may bind to THP-1 cell surface receptors and reduce the concentration of IL-18 in the culture medium;the interaction between the two types of cells can promote the secretion of IL-1β;the secretion of THP-1 cells.IL-8 is not affected by HaCaT cells.ConclusionIn this study,HaCaT cells and THP-1 cells were cultured in vitro to explore the possible sensitization mechanisms of two kinds by nickel compounds.The possible mechanism of OCD induced by NiCl₂·6H₂O and NiSO₄·6H₂O may be related to the damage of HaCaT cells,and not related to the level of ROS in THP-1 cells.The OCD induced by NiCl₂·6H₂O may not be related to the activation of THP-1 cells.NiSO₄·6H₂O may induce OCD through activation of THP-1 cells;during the course of OCD,IL-18 produced by HaCaT cells may act on THP-1cells,and both types of cells can promote secretion of IL-1βwhen cocultured.The secretion of IL-8 by THP-1 cells may not be regulated by HaCaT cells.