Uric acid is a major inducer of inflammation in renal interstitium and may play a role in the progression of renal damage in hyperuricemic subjects with primary
nephropathies, renal vascular disease, and essential hypertension. At the same time, UA also acts as a water-soluble scavenger of reactive oxygen species. We evaluated the cellular effects of UA on cultured HMC as a potential interstitial target for abnormally elevated levels in acute and chronic renal disease. Intracellular free Ca2+
([Ca2+]i) was monitored by microfluorometry of fura 2-loaded cells, while oxidation of intracellularly trapped non-fluorescent 2,7-dichlorofluorescein diacetate (DCFHDA,
20 uM) was employed to assess the generation of reactive oxygen species during 12-hr incubations with various concentrations of UA or monosodium urate. Fluorescent metabolites of DCFH-DA in the culture media of HMC were detected at 485/530 nm excitation/emission wavelengths, respectively. UA dose-dependently lowered resting [Ca2+]i (from 102±9 nM to 95±3, 57±2, 48±6 nM at 1-100 uM UA,
respectively, p <0.05), leaving responses to vasoconstrictors such as angiotensin II unaffected. The effect was not due to Ca2+/H+ exchange upon acidification of the bathing media, as acetate, glutamate, lactate and other organic acids rather increased [Ca2+]i (to max. levels of 497±42 nM with 0.1 mM acetate). The decrease of [Ca2+]i was abolished by raising extracellular Ca2+ and not due to effects on Ca2+ channels or activation of Ca2+-ATPases, since unaffected by thapsigargin. The process rather
appeared sensitive to removal of extracellular Na+ in combination with blockers of Na+/Ca2+ exchange, such as 2’,4’-dichlorobenzamil, pointing to a countertransport
mechanism. UA dose-dependently prompted the extracellular release of oxidised DCFH (control 37±2 relative fluorescence units (RFU)/ml, 0.1uM 47±2, 1 uM 48±2, 10 uM 51±4, 0.1 mM 53±4; positive control, 10 uM sodium nitroprusside 92±5
RFU/ml, p<0.01). In summary, UA interferes with Ca2+ transport in cultured HMC, triggering oxidative stress which may initiate a sequence of events leading to interstitial injury and possibly amplifying renal vascular damage and/or the progression of chronic disease.
| Identifer | oai:union.ndltd.org:unibo.it/oai:amsdottorato.cib.unibo.it:216 |
| Date | 30 May 2007 |
| Creators | Festuccia, Francescaromana <1973> |
| Contributors | Menè, Paolo |
| Publisher | Alma Mater Studiorum - Università di Bologna |
| Source Sets | Università di Bologna |
| Language | Italian |
| Detected Language | English |
| Type | Doctoral Thesis, PeerReviewed |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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