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Physiology and pathophysiology of cyclooxygenase-2 and prostaglandin E2 in the kidney
( Rikke Nørregaard ),( Tae Hwan Kwon ),( Jørgen Frøkiær ) 대한신장학회 2015 Kidney Research and Clinical Practice Vol.34 No.4
The cyclooxygenase (COX) enzyme system is the major pathway catalyzing the conversion of arachidonic acid into prostaglandins (PGs). PGs are lipid mediators implicated in a variety of physiological and pathophysiological processes in the kidney, including renal hemodynamics, body water and sodium balance, and the inflammatory injury characteristic in multiple renal diseases. Since the beginning of 1990s, it has been confirmed that COX exists in 2 isoforms, referred to as COX-1 and COX-2. Even though the 2 enzymes are similar in size and structure, COX-1 and COX- 2 are regulated by different systems and have different functional roles. This review summarizes the current data on renal expression of the 2 COX isoforms and highlights mainly the role of COX-2 and PGE2 in several physiological and pathophysiological processes in the kidney.
Renal Potassium Excretion Visualized on 82Rubidium PET/CT
Mads Ryø Jochumsen,Lars Poulsen Tolbod,Michael Borre,Jørgen Frøkiær,Kirsten Bouchelouche,Jens Sörensen 대한핵의학회 2020 핵의학 분자영상 Vol.54 No.2
The positron emission tomography (PET) flow tracer 82Rubidium is a known potassium analogue. During our studies of tumor blood flow in prostate cancer, we found that approximately 10% of the patients had high urinary 82Rubidium activity. In roughly half of these patients, the increased renal rubidium/potassium excretion was either causing hypokalemia or explained by Thiazide treatment. In the other half, there was no obvious explanation or clinical consequence of the renal rubidium/potassium excretion. This is the first time enhanced renal potassium excretion is visualized on 82Rubidium PET/CT.
Lee, Yu-Jung,Choi, Hyo-Jung,Lim, Jung-Suk,Earm, Ji-Hyun,Lee, Byung-Heon,Kim, In-San,Frøkiær, Jørgen,Nielsen, Søren,Kwon, Tae-Hwan American Physiological Society 2008 American Journal of Physiology Vol.295 No.1
<P>Aquaporin-2 (AQP2), the vasopressin-regulated water channel in collecting duct principal cells, plays a key role in the regulation of body water balance. We aimed to isolate high-affinity peptide ligands that bind to immunoisolated AQP2-expressing plasma membrane (PM) or intracellular vesicle (ICV) preparations from rat kidney by the in vitro phage display technique. Immunoblotting revealed that AQP2 was exclusively expressed in the immunoisolated AQP2 membrane fractions (PM and ICV), compared with the nonimmunoisolated or preimmune IgG pulldown rat kidney samples. Moreover, AQP1 or H<SUP>+</SUP>-ATPase (B1 subunit) expression was minimal in the immunoisolated AQP2 membrane fractions, indicating the specificity of AQP2 membrane isolation. A phage peptide library based on T7 415-1b phage vector displaying CX7C was constructed. After three rounds of biopanning, seven phage clones of high frequency were selected, which showed high affinity to the AQP2-containing PM or ICV fractions compared with a nonrecombinant T7 insertless phage clone. In contrast, these phage clones showed lower affinity to H<SUP>+</SUP>-ATPase-containing fractions. Fluorescein-conjugated peptide labeling was associated with intracellular compartment and PM of primary cultured inner medullary collecting duct cells, relative to absent or very weak labeling with fluorescein-conjugated control peptide. Library analyses demonstrated proteins that had motifs homologous to the peptide ligands, albeit with a high probability of a random match due to short peptide sequences. In summary, we applied the in vitro phage display technique to identify high-affinity peptide ligands to AQP2-expressing membranes. Library analyses identified proteins having homologous motifs, which need to be examined for involvement in AQP2 trafficking and regulation.</P>
( Martin Skott ),( Rikke Nørregaard ),( Hanne Birke Sørensen ),( Johan Palmfeldt ),( Tae Hwan Kwon ),( Thomas Jonassen ),( Jørgen Frøkiær ),( Søren Nielsen ) 대한신장학회 2014 Kidney Research and Clinical Practice Vol.33 No.2
Background: The primary aim of the study was to investigate the cytokine/chemokine response in the kidney, lung, and liver following acute kidney injury(AKI). The secondary aim was to test whether α-melanocyte-stimulating hormone(α-MSH) could prevent a reduction in organ function, and attenuate the inflammatorycytokine/chemokine response within the kidney, lung, and liver following AKIin rats with or without preexisting chronic kidney disease (CKD). Methods: A two-stage animal model, in which AKI was induced in rats withpreexisting CKD, induced by 5/6 nephrectomy (Nx), was used. Six weeks later, AKIwas induced by intestinal ischemia and reperfusion (IIR). Sham procedures [S(Nx)and S(IIR)] were also performed. Results: Increasing levels of serum creatinine (sCr) demonstrated progressive developmentof CKD in response to Nx, and following IIR sCr levels increased furthersignificantly, except in the S(Nx) group treated with α-MSH. However, no significantdifferences in the fractional increase in sCr were observed between any of the groupsexposed to IIR. In kidney, lung, and liver tissue the levels of interleukin (IL)-1β weresignificantly higher in rats undergoing IIR when compared to the S(IIR) and control rats. The same pattern was observed for the chemokine monocyte chemoattractant protein(MCP)-1 in lung and liver tissue. Furthermore, kidney IL-1β and RANTES levels weresignificantly increased after IIR in the Nx rats compared to the S(Nx) rats. Conclusion: Both the functional parameters and the cytokine/chemokine response areas dramatic when AKI is superimposed onto CKD as onto non-CKD. No convincingprotective effect of α-MSH was detected.