Nickel-induced proteins in human HaCaT keratinocytes: annexin II and phosphoglycerate kinase

Effects of metal nanoparticles on tight junction-associated proteins via HIF-1α/miR-29b/MMPs pathway in human epidermal keratinocytes

Background

The increasing use of metal nanoparticles in industry and biomedicine raises the risk for unintentional exposure. The ability of metal nanoparticles to penetrate the skin ranges from stopping at the stratum corneum to passing below the dermis and entering the systemic circulation. Despite the potential health risks associated with skin exposure to metal nanoparticles, the mechanisms underlying the toxicity of metal nanoparticles on skin keratinocytes remain unclear. In this study, we proposed that exposure of human epidermal keratinocytes (HaCaT) to metal nanoparticles, such as nickel nanoparticles, dysregulates tight-junction associated proteins by interacting with the HIF-1α/miR-29b/MMPs axis.

Methods

We performed dose-response and time-response studies in HaCaT cells to observe the effects of Nano-Ni or Nano-TiO₂ on the expression and activity of MMP-2 and MMP-9, and on the expression of tight junction-associated proteins, TIMP-1, TIMP-2, miR-29b, and HIF-1α. In the dose-response studies, cells were exposed to 0, 10, or 20 μg/mL of Nano-Ni or Nano-TiO₂ for 24 h. In the time-response studies, cells were exposed to 20 μg/mL of Nano-Ni for 12, 24, 48, or 72 h. After treatment, cells were collected to either assess the expression of mRNAs and miR-29b by real-time PCR or to determine the expression of tight junction-associated proteins and HIF-1α nuclear accumulation by Western blot and/or immunofluorescent staining; the conditioned media were collected to evaluate the MMP-2 and MMP-9 activities by gelatin zymography assay. To further investigate the mechanisms underlying Nano-Ni-induced dysregulation of tight junction-associated proteins, we employed a HIF-1α inhibitor, CAY10585, to perturb HIF-1α accumulation in one experiment, and transfected a miR-29b-3p mimic into the HaCaT cells before Nano-Ni exposure in another experiment. Cells and conditioned media were collected, and the expression and activities of MMPs and the expression of tight junction-associated proteins were determined as described above.

Results

Exposure of HaCaT cells to Nano-Ni resulted in a dose-dependent increase in the expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 and the activities of MMP-2 and MMP-9. However, exposure of cells to Nano-TiO₂ did not cause these effects. Nano-Ni caused a dose-dependent decrease in the expression of miR-29b and tight junction-associated proteins, such as ZO-1, occludin, and claudin-1, while Nano-TiO₂ did not. Nano-Ni also caused a dose-dependent increase in HIF-1α nuclear accumulation. The time-response studies showed that Nano-Ni caused significantly increased expressions of MMP-2 at 24 h, MMP-9 at 12, 24, and 48 h, TIMP-1 from 24 to 72 h, and TIMP-2 from 12 to 72 h post-exposure. The expression of miR-29b and tight junction-associated proteins such as ZO-1, occludin, and claudin-1 decreased as early as 12 h post-exposure, and their levels declined gradually over time. Pretreatment of cells with a HIF-1α inhibitor, CAY10585, abolished Nano-Ni-induced miR-29b down-regulation and MMP-2/9 up-regulation. Introduction of a miR-29b-3p mimic into HaCaT cells by transfection before Nano-Ni exposure ameliorated Nano-Ni-induced increased expression and activity of MMP-2 and MMP-9 and restored Nano-Ni-induced down-regulation of tight junction-associated proteins.

Conclusion

Our study herein demonstrated that exposure of human epidermal keratinocytes to Nano-Ni caused increased HIF-1α nuclear accumulation and increased transcription and activity of MMP-2 and MMP-9 and down-regulation of miR-29b and tight junction-associated proteins. Nano-Ni-induced miR-29b down-regulation was through Nano-Ni-induced HIF-1α nuclear accumulation. Restoration of miR-29b level by miR-29b-3p mimic transfection abolished Nano-Ni-induced MMP-2 and MMP-9 activation and down-regulation of tight junction-associated proteins. In summary, our results demonstrated that Nano-Ni-induced dysregulation of tight junction-associated proteins in skin keratinocytes was via HIF-1α/miR-29b/MMPs pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00405-2.

Nickel Nanoparticles Induce the Synthesis of a Tumor-Related Polypeptide in Human Epidermal Keratinocytes

Although nickel allergy and carcinogenicity are well known, their molecular mechanisms are still uncertain, thus demanding studies at the molecular level. The nickel carcinogenicity is known to be dependent on the chemical form of nickel, since only certain nickel compounds can enter the cell. This study investigates, for the first time, the cytotoxicity, cellular uptake, and molecular targets of nickel nanoparticles (NiNPs) in human skin cells in comparison with other chemical forms of nickel. The dose-response curve that was obtained for NiNPs in the cytotoxicity assays showed a linear behavior typical of genotoxic carcinogens. The exposure of keratinocytes to NiNPs leads to the release of Ni²⁺ ions and its accumulation in the cytosol. A 6 kDa nickel-binding molecule was found to be synthesized by cells exposed to NiNPs at a dose corresponding to medium mortality. This molecule was identified to be tumor-related p63-regulated gene 1 protein.

MCP-1 produced by keratinocytes is associated with leucocyte recruitment during elicitation of nickel-induced occupational allergic contact dermatitis

To investigate the expression profile of monocyte chemoattractant peptide-1 (MCP-1) by keratinocytes after nickel exposure and to identify its role for leucocyte migration during nickel-induced occupational allergic contact dermatitis (OACD), 26 workers diagnosed with nickel-induced OACD were enrolled. Skin biopsies from the positive nickel-challenged sites at different time points were assessed by immunohistochemistry (IHC) for MCP-1, CD68, CD45RO, and in situ hybridization (ISH) for MCP-1, using chronic periumbilical dermititis as controls. The expressions of MCP-1 in HaCaT cell culture after nickel treatment were quantified by enzyme-linked immunosorbent assay. The results showed that at positive nickel-challenged sites, strong expressions of MCP-1, both messenger RNA (mRNA) and protein, were detected in the basal keratinocytes during the early phase (24-48 h after nickel application), paralleled by the recruitment of CD68⁺ and CD45RO⁺ cells to the skin compartments. The expressions of MCP-1 declined gradually in the late phase (72-96 h after nickel application). Treatment with nickel sulfate at noncytotoxic concentrations (0.01-100 µM) induced a concentration-related elevation of MCP-1 expression by HaCaT cells compared to the untreated cells. The data indicated that a temporal expression pattern of MCP-1 produced by keratinocytes after nickel exposure was involved in the complex process of mononuclear cell infiltration during elicitation of nickel-induced OACD. Targeting MCP-1 might be a potential therapeutic strategy for OACD.

Analytical approaches for the characterization of nickel proteome

Analytical strategies to study the nickel proteome and their advantages and limitations.

Potentiation of endothelin-1-induced prostaglandin E2 formation by Ni(2+) and Sr(2+) in murine osteoblastic MC3T3-E1 cells

Cation recognition mechanisms beyond calcium-sensing receptors are still largely unexplored and consequently there is surprisingly little information on linking of this primary event to key metabolic features of different cell systems, such as arachidonic acid metabolism. However, information on the modulatory role of extracellular cations in cellular function is scarce. In this study we have demonstrated, that Ni(2+) and Sr(2+) potentiate endothelin-1 induced prostaglandin E2 formation in the osteoblastic cell line, MC3T3-E1, even in the absence of extracellular calcium. The effect is strictly dependent of receptor-mediated signal transduction processes evoked by endothelin-1 and arachidonate release involves cytosolic phospholipase A2 activity. The ligation sites, at least for Ni(2+) are extracellular. The data suggest a novel activation mechanism for arachidonate release and subsequent prostaglandin formation that does not require calcium.

Human annexins A1, A2, and A8 as potential molecular targets for Ni(II) ions

Nickel is harmful for humans, but molecular mechanisms of its toxicity are far from being fully elucidated. One of such mechanisms may be associated with the Ni(II)-dependent peptide bond hydrolysis, which occurs before Ser/Thr in Ser/Thr-Xaa-His sequences. Human annexins A1, A2, and A8, proteins modulating the immune system, contain several such sequences. To test if these proteins are potential molecular targets for nickel toxicity we characterized the binding of Ni(II) ions and hydrolysis of peptides Ac-KALTGHLEE-am (A1-1), Ac-TKYSKHDMN-am (A1-2), and Ac-GVGTRHKAL-am (A1-3), from annexin A1, Ac-KMSTVHEIL-am (A2-1) and Ac-SALSGHLET-am (A2-2), from annexin A2, and Ac-VKSSSHFNP-am (A8-1), from annexin A8, using UV-vis and circular dichroism (CD) spectroscopies, potentiometry, isothermal titration calorimetry, high-performance liquid chromatography (HPLC), and electrospray ionization mass spectrometry (ESI-MS). We found that at physiological conditions (pH 7.4 and 37 °C) peptides A1-2, A1-3, A8-1, and to some extent A2-2 bind Ni(II) ions sufficiently strongly in 4N complexes and are hydrolyzed at sufficiently high rates to justify the notion that these annexins can undergo nickel hydrolysis in vivo. These results are discussed in the context of specific biochemical interactions of respective proteins. Our results also expand the knowledge about Ni(II) binding to histidine peptides by determination of thermodynamic parameters of this process and spectroscopic characterization of 3N complexes. Altogether, our results indicate that human annexins A1, A2, and A8 are potential molecular targets for nickel toxicity and help design appropriate cellular studies.

Proteomic analysis of cardiomyocytes differentiation in mouse embryonic carcinoma P19CL6 cells

A clonal derivative named P19CL6 has been isolated from pluripotent P19 mouse embryonic carcinoma cells, and this subline efficiently differentiates into beating cardiomyocytes when treated with 1% dimethyl sulfoxide (DMSO). It offers a valuable model to study cardiomyocytes differentiation in vitro. In this study, comparative proteomic analysis was used to characterize the protein profiles associated with the DMSO-induced cardiomyocytes differentiation of P19CL6 cells. We demonstrated that P19CL6 cells indeed differentiated into cardiomyocytes after DMSO inducement as they expressed sarcomeric myosin heavy chain (MHC) as well as three cardiac-specific transcription factors (Csx/Nkx-2.5, GATA-4, and MEF2C). Image analysis of silver-stained two-dimensional gels was used to find protein spots that exhibited an at least 1.5-fold change in abundance after successful differentiation. Seventeen protein spots were selected for further analysis by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) and/or nano-electrospray ionization MS/MS (ESI-MS/MS), and 16 protein spots were identified. The identified proteins are involved in different cellular functions such as metabolism, signal transduction, and cellular organization. To confirm the expression changes of the identified proteins during differentiation, the mRNA levels of six identified proteins (including seven protein spots) were assessed by the real-time polymerase chain reaction and three showed a correlation between mRNA level and protein abundance. As an initial step toward identifying proteins involved in maintaining the differentiated state of cardiomyocytes derived from P19CL6 cells, our data provide some helpful information that may lead to a better understanding of the molecular mechanisms by which P19CL6 cells differentiate into cardiomyocytes after treatment with DMSO.

The effects of nickel and chromium on human keratinocytes: Differences in viability, cell associated metal and IL-1α release

This study was carried out to assess the effects of chromium and nickel upon isolated keratinocytes as an in vitro model of human skin. Keratinocytes were isolated from healthy volunteer skin samples of unknown metal sensitivity (n=10) and were compared with cells from patient biopsies of known metal sensitivity (n=7). Cells were dosed with a concentration range of nickel and chromium (0-10,000 microM) and cellular mitochondrial activity, viability, metal uptake and cytokine release were measured. Responses of primary versus passaged keratinocytes were also compared. Toxicity data from primary and passaged keratinocytes was statistically analysed by the non-linear Hill Plot model. Results showed that hexavalent chromium was significantly more cytotoxic, associated more with keratinocytes and induced a dose dependant release of IL-1alpha compared to nickel. Significant differences were observed between primary and passaged keratinocytes with regard to the toxicity of chromium and nickel and variation of response. No differences were observed in the cytotoxicity or cytokine release induced by chromium or nickel for the known sensitised biopsy patient samples (n=4) compared to patch test negative controls (n=3). The results from this study suggest human keratinocytes in vitro respond very differently to chromium and nickel.

Analysis of the signal transduction pathway of nickel-induced matrix metalloproteinase-2 expression in the human keratinocytes in vitro: preliminary findings

BACKGROUND

Nickel can induce cellular and nuclear damages responsible for chronic diseases, like allergic contact dermatitis (ACD). We previously showed that matrix metalloproteinase-2 (MMP-2) gene expression was induced by nickel in nontumorigenic human keratinocytes cell line (HaCat).

OBJECTIVE

To investigate the signal transduction pathways involved in gelatinolytic activity induced in HaCat under nickel stimulation.

METHODS

We analyzed the involvement of protein kinase A (PKA), protein kinase C (PKC), tyrosine kinase (PTK), nuclear factor-kB (NF-kB) and activator protein-1 (AP-1) using specific inhibitors (H89, calphostin C, genistein, carpain and curcumin) by electrophoretic mobility shift assay, reverse transcription-polymerase chain reaction and gelatin zymography.

RESULTS

Our results indicate that nickel-induced MMP-2 production was inhibited with PTK, PKC and AP-1 specific inhibitors. Moreover, both PKA and NF-kB were not involved in nickel pathway.

CONCLUSIONS

Using HaCat, we showed that curcumin and genistein can revert nickel-induced MMP-2 upregulation. Whether the use of PTK and AP-1 inhibitors has therapeutic ramifications in the management of ACD remains to be investigated.

MIP-1β, a novel biomarker for in vitro sensitization test using human monocytic cell line

In order to seek a novel biomarker for predicting skin sensitization, changes in the gene expression profile of THP-1 cells on exposure to 2,4-dinitrochlorobenzene (DNCB), p-phenylenediamine (pPD) and nickel sulfate (Ni) were assessed using oligo-DNA microarrays. While the change in gene expression varied depending on the sensitizers, up-regulation of MIP-1 beta mRNA expression was detected in both DNCB-treated and Ni-treated THP-1 cells. This finding was validated by RT-PCR and confirmed at the protein level by ELISA. Secretion of MIP-1 beta from THP-1 was detected after 24-h treatment with sensitizers such as DNCB, Ni, 2-mercaptobenzothiazole (2-MBT) and cobalt sulfate (Co), while pPD and non-sensitizers such as sodium dodecyl sulfate (SDS) and benzalkonium chloride (BC) had no effect. The use of both MIP-1 beta production and CD86 expression as criteria reduced the number of false-negatives, and the results were in good agreement with those of in vivo assays. MIP-1 beta may be useful as a novel biomarker in in vitro sensitization assay using THP-1 cells, either alone or in combination with known markers.

Differential display of proteins involved in the neural differentiation of mouse embryonic carcinoma P19 cells by comparative proteomic analysis

Mouse embryonic carcinoma P19 cell has been used extensively as a model to study molecular mechanisms of neural differentiation in vitro. After retinoic acid (RA) treatment and aggregation, P19 cells can differentiate into neural cells including neurons and glial cells. In this study, comparative proteomic analysis is utilized to approach the protein profiles associated with the RA-induced neural differentiation of P19 cells. Image analysis of silver stained two-dimensional gels indicated that 28 protein spots had significantly differential expression patterns in both quantity and quality. With mass spectrometry analysis and protein functional exploration, many proteins demonstrated an association with distinct aspects of neural differentiation. These proteins were gag polyprotein, rod cGMP-specific 3',5'-cyclic phosphodiesterase, 53 kDa BRG1-associated factor A, N-myc downstream regulated 1, Vitamin D receptor associated factor 1, stromal cell derived factor receptor 1, phosphoglycerate mutase, Ran-specific GTPase-activating protein, and retinoic acid (RA)-binding protein. While some cytoskeleton-related proteins such as beta cytoskeletal actin, gamma-actin, actin-related protein 1, tropomyosin 1, and cofilin 1 are related to cell migration and aggregation, other proteins have shown a relationship with distinct aspects of neural differentiation including energy production and utilization, protein synthesis and folding, cell signaling transduction, and self-protection. The differential expression patterns of these 28 proteins indicate their different roles during the neural differentiation of P19 cells. As an initial step toward unveiling the regulations involved in the commitment of pluripotent cells to a neural fate, information from this study may be helpful to uncover the molecular mechanisms of neural differentiation.

In vitro evaluation of matrix metalloproteinases as predictive testing for nickel, a model sensitizing agent

The identification of potential damage due to chemical exposure in the workplace is a major health and regulatory concern. Traditional tests that measure both sensitization and elicitation responses require the use of animals. An alternative to this widespread use of experimental animals could have a crucial impact on risk assessment, especially for the preliminary screening of new molecules. We developed an in vitro model for the screening of potential toxic compounds. Human keratinocytes (HaCat) were used as target cells while matrix metalloproteinases (MMP) were selected as responders because they are key enzymes involved in extracellular matrix (ECM) degradation in physiological and pathological conditions. Chemical exposure was performed using nickel sulphate as a positive tester. Nickel contact induced upregulation of MMP-2 and IL-8 mRNA production. Molecular activation occurred even at very low nickel concentrations even though no phenotypic changes were observed. MMP-9 accumulation was found in the medium of treated cells with respect to controls. These observations led to the hypothesis that even minimal exposure can accumulate transcriptional activity resulting in long-term clinical signs after contact. Our simple in vitro model can be applied as a useful preliminary complement to the animal studies to screen the effects of new potential toxic compounds.

Nickel, cobalt and chromium-induced cytotoxicity and intracellular accumulation in human hacat keratinocytes

Nickel, cobalt and chromium can induce allergic contact dermatitis (ACD) and may provoke irritant reactions in the skin. This study aimed at investigating cytotoxicity and cell viability along with intracellular metal accumulation in HaCaT human keratinocytes exposed to soluble forms of nickel, cobalt or chromium. The EC50 (24 h) values as detected by MTT test were 30 microM for sodium chromate (Na2CrO4), 475 microM for cobalt chloride (CoCl2) and 600 microM for nickel chloride (NiCl2). Chromium chloride (CrCl3) was not toxic up to 1 mM. No clear effects were observed after 4 h, but 24-h treatments with 1 mM CoCl2 or 10 microM Na2CrO(4) were found to almost completely abolish the ability of the cells to form colonies, whilst 1 mM NiCl2 reduced cellular survival to only 70% of control cultures. Intracellular accumulation of metals was evaluated by the use of radioisotopes at the EC50 value and at 1/10-1/5 of this concentration. Accumulation of Na2(51)CrO4 was linear with increasing dose. This was not the case for 63NiCl2 and 58CoCl2. All the metals were accumulated preferentially in the cytosols; 96% or more for 63NiCl2, approximately 90% for 58CoCl2 and 60-70% for Na2(51)CrO4. Finally, it was observed that HaCaT human keratinocytes can concentrate the metals present in the media up to 3.9 and 12.5 times for NiCl2 and CoCl2, respectively, and up to 167 for Na2CrO4. These striking metal intracellular accumulation patterns, which have not been earlier described in keratinocytes, highlight the relevance of searching for specific biomarkers of early cellular toxic effects, such as cytosolic proteins that bind the metals.