The calcium channel blocker diltiazem ameliorates parthanatos in juvenile neuronal ceroid lipofuscinosis.
Kim Hyungkuen H, Hwang Eunmi E, Kim Sung-Jo SJ
Accumulation of pre-mutagenic 8-oxoguanine and impaired DNA repair can lead to poly(ADP-ribose) (PAR) accumulation and parthanatos in Alzheimer's disease, the leading cause of age-dependent dementia. However, the occurrence of parthanatos has not been well established in other types of dementia, including juvenile neuronal ceroid lipofuscinosis (JNCL), a major form of juvenile dementia. In this study, we investigated parthanatos-associated pathology in JNCL using patient-derived lymphoblasts (PDLs). Quantitative immunofluorescence microscopy revealed increased accumulation of 8-oxoguanine and PAR in JNCL-PDLs. JNCL is known to exhibit elevated intracellular calcium, which activates PAR polymerase - 1 (PARP1). The L-type calcium channel blocker diltiazem effectively suppressed PAR accumulation in JNCL-PDLs, even under co-treatment with a calcium ionophore. Diltiazem also reduced 8-oxoG accumulation in JNCL-PDLs, although this effect was largely calcium independent. Subcellular fractionation followed by immunoblotting showed that diltiazem enhanced nuclear recruitment of OGG1 and its partner proteins. These protective effects were abolished by OGG1 knockdown, suggesting a dual role of diltiazem in regulating both calcium signaling and OGG1 activity. Collectively, our data identify that parthanatos as novel therapeutic target for JNCL and propose diltiazem as a potential therapeutic agent. KEY MESSAGES: Increased poly(ADP-ribose) accumulation represents a novel therapeutic target in juvenile neuronal ceroid lipofuscinosis caused by CLN3 mutations. Increased PARP1 expression and decreased PARP1 cleavage lead to elevated poly(ADP-ribose) accumulation in juvenile neuronal ceroid lipofuscinosis. Diltiazem ameliorates poly(ADP-ribose) accumulation in patient-derived cell models of juvenile neuronal ceroid lipofuscinosis by suppressing PARP1 expression and 8-oxoguanine accumulation.