Mast cells play important roles in many pathological conditions where local hypoxia is observed, including asthma, rheumatic diseases, and certain types of cancer. Here, we investigated how expression of the hypoxia-inducible factor 1, α subunit gene (HIF1A), is regulated in mast cells. The product of HIF1A is hypoxia-inducible factor 1α (HIF-1α), is a major nuclear transcription factor modulating gene expression in response to hypoxic conditions. We observed that under hypoxic conditions, exposure of mast cells to ionomycin and substance P resulted in significant up-regulation of HIF1A expression as compared with resting mast cells incubated under identical conditions. The ionomycin-mediated increase in HIF-1α protein levels was sensitive to the transcription inhibitor actinomycin D and to inhibitors of calcineurin, cyclosporin A (CsA), and FK506. The increased HIF-1α protein level was paralleled by a severalfold increase in HIF-1α mRNA that could be also inhibited with actinomycin D and CsA. The HIF1A promoter activity was significantly increased in ionomycin-activated mast cells, and the promoter activity could be inhibited by CsA and FK506. Furthermore, in situ mutagenesis experiments showed that the ionomycin-mediated HIF1A promoter activity depends on a conservative NFAT-binding site. Thus, accumulation of HIF-1α in activated mast cells requires up-regulation of HIF1A gene transcription and depends on the calcineurin-NFAT signaling pathway.

Melanoma is considered one of the most aggressive skin cancers. It spreads and metastasizes quickly and is intrinsically resistant to most conventional chemotherapeutics, thereby presenting a challenge to researchers and clinicians searching for effective therapeutic strategies to treat patients with melanoma. The use of inhibitors of mutated serine/threonine-protein kinase B-RAF (BRAF), e.g., vemurafenib and dabrafenib, has revolutionized melanoma chemotherapy. Unfortunately, the response to these drugs lasts a limited time due to the development of acquired resistance. One of the proteins responsible for this process is epidermal growth factor receptor (EGFR). In this review, we summarize the role of EGFR signaling in the multidrug resistance of melanomas and discuss possible applications of EGFR inhibitors to overcome the development of drug resistance in melanoma cells during therapy.

The pandemic of the new coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) has led to the deaths of more than 1.5 million people worldwide. SARS-CoV-2 causes COVID-19, which exhibits wide variation in the course of disease in different people, ranging from asymptomatic and mild courses to very severe courses that can result in respiratory failure and death. Despite the rapid progression of knowledge, we still do not know how individual cells of the immune system interact with the virus or its components, or how immune homeostasis becomes disrupted, leading to the rapid deterioration of a patient’s condition. In the present work, we show that SARS-CoV-2 proteins induce the expression and secretion of IL-6 by human monocytes and macrophages, the first line cells of antiviral immune responses. IL-6 may play a negative role in the course of COVID-19 by inhibiting Th1-dependent immunity and stimulating Th17 lymphocytes, thus leading to an increased probability of a cytokine storm.

ABCC6 mutations are responsible for the development of pseudoxanthoma elasticum, a rare recessive disease characterized by calcification of elastic fibers. Although ABCC6 is mainly expressed in the liver the disease has dermatologic, ocular, and cardiovascular symptoms. We investigated the transcriptional regulation of the gene and observed that hepatocyte growth factor (HGF) inhibits its expression in HepG2 cells via the activation of ERK1/2. Similarly, other factors activating the cascade also inhibited ABCC6 expression. We identified the ERK1/2 response element in the proximal promoter by luciferase reporter gene assays. This site overlapped with a region conferring the tissue-specific expression pattern to the gene and with a putative hepatocyte nuclear factor 4alpha (HNF4alpha) binding site. We demonstrated that HNF4alpha regulates the expression of ABCC6, acts through the putative binding site, and determines its cell type-specific expression. We also showed that HNF4alpha is inhibited by the activation of the ERK1/2 cascade. In conclusion we describe here the first regulatory pathway of ABCC6 expression showing that the ERK1/2-HNF4alpha axis has an important role in regulation of the gene.

Th17 cells are important players in host defense against pathogens such as Staphylococcus aureus, Candida albicans, and Bacillus anthracis. Th17 cell-mediated inflammation, under certain conditions in which balance in the immune system is disrupted, is the underlying pathogenic mechanism of certain autoimmune disorders, e.g., rheumatoid arthritis, Graves’ disease, multiple sclerosis, and psoriasis. In the present study, using transcriptomic profiling, we selected genes and analyzed the expression of these genes to find potential novel markers of Th17 lymphocytes. We found that APOD (apolipoprotein D); C1QL1 (complement component 1, Q subcomponent-like protein 1); and CTSL (cathepsin L) are expressed at significantly higher mRNA and protein levels in Th17 cells than in the Th1, Th2, and Treg subtypes. Interestingly, these genes and the proteins they encode are well associated with the function of Th17 cells, as these cells produce inflammation, which is linked with atherosclerosis and angiogenesis. Furthermore, we found that high expression of these genes in Th17 cells is associated with the acetylation of H2BK12 within their promoters. Thus, our results provide new information regarding this cell type. Based on these results, we also hope to better identify pathological conditions of clinical significance caused by Th17 cells.

Retinoic acid-related orphan receptor γT (RORγT) is the orphan nuclear receptor that regulates the development of Th17 cells and the expression of IL-17. The differentiation of Th17 cells is associated with the upregulation of RORγT mRNA, and the mechanisms regulating that process in human cells are not well understood. We investigated the transcriptional regulation of RORγT in a human lymphocytic cell line and Th17 differentiated from naive CD4⁺ cells from human peripheral blood. A series of experiments, including 5′ deletion and in situ mutagenesis analysis of the human RORγT promoter, chromatin immunoprecipitation, and overexpression of selected transcription factors, revealed that the transcription factors upstream stimulatory factor 1 (USF-1) and USF-2 are indispensable for the transcription of RORγT in human lymphocytes. There was also upregulation of USF-1 and USF-2 during the differentiation of Th17 cells from naive CD4⁺ cells. In this article, we report the first analysis, to our knowledge, of the human RORγT promoter and demonstrate the role of the USF-1 and USF-2 transcription factors in regulating the expression of RORγT in human lymphocytes. Thus, USFs are important for the molecular mechanisms of Th17 differentiation, and possible changes in the expression of USFs might be of interest for inflammatory conditions with a Th17 component. Furthermore, these observations suggest a possible link between metabolic disorders in which the role of glucose-induced USF expression has already been established and autoimmune diseases in which the upregulation of RORγT is frequently detected.