The above findings suggest the following mechanism of events underlying KLK8/neuropsin-induced hyperkeratosis: (i) skin inflammation increases KLK8/neuropsin expression in the stratum spinosum; (ii) the released KLK8/neuropsin inhibits AP-2α expression in the cells of the stratum basale and stratum spinosum; (iii) the decrease in AP-2α results in cell proliferation in the stratum basale and cell differentiation in the stratum spinosum, with an increase in keratin 10 expression.