ABSTRACT
Objective
To investigate and compare the enantiomer-specific nephrotoxicity of tartaric acid (TTA) in Madin–Darby canine kidney (MDCK) cells and human kidney (HK-2) cells. Secondary aims were to determine the enantiomeric-specific TTA accumulation to induce these effects through distinct influx and efflux pathways via organic anion transporter (OAT)-1 and OAT-4. Subsequently, a critical objective was to determine the mitochondrial mechanisms of toxicity via citrate synthase inhibition and assess supplemental substrate mitigation within this reaction.
Design
In vitro concentration–response experiments and transporter transfection studies using racemic and enantiomeric forms of TTA in canine and human immortalized renal cell lines over a 48-h exposure period.
Setting
School of Pharmacy biomedical research laboratory and tissue culture facility.
Animals/Samples
Immortalized MDCK and HK-2 proximal tubule epithelial cell lines.
Interventions
MDCK and HK-2 cells were treated with 5–50 mmol/L of racemic or enantiomeric TTA for 48 h. Cotreatment of 0.08 mmol/L oxaloacetate (OAA) was used to assess the mitigation of citrate synthase inhibition. Additional transporter transfection experiments were conducted using probenecid (PBD) as a cotreatment to gain a greater understanding of TTA accumulation and toxicity prevention.
Measurements and Main Results
Cellular ATP levels and citrate synthase activity were measured. L-Tartaric acid (L-TTA) caused significant ATP depletion (8.5%–24.8%) and citrate synthase inhibition (36.5%–45.0%) in MDCK cells but not in HK-2 cells, suggesting species-specific toxicity. OAT-4 transfection reduced ATP loss by 8.0%–11.2% after L-TTA exposure. Cotreatment with PBD reduced cytotoxic L-TTA effects by 11.7%, suggesting that OAT-1 uptake and insufficient OAT-4 efflux are central to TTA accumulation. Cotreatment with OAA rescued ATP loss by 15.6%.
Conclusions
L-TTA is a species- and enantiomer-specific nephrotoxicant in dogs resulting from a lack of transporter-mediated efflux and subsequent citrate synthase inhibition. OAT-1 inhibition or OAT-4 transfection mitigates toxicity, supporting a transporter-driven mechanism for TTA accumulation.
Journal of Veterinary Emergency and Critical Care, EarlyView.Wiley: Journal of Veterinary Emergency and Critical Care: Table of Contents