Cyclooxygenase-independent inhibition of H2O2-induced cell death by S-ketoprofen in renal cells

15-Deoxy-Δ12,14-prostaglandin J2 Exerts Antioxidant Effects While Exacerbating Inflammation in Mice Subjected to Ureteral Obstruction

Urinary obstruction is associated with inflammation and oxidative stress, leading to renal dysfunction. Previous studies have shown that 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has both antioxidant and anti-inflammatory effects. Using a unilateral ureteral obstruction (UUO) mouse model, we examined the effects of 15d-PGJ₂ on oxidative stress and inflammation in the kidney. Mice were subjected to UUO for 3 days and treated with 15d-PGJ₂. Protein and RNA expression were examined using immunoblotting and qPCR. 15d-PGJ₂ increased NF-E2-related nuclear factor erythroid-2 (Nrf2) protein expression in response to UUO, and heme oxygenase 1 (HO-1), a downstream target of Nrf2, was induced by 15d-PGJ₂. Additionally, 15d-PGJ₂ prevented protein carbonylation, a UUO-induced oxidative stress marker. Inflammation, measured by nuclear NF-κB, F4/80, and MCP-1, was increased in response to UUO and further increased by 15d-PGJ₂. Renal injury was aggravated by 15d-PGJ₂ treatment as measured by kidney injury molecule-1 (KIM-1) and cortical caspase 3 content. No effect of 15d-PGJ₂ was observed on renal function in mice subjected to UUO. This study illustrates differentiated functioning of 15d-PGJ₂ on inflammation and oxidative stress in response to obstructive nephropathy. High concentrations of 15d-PGJ₂ protects against oxidative stress during 3-day UUO in mice; however, it aggravates the associated inflammation.

Cyclooxygenase 1 mRNA expression is undetectable in Madin Darby Canine Kidney cells

Background

Madin Darby Canine Kidney (MDCK) cells form polarized epithelium in vitro and are routinely used in research fields ranging from protein trafficking to influenza. However, the canine origin of these cells also means that compared to man or mouse, genomic resources are more limited and performance of commercially available antibodies often untested. The synthesis of pro-inflammatory prostaglandins in the kidney is mediated by the constitutively expressed cyclooxygenase 1 and the inducible cyclooxygenase 2 (COX-1 and COX-2, respectively). There are conflicting reports on the expression of COX-1 and COX-2 in MDCK cells and this lingering uncertainty about such important pharmacological targets may affect the interpretation of results obtained from this cell line.

Results

In order to definitively settle the issue of cyclooxygenase expression in MDCK cells, we designed PCR primers based on dog genomic sequences to probe COX-1 and COX-2 mRNA expression in MDCK cells and dog kidney. We report that while COX-1 and COX-2 genes are both expressed in dog kidney, COX-1 expression is undetectable in MDCK cells.

Conclusions

By improving the characterization of cyclooxygenase expression in MDCK cells, this study will contribute to a better understanding of the properties of this cell line and lead to improved experimental designs and data interpretations.

Control of tight junctional sealing: roles of epidermal growth factor and prostaglandin E2

Epithelia can adjust the permeability of the paracellular permeation route by regulating the degree of sealing of the tight junction. This is reflected by a transepithelial electrical resistance (TER) ranging from a few tenths to several thousand ohms times square centimeters, depending on the difference in composition between the fluid in the lumen and the interstitial fluid. Although teleologically sound, such correlation requires a physiological explanation. We have previously shown that urine extracts from different animal species increase the TER of Madin-Darby canine kidney (MDCK) monolayers and that these effects are mediated by epidermal growth factor (EGF) contained in the flowing intratubular fluid that eventually reaches the urine. This increase in TER is accompanied by an enhanced expression of claudin-4 (cln-4) and a decrement of cln-2. These changes are transient, peaking at approximately 16 h and returning to control values in approximately 24 h. In the present work we investigated how EGF provokes this transient response, and we found that the activation of extracellular-regulated kinases 1/2 (ERK1/2) by EGF is essential to increase TER and cln-4 content, but it does not appear to participate in cln-2 downregulation. On the other hand, prostaglandin synthesis, stimulated by EGF, functions as a negative feedback, turning off the signal initiated by EGF. Thus, PGE(2) blocks ERK1/2 by a mechanism that involves the G alpha(s) protein, adenylyl cyclase as well as protein kinase A in MDCK cells. In summary, the permeability of a given segment of the nephron depends on the expression of different claudin types, which may be modulated by EGF and prostaglandins.

Epigallocatechin-3-gallate induced primary cultures of rat hippocampal neurons death linked to calcium overload and oxidative stress

Epigallocatechin-3-gallate (EGCG), a catechin polyphenols component, is the main ingredient of green tea extract. It has been reported that EGCG is a potent antioxidant and beneficial in oxidative stress-related diseases, but others and our previous study showed that EGCG has pro-oxidant effects at high concentration. Thus, in this study, we tried to examine the possible pathway of EGCG-induced cell death in cultures of rat hippocampal neurons. Our results showed that EGCG caused a rapid elevation of intracellular free calcium levels ([Ca(2+)](i)) in a dose-dependent way. Exposure to EGCG dose- and time-dependently increased the production of reactive oxygen species (ROS) and reduced mitochondrial membrane potential (Deltapsi(m)) as well as the Bcl-2/Bax expression ratio. Importantly, acetoxymethyl ester of 5,5'-dimethyl-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, ethylene glycol-bis-(2-aminoethyl)-N,N,N',N'-tetraacetic acid, and vitamin E could attenuate EGCG-induced apoptotic responses, including ROS generation, mitochondrial dysfunction, and finally partially prevented EGCG-induced cell death. Furthermore, treatment of hippocampal neurons with EGCG resulted in an elevation of caspase-3 and caspase-9 activities with no significant accompaniment of lactate dehydrogenase release, which provided further evidence that apoptosis was the dominant mode of EGCG-induced cell death in cultures of hippocampal neurons. Taken together, these findings indicated that EGCG induced hippocampal neuron death through the mitochondrion-dependent pathway.