Interleukin-19 upregulates keratinocyte growth factor and is associated with psoriasis.

BACKGROUND: Interleukin (IL)-19, a member of the IL-10 family, signals through the IL-20R1/IL-20R2 heterodimer, which is shown to be involved in abnormal keratinocyte differentiation and proliferation. Little is known about its in vitro biological functions or its role in psoriasis. OBJECTIVES: To investigate the role of IL-19 in the psoriatic process. METHODS: The expression of keratinocyte growth factor (KGF) transcripts was measured by polymerase chain reaction in CD8+ T cells treated with IL-19. Next, we developed monoclonal and polyclonal antibodies to measure the levels of IL-19 in the sera of patients with psoriasis and healthy volunteers using an enzyme-linked immunosorbent assay. In addition, we performed immunohistochemical staining on psoriatic skin and normal controls. RESULTS: We found that IL-19 upregulated KGF transcripts on CD8+ T cells. Patients with psoriasis had a lower level of IL-19 in serum than healthy volunteers. The difference between these two groups was statistically significant (P < 0.05). IL-19 expression was seen in basal and suprabasal keratinocytes in a continuous pattern, and was increased in psoriatic epidermis. CONCLUSIONS: These results suggest that IL-19 plays a role in the complex pathological cytokine network in psoriasis.

Reduced joining of DNA double strand breaks with an abnormal mutation spectrum in rodent mutants of DNA-PKcs and Ku80.

PURPOSE: To characterize further the contribution of the DNA-PK-dependent dsb repair pathway in mammalian cells. MATERIALS AND METHODS: The efficiency and fidelity of the joining of linear plasmids by DNA-PKcs-defective mouse cells (SCID) and Ku80-defective Chinese hamster ovary cells (xrs-6) was measured using either linear or circular replicating shuttle vector pZ189. RESULTS: The authors found a 3.9-10.7-fold reduced joining of the DNA ends, as compared with wild-type cells. Mutation analysis of the joining site revealed that the joining process was not hypermutable in the mutated cells. However, the SCID and xrs-6 cells produced a different spectrum of mutations at the joining site with a significantly lower proportion of insertions or more complex mutations. CONCLUSIONS: The remaining joining ability of the mutant cells points to an alternative DNA-PK-independent pathway of dsb repair. Comparison of these data with similar data from yeast suggest that the postulated alternative pathway of dsb repair is at least as efficient and less error-prone in rodent cells.

Assessment of DNA damage induced by broadband and narrowband UVB in cultured lymphoblasts and keratinocytes using the comet assay.

Phototherapy with broadband UVB is an effective treatment for inflammatory dermatoses. A newly developed fluorescent UVB lamp (Philips TL01) that emits a narrowband UVB around 311 nm was shown to be superior for the phototherapy of psoriasis. In order to contribute to the knowledge about the carcinogenic potential of this UVB source, we measured the DNA damage in lymphoblasts and keratinocytes induced by narrowband UVB and compared it with that by conventional broadband UVB using the single cell gel electrophoresis (comet assay). At equal doses, broadband UVB produced more DNA damage than narrowband UVB. However, in phototherapy of psoriasis, up to 10-fold higher doses are used with TL01. When therapeutically equivalent doses were compared (10-fold correction for narrowband UVB), we found only slight differences in the amount of DNA damage produced by broadband and narrowband UVB. This supports the already existing evidence that for phototherapy narrowband UVB is not more carcinogenic than broadband UVB.

Assessment of microsatellite instability in a cell line from a patient with xeroderma pigmentosum variant.

Cells from patients with xeroderma pigmentosum (XP) variant are thought to be defective in postreplication repair. This DNA repair pathway is not well defined in human cells and the exact genetic defect of XP variant is unknown. In another cancer-prone hereditary disorder, hereditary nonpolyposis colon cancer, tumors are characterized by a DNA mismatch repair defect with microsatellite instability. Since there are some similarities between postreplication repair and mismatch repair, we investigated microsatellite instability, the hallmark of a DNA mismatch repair defect, in a lymphoblastoid cell line from a patient with XP variant. Two normal lines and one nucleotide excision repair-defective XP group A line were used as controls. In a host cell microsatellite instability assay, the recently developed shuttle vector pZCA29 was transfected into these cells and replicated plasmid recovered after 3 days. The plasmid contains two CA repeat tracts that interrupt the reading frame of the lacZ gene. Reversion to active beta-galactosidase, detectable by a color reaction of bacterial transformants, represents the frequency of frameshift mutations in the CA repeat tracts during replication of the plasmid, and thereby the host cells' microsatellite instability. We did not find any significant differences in the mutation frequencies of the plasmids after passage through either cell line. This indicates that there is no microsatellite instability in the examined XP variant cell line.