Effect of experimental hyperoxaluria on renal calcium oxalate monohydrate binding proteins in the rat

Beneficial effect of Citrus limon peel aqueous methanol extract on experimentally induced urolithic rats

CONTEXT

Citrus limon (L.) Burm.f. (Rutaceace) is a commonly available fruit variety with high medicinal and industrial values.

OBJECTIVE

Lemon peel (LP) extract was studied as a potent preventive and curative agent for experimentally induced hyperoxaluric rats.

MATERIALS AND METHODS

Gas chromatography-mass spectrometry (GC-MS) analyses and toxicity study were performed for aqueous methanol LP extract. Twenty-four Wistar rats were segregated into four groups. Group 1: Control; Group 2: Urolithic (ethylene glycol (EG) - 0.75%); Group 3: Preventive study (EG + LP extract administration from 0th to 7th week); Group 4: Curative study (EG + LP extract administration from 4th to 7th week). Animals received LP extract daily by oral administration (100 mg/kg body weight) for 7 weeks.

RESULTS AND DISCUSSION

GC-MS analyses revealed that compound 6 was abundant in the LP extract (32%) followed by compound 1 (∼21%). The LD50 value of LP extract was found to be >5000 mg/kg of body weight. Urolithic rats showed significantly higher urinary calcium and oxalate (4.47 ± 0.44 and 18.86 ± 0.55 mg/24 h, respectively) excretion compared with control and experimental rats. Renal function parameters like urea (84 ± 8.5 and 96.1 ± 3.6 mg/dL), creatinine (1.92 ± 0.27 and 1.52 ± 0.22 mg/dL), and urinary protein (2.03 ± 0.02 and 2.13 ± 0.16 mg/24 h) were also reduced by LP extract (p < 0.001) and corroborated with tissue analyses (SOD, catalase, and MDA levels) and histological studies in normal and experimental animals. Immunohistochemical staining of THP and NF-κB in urolithic animals showed elevated expression than the control, while LP extract suppressed the expression of these proteins.

CONCLUSION

In conclusion, lemon peel is effective in curing kidney stone disease and also can be used to prevent the disease and its recurrence.

Transcriptional repression mediated by 45-kDa calcium oxalate monohydrate binding protein

BACKGROUND

This study was done to investigate the DNA binding ability of a diagnostic biomarker, 45-kDa calcium oxalate monohydrate (COM) binding protein, isolated from human kidney and its effect on transcription.

METHODS

The 45-kDa COM binding protein was isolated and purified from human kidney. The subcellular localization of the protein and the amino acid composition of the protein were analyzed. Oxalate-binding activity in the presence or absence of DNA was determined. The possibility of forming DNA-protein adducts was checked by diethylaminoethyl (DEAE)-Sephadex column chromatography. The effect of the protein on in vitro transcription was also studied.

RESULTS

The isolated 45-kDa protein was found to be basic in nature and its AACompIdent analysis showed it to be related to known transcription factors. The protein was found to be present in kidney cytosol and nucleus. The decreased oxalate binding activity in the presence of the DNA, and the shift in the DEAE-Sephadex elution profile established the DNA-binding ability of the protein. The in vitro transcription assay demonstrated the repression effect of the protein on gene expression during hyperoxaluria.

CONCLUSIONS

Transcriptional repression by the 45-kDa COM binding protein in an in vitro transcription assay system was reduced in the presence of oxalate. Hence, altered expression of certain genes involved in the prognosis of urolithiasis might be mediated by this 45-kDa protein.