Juvenile neuronal ceroid lipofuscinosis, also known as juvenile Batten disease, is caused by mutations in the CLN3 gene and represents a major form of juvenile dementia. Children with the condition typically develop vision loss in early childhood, followed by seizures, motor decline, and progressive cognitive deterioration, usually dying in their late twenties or thirties. The disease belongs to a family of lysosomal storage disorders in which cellular waste-processing machinery fails, leading to the accumulation of fatty waste materials called ceroid lipofuscin inside cells. Despite decades of research into the underlying genetics, effective therapies that slow the relentless neurodegeneration remain painfully out of reach.

The Korean team, led by Hyungkuen Kim, Eunmi Hwang, and Sung-Jo Kim, focused their investigation on parthanatos, a distinctive form of programmed cell death that has been extensively studied in Alzheimer’s disease but never before systematically characterized in JNCL. Parthanatos takes its name from poly(ADP-ribose), or PAR, a polymer produced by the enzyme PARP1. When cells experience excessive DNA damage, PARP1 becomes hyperactivated and floods the nucleus with PAR chains. These polymers eventually trigger the release of apoptosis-inducing factor from mitochondria, which migrates to the nucleus and orchestrates large-scale DNA fragmentation, killing the cell in a way that is distinct from classical apoptosis.

Using patient-derived lymphoblasts, immortalized white blood cells generated from JNCL patients, the researchers employed quantitative immunofluorescence microscopy to compare the disease cells with healthy controls. The results were striking. JNCL cells accumulated significantly higher levels of 8-oxoguanine, a pre-mutagenic DNA lesion produced when reactive oxygen species attack guanine bases, as well as elevated levels of PAR, the molecular signature of parthanatos. The accumulation of 8-oxoguanine is particularly insidious because it impairs DNA repair pathways, creating a vicious cycle in which oxidative damage begets repair failure, which begets further PARP1 overactivation and ultimately cell death.

The mechanistic logic connecting these observations to calcium is central to the study. JNCL is known to exhibit elevated intracellular calcium levels, a disturbance that has been documented in previous work on CLN3-deficient cells. Calcium overload is a well-established activator of PARP1, and studies in cardiomyocytes and other cell types have shown that calcium influx can directly stimulate PAR polymer production. In JNCL, this calcium-PARP1 axis appeared to be running unchecked, pushing vulnerable cells toward the parthanatos threshold. The researchers reasoned that if excess calcium was fueling the PARP1 fire, then dampening calcium entry might extinguish it.

Enter diltiazem. This L-type calcium channel blocker, which has been on pharmacy shelves since the 1970s, works by blocking voltage-gated calcium channels in heart and vascular smooth muscle. When the team treated JNCL patient-derived lymphoblasts with diltiazem, PAR accumulation dropped markedly. Critically, the protective effect persisted even when the cells were simultaneously exposed to a calcium ionophore, a chemical that forcibly floods cells with calcium. This suggested that diltiazem was not merely plugging calcium channels at the membrane but was intervening in the downstream signaling cascade that translates calcium excess into PARP1 activation, suppressing the expression of PARP1 itself and thereby limiting the raw material for parthanatos.

The drug’s benefits did not stop there. Diltiazem also reduced the accumulation of 8-oxoguanine in the JNCL cells, though intriguingly, this effect appeared to be largely independent of its calcium-blocking activity. Subcellular fractionation followed by immunoblotting, a technique that separates cellular compartments and identifies which proteins reside where, revealed that diltiazem enhanced the nuclear recruitment of OGG1, the primary enzyme responsible for excising 8-oxoguanine from DNA, along with its partner proteins. In other words, the drug was not just reducing the damage signal but was actively bolstering the cell’s repair crew, delivering the fix-it enzymes to the nucleus where the oxidative lesions accumulate.

To confirm that OGG1 was genuinely central to the drug’s protective mechanism, the researchers performed knockdown experiments, silencing the OGG1 gene in the treated cells. The results were unambiguous: when OGG1 was removed, diltiazem’s protective effects vanished entirely. This dependency establishes a dual role for the drug, acting simultaneously on calcium signaling to suppress PARP1 expression and on the OGG1-dependent base excision repair pathway to clear oxidative DNA damage. The finding also underscores a broader biological principle that has emerged from studies in Alzheimer’s disease and aging: OGG1-initiated repair is a double-edged sword, essential for genome maintenance but capable of exacerbating parthanatos when repair intermediates overstimulate PARP1.

The therapeutic implications are considerable. Diltiazem is an approved, well-characterized medication with decades of clinical safety data, which means that repurposing it for JNCL could potentially bypass some of the lengthy development timelines that plague novel drug candidates. Previous studies have already hinted at the drug’s relevance to neurodegeneration, with earlier work showing that L-type calcium channel blockers significantly lower intracellular calcium in CLN3-deficient neuroblastoma cells, and animal research demonstrating protective effects of diltiazem in chemically induced dementia models in mice. The new study adds a specific molecular mechanism, parthanatos suppression via PARP1 and OGG1 modulation, to this growing body of evidence.

Significant caveats remain before patients can benefit. The current findings derive from patient-derived lymphoblasts, which are accessible but imperfect proxies for the neurons that actually die in JNCL, and the researchers note that their data identify parthanatos as a novel therapeutic target rather than a validated clinical intervention. Whether diltiazem can cross the blood-brain barrier at sufficient concentrations, whether it will slow neurodegeneration in living organisms, and what dosing regimens would be appropriate for children all require further study. Nevertheless, by pinpointing PAR accumulation as a hallmark of JNCL pathology and demonstrating that an existing cardiovascular drug can interrupt this deadly cascade at two distinct points, the Hoseo University team has given the Batten disease research community something it has long needed: a concrete, pharmacologically tractable target in a disease where hope has been in short supply.

Subject of Research: Parthanatos and DNA repair dysfunction in juvenile neuronal ceroid lipofuscinosis and its modulation by the calcium channel blocker diltiazem

Article Title: The calcium channel blocker diltiazem ameliorates parthanatos in juvenile neuronal ceroid lipofuscinosis

Article References: Kim, H., Hwang, E., & Kim, S.-J. (2026). The calcium channel blocker diltiazem ameliorates parthanatos in juvenile neuronal ceroid lipofuscinosis. Journal of Molecular Medicine, 104(1), Article 118. https://doi.org/10.1007/s00109-026-02726-1

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02726-1

Keywords: juvenile neuronal ceroid lipofuscinosis, Batten disease, CLN3, parthanatos, PARP1, diltiazem, 8-oxoguanine, OGG1, calcium signaling, DNA repair, drug repurposing, neurodegeneration

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