The pa raoxo na se 1, 2 and 3 in hu ma ns Ma ri ja Gr dic Raj ko vic * , La da Ru mo ra, Kar me la Ba ri sic De par tme nt of Me di cal Bioc he mis try and He ma to lo gy, Fa cul ty of Phar ma cy and Bioc he mis try, Uni ver si ty of Zag reb, Zag reb, Croa tia *Cor res pon di ng aut hor: m_gr dic @ya hoo.com Ab stra ctThe pa raoxo na se ge ne fa mi ly in hu ma ns in clu des three mem be rs: PON1, PO N2 and PO N3. The pro duc ts of tho se three ge nes are the fol lowi ng enzymes: pa raoxo na se 1 (PO N1), pa raoxo na se 2 (PO N2) and paraoxo na se 3 (PO N3). PO N1 is main ly as so cia ted wi th a hi gh den si ty li pop ro tein (HDL). A sma ll amou nt of this en zyme is al so bou nd to ve ry low-den si ty li pop ro tein (VLDL) and pos tpran dial chylo mic ro ns. PO N1 pos se ss or ga nop hos pha tase, aryles te ra se and lac to na se ac ti vi ty and it hydro lyzes ma ny diff e re nt sub stra tes. It is al so known that PO N1 may ha ve an tiat he ro ge nic fun ction. Com pa red to the PO N1, PO N2 and PO N3 are mu ch le ss stu died and des cri bed. PO N2 is ubiqui tous ly expres sed in tra cel lu lar pro tein, whi le PO N3 is bou nd to HDL, li ke PO N1. The bo th en zymes pos se ss an tioxi da nt pro per ties.

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of fungi. OTA induces a tubular-interstitial nephropathy in humans and in animals. It has been implicated as one of the aetiological agents involved in the development of endemic nephropathy. OTA-induced oxidative stress and apoptosis may play key roles in the development of chronic tubulointerstitial nephritis connected to the long-term exposure to this food contaminant. We studied the effects of low doses of OTA on kidney cells. Wistar rats were treated with 120 microg OTA/kg bodyweight daily, for 10, 30 or 60 days. Toxin concentration in kidney was proportional to the time of exposure, and amounted to 547.2, 752.5 and 930.3 ng OTA/g kidney tissue after 10, 30 and 60 days, respectively. OTA treatment caused an increased number of cells undergoing apoptosis in both proximal and distal epithelial kidney cells. The apoptotic cells were visualised using the TUNEL assay and staining with haematoxylin and eosin in situ. The number of apoptotic cells in rats treated for 10, 30 and 60 days increased by 5-, 6.4- and 12.7-fold, respectively, compared with the control cells. However, DNA electrophoresis did not show characteristic fragmentation (DNA laddering). The oxidative stress was evident via increased malondialdehyde formation. The concentration of lipid peroxides showed an increase (36%), but the activity of superoxide dismutase decreased (26%) in 60-day treated rats. In spite of the observed biochemical and morphological changes in the kidney cells, renal functional status was preserved to the end of experiment. This study demonstrates that a combination of morphologic and biochemical markers can be used to monitor early cell death in OTA-induced renal injury. We have shown that the exposure to the relatively low OTA concentrations has activated apoptotic processes and oxidative damage in kidney cells.

No abstract

No abstract

Nanomolar concentrations of human amylin promote death of RINm5F cells in a time- and concentrationdependent manner. Morphological changes of chromatin integrity suggest that cells are predominantly undergoing apoptosis. Human amylin induces significant activation of caspase-3 and strong and sustained phosphorylation of stress-activated protein kinases, c-Jun N-terminal kinase (JNK) and p38, that precedes cell death. Extracellular signal-regulated kinase (ERK) activation was not concomitant with JNK and/or p38 activation. Activation of caspase-3 and mitogen-activated protein kinases (MAPKs) was detected by Western blot analysis. Addition of the MEK1 inhibitor PD 98059 had no effect on amylin-induced apoptosis, suggesting that ERK activation does not play a role in this apoptotic scenario. A correlative inhibition of JNK activation by the immunosuppressive drug FK506, as well as a selective inhibition of p38 MAPK activation by SB 203580, significantly suppressed procaspase-3 processing and the extent of amylin-induced cell death. Moreover, simultaneous pretreatment with both FK506 and SB 203580, or with the caspase-3 inhibitor Ac-DEVD-CHO alone, almost completely abolished procaspase-3 processing and cell death. Thus, our results suggest that amylin-induced apoptosis proceeds through sustained activation of JNK and p38 MAPK followed by caspase-3 activation.