Abstract: 【Abstract】 Objective To explore the relationships of neutrophil gelatinase-associated lipocalin （NGAL） with severity of skin lesions in children with psoriasis and peripheral neutrophil count, and to evaluate in vitro effect of NGAL on expression of tumor necrosis factor-α （TNF-α） and interleukin-22 （IL-22） by a human immortalized keratinocyte cell line HaCaT. Methods From January 1st 2017 to December 31st 2018, 98 children who newly developed psoriasis were enrolled from Department of Dermatology of 6 hospitals in China, including 51 males and 47 females. Their age was 7.00 ± 2.99 years （range: 3 - 14 years）, and their course of disease was 7.4 ± 5.85 days （range: 3 - 28 days）. The serum level of NGAL was detected in all the patients before and two weeks after treatment, and the relationships of NGAL with psoriasis area and severity index （PASI） scores and peripheral neutrophil count were evaluated. Western blot analysis and reverse-transcription （RT）-PCR were performed to determine the protein and mRNA expression of TNF-α and IL-22 in HaCaT cells, respectively, after 12-hour treatment with NGAL at concentrations of 0 （control group）, 0.125, 0.25, 0.5, 1 mg/L. Statistical analysis was carried out with SPSS 16 software. by using t test and one-way analysis of variance. Results After 2-week treatment, the PASI score, neutrophil count and NGAL level in children with psoriasis significantly decreased （1.80 ± 1.19, ［6.16 ± 0.76］ × 109/L, 90.86 ± 0.75 μg/L, respectively） compared with those before the treatment （10.38 ± 3.42, ［11.01 ± 2.85］ × 109/L, 113.48 ± 21.26 μg/L, respectively; t = 31.42, 18.34, 16.37 respectively, all P < 0.001）. Before the treatment, the serum level of NGAL in the patients was positively correlated with the PASI score and peripheral neutrophil count （r = 0.918, 0.799 respectively, both P < 0.05）. The mRNA and protein expression of IL-22 in HaCaT cells significantly differed among these groups treated with different concentrations of NGAL （F = 176.31, 296.96 respectively, both P < 0.001）, so did the mRNA and protein expression of TNF-α （F = 193.28, 318.80 respectively, both P < 0.001）. Additionally, the protein and mRNA expression of IL-22 and TNF-α in HaCaT cells was significantly higher in the 0.125-, 0.25-, 0.5- and 1-mg/L NGAL group than in the control group （all P < 0.05）. The NGAL level was positively correlated with the protein and mRNA expression of TNF-α and IL-22 in HaCaT cells （all P < 0.05）. Conclusions The serum level of NGAL was high in children with psoriasis, and positively correlated with severity of skin lesions and peripheral neutrophil count. NGAL can upregulate the expression of TNF-α and IL-22 in HaCaT cells in vitro.

Key words: Psoriasis, Child, Tumor necrosis factor-alpha, Interleukin-22, Neutrophil gelatinase associated lipocalin