The expression of TRPV1 is upregulated by heat, UV irradiation, and blue light in human KCs, where TRPV1 mediated the expression of metalloproteinase-1 (MMP-1), MMP-2, MMP-3, MMP-9, and MMP-13 via a Ca2+-dependent protein kinase C-α (PKC-α) pathway (Li et al., 2007; Lee et al., 2008, 2009, 2011; Yoo et al., 2020). Here, TRPV1 is linked to dry eye syndrome.