Wojciech Kalas

Non-genomic effects of the NR4A1/Nur77/TR3/NGFIB orphan nuclear receptor

The orphan nuclear receptor NR4A1/Nur77/TR3/NGFIB acts primarily as a transcription factor to regulate the expression of multiple genes. However, increasing research attention has recently been given to non-genomic activities of NR4A1. The first description of a non-genomic action of NR4A1 referred to the conversion of anti-apoptotic Bcl-2 into a pro-apoptotic protein by direct interaction with NR4A1. In response to certain apoptotic stimuli, NR4A1 translocates from the nucleus to the mitochondrial outer membrane (MOM) where it associates with Bcl-2 and thereby causes apoptosis. Afterwards, it appeared that NR4A1 could also bind and convert other anti-apoptotic Bcl-2 family members. The latest studies indicate a significant role of NR4A1 in the process of autophagy. For example, a new NR4A1-mediated pathway specific for melanoma cells has been described where NR4A1 interacts with the adenine nucleotide translocase 1 (ANT1) on the mitochondrial inner membrane (MIM) leading to induction of the autophagy pathway. Moreover, NR4A1 interaction with cytoplasmic p53 may also contribute to the induction of autophagy. In addition to mitochondria, NR4A1 could be translocated to the outer membrane of the endoplasmic reticulum (ER) and associate with Bcl-2 or translocon-associated protein subunit γ (TRAPγ) causing ER stress-induced apoptosis. NR4A1 also contributes to the proteasomal degradation of β-catenin in colon cancer cells in vitro and in vivo, as well as to the stabilization of hypoxia-inducible factor-1α (HIF-1α) under non-hypoxic conditions. This review summarizes research findings on non-genomic effects of NR4A1 in normal and cancer cells.

Inhibition of MEK induces fas expression and apoptosis in lymphomas overexpressing Ras.

Published results implicate PI3 kinase as a target of oncogenic Ras activity leading to the suppression of Fas but whether other Ras targets (e.g. Raf-1) are also involved is unclear. Here we report that thymic lymphomas overexpressing Ras and Raf-1 exhibit low expression of Fas. We show that expression of Fas in these lymphomas can be increased not only in the presence of a specific inhibitor (LY294002) of PI3 kinase, but also in the presence of specific inhibitor (PD98059) of MEK, downstream target of Raf-1. Both treatments result in accumulation of ERK in cytosol of lymphoma cells suggesting cross-talk between these two pathways regulating Fas expression. Treatment with PD98059 also results in apoptosis of the lymphoma cells but not of normal thymocytes expressing low Raf-1 levels. These observations provide evidence for involvement of Raf-1/MEK/ERK pathway in Ras-mediated inhibition of Fas expression and in selective promotion of survival of lymphoma cells.

HA1004, an inhibitor of serine/threonine protein kinases, restores the sensitivity of thymic lymphomas to Ca2+-mediated apoptosis through a protein kinase A-independent mechanism.

Our previous reports showed that thymic lymphomas arising in TCR transgenic mice are resistant to Ca2+-mediated apoptosis. Here we show that induction of apoptosis in thymic lymphomas involves a process that is cAMP-mediated and which depends on the activation of protein kinase A (PKA) despite the lower level of PKA type I in these lymphomas compared to thymocytes. Further, we show that treatment of the lymphomas with HA1004, a serine/threonine protein kinase inhibitor, restores their susceptibility to ionomycin-induced apoptosis. Results indicate that HA1004-induced restoration of sensitivity to ionomycin proceeds through a PKA-independent mechanism. Moreover, activation of PKA instead of its inhibition induces apoptosis of lymphoma cells.

Topically applied azaphenothiazines inhibit experimental psoriasis in mice

ABSTRACT The therapeutic efficacy of topically applied azaphenothiazine derivatives: 9‐chloro‐6‐acetylaminobutylquinobenzo[3,2‐b][1,4]thiazine (compound 4) and 6‐chloroethylureidoethyldiquino[3,2‐b;2′;3′‐e][1,4]thiazine (compound 5) in the amelioration of inflammatory symptoms of imiquimod‐induced psoriasis in mice was investigated. Clobederm®, containing clobetasol propioniate, served as a reference drug. The application of the compounds led to thinning of the epidermis and reduction of the cell layers. The suppressive actions of the compounds were even stronger with regard to pathological changes of the dermis. The compounds also exerted generalized, anti‐inflammatory effects by decreasing the number of circulating leukocytes, lowering subiliac lymph node weight and partially normalizing an altered blood cell composition. The changes in the composition of main cell types in the epidermis and dermis were less affected by the compounds. In addition, both compounds inhibited to a similar degree production of tumor necrosis factor &agr; (TNF &agr;) in human whole blood cell culture. Whereas compound 5 strongly inhibited IL‐8 and CXCL10 chemokines in human keratinocytes – KERTr cell line, transfected with poly(I:C), the suppressive action of compound 4 in this model was weak. In addition, compound 5, but not compound 4, exhibited at low doses proapoptotic properties with regard to colonic cell lines. In summary, we demonstrated the therapeutic potential of two selected azaphenotiazines in the amelioration of the skin pathology elicited in a mouse experimental model of psoriasis. HIGHLIGHTSTopical azaphenothiazines inhibit pathological skin changes in psoriatic mice.Azaphenothiazines suppress generalized cellular changes in lymphoid organs and circulating blood of psoriatic mice.Azaphenothiazines do not show side‐effects in psoriatic mice in contrast to the reference drug Clobederm®.Azaphenothiazines inhibit production of chemokines by a keratinocyte cell line.