ANALYSIS OF ETHACRYNIC ACID IN URINE BY HPLC-FLUORESEENCE DETECTOR

A sensitive and selective method has been developed for the detection of free ethacrynic acid in human urine. Using 4-(bromomethyl)-7-methoxycoumarin, ethacrynic acid was transformed into a fluorescent derivative, and was analysed by HPLC-fluorescence detector. The detection limit is 0.1ug/ml urine. The method is suitable for screening ethacrynic acid in doping control and studying its metabolism.

Ototoxic destruction by co-administration of kanamycin and ethacrynic acid in rats

It is well known that ethacrynic acid (EA) can potentiate the ototoxicity of aminoglycoside antibiotics (AmAn) such as kanamycin (KM),if they were applied at the same time.Currently,to create the model of EA-KMinduced cochlear lesion in rats,adult rats received a single injection of EA (75 mg/kg,intravenous injection),or followed immediately by KM (500 mg/kg,intramuscular injection).The hearing function was assessed by auditory brainstem response (ABR) measurement in response to click and/or tone bursts at 4,8,12,16,20,24,and 32 kHz.The static microcirculation status in the stria vascularis after a single EA injection was evaluated with eosin staining.The pathological changes in cochlear and vestibular hair cells were also quantified after co-administration of EA and KM.After a single EA injection,blood flow in vessels supplying the stria vascularis rapidly diminished.However,the blood supply to the cochlear lateral wall partially recovered 5 h after EA treatment.Threshold changes in ABR were basically parallel to the microcirculation changes in stria vascularis after single EA treatment.Importantly,disposable co-administration of EA and KM resulted in a permanent hearing loss and severe damage to the cochlear hair cells,but spared the vestibular hair cells.Since the cochlear lateral wall is the important part of the blood-cochlea barrier,EA-induced anoxic damage to the epithelium of stria vascularis may enhance the entry of KM to the cochlea.Thus,experimental animal model of selective cochlear damage with normal vestibular systems can be reliably created through co-administration of EA and KM.

“Pincer movement”:Reversing cisplatin resistance based on simultaneous glutathione depletion and glutathione S-transferases inhibition by redox-responsive degradable organosilica hybrid nanoparticles

The therapeutic efficacy of cisplatin has been restricted by drug resistance of cancers.Intracellular glutathione(GSH)detoxification of cisplatin under the catalysis of glutathione S-transferases(GST)plays important roles in the development of cisplatin resistance.Herein,a strategy of“pincer movement”based on simultaneous GSH depletion and GST inhibition is proposed to enhance cisplatin-based chemotherapy.Specifically,a redox-responsive nanomedicine based on disulfide-bridged degradable organosilica hybrid nanoparticles is developed and loaded with cisplatin and ethacrynic acid(EA),a GST inhibitor.Responding to high level of intracellular GSH,the hybrid nanoparticles can be gradually degraded due to the break of disulfide bonds,which further promotes drug release.Meanwhile,the disulfide-mediated GSH depletion and EA-induced GST inhibition cooperatively prevent cellular detoxification of cisplatin and reverse drug resistance.Moreover,the nanomedicine is integrated into microneedles for intralesional drug delivery against cisplatin-resistant melanoma.The in vivo results show that the nanomedicine-loaded microneedles can achieve significant GSH depletion,GST inhibition,and consequent tumor growth suppression.Overall,this research provides a promising strategy for the construction of new-type nanomedicines to overcome cisplatin resistance,which extends the biomedical application of organosilica hybrid nanomaterials and enables more efficient chemotherapy against drug-resistant cancers.