The study focused on Madin-Darby Bovine Kidney cells, a widely used laboratory model of renal epithelial tissue. The choice of a bovine kidney line is not incidental. Livestock are chronically exposed to phthalates through contaminated feed, water, and environmental matrices, and renal epithelial cells represent a plausible first line of contact for circulating plasticizer metabolites. What the researchers found was a stark, concentration-dependent pattern of cellular injury that unfolded across multiple independent assays, each interrogating a different layer of genomic integrity.

The first layer was simple survival. Using the MTT assay, a colorimetric test in which metabolically active cells convert a yellow tetrazolium compound into purple formazan crystals, the team exposed MDBK cells to DBP concentrations ranging from 5 to 200 micromolar. Cell viability declined in a dose-dependent fashion, and the concentration that killed half the cells, the LC50, came out at 50 micromolar after 24 hours of exposure. That figure anchored the rest of the experimental design: the researchers selected 25, 50, and 75 micromolar as their working concentrations, spanning a range from sublethal stress to severe toxicity, to probe what happens to cells that survive a phthalate encounter.

What happens, it turns out, is a cascade of genetic damage. The alkaline comet assay, a single-cell gel electrophoresis technique that untangles DNA and allows broken strands to migrate out of the cell nucleus like the tail of a comet, revealed significant, dose-dependent increases in the DNA damage index and in the percentage of tail DNA. In parallel, the genomic instability index climbed with rising DBP concentration. These are not subtle statistical whispers; the damage signals rose consistently across the concentration range, and at the highest dose of 75 micromolar, the genotoxic response was comparable to that of the positive control group, the benchmark of maximal damage against which test chemicals are judged.

Chromosomal-level injury told the same story. In the cytokinesis-block micronucleus assay, cells are trapped at the point of division with cytochalasin B, and any chromosome fragments or whole chromosomes left behind during mitosis appear as micronuclei, tiny satellite nuclei outside the main nucleus. DBP-treated cells showed significant increases in micronucleus frequency and in the proportion of binucleated cells, alongside a rise in cytostasis, the halting of cell division. Meanwhile, the cytokinesis-block proliferation index, a measure of how many rounds of nuclear division cells manage to complete, fell as DBP concentration rose. Together, these results indicate that the chemical does not merely nick DNA; it leaves behind chromosomal debris that cells carry into division while simultaneously slowing the very process of proliferation.

Perhaps the most intriguing finding lies in the transcriptional response. Quantitative real-time PCR revealed that two DNA damage-associated genes, OGG1 and HPRT1, were both significantly upregulated in exposed cells. OGG1, which encodes a glycosylase that excises oxidized guanine bases, one of the most common lesions produced by oxidative stress, was elevated 5.33-fold. HPRT1, involved in the salvage pathway of purine nucleotide synthesis and long used as a sentinel of genotoxic stress, rose 6.57-fold. Crucially, higher DBP concentrations drove greater gene expression, suggesting a graded molecular alarm that tracks the dose of exposure.

The upregulation of repair genes is a double-edged signal. On one hand, it demonstrates that the cells recognized the damage and attempted to mount a repair response, a hallmark of activated DNA damage signaling. On the other hand, sustained elevation of repair machinery is itself an indicator of overwhelming or persistent genotoxic stress, and the concurrent rise in micronuclei and cytostasis suggests that the repair effort was not fully keeping pace with the injury. The authors interpret this coordinated pattern as evidence that DBP induces cellular stress and DNA damage while altering the expression of the genes tasked with fixing it, a combination that could erode genomic stability over time.

The broader context makes these results resonate. DBP is frequently detected not only in PVC consumer products but also in environmental matrices, meaning that humans, wildlife, and livestock encounter it continuously through ingestion, inhalation, and dermal contact. As an endocrine-disrupting chemical, it has already been implicated in reproductive and developmental toxicity, and regulatory frameworks in several jurisdictions have restricted its use in toys, cosmetics, and food-contact materials. What this study adds is mechanistic evidence from a renal epithelial model that DBP can act directly on the genome, independent of its hormonal effects, and that the damage is accompanied by transcriptional perturbation of the repair apparatus itself.

There are, of course, important caveats in translating a cell-culture experiment to whole organisms. The concentrations used here, particularly the 50 micromolar LC50, reflect acute exposure in vitro, and the actual internal doses experienced by animals or humans depend on absorption, metabolism, and excretion, processes that the cell line does not capture. MDBK cells, while a robust epithelial model, are bovine rather than human, and species differences in phthalate metabolism could shift the toxic threshold. Nonetheless, the internal consistency of the data, with cytotoxicity, comet-based strand breakage, micronucleus formation, proliferation arrest, and gene expression changes all pointing in the same direction across a coherent dose range, lends the findings considerable weight.

The authors conclude that DBP induces concentration-dependent cyto-genotoxicity and transcriptional alterations in MDBK cells, and they frame the result as an argument for developing safer plasticizer alternatives. As phthalates continue to leach from the built environment into water, food, and tissue, studies like this one sharpen the scientific case for that transition. The genetic alarm bells rung by OGG1 and HPRT1 in these kidney cells are a reminder that the cost of convenience chemistry is not always visible on the label, and that the molecules holding our plastics together may be prying apart something far more delicate inside our cells.

Subject of Research: Cyto-genotoxic effects of the plasticizer dibutyl phthalate in bovine kidney epithelial cells

Article Title: The cyto-genotoxic potential of dibutyl phthalate promotes DNA damage and cellular stress with altered DNA repair gene expression in Madin-Darby Bovine Kidney (MDBK) cells

Article References: Ali, M. M., Ullah, A., Firyal, S., Akhtar, R., Awan, F., Ataya, F. S., Mehmood, H., Raza, S., Majeed, K. A., & Fouad, D. (2026). The cyto-genotoxic potential of dibutyl phthalate promotes DNA damage and cellular stress with altered DNA repair gene expression in Madin-Darby Bovine Kidney (MDBK) cells. BMC Pharmacology and Toxicology. https://doi.org/10.1186/s40360-026-01239-4

Image Credits: AI Generated

DOI: 10.1186/s40360-026-01239-4

Keywords: dibutyl phthalate, phthalates, genotoxicity, DNA damage, MDBK cells, comet assay, micronucleus, OGG1, HPRT1, endocrine disruptors, plasticizers, genomic instability