Granulysin-mediated reduction of PDZRN3 induces Cx43 gap junctions activity exacerbating skin damage in trichloroethylene hypersensitivity syndrome

Trichloroethylene (TCE)-induced hypersensitivity syndrome (THS) has been a concern for many researchers in the field of environmental and occupational health. Currently, there is no specific treatment for THS, leaving patients to contend with severe infections arising from extensive skin lesions, consequently leading to serious adverse effects. However, the pathogenesis of severe skin damage in THS remains unclear. This study aims to investigate the specific danger signals and mechanisms underlying skin damage in THS through in vivo and in vitro experiments. We identified that cell supernatant containing 15 kDa granulysin (GNLY), released from activated CD3-CD56+NK cells or CD3+CD56+NKT cells in PBMC induced by TCE or its metabolite, promoted apoptosis in HaCaT cells. The apoptosis level decreased upon neutralization of GNLY in the supernatant by a GNLY-neutralizing antibody in HaCaT cells. Subcutaneous injection of recombinant 15 kDa GNLY exacerbated skin damage in the THS mouse model and better mimicked patients' disease states. Recombinant 15 kDa GNLY could directly induce cellular communication disorders, inflammation, and apoptosis in HaCaT cells. In addition to its cytotoxic effects, GNLY released from TCE-activated NK cells and NKT cells or synthesized GNLY alone could induce aberrant expression of the E3 ubiquitin ligase PDZRN3, causing dysregulation of the ubiquitination of the cell itself. Consequently, this resulted in the persistent opening of gap junctions composed of connexin43, thereby intensifying cellular inflammation and apoptosis through the "bystander effect". This study provides experimental evidence elucidating the mechanisms of THS skin damage and offers a novel theoretical foundation for the development of effective therapies targeting severe dermatitis induced by chemicals or drugs.

Trichloroethylene and trichloroethanol induce skin sensitization with focal hepatic necrosis in guinea pigs

OBJECTIVES

Occupational exposure to trichloroethylene (TCE) induces trichloroethylene hypersensitivity syndrome (TCEHS), which causes hypersensitivity dermatitis and hepatitis. However, whether TCE itself or its two metabolites, trichloroethanol (TCEOH) and trichloroacetic acid (TCA), are involved in TCEHS remains unclear. Therefore, in this study we explored the allergens causing TCEHS and characterized TCEHS-related liver injury in guinea pigs.

METHOD

The guinea pig maximization test was performed using TCE, TCEOH, and TCA as candidate allergens. Skin inflammation was scored, and liver function and histopathological changes were evaluated by biochemical tests and hematoxylin and eosin staining, respectively.

RESULTS

The sensitization rates for TCE, TCEOH, and TCA were 90.0%, 50.0%, and 0.0%, respectively. In the TCE and TCEOH experimental groups, the skin showed varying degrees of erythema with eosinophil granulocyte infiltration in the dermis. Additionally, serum alanine aminotransferase and γ-glutamyl transpeptidase levels increased significantly, and histological analysis revealed focal hepatocellular necrosis with inflammatory cell infiltration in the liver.

CONCLUSIONS

TCE is the main cause of allergy and TCEOH is a secondary factor for allergy in guinea pigs. TCE and TCEOH can cause immune-mediated skin sensitization complicated by focal hepatic necrosis.

The critical role for TAK1 in trichloroethylene-induced contact hypersensitivity in vivo and in CD4+ T cell function alteration by trichloroethylene and its metabolites in vitro

Occupational exposure to trichloroethylene (TCE) has been associated with severe, generalized contact hypersensitivity (CHS) skin disorder, which is considered a delayed-type hypersensitivity reaction mediated by antigen-specific T cells. Transforming growth factor-β activated kinase-1 (TAK1) is essential for regulating the development and effector function of T cells. We hypothesized that disrupting TAK1 activity might inhibit TCE-induced CHS response. In this study, a local lymph node assay was employed to build a CHS model induced by TCE combined with the inducible-TAK1 deletion system to study the effect of TAK1 on it. It was observed that TAK1 deficiency ameliorated the TCE-induced CHS response and was associated with defective T cell expansion and activation and IFN-γ production in vivo. Furthermore, we investigated the effects of TCE and its metabolites trichloroacetic acid (TCA) and dichloroacetic acid (DCA) on CD4⁺ T cell function and the effect of TAK1 on it in vitro. The results showed that TCE, TCA and DCA augmented the proliferation, activation and differentiation of CD4⁺ T cells through Jnk MAPK and NF-κB pathways. TAK1 deletion significantly attenuated these effects induced by TCE, TCA or DCA on CD4⁺ T cells. In conclusion, it is suggested that TAK1 plays a critical role both in TCE-induced CHS response in vivo and in TCE and its metabolite-induced CD4⁺ T cell activation in vitro. Local inhibition of TAK1 might offer a promising alternative feasible strategy for TCE-induced CHS.

The toll like receptor 4-myeloid differentiation factor 88 pathway is essential for particulate matter-induced activation of CD4-positive cells

Asian sand dust (ASD), a type of particulate matter (PM) found in Asia, can be transported to East Asia. We recently found that acute splenic inflammation is induced by ASD in mouse models. In this study, we examined the effect of sub-chronic ASD exposure on mouse immune cells. Mice were intratracheally administered ASD once every 2 weeks for 8 weeks and killed 24 hours after the final administration. Wild-type (WT) mice showed increased cell viability after ASD administration. In contrast, ASD administration induced splenocyte activation in toll-like receptor (TLR)2^-/- , but not TLR4^-/- mice. Furthermore, concanavalin A-induced interleukin-2 production increased after ASD administration in WT and TLR2^-/- mice, but not in TLR4^-/- or myeloid differentiation factor (MyD)88^-/- mice. Immunoblotting demonstrated that nuclear factor κB (NF-κB) was activated in WT mice, but not in TLR4^-/- or MyD88^-/- mice. The NF-κB-dependent gene products CDK2 and intercellular cell adhesion molecule-1 were upregulated upon ASD administration in WT mice, but not in TLR4^-/- or MyD88^-/- mice. Furthermore, the particles themselves, rather than particle constituents, activated NF-κB in CD4-positive cells through the TLR4 or MyD88 pathway. Taken together, these results indicate that particle-induced splenic inflammation occurs via TLR4-MyD88 signaling.

The immune response in trichloroethylene hypersensitivity syndrome: A review

Trichloroethylene (TCE) has been used for a variety of industrial and consumer cleaning purposes because of its ability to dissolve organic substances. The multisystem injuries include those of skin, liver, and kidney, which are defined as TCE hypersensitivity syndrome (THS). THS is a serious occupational health issue. However, the mechanism of immune dysfunction leading to organ injury is poorly understood. Many studies reveal that skin lesions and organ injury caused by TCE are consistent with type IV hypersensitivity, also called delayed hypersensitivity, mediated by T cells. However, many researchers found T cell-mediated type IV hypersensitivity could not account for the pathogenesis of THS fully. Humoral immunity, including immunoglobulins and complement activation, may also play a possible role in THS pathogenesis. This review will describe the history, current understanding, and future research directions of the mechanism of THS.