Aquaporin-9 and aquaporin-10 but not aquaporin-3 confer susceptibility to dimethylarsinic acid genotoxicity in human cells.

UNLABELLED: Human metabolism converts inorganic arsenic to the pentavalent methylated species MMA(V) and DMA(V), the forms most people excrete, and the forms long read as the end of a detoxification pathway. Whether a transporter sets how much of these metabolites reaches the genome has not been tested in a mammalian cell. We expressed human AQP3, AQP7, AQP9 or AQP10 in HEK293T and MRC5-SV40 cells and measured γH2AX by flow cytometry across dose series of As(V), MMA(V) and DMA(V), pairing every aquaporin with a GFP-Tubulin control and an untransfected mock acquired in the same run. As(V) was inactive in HEK293T cells and only weakly active in MRC5-SV40 cells to 20 µM, and both methylated species damaged DNA only in the millimolar range, DMA(V) being the more potent of the two in both cell lines. Against that weak baseline, AQP9 and AQP10 raised DMA(V)-induced γH2AX in HEK293T cells by roughly 17 percentage points over the matched control, more than doubling the damage the same exposure produced in control cells, whereas AQP3 and AQP7 changed it not at all. AQP9 alone remained active with MMA(V). The ranking held in MRC5-SV40 fibroblasts at one-sixth the size, and within single wells the damage rose with the amount of AQP9 a cell carried while the control was flat. Aquaglyceroporins therefore discriminate among arsenic species, and AQP9 and AQP10 turn a weakly genotoxic metabolite into a substantially more genotoxic one.

HIGHLIGHTS: • AQP9 and AQP10 more than double DMA(V)-induced DNA damage in human cells.• AQP3 and AQP7 show no such effect: permeability differs between paralogues.• AQP9 alone remains active with MMA(V); AQP10 does not.• Damage rises with the amount of AQP9 a single cell carries.• Genotoxic potency depends on the transporter complement of the exposed cell.

IMPACT STATEMENT: Arsenic risk assessment treats the pentavalent methylated metabolites as detoxification products, and on their own they are weak genotoxins. We show that this weakness is conditional on the transporter complement of the exposed cell. AQP9 and AQP10 more than double the DNA damage a given DMA(V) exposure produces in human cells, while AQP3, which confers arsenite susceptibility in the same laboratory, does not. An aquaglyceroporin and a poorly toxic arsenical therefore act together to produce damage that neither produces alone, so the genotoxic potency of an arsenical cannot be read from the species and the dose without knowing which channels admit it. Uptake capacity, which differs between tissues and between people, belongs alongside metabolism among the factors that set internal dose and susceptibility.