Reduction of cisplatinum-induced renal toxicity in mice by tetrahydroindazolonecarboxylic acid (HIDA) [corrected]

Cisplatin Nephrotoxicity Is Mediated by Deoxyribonuclease I

Cisplatin is commonly used for chemotherapy in a wide variety of tumors; however, its use is limited by kidney toxicity. Although the exact mechanism of cisplatin-induced nephrotoxicity is not understood, several studies showed that it is associated with DNA fragmentation induced by an unknown endonuclease. It was demonstrated previously that deoxyribonuclease I (DNase I) is a highly active renal endonuclease, and its silencing by antisense is cytoprotective against the in vitro hypoxia injury of kidney tubular epithelial cells. This study used recently developed DNase1 knockout (KO) mice to determine the role of this endonuclease in cisplatin-induced nephrotoxicity. The data showed that DNase I represents approximately 80% of the total endonuclease activity in the kidney and cultured primary renal tubular epithelial cells. In vitro, primary renal tubular epithelial cells isolated from KO animals were resistant to cisplatin (8 microM) injury. DNase I KO mice were also markedly protected against the toxic injury induced by a single injection of cisplatin (20 mg/kg), by both functional (blood urea nitrogen and serum creatinine) and histologic criteria (tubular necrosis and in situ DNA fragmentation assessed by the terminal deoxynucleotidyl transferase nick end-labeling). These data provide direct evidence that DNase I is essential for kidney injury induced by cisplatin.

Use of tetrahydraindazolone dicarboxylic acid (HIDA) to improve the therapeutic effect in vivo of combined cisplatin, heat and radiation treatment

The effect of tetrahydraindazolone dicarboxylic acid (HIDA) on tumour response and mouse lethality after treatment with cisplatin given either alone or combined with hyperthermia (43.5 degrees C/60 min) with or without radiation, was studied in the CDF1 mouse bearing a foot transplanted C3H mouse mammary carcinoma. The tumour response to a combined heat, cisplatin and HIDA treatment was assessed by tumour growth time, while local tumour control was used when irradiation was added to that treatment scheme. Toxicity was estimated as lethality within 14 days. Cisplatin and heat exerted the highest antitumour effect when given simultaneously, but at the same time there was a substantial increase in lethality. No sensitization of the tumour response or enhanced toxicity to cisplatin was observed if heat was given sequentially (i.e. 4 h) after cisplatin. The effect of this sequential schedule being only additive. When HIDA (100 mg/kg) was given 150 min before cisplatin and tumours heated 15 min later, the lethal toxicity was significantly reduced. HIDA did not, however, influence tumour growth time results. In tumour control studies combining radiation, drug and heat, cisplatin (6 mg/kg) and heat (43.5 degrees C/60 min) were given simultaneously 4 h after local irradiating the leg of tumour-bearing mice. The lethality of this regime was more than 55%, but when HIDA was added to the protocol, the toxicity fell to 5% without affecting local tumour control. In conclusion, HIDA administered before cisplatin protects against drug-induced toxicity without reducing the drug's antitumour activity when used alone or in combination with hyperthermia and/or radiation, and thus results in a significantly improved therapeutic benefit.