Exploring the IL-21–STAT3 Axis as Therapeutic Target for Sézary Syndrome

Sézary syndrome is an aggressive cutaneous T-cell lymphoma. The malignant cells (Sézary cells) are present in skin, lymph nodes, and blood, and express constitutively activated signal transducer and activator of transcription (STAT)3. STAT3 can be activated by IL-21 in vitro and the IL-21 gene itself is a STAT3 target gene, thereby creating an autocrine positive feedback loop that might serve as a therapeutic target. Sézary cells underwent apoptosis when incubated with Stattic, a selective STAT3 inhibitor. STAT3 activation in Sézary cells did not affect expression of the supposed anti-apoptotic STAT3 target genes BCL2, BCL-xL, and SURVIVIN, whereas expression of (proto)oncogenes miR-21, TWIST1, MYC, and PIM1 was significantly increased. CD3/CD28-mediated activation of Sézary cells induced IL-21 expression, accompanied by STAT3 activation and increased proliferation. Blocking IL-21 in CD3/CD28-activated cells had no effects, whereas Stattic abrogated IL-21 expression and cell proliferation. Thus, specific inhibition of STAT3 is highly efficient in the induction of apoptosis of Sézary cells, likely mediated via the regulation of (proto)oncogenes. In contrast, blocking IL-21 alone seems insufficient to affect STAT3 activation, cell proliferation, or apoptosis. These data provide further insights into the pathogenic role of STAT3 in Sézary syndrome and strengthen the notion that STAT3 represents a promising therapeutic target in this disease

Deep-Sequencing Analysis Reveals that the miR-199a2/214 Cluster within DNM3os Represents the Vast Majority of Aberrantly Expressed MicroRNAs in Sézary Syndrome

Dermatology-oncolog

GATA3 Expression Is Decreased in Psoriasis and during Epidermal Regeneration; Induction by Narrow-Band UVB and IL-4

Psoriasis is characterized by hyperproliferation of keratinocytes and by infiltration of activated Th1 and Th17 cells in the (epi)dermis. By expression microarray, we previously found the GATA3 transcription factor significantly downregulated in lesional psoriatic skin. Since GATA3 serves as a key switch in both epidermal and T helper cell differentiation, we investigated its function in psoriasis. Because psoriatic skin inflammation shares many characteristics of epidermal regeneration during wound healing, we also studied GATA3 expression under such conditions

In Psoriasis Lesional Skin the Type I Interferon Signaling Pathway Is Activated, whereas Interferon-α Sensitivity Is Unaltered

The epidermal phenotype as observed in psoriatic skin results from inflammation and abnormal proliferation and terminal differentiation of keratinocytes. Mice deficient for interferon regulatory factor-2, a repressor of interferon signaling, display psoriasis-like skin inflammation. The development of this phenotype is strictly dependent on type I interferon (interferon-α/β) signaling. The aim of this study was to assess the involvement of interferon-α/β in the pathogenesis of human psoriasis. In psoriatic skin, we measured an increased expression of components that play central and crucial roles in interferon-α/β signal transduction. Culturing keratinocytes or healthy skin biopsies with recombinant interferon-α stimulated this signaling pathway; however, this did not induce the expression of markers that are generally used to define the psoriasis phenotype. Furthermore, skin from psoriasis patients responded identically to interferon-α stimulation, demonstrating that psoriatic skin does not have an aberrant sensitivity to type I interferon. We conclude that in psoriatic lesional skin the type I interferon signaling pathway is activated, despite an unaltered interferon-α sensitivity. Our data furthermore show that type I interferon, in contrast to interferon-γ, does not act directly on keratinocytes to induce a psoriatic phenotype. Thus, if the observed activated type I interferon signaling is indeed functionally involved in the pathogenesis of psoriasis, its contribution might be indirect, putatively involving other cell types besides keratinocytes

Effects of over-expression of strictosidine synthase and tryptophan decarboxylase on alkaloid production by cell cultures of Catharanthus roseus

Cells of Catharanthus roseus (L.) G. Don were genetically engineered to over-express the enzymes strictosidine synthase (STR; EC 4.3.3.2) and tryptophan decarboxylase (TDC; EC 4.1.1.28), which catalyze key steps in the biosynthesis of terpenoid indole alkaloids (TIAs). The cultures established after Agrobacteriummediated transformation showed wide phenotypic diversity, re¯ecting the complexity of the biosynthetic pathway. Cultures transgenic for Str consistently showed tenfold higher STR activity than wild-type cultures, which favored biosynthetic activity through the pathway. Two such lines accumulated over 200 mg á L)1 of the glucoalkaloid strictosidine and/or strictosidine-derived TIAs, including ajmalicine, catharanthine, serpentine, and tabersonine, while maintaining wild-type levels of TDC activity. Alkaloid accumulation by highly productive transgenic lines showed considerable instability and was strongly in¯uenced by culture conditions, such as the hormonal composition of the medium and the availability of precursors. High transgene-encoded TDC activity was not only unnecessary for increased productivity, but also detrimental to the normal growth of the cultures. In contrast, high STR activity was tolerated by the cultures and appeared to be necessary, albeit not su cient, to sustain high rates of alkaloid biosynthesis. We conclude that constitutive over-expression of Str is highly desirable for increased TIA production. However, given its complexity, limited intervention in the TIA pathway will yield positive results only in the presence of a favorable epigenetic environment.info:eu-repo/semantics/publishedVersio

Effects of over-expression of strictosidine synthase and tryptophan decarboxylase on alkaloid production by cell cultures of Catharanthus roseus

Cells of Catharanthus roseus (L.) G. Don were genetically engineered to over-express the enzymes strictosidine synthase (STR; EC 4.3.3.2) and tryptophan decarboxylase (TDC; EC 4.1.1.28), which catalyze key steps in the biosynthesis of terpenoid indole alkaloids (TIAs). The cultures established after Agrobacteriummediated transformation showed wide phenotypic diversity, re¯ecting the complexity of the biosynthetic pathway. Cultures transgenic for Str consistently showed tenfold higher STR activity than wild-type cultures, which favored biosynthetic activity through the pathway. Two such lines accumulated over 200 mg á L)1 of the glucoalkaloid strictosidine and/or strictosidine-derived TIAs, including ajmalicine, catharanthine, serpentine, and tabersonine, while maintaining wild-type levels of TDC activity. Alkaloid accumulation by highly productive transgenic lines showed considerable instability and was strongly in¯uenced by culture conditions, such as the hormonal composition of the medium and the availability of precursors. High transgene-encoded TDC activity was not only unnecessary for increased productivity, but also detrimental to the normal growth of the cultures. In contrast, high STR activity was tolerated by the cultures and appeared to be necessary, albeit not su cient, to sustain high rates of alkaloid biosynthesis. We conclude that constitutive over-expression of Str is highly desirable for increased TIA production. However, given its complexity, limited intervention in the TIA pathway will yield positive results only in the presence of a favorable epigenetic environment.info:eu-repo/semantics/publishedVersio

IFN-α enhances poly-IC responses in human keratinocytes by inducing expression of cytosolic innate RNA receptors: Relevance for psoriasis

Keratinocytes play a key role in innate immune responses of the skin to bacterial and viral pathogens. Viral double-stranded RNA and its synthetic analogue polyriboinosinic-polyribocytidylic acid (poly-IC) are recognized via multiple pathways involving the receptors Toll-like receptor 3 (TLR3), protein kinase R (PKR), and the recently described cytosolic RNA helicases retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). We show that preincubation of human keratinocytes with IFN-α enhances the proinflammatory responses to poly-IC. Kinetic studies suggest that this is mediated via upregulation of the receptors TLR3, PKR, RIG-I, and MDA5. Interestingly, expression of RIG-I, MDA5, and PKR was significantly increased in lesional skin from patients with psoriasis, a chronic inflammatory skin disease that is characterized by high IFN-α levels. These results suggest that psoriatic keratinocytes show increased sensitivity to viral RNA intermediates, thereby leading to excessive proinflammatory responses and maintenance of the inflammatory skin phenotype. Here, we provide early evidence that point toward a role for the recently described cytosolic innate RNA receptors in non-viral chronic inflammatory diseases

Cellular and molecular effects of pulsed dye laser and local narrow-band UVB therapy in psoriasis

BACKGROUND AND OBJECTIVES: Pulsed dye laser (PDL) therapy is effective in clearing psoriasis plaques, but the mechanism of action is only partially understood. Local narrow-band ultraviolet B (NB-UVB), which has a better-defined mode of action, is an effective standard treatment for psoriasis. Our aim was to evaluate the cellular and molecular effects of PDL and to compare them with those of local NB-UVB in order to gain further insight into their mechanisms of action in psoriasis. STUDY DESIGN/PATIENTS AND METHODS: Nineteen patients with stable plaque-type psoriasis were treated either with PDL or NB-UVB. Lesional punch biopsies were obtained from all patients before treatment. Additional biopsies were obtained at 3 and 24 hours after PDL treatment in five of these patients. In 14 patients additional biopsies were taken after 7 and 13 weeks of treatment. Samples were histopathologically examined for the level of dermal T cell infiltrate, and the expression of epidermal beta-defensin 2, immune cell-derived tumor necrosis factor (TNF)-alpha, endothelial E-selectin, vascular endothelial growth factor receptor (VEGFR) 2 and 3, and the expression of interleukin (IL)-23 before and after treatment. RESULTS: The expression of VEGFR2, VEGFR3, and E-selectin was decreased in clinically high responders within 24 hours after PDL treatment. The expression of IL-23, TNF-alpha mRNA, and E-selectin protein were significantly reduced after two PDL treatments, whereas the expression of all epidermal markers and dermal T cell infiltrates had normalized after four treatments. The expression of epidermal activation markers and E-selectin were significantly reduced after 13 weeks of NB-UVB treatment. CONCLUSIONS: The expression of epidermal activation markers and the dermal T cell infiltrates were decreased after both treatments. The decreased expression of VEGFR2 and VEGFR3 followed by the down-regulation of TNF-alpha and IL-23p19 may be contributory factors in the efficacy of PDL in stable plaque-type psoriasis