Tong Shen

Trichloroethylene induced cutaneous irritation in BALB/c hairless mice: Histopathological changes and oxidative damage

Trichloroethylene (TCE), a colorless and volatile organic solvent, has long been a major chemical hazard during occupational exposure because of its extensive use in industry. Exposure to TCE can cause significant skin lesions, but the effect of TCE on skin irritation has received little attention. We therefore investigated the effect of TCE on skin irritation and oxidative stress using hairless mice. BALB/c hairless mice were subjected to acute and cumulative topical TCE treatment. Skin reactions were evaluated by visual inspection, histopathology examined by microscopy and oxidative stress assessed by measurement of malondialdehyde (MDA) levels, superoxide dismutase (SOD) activities and nitric oxide (NO) production. Under acute and cumulative TCE irritation, the skin developed erythema and edema, and the predominant histopathological features were hyperkeratosis, spongiosis and inflammatory cell infiltrates. In parallel to these morphological changes, acute TCE irritation also concentration-dependently increased MDA levels and inhibited SOD activities of the skin. However, in cumulative irritation, the MDA levels and SOD activities were initially elevated with increased TCE concentrations, but thereafter reduced with further concentration increments; the linear dose-response relationship was not preserved. TCE also concentration-dependently increased NO production both in acute and cumulative irritation. These results suggest that TCE is capable of producing skin irritation effect in vivo, with histopathological changes characterized by hyperkeratosis, spongiosis and inflammatory cell infiltrates. Moreover, oxidative stress may be associated with the clinical manifestations and histopathological abnormalities in TCE-induced skin irritation.

Complement C3a binding to its receptor as a negative modulator of Th2 response in liver injury in trichloroethylene-sensitized mice.

Trichloroethylene (TCE) is a major occupational health hazard and causes occupational medicamentosa-like dermatitis (OMLDT) and liver damage. Recent evidence suggests immune response as a distinct mode of action for TCE-induced liver damage. This study aimed to explore the role of the key complement activation product C3a and its receptor C3aR in TCE-induced immune liver injury. A mouse model of skin sensitization was induced by TCE in the presence and absence of the C3aR antagonist SB 290157. Liver function was evaluated by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in conjunction with histopathological characterizations. C3a and C3aR were detected by immunohistochemistry and C5b-9 was assessed by immunofluorescence. IFN-γ and IL4 expressions were determined by flow cytometry and ELISA. The total sensitization rate was 44.1%. TCE sensitization caused liver cell necrosis and inflammatory infiltration, elevated serum ALT and AST, expression of C3a and C3aR, and deposition of C5b-9 in the liver. IFN-γ and IL-4 expressions were up-regulated in spleen mononuclear cells and their serum levels were also increased. Pretreatment with SB 290157 resulted in more inflammatory infiltration in the liver, higher levels of AST, reduced C3aR expression on Kupffer cells, and decreased IL-4 levels while IFN-γ remained unchanged. These data demonstrate that blocking of C3a binding to C3aR reduces IL4, shifts IFN-γ and IL-4 balance, and aggravates TCE-sensitization induced liver damage. These findings reveal a novel mechanism whereby modulation of Th2 response by C3a binding to C3a receptor contributes to immune-mediated liver damage by TCE exposure.

Protective Effects of Ginkgo biloba Leaf Extracts on Trichloroethylene-Induced Human Keratinocyte Cytotoxicity and Apoptosis

The objective of this study was to assess the protective effects of Ginkgo biloba leaf extracts (EGb) on trichloroethylene (TCE)-induced cytotoxicity and apoptosis in normal human epidermal keratinocytes (NHEK). Cytotoxicity was determined by neutral red uptake, and lipid peroxidation of the cells was assessed by malondialdehyde (MDA) and superoxide dismutase (SOD). Electron microscopy and flow cytometry were used to evaluate NHEK apoptosis. Treatment of NHEK with various concentrations of TCE caused a substantial decrease in cell viability. NR50 from the cytotoxicity assay was found to be 4.53 mM. TCE caused an increase in MDA, while an inhibition of SOD activity, in a concentration-dependent manner. Electron microscopic examination revealed typical morphologic changes of apoptosis in cells treated with TCE. Incubation of NHEK with TCE (0, 0.125, 0.5, 2.0 mM) for 4 h increased the proportion of apoptotic cells from control of 19.23% to nearly 44.35%. Pretreatment of EGb at 10–200 mg/l dose-dependently attenuated the cytotoxic effect of TCE, prevented TCE-induced elevation of lipid peroxidation and decline of antioxidant enzyme activities. Similar inhibition by EGb on TCE-mediated NHEK apoptosis was also observed. These results suggest that EGb can protect NHEK from TCE-induced cytotoxicity and apoptosis, which may be associated with the superoxide scavenging effect and enhancement of antioxidant enzyme activities.

Complement Activation and Liver Impairment in Trichloroethylene-Sensitized BALB/c Mice:

Our recent studies have shown that trichloroethylene (TCE) was able to induce multisystem injuries in the form of occupational medicamentosa-like dermatitis, including skin, kidney, and liver damages. However, the role of complement activation in the immune-mediated liver injury is not known. This study examined the role of complement activation in the liver injury in a mouse model of TCE-induced sensitization. Treatment of female BALB/c mice with TCE under specific dosing protocols resulted in skin inflammation and sensitization. Skin edema and erythema occurred in TCE-sensitized groups. Trichloroethylene sensitization produced liver histopathological lesions, increased serum alanine aminotransferase, aspartate transaminase activities, and the relative liver weight. The concentrations of serum complement components C3a-desArg, C5a-desArg, and C5b-9 were significantly increased in 24-hour, 48-hour, and 72-hour sensitization-positive groups treated with TCE and peaked in the 72-hour sensitization-positive group. Depositions of C3a, C5a, and C5b-9 into the liver tissue were also revealed by immunohistochemistry. Immunofluorescence further verified high C5b-9 expression in 24-hour, 48-hour, and 72-hour sensitization-positive groups in response to TCE treatment. Reverse transcription–polymerase chain reaction detected C3 messenger RNA expression in the liver, and this was significantly increased in 24-hour and 48-hour sensitization-positive groups with a transient reduction at 72 hours. These results provide the first experimental evidence that complement activation may play a key role in the generation and progression of immune-mediated hepatic injury by exposure to TCE.

Complement C5a–C5aR interaction enhances MAPK signaling pathway activities to mediate renal injury in trichloroethylene sensitized BALB/c mice

We have previously shown complement activation as a possible mechanism for trichloroethylene (TCE) sensitization, leading to multi‐organ damage including the kidneys. In particular, excessive deposition of C5 and C5b‐9‐the membrane attack complex, which can generate significant tissue damage, was observed in the kidney tissue after TCE sensitization. The present study tested the hypothesis that anaphylatoxin C5a binding to its receptor C5aR mediates renal injury in TCE‐sensitized BALB/c mice. BALB/c mice were sensitized through skin challenge with TCE, with or without pretreatment by the C5aR antagonist W54011. Kidney histopathology and the renal functional test were performed to assess renal injury, and immunohistochemistry and fluorescent labeling were carried out to assess C5a and C5aR expressions. TCE sensitization up‐regulated C5a and C5aR expressions in kidney tissue, generated inflammatory infiltration, renal tubule damage, glomerular hypercellularity and impaired renal function. Antagonist pretreatment blocked C5a binding to C5aR and attenuated TCE‐induced tissue damage and renal dysfunction. TCE sensitization also caused the deposition of major pro‐inflammatory cytokines IL‐2, TNF‐α and IFN‐γ in the kidney tissue (P < 0.05); this was accompanied by increased expression of P‐p38, P‐ERK and P‐JNK proteins (P < 0.05). Pretreatment with the C5aR antagonist attenuated the increase of expression of P‐p38, P‐ERK and P‐JNK proteins (P < 0.05) and also consistently reduced the TCE sensitization‐induced increase of IL‐2, TNF‐α and IFN‐γ (P < 0.05). These data identify C5a binding to C5aR, MAP kinase activation, and inflammatory cytokine release as a novel mechanism for complement‐mediated renal injury by sensitization with TCE or other environmental chemicals. Copyright

Gestational and lactational exposure to low-dose bisphenol A increases Th17 cells in mice offspring.

Increasing evidence demonstrates that perinatal exposure to Bisphenol A (BPA) can cause immune disorders throughout the life span. However, the biological basis for these immune disorders is poorly understood and the effects of exposure to BPA on Th17 development are unknown. The present study sought to characterize alterations of Th17 cells in childhood and adulthood following gestational and lactational exposure to environmentally relevant low-dose of BPA and the underlying mechanisms. Pregnant dams were exposed to BPA (10, 100 or 1000nM) via drinking water from gestational day (GD) 0 to postnatal day (PND) 21. At PNDs 21 and 42, offspring mice were anesthetized, blood was obtained for cytokine assay and spleens were collected for Th17 cell frequency and RORγt mRNA expression analysis. Perinatal exposure to low-dose BPA resulted in a dose-dependent and gender-specific persistent rise in Th17 cells accompanied by an increase of RORγt mRNA expression in the offsprings. The contents of major Th17 cell-derived cytokines (IL-17 and IL-21) and those essential for Th17 cell differentiation (IL-6 and IL-23) were also increased compared to those in controls. These changes were more pronounced in female than in male offsprings. However, perinatal exposure to low-dose BPA had little effect on serum TGF-β, another key regulator for Th17 cell development. Our results suggest that gestational and lactational exposure to a low-dose of BPA can affect Th17 cell development via an action on its transcription factor and the regulatory cytokines. These findings provide novel insight into sustained immune disorders by BPA exposure during development.

Association of a disintegrin and metalloprotease 33 (ADAM33) gene polymorphisms with the risk of COPD: an updated meta-analysis of 2,644 cases and 4,804 controls

A series of observational studies have been made to investigate the association of the ADAM33 gene polymorphisms with the risk of COPD, but their results were conflicting. Therefore, we performed an updated meta-analysis to quantitatively summarize the associations of ADAM33 gene polymorphisms with the risk of COPD. Thirteen case–control studies referring to nine SNPs were identified: V4 (rs2787094), T+1 (rs2280089), T2 (rs2280090), T1 (rs2280091), S2 (rs528557), S1 (rs3918396), Q−1 (rs612709), F+1 (rs511898) and ST+5 (rs597980). A dominant model (AA+Aa vs. aa), recessive model (AA vs. Aa+aa), additive model (AA vs. aa) and allelic model (A vs. a) were used to evaluate the association of ADAM33 polymorphism with the risk of COPD. The results indicated that significant associations were found for ADAM33 T1, T2, S1, Q−1, F+1 and ST+5 polymorphisms associated with the risk of COPD in different populations. However, no significant associations were found for V4, T+1 and S2 polymorphisms with the risk of COPD in all genetic models, even in the subgroup analysis by ethnicity. This meta-analysis provided evidence that the ADAM33 T1, T2, S1, Q−1, F+1 and ST+5 six locus polymorphisms association with the risk of COPD. Furthermore, T2, Q−1 and ST+5 indicated an association with the risk of COPD in the European populations, whereas T1, T2, S1, F+1 and Q−1 indicated an association with the risk of COPD in the Asian populations.

An Animal Model of Trichloroethylene-Induced Skin Sensitization in BALB/c Mice.

Trichloroethylene (TCE) is a major occupational hazard and environmental contaminant that can cause multisystem disorders in the form of occupational medicamentosa-like dermatitis. Development of dermatitis involves several proinflammatory cytokines, but their role in TCE-mediated dermatitis has not been examined in a well-defined experimental model. In addition, few animal models of TCE sensitization are available, and the current guinea pig model has apparent limitations. This study aimed to establish a model of TCE-induced skin sensitization in BALB/c mice and to examine the role of several key inflammatory cytokines on TCE sensitization. The sensitization rate of dorsal painted group was 38.3%. Skin edema and erythema occurred in TCE-sensitized groups, as seen in 2,4-dinitrochlorobenzene (DNCB) positive control. Trichloroethylene sensitization-positive (dermatitis [+]) group exhibited increased thickness of epidermis, inflammatory cell infiltration, swelling, and necrosis in dermis and around hair follicle, but ear painted group did not show these histological changes. The concentrations of serum proinflammatory cytokines including tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL)-2 were significantly increased in 24, 48, and 72 hours dermatitis [+] groups treated with TCE and peaked at 72 hours. Deposition of TNF-α, IFN-γ, and IL-2 into the skin tissue was also revealed by immunohistochemistry. We have established a new animal model of skin sensitization induced by repeated TCE stimulations, and we provide the first evidence that key proinflammatory cytokines including TNF-α, IFN-γ, and IL-2 play an important role in the process of TCE sensitization.

Plasma Kallikrein-Kinin system mediates immune-mediated renal injury in trichloroethylene-sensitized mice.

Abstract Trichloroethylene (TCE) is a major environmental pollutant. An immunological response is a newly-recognized mechanism for TCE-induced kidney damage. However, the role of the plasma kallikrein-kinin system (KKS) in immune-mediated kidney injury has never been examined. This study aimed to explore the role of the key components of the KKS, i.e. plasma kallikrein (PK), bradykinin (BK) and its receptors B1R and B2R, in TCE-induced kidney injury. A mouse model of skin sensitization was used to explore the mechanism of injury with or without a PK inhibitor PKSI. Kidney function was evaluated by measuring blood urea nitrogen (BUN) and creatinine (Cr) in conjunction with histopathologic characterization. Plasma BK was determined by ELISA; Renal C5b-9 membrane attack complex was evaluated by immunohistochemistry. Expression of BK and PK in the kidney was detected by immunofluorescence. mRNA and protein levels of B1R and B2R were assessed by real-time qPCR and Western blot. As expected, numerous inflammatory cell infiltration and tubular epithelial cell vacuolar degeneration were observed in TCE-sensitized mice. Moreover, serum BUN and Cr and plasma BK were increased. In addition, deposition of BK, PK and C5b-9 were observed and B1R and B2R mRNA and proteins levels were up-regulated. Pre-treatment with PKSI, a highly selective inhibitor of PK, alleviated TCE-induced renal damage. In addition, PKSI attenuated TCE-induced up-regulation of BK, PK and its receptors and C5b-9. These results provided the first evidence that activation of the KKS contributed to immune-mediated renal injury induced by TCE and also helped to identify the KKS as a potential therapeutic target for mitigating chemical sensitization-induced renal damage.

Trichloroethylene Alters Th1/Th2/Th17/Treg Paradigm in Mice: A Novel Mechanism for Chemically Induced Autoimmunity.

The role of environmental factors in autoimmune diseases has been increasingly recognized. While major advance has been made in understanding biological pathogen-induced autoimmune diseases, chemically triggered autoimmunity is poorly understood. Trichloroethylene (TCE), a common environmental pollutant, has recently been shown to induce autoimmunity. This study explored whether TCE could cause imbalance of T helper (Th) cell subsets which would contribute to the pathogenesis of TCE-induced medicamentosa-like dermatitis. BALB/c mice were treated with TCE via drinking water at doses of 2.5 or 5.0 mg/mL for 2, 4, 8, 12, and 16 weeks. Trichloroethylene exposure caused time- and dose-dependent increase in Th1, Th2, and Th17 and decrease in regulatory cell (Treg) in the spleen at 2, 4, 8, 12, and 16 weeks, with greatest changes mainly at 4 weeks. These effects were mirrored by similar changes in the expression of their corresponding cytokines interferon-γ, interleukin 4 (IL-4), IL-17A, and IL-10. Mechanistically, these phenotypic changes were accounted for by alterations to their respective master transcription factors T-box expressed in T cells, GATA-binding protein 3, Retinoic acid-related orphan receptor ct (RORct), and forkhead box P3. Of interest, TCE treatment shifted the ratios of Th1/Th2 and Th17/Treg; specifically, TCE increased Th17/Treg. These findings provide the first evidence that TCE exposure significantly changes the Th1/Th2/Th17/Treg paradigm and their specific cytokines driven by altered master transcription factors. This may promote autoimmune reactions in the pathogenesis of TCE-induced skin sensitization and associated damage to other tissues.