Alkyl-chain-length-associated responses of K562 leukemia cells to methyl-, ethyl-, and butylparaben with a focus on PPARγ and WNT/β-catenin signaling.

Parabens are antimicrobial preservatives with endocrine-disrupting potential. Because methylparaben (MeP), ethylparaben (EtP), and butylparaben (BuP) differ in alkyl-chain length and biological potency, their comparison may reveal structure-dependent cellular responses. Using K562 chronic myeloid leukemia cells, we compared the effects of MeP, EtP, and BuP on cytotoxicity, metabolic activity assessed by resazurin reduction, proliferation- and stress-related markers, and WNT/β-catenin- and PPARγ-associated signaling. Cells were exposed to MeP, EtP, or BuP for 24 or 48 h; pathway-focused experiments used 1 μM parabens alone or with methyl 3-{[(4-methylphenyl)sulfonyl]amino}benzoate (MSAB), a β-catenin-directed WNT/β-catenin inhibitor, or GW9662, a PPARγ antagonist. MeP did not significantly affect LDH release or resazurin reduction. In contrast, EtP and BuP increased resazurin reduction at nanomolar and low-micromolar concentrations. At 1 μM, this response was not accompanied by marked LDH release, ROS generation, or cell-cycle alterations and therefore did not indicate overt acute cytotoxicity or robust proliferation. This response was accompanied by increased expression of WNT-related and glycolysis-associated genes, including AXIN2, LEF1, SLC2A1, HK2, PDK1, and PFKFB3. Parabens also induced divergent c-MYC regulation, with decreased c-MYC mRNA but increased protein abundance, and modulated PPARγ-associated signaling, antioxidant enzymes, caspase-related responses, and p-p62-related signaling. MSAB and GW9662 modified the resazurin-reduction response; however, these pharmacological effects did not establish direct β-catenin or PPARγ dependence. Overall, EtP and BuP, particularly BuP, produced stronger effects than MeP on resazurin reduction and several WNT/β-catenin-, PPARγ-, and p-p62-associated readouts.