Chronic Low-Dose Cadmium Exposure Impairs Cutaneous Wound Healing With Defective Early Inflammatory Responses After Skin Injury

Novel approach for enhancing skin allograft survival by bioadhesive nanoparticles loaded with rapamycin

Skin graft rejection is a significant challenge in skin allografts for skin defects, particularly in extensive burn injury patients when autografts are insufficient. Enhancing the survival duration of allogeneic skin grafts can improve the success rate of subsequent autologous skin grafting, thereby promoting the therapeutic efficacy for wound healing. Rapamycin (Rapa), a potent immunosuppressant with favorable efficacy in organ transplantation, is limited by its systemic administration-associated toxicity and side effects. Therefore, addressing the short survival time of allogeneic skin grafts and minimizing the toxicity related to systemic application of immunosuppressive agents is an urgent requirement. Here, we present a topical formulation based on bioadhesive poly (lactic acid)-hyperbranched polyglycerol nanoparticles (BNPs) with surface-modified encapsulation of Rapamycin (Rapa/BNPs), applied for local immunosuppression in a murine model of allogeneic skin grafts. Our Rapa/BNPs significantly prolong nanoparticle retention, reduce infiltration of T lymphocytes and macrophages, decrease the level of pro-inflammatory cytokines and ultimately extend skin allograft survival with little systemic toxicity compared to free Rapa or Rapamycin-loaded non-bioadhesive nanoparticles (Rapa/NNPs) administration. In conclusion, Rapa/BNPs effectively deliver local immunosuppression and demonstrate potential for enhancing skin allograft survival while minimizing localized inflammation, thus potentially increasing patient survival rates for various types of skin defects.

Effect of amendments on bioavailability of cadmium in soil-rice system: a field experiment study

The field experiment study investigated the effect of lime (L), manure compost (M), combination of lime and manure (LM), and combinations of lime with four kinds of passivators (LP1, LP2, LP3, and LP4) on the bioavailability of cadmium (Cd) in soil and Cd accumulation in rice plants. These four passivating products were composed of organic and inorganic compounds such as silicon-sulfhydryl group, CaO, SiO₂, and so on. The results indicated that the application of these amendments improved soil pH, organic matter content, and cation exchange capacity (CEC) by 0.19-0.73 unit, 0.6-8.2%, and 5.7-38.9%, respectively; meanwhile, decreased soil acid-extractable Cd by 4.0-13.9% compared with before remediation. Alleviating Cd stress to rice also resulted in a significant increase in rice grains yield, whereas the LP4 showed an increment of 15.8-27.6%. Among these amendments, LP4 had a relatively high effectiveness, it promoted the decrease of extractable Cd by 13.9% and the increase of residual Cd by 8.1%; meanwhile, the bioconcentration factor of rice grain in LP4 decreased by 71.3%. The high pH, CEC, and rich functional groups in amendments might cause soil Cd transform from mobile fraction to residual fraction, and the cation ions in amendments also competed with Cd ions due to the antagonism. Taken all of these effects, the amendments alleviated Cd pollution in soil-rice system, decreasing Cd migration from soil to grain. In future, the long-term field experiment will need to be done for verify the long-term effect of soil amendments.

Cadmium impairs the development of natural killer cells and bidirectionally modifies their capacity for cytotoxicity

Cadmium (Cd) is a highly toxic heavy metal in the environment. The aim of this study was to investigate the impact of Cd on natural killer (NK) cells. C57BL/6 mice were treated with 10 ppm Cd via drinking water for 3 months, and the development of NK cells in the bone marrow (BM) and the cytotoxicity of mature NK (mNK) cells in the peripheral immune organs were evaluated thereafter; the impact of Cd on the cytotoxicity of mNK cells from human peripheral blood mononuclear cells (PBMC) was also investigated. Whereas Cd treatment impaired the differentiation of NK progenitors in the BM, Cd treatment activated the JAK3/STAT5 signaling to drive the proliferation of mNK cells and thereby lead to a compensation increase of mNK cells in the peripheral immune organs of mice. Additionally, Cd treatment bidirectionally regulated the cytotoxicity of mouse mNK cells to differential tumor cells, dependent on the levels of Fas expression in the tumor cells; mechanically, Cd treatment activated the JAK3/STAT5 signaling to promote the expression of FasL in mNK cells to increase their cytotoxicity, while Cd treatment reduced the expression of granzyme B in mNK cells to impair their cytotoxicity in the peripheral immune organs of mice. Likewise, in vitro assays indicated that Cd treatment also activated the JAK3/STAT5 signaling to increase the expression of FasL, whereas Cd treatment reduced the expression of granzyme B in human mNK cells. Thus Cd treatment impaired the development of NK cells in the BM and bidirectionally regulated the cytotoxicity of mNK cells in the peripheral immune organs, which may extend our current understanding for the immunotoxicity of Cd.

Study on the mechanism of cadmium chloride pollution accelerating skin tissue metabolism disorder, aging and inhibiting hair regeneration

Drinking water contaminated by Cd2⁺ is one of the main pathways for Cd to enter the body. The skin barrier is destroyed when the skin is contaminated by environmental Cd2⁺, however, the detailed mechanism by which Cd2⁺ induces skin metabolic disorder, and senescence and affects hair regeneration is not completely understood. In this study, 18 C57BL/6 mice were randomly divided into a Control group, a Low-dose group, and a High-dose group with 6 mice in each group, and intragastrically administered with different concentrations of cadmium chloride once a day, respectively. After 1 month of intervention, the skin tissues on the back of mice were collected for non-targeted metabolomics analysis, and the related proteins were detected by immunofluorescence assay. Non-targeted metabolomics analysis result showed that compared with the Control group, there were 29 different metabolites, mainly including lysophospholipids, fatty acids, and bile acids, in the Low-dose group, and 39 differential metabolites in the High-dose group, in addition to the above compounds, there were more amino acid compounds, and most of the metabolites had a reduced response after administration. Immunofluorescence assay result showed that the higher the concentration of cadmium chloride led to the more obvious the proliferation inhibition and apoptosis promotion effects of skin cells, and the more significant damage to hair follicle stem cells. Thus, our findings demonstrate that cadmium chloride pollution can accelerate skin metabolism disorder, and aging and impair hair regeneration.

Diet supplementation of astaxanthin mitigates cadmium induced negative effects on oxidative, inflammatory and non-specific immune responses, and the intestinal morphology in Trachinotus ovatus

Knowledge about additive on alleviating the negative effects of fish exposed to cadmium (Cd) needs to be more identified in the aquaculture. Therefore, the present study aims to investigate whether diet supplemented with astaxanthin could mitigate adverse effects on hepatic Cd deposition, oxidative, inflammatory and non-specific immune responses, and intestinal morphology of Trachinotus ovatus exposed to dietary Cd treatment. Three isonitrogen-isolipid experimental diets supplemented with/without CdCl₂/Astaxanthin were formulated to feed the T. ovatus for 30 days. Results demonstrated that considerably higher hepatic Cd level was found in two Cd supplementing groups compared to the control group (p < 0.05), while no statistical difference of hepatic Cd concentration between these two Cd supplementing groups (p > 0.05). The activity of hepatic total superoxide dismutase, RNA expression levels of hepatic Nrf2-keap1 pathway genes, pro-inflammatory genes, and non-specific immune genes were no statistical differences between the control group and the dietary Cd supplementing group (p > 0.05), while these data in the dietary Cd with astaxanthin group showed significantly higher than that in the dietary Cd without astaxanthin group (p < 0.05). On the contrary, hepatic malondialdehyde content in the dietary Cd group showed significantly higher than that in the control group and dietary Cd with astaxanthin group (p < 0.05). Significantly lower mid-intestine morphology parameters were obtained in the dietary Cd group than the control group (p < 0.05), while significantly higher data were found in the dietary Cd with astaxanthin group compared to the dietary Cd group (p < 0.05). These results indicated that astaxanthin could mitigate the inhibitory effects of Cd on the oxidative, inflammatory and non-specific immune responses, and intestinal morphology of T. ovatus while not reduce the hepatic Cd deposition.

Comparing the effects of calcium and magnesium ions on accumulation and translocation of cadmium in rice

Rice (Oryza sativa L.) is one of China's most important food crops, and it is considered the primary source of human exposure to cadmium (Cd) pollution. Adding calcium (Ca) and magnesium (Mg) to the plant nutrient solutions reduces the accumulation of Cd in the rice, but under the same condition, which one has the better effect remains unclear. Thus, hydroponic experiments were performed to compare the effects of Ca and Mg ions with concentration gradients (0.10, 0.25, and 0.50 g/L, respectively) on the absorption, distribution, and translocation of Cd in rice. The Cd contents of roots, stems, leaves, panicles, husks, and grains in different growth stages were determined. The results revealed that the supplementation of both Ca and Mg influenced the Cd accumulation and translocation in rice tissues. The Cd concentrations of different patterns were in the following order: roots > stems > leaves ≈ panicles ≈ husks > grains. Both of Ca and Mg had an apparent antagonism with Cd in different parts of the rice plant, and the antagonism was more obvious in the high Cd stress treatments. With the addition of 0.1 g/L Ca²⁺ and Mg²⁺ ions, the grain Cd contents increased, while the application of 0.25 and 0.5 g/L Ca²⁺ and Mg²⁺ ions reduced grains Cd by 19.08-38.99%, with the average value of 26.75%. Under the same concentrations, the grain Cd content of Ca treatments was lower than that of Mg treatments by 8.74%. In the Ca (Mg)-deficient and Ca (Mg)-sufficient conditions, the husks and panicles accumulated Cd to hinder Cd translocation, respectively. Altogether, the results of this study indicated that Ca had a greater effect for decreasing rice Cd accumulation and translocation than Mg, and the panicle and husk were the important parts for reducing Cd translocation to grain, and these might be a focal point for the future research. It was possible to plant and grow rice in Cd-polluted soil and that the accumulation and translocation of Cd in rice plants could be reduced by optimizing soil nutrient elements.

Cadmium exposure reprograms energy metabolism of hematopoietic stem cells to promote myelopoiesis at the expense of lymphopoiesis in mice

Cadmium (Cd) is a highly toxic heavy metal in our living environment. Hematopoietic stem cells (HSC) are ancestors for all blood cells. Therefore understanding the impact of Cd on HSC is significant for public health. The aim of this study was to investigate the impact of Cd²⁺ on energy metabolism of HSC and its involvement in hematopoiesis. Wild-type C57BL/6 mice were treated with 10 ppm of Cd²⁺ via drinking water for 3 months, and thereafter glycolysis and mitochondrial (MT) oxidative phosphorylation (OXPHOS) of HSC in the bone marrow (BM) and their impact on hematopoiesis were evaluated. After Cd²⁺ treatment, HSC had reduced lactate dehydrogenase (LDH) activity and lactate production while having increased pyruvate dehydrogenase (PDH) activity, MT membrane potential, ATP production, oxygen (O₂) consumption and reactive oxygen species (ROS), indicating that Cd²⁺ switched the pattern of energy metabolism from glycolysis to OXPHOS in HSC. Moreover, Cd²⁺ switch of HSC energy metabolism was critically dependent on Wnt5a/Cdc42/calcium (Ca²⁺) signaling triggered by a direct action of Cd²⁺ on HSC. To test the biological significance of Cd²⁺ impact on HSC energy metabolism, HSC were intervened for Ca²⁺, OXPHOS, or ROS in vitro, and thereafter the HSC were transplanted into lethally irradiated recipients to reconstitute the immune system; the transplantation assay indicated that Ca²⁺-dependent MT OXPHOS dominated the skewed myelopoiesis of HSC by Cd²⁺ exposure. Collectively, we revealed that Cd²⁺ exposure activated Wnt5a/Cdc42/Ca²⁺ signaling to reprogram the energy metabolism of HSC to drive myelopoiesis at the expense of lymphopoiesis.

Effect of occupational co-exposure to lead and cadmium on selected immunomodulatory cytokines

Occupational exposure to heavy metals like lead (Pb) and cadmium (Cd) is associated with the development of several diseases. The objective of this study was to determine the effect of occupational co-exposure to Pb and Cd on the blood levels of selected immune-modulatory cytokines related to T helper (Th), that is, Th1, interleukin-2 (IL-2), Th2, (IL-4 and IL-10), and Th17, (IL-17) cells. The study comprised 207 individuals divided into two groups: exposed (n = 110) and nonexposed (n = 97). Blood Pb and Cd were determined using Graphite Furnace Atomic Absorption Spectroscopy, and serum levels of cytokines were measured using enzyme-linked immunosorbent assay (ELISA). The study revealed significantly higher blood Pb and Cd levels in the exposed group. A significant decrease in Th1 cytokine-IL-2 and Th2 cytokine-IL-10 was found, while IL-4 (Th2 cytokine) and IL-17 (Th17) levels were higher in the exposed group. In the mixed exposure analysis, among all the selected cytokines, IL-4 levels were significantly different between individuals having higher levels of both Pb and Cd versus lower levels of Pb and Cd. While IL-2 levels were highest among the low Pb and Cd group, the IL-17 levels were highest among individuals with higher Cd levels. The study demonstrated that co-exposure to low levels of Pb and Cd might have an immune-modulatory effect. The data suggested a metal-induced pro-inflammatory immune response.

Immunotoxicology of cadmium: Cells of the immune system as targets and effectors of cadmium toxicity

Cadmium (Cd) has been listed as one of the most toxic substances affecting numerous tissues/organs, including the immune system. Due to variations in studies examining Cd effects on the immune system (exposure regime, experimental systems, immune endpoint measured), data on Cd immunotoxicity in humans and experimental animals are inconsistent. However, it is clear that Cd can affect cells of the immune system and can modulate some immune responses. Due to the complex nature of the immune system and its activities which are determined by multiple interactions, the underlying mechanisms involved in the immunotoxicity of this metal are still vague. Here, the current knowledge regarding the interaction of Cd with cells of the immune system, which may affect immune responses as well as potential mechanisms of consequent biological effects of such activities, is reviewed. Tissue injury caused by Cd-induced effects on innate cell activities depicts components of the immune system as mediators/effectors of Cd tissue toxicity. Cd-induced immune alterations, which may compromise host defense against pathogenic microorganisms and homeostatic reparative activities, stress this metal as an important health hazard.

Exogenous selenium (cadmium) inhibits the absorption and transportation of cadmium (selenium) in rice

Antagonism between selenium (Se) and cadmium (Cd) has been demonstrated in plants. However, a mutual suppression threshold for Se and Cd has not been identified in previous studies using Cd or Se individually. To fill this knowledge gap, we determined the levels of Se and Cd in various tissues of rice under concentration gradients of Se and Cd with different Se application times via hydroponic experiments. The results showed that the application of exogenous Se or Cd reduced the uptake and transport of the other. When the molar ratio of Se/Cd (R (Se/Cd)) was higher than 1, the concentration and transfer factor of Cd (TF-Cd) in all parts of rice simultaneously reached the lowest values. The minimum Se absorption in rice was obtained at R (Cd/Se) greater than 20, while no inhibition threshold was found for Se transport. In addition, approximately 1:1 R (Se/Cd) was observed in roots and the addition of exogenous Cd or Se promoted the enrichment of the other element in roots. These data suggested a mutual inhibition of Se and Cd in their absorption, transportation and accumulation in rice, which might be related to the formation of insoluble Cd-Se complexes in roots. This study provided new insights into a plausible explanation of the interactions between Se and Cd and contributed to the remediation and treatment of combined Se and Cd pollution in farmland systems.

Cadmium and immunologically-mediated homeostasis of anatomical barrier tissues

Cadmium (Cd) is a toxic heavy metal that when absorbed into the body causes nephrotoxicity and effects in other tissues.Anatomical barrier tissues are tissues that prevent the entry of pathogens and include skin, mucus membranes and the immune system. The adverse effects of Cd-induced immune cell's activity are the most extensively studied in the kidneys and the liver. There are though fewer data relating the effect of this metal on the other tissues, particularly in those in which cells of the immune system form local circuits of tissue defense, maintaining immune-mediated homeostasis. In this work, data on the direct and indirect effects of Cd on anatomical barrier tissue of inner and outer body surfaces (the lungs, gut, reproductive organs, and skin) were summarized.

Dermatotoxicity of oral cadmium is strain-dependent and related to differences in skin stress response and inflammatory/immune activity

Adverse effects of non-occupational exposure to cadmium (Cd) are increasingly acknowledged. Since our previous study has showed that orally acquired Cd affects skin, the contribution of genetic background to dermatotoxicity of oral cadmium was examined in two rat strains, Albino Oxford (AO) and Dark Agouti (DA), which differed in response to chemicals. While similar accumulation of Cd in the skin of both strains was noted, the skin response to the metal differed. DA rat individuals mounted antioxidant enzyme defense in the skin already at lower Cd dose, in contrast to AO rats which reacted to higher metal dose solely (and less pronounced), implying higher susceptibility of DA strain to Cd dermatotoxicity. Epidermal cells from both strains developed stress response, but higher intensity of antioxidant response in AO rats implied this strain`s better ability to defend against Cd insult. Cd induced epidermal cells' proinflammatory cytokine response only in DA rats. Increased IL-10 seems responsible for the lack of response in AO rats. Differences in the pattern of skin/epidermal cell responsiveness to cadmium give a new insight into repercussion of genetic variability to dermatotoxicity of orally acquired cadmium, bearing relevance for variations in the link between dietary cadmium and inflammation-based skin pathologies.

Cadmium regulates von Willebrand factor and occludin expression in glomerular endothelial cells of mice in a TNF-α-dependent manner

Background: Cadmium (Cd) is an environmental pollutant that leads to nephrotoxicity. However, the mechanisms of Cd-induced glomerular injury have not been fully clarified. Von Willebrand factor (vWF) and occludin are important endothelial cell markers in renal vasculature. In this study, the effects of Cd on the vWF and occludin expression in mouse glomeruli was investigated.

Objectives: The goal of this study was to analyze the expression of von Willebrand factor and occludin in glomerular endothelial cells of tumor necrosis factor-α^−/− (TNF-α^−/−) mice after treatment with Cd.

Material and methods: C57BL6/J wild-type (WT) mice and TNF-α^−/− mice (n = 6) were treated with Cd, and the kidney tissues were collected. The expression of von Willebrand factor and occludin was detected by using quantitative real-time PCR, immunofluorescence, and immunohistochemistry. In vitro, Human umbilical vascular endothelial cells (HUVECs) were used to examine the regulatory role of TNF-α on expression of von Willebrand factor and occludin.

Results: We found that Cd significantly increases mRNA and protein expressions of von Willebrand factor and occludin in TNF-α^−/− mice, but not in WT mice. In vitro, Cd significantly increased mRNA and protein expression of von Willebrand factor and occludin in HUVECs with TNF-α small interfering RNA (siRNA) transfection.

Conclusions: These results suggest that TNF-α acts to balance homeostasis of glomerular endothelium after Cd treatments.

Fpr2 Deficiency Alleviates Diet-Induced Insulin Resistance Through Reducing Body Weight Gain and Inhibiting Inflammation Mediated by Macrophage Chemotaxis and M1 Polarization

Obesity and related inflammation are critical for the pathogenesis of insulin resistance, but the underlying mechanisms are not fully understood. Formyl peptide receptor 2 (FPR2) plays important roles in host immune responses and inflammation-related diseases. We found that Fpr2 expression was elevated in the white adipose tissue of high-fat diet (HFD)-induced obese mice and db/db mice. The systemic deletion of Fpr2 alleviated HFD-induced obesity, insulin resistance, hyperglycemia, hyperlipidemia, and hepatic steatosis. Furthermore, Fpr2 deletion in HFD-fed mice elevated body temperature, reduced fat mass, and inhibited inflammation by reducing macrophage infiltration and M1 polarization in metabolic tissues. Bone marrow transplantations between wild-type and Fpr2^-/- mice and myeloid-specific Fpr2 deletion demonstrated that Fpr2-expressing myeloid cells exacerbated HFD-induced obesity, insulin resistance, glucose/lipid metabolic disturbances, and inflammation. Mechanistic studies revealed that Fpr2 deletion in HFD-fed mice enhanced energy expenditure probably through increasing thermogenesis in skeletal muscle; serum amyloid A3 and other factors secreted by adipocytes induced macrophage chemotaxis via Fpr2; and Fpr2 deletion suppressed macrophage chemotaxis and lipopolysaccharide-, palmitate-, and interferon-γ-induced macrophage M1 polarization through blocking their signals. Altogether, our studies demonstrate that myeloid Fpr2 plays critical roles in obesity and related metabolic disorders via regulating muscle energy expenditure, macrophage chemotaxis, and M1 polarization.

Oral cadmium exposure affects skin immune reactivity in rats

Skin can acquire cadmium (Cd) by oral route, but there is paucity of data concerning cutaneous effects of this metal. Cd acquired by oral route can affect skin wound healing, but the effect of Cd on other activities involved in skin homeostasis, including skin immunity, are not explored. Using the rat model of 30-day oral administration of Cd (5 ppm and 50 ppm) in drinking water, basic aspects of immune-relevant activity of epidermal cells were examined. Dose-dependent Cd deposition in the the skin was observed (0.035 ± 0.02 µg/g and 0.127 ± 0.04 µg/g at 5 ppm and 50 ppm, respectively, compared to 0.012 ± 0.009 µg/g at 0 ppm of Cd). This resulted in skin inflammation (oxidative stress at both Cd doses and dose-dependent structural changes in the skin and the presence/activation of innate immunity cells). At low Cd dose inflammatory response (nitric oxide and IL-1β) was observed. Other inflammatory cytokines (IL-6 and TNF) response occurred at 50 ppm, which was increased further following skin sensitization with contact allergen dinitro-chlorobenzene (DNCB). Epidermal cells exposed to both Cd doses enhanced concanavalin A (ConA)-stimulated lymphocyte production of IL-17. This study showed for the first time the effect of the metal which gained access to the skin via gut on immune reactivity of epidermal cells. Presented data might be relevant for the link between dietary Cd and the risk of skin pathologies.

Low dose cadmium upregulates the expression of von Willebrand factor in endothelial cells

Cadmium (Cd) is a persistent and widespread environmental pollutant of continuing worldwide concern. Previous studies have suggested that Cd exposure increases the risk of cardiovascular diseases, such as atherosclerosis and hypertension. However, the underlying mechanisms are poorly understood. In this study, we observed that low dose Cd treatment induced von Willebrand factor (vWF) expression in vascular endothelial cells in mouse lung and kidney tissues. In vitro analysis showed that 1 μM Cd specifically upregulated vWF mRNA and protein expression in human umbilical vein endothelial cells (HUVECs), indicating that Cd targets vascular endothelial cells even at relatively low concentrations. Further study demonstrated that nuclear factor kappa B (NF-κB) and GATA3, two established transcription regulators of the vWF gene, were not altered in the presence of Cd. However, ETS-related gene (ERG) was significantly induced by 1 μM Cd. When ERG was knocked down by siRNA, Cd induced upregulation of vWF was totally blocked. Chromatin immunoprecipitation (ChIP) assay showed that Cd increases the binding of ERG on the -56 ETS motif on the human vWF promoter. These results indicated that ERG mediated the increased expression of vWF by Cd. Since vWF is a key regulator for vascular homeostasis, our findings may provide a novel mechanism for understanding low dose Cd induced development of vascular diseases.

Genetic modification to induce CXCR2 overexpression in mesenchymal stem cells enhances treatment benefits in radiation-induced oral mucositis

Radiation-induced oral mucositis affects patient quality of life and reduces tolerance to cancer therapy. Unfortunately, traditional treatments are insufficient for the treatment of mucositis and might elicit severe side effects. Due to their immunomodulatory and anti-inflammatory properties, the transplantation of mesenchymal stem cells (MSCs) is a potential therapeutic strategy for mucositis. However, systemically infused MSCs rarely reach inflamed sites, impacting their clinical efficacy. Previous studies have demonstrated that chemokine axes play an important role in MSC targeting. By systematically evaluating the expression patterns of chemokines in radiation/chemical-induced oral mucositis, we found that CXCL2 was highly expressed, whereas cultured MSCs negligibly express the CXCL2 receptor CXCR2. Thus, we explored the potential therapeutic benefits of the transplantation of CXCR₂-overexpressing MSCs (MSCs^CXCR2) for mucositis treatment. Indeed, MSCs^CXCR2 exhibited enhanced targeting ability to the inflamed mucosa in radiation/chemical-induced oral mucositis mouse models. Furthermore, we found that MSC^CXCR2 transplantation accelerated ulcer healing by suppressing the production of pro-inflammatory chemokines and radiogenic reactive oxygen species (ROS). Altogether, these findings indicate that CXCR2 overexpression in MSCs accelerates ulcer healing, providing new insights into cell-based therapy for radiation/chemical-induced oral mucositis.