12-hydroxy-5-8-10-14-eicosatetraenoic-acid and Diabetic-Nephropathies

The characteristic features of diabetic nephropathy include thickening of the glomerular basement membranes, expansion of mesangium, and appearance of albumin in the urine (microalbuminuria and macroalbuminuria). Experimental studies have documented that 12-lipoxygenase (12-LOX) and its metabolite 12(S)-hydroxyeicosatetraenoic acid (HETE) play an important role in the pathogenesis of diabetic nephropathy. 12(S)-HETE may work in association with angiotensin II and transforming growth factor- β (TGF-β) reciprocally to induce fibrotic changes in the diabetic kidneys. The fibrotic actions of angiotensin II on the kidneys are mediated indirectly through an increase in the synthesis of 12(S)-HETE. Conversely, 12(S)-HETE may also enhance the actions of angiotensin II by upregulating the expression of AT

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Albuminuria; Angiotensin II; Animals; Arachidonate 12-Lipoxygenase; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Diabetic Nephropathies; Epigenesis, Genetic; Epoprostenol; Humans

The 12-lipoxygenase (12-LO) and angiotensin II (Ang II) interaction plays an important role in diabetic nephropathy (DN). Proteinuria in DN is associated with decreased slit diaphragm proteins including nephrin and P-cadherin. Therefore, we investigated whether Ang II type 1 receptor (AT1) blocker (ARB) regulates 12-LO activity and slit diaphragm protein expression in diabetic rat glomeruli.. Glomeruli were isolated with the sieving method, and classified into small glomeruli (SG; 75-μm sieve) and large glomeruli (LG; 125-μm sieve).. 12(S)-HETE, a lipid product of 12-LO, was increased by Ang II in the glomeruli. Infusion of 12(S)-HETE and Ang II significantly decreased nephrin expression in LG, but increased it in SG compared to control. Glomerular P-cadherin expression was reduced after Ang II and 12(S)-HETE treatment without differences between LG and SG. ARB did not influence glycemic levels but completely abolished the increases in 12(S)-HETE, AT1 expression, and proteinuria in diabetic rats. Nephrin expression was significantly reduced in LG but increased in SG in diabetic rats compared to control. P-cadherin expression decreased in both diabetic LG and SG. The abnormalities of nephrin and P-cadherin were partially but significantly reversed by ARB.. ARB potentially ameliorates DN via the up-regulation of glomerular nephrin and P-cadherin expression through the inhibition of 12-LO activation in the glomeruli of rats with DN.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Arachidonate 12-Lipoxygenase; Cadherins; Cells, Cultured; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Diet, High-Fat; Kidney Glomerulus; Lipoxygenase Inhibitors; Losartan; Male; Membrane Proteins; Mice; Podocytes; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; Streptozocin

(1) BACKGROUND: 12-lipoxygenase (12-LO) is involved in the development of diabetic nephropathy (DN). In the present study, we investigated whether 12-LO inhibition may ameliorate type-2 DN (T2DN) by interfering with insulin resistance (IR); (2) METHODS: Rat glomerular mesangial cells, glomeruli and skeletal muscles were isolated and used in this study. Kidney histological changes were confirmed by periodic-acid Schiff staining; mRNA expression was detected by competitive reverse transcription polymerase chain reaction; and the protein level was determined by Western blot and the enzyme-linked immunosorbent assay, respectively; (3) RESULTS: The inhibition of 12-LO attenuated microalbuminuria (MAU) increases in type-2 diabetic rats, but not in type-1 diabetic rats. Infusion of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) significantly increased the expression of angiotensin II (Ang II) and Ang II type 1 receptor (AT1R), but decreased the expression of AT1R-associated protein (ATRAP) in rat glomeruli, compared to the control. An in vitro study revealed that both 12(S)-HETE and insulin upregulated AT1R expression in rat mesangial cells. In the presence of p38 mitogen-activated protein kinase (MAPK) inhibitor, SB202190, the 12(S)-HETE-induced ATRAP reduction was significantly abolished. Interestingly, 12-LO inhibition did not influence AT1R expression in type-1 diabetic rats, but significantly abolished the increased AT1R and Ang II expression in glomeruli of type-2 diabetic rats. Furthermore, the inhibition of 12-LO significantly corrected impaired insulin sensitivity and fast serum insulin level, as well as the p-AMP-activated protein kinase (AMPK) reduction in skeletal muscle of type-2 diabetic rats; (4) CONCLUSION: The inhibition of 12-LO potentially ameliorated MAU by preventing IR through the downregulation of glomerular AT1R expression in T2DN.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Albuminuria; Animals; Arachidonate 12-Lipoxygenase; Cells, Cultured; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Down-Regulation; Insulin Resistance; Kidney Glomerulus; Lipoxygenase Inhibitors; Male; Muscle, Skeletal; Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1

Arachidonic acid-metabolizing enzyme, 12-lipoxygenase (12-LO), is involved in the glomerular hypertrophy of diabetic nephropathy (DN), in which cyclin-dependent kinase inhibitors (CKIs) play important roles. However, it is unclear whether 12-LO regulates the expression of the CKI p16(ink4a) in DN.. Primary glomerular mesangial cells (MCs) and glomeruli isolated from rats were used in this study. The rats were fed a high-fat diet and given low-dose streptozotocin to induce type 2 diabetes. The 12-LO product, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), was infused through an osmotic minipump. Enzyme-linked immunosorbent assay, Western blot, and morphometric analyses were performed.. High glucose (HG) increased the p16(ink4a) protein expression in MCs, but this increase was prevented by the 12-LO inhibitor, cinnamyl-3,​4-dihydroxy-α-cynanocinnamate (CDC). The levels of p-p38MAPK and p16(ink4a) in MCs were significantly elevated after the 12(S)-HETE treatment, whereas the p38MAPK inhibitor SB203580 prevented these increases. Compared with levels in control MCs, marked increases in p38MAPK activation and p16(ink4a) expression were observed in MCs plated on collagen IV, while the CDC treatment prevented these changes. Subcutaneous injection of CDC did not affect glucose levels, but completely attenuated the diabetes-related increases in the 12(S)-HETE content, p16(ink4a) expression, p-p38MAPK levels, glomerular volume, and the kidney/body weight ratio. Compared with levels in controls, p16(ink4a) and p-p38MAPK in the glomeruli derived from 12(S)-HETE-treated rats were significantly higher.. 12-LO-p38MAPK mediates the upregulation of p16(ink4a) in HG-stimulated MCs and type 2-diabetic glomeruli, and new therapies aimed at 12-LO inhibition may prove beneficial in ameliorating diabetes-induced glomerular hypertrophy.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Arachidonate 12-Lipoxygenase; Cells, Cultured; Collagen Type IV; Cyclin-Dependent Kinase Inhibitor p16; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Glomerular Mesangium; Glucose; p38 Mitogen-Activated Protein Kinases; Rats; Rats, Sprague-Dawley

Diabetes is associated with increased production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE]. The mechanisms involved in this process remain unclear. We hypothesized that hyperglycemia and angiotensin II (ANG II) regulate renal 12(S)-HETE production via a balance between angiotensin AT(1) and AT(2) receptors activities. Using a microdialysis technique, renal interstitial fluid (RIF) levels of ANG II and 12(S)-HETE were monitored in normal control and streptozotocin-induced diabetic rats at baseline and then weekly thereafter for 12 wk. In a second group of normal and diabetic rats, 3 wk after development of diabetes, we monitored RIF 12(S)-HETE levels in response to acute AT(1) receptor blockade with valsartan or AT(2) receptor blockade with PD123319 individually or combined. Two weeks after induction of diabetes there was a 404% increase in ANG II (P < 0.05), a 149% increase in 12S-HETE (P < 0.05), and a 649% increase in urinary albumin excretion (P < 0.05). These levels remained elevated throughout the study. PD123319 given alone had no effect on 12(S)-HETE. Valsartan decreased 12(S)-HETE by 61.6% (P < 0.0001), a response that was abrogated when PD123319 was given with valsartan. These data demonstrate that hyperglycemia increases renal ANG II and 12(S)-HETE levels. The increase in 12(S)-HETE is mediated via AT(1) receptor. The attenuation of the effects of AT(1) receptor blockade by PD123319 suggests that AT(2) receptor contributes to the downregulation of renal 12(S)-HETE production.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensin II Type 2 Receptor Blockers; Animals; Blood Glucose; Blood Pressure; Body Weight; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Hypoglycemic Agents; Imidazoles; In Vitro Techniques; Insulin; Kidney; Male; Microdialysis; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Tetrazoles; Valine; Valsartan

Angiotensin II and its type 1 receptor (AT1R) play important roles in the pathogenesis of renal disease and diabetic nephropathy. The 12/15-lipoxygenase pathway of arachidonate metabolism and its lipid products have also been implicated in diabetic nephropathy. However, it is unclear whether 12/15-lipoxygenase regulates expression of AT1R. In cultured rat mesangial cells, we found that the 12/15-lipoxygenase product 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) increased AT1R mRNA and protein expression, primarily by stabilizing AT1R mRNA. Pretreatment with 12(S)-HETE also amplified the signaling effects of angiotensin II, likely due to the increased AT1R expression. Levels of AT1R protein expression decreased when 12/15-lipoxygenase was knocked down with specific short hairpin RNA (shRNA) compared with control cells. Similarly, levels of the AT1 receptor, but not the AT2 receptor, were significantly lower in mesangial cells and glomeruli derived from 12/15-lipoxygenase knockout mice compared with control mice. Reciprocally, stable overexpression of 12/15-lipoxygenase increased AT1R expression in cultured mesangial cells. In vivo, modified siRNA targeting 12/15-lipoxygenase reduced glomerular AT1R expression in a diabetic mouse model. Interestingly, angiotensin II induced greater levels of 12/15-lipoxygenase, TGF-beta1, and fibronectin (FN) in AT1R-overexpressing mesangial cells compared with control cells. Therefore, oxidized lipids generated by the 12/15-lipoxygenase-mediated metabolism of arachidonic acid can enhance AT1R expression in mesangial cells and augment the profibrotic effects of angiotensin II.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Angiotensin II; Animals; Arachidonate 12-Lipoxygenase; Arachidonate 15-Lipoxygenase; Cells, Cultured; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Lipid Metabolism; Mesangial Cells; Mice; Mice, Inbred C57BL; Oxidation-Reduction; p38 Mitogen-Activated Protein Kinases; Rats; Rats, Sprague-Dawley; Receptors, Angiotensin; Renin-Angiotensin System; RNA, Messenger; RNA, Small Interfering; Up-Regulation

The 12/15-lipoxygenase (12/15-LO) and cyclooxygenase-2 (COX-2) pathways of arachidonate metabolism have been implicated in the pathogenesis of diabetic nephropathy (DN). In this study, we evaluated whether there is an interplay between 12/15-LO and COX-2 pathways in mesangial cells (MC). We utilized MC, microdissected glomeruli and renal cortical tissues. Transfections with cDNAs or short hairpin RNAs (shRNAs) were performed to overexpress or knockdown 12/15-LO and COX-2, respectively. Reverse transcription-polymerase chain reactions and Western blotting were used for evaluating mRNA and protein expression, respectively. We observed that the expression of both 12/15-LO and COX-2 were increased in high glucose stimulated rat MC relative to normal glucose, and also in cortical tissues from diabetic db/db and streptozotocin-injected mice relative to corresponding control mice. Treatment of rat MC with the 12/15-LO product, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), significantly increased COX-2 expression as well as levels of the COX-2 product, prostaglandin E(2) (PGE(2)). Interestingly, treatment of rat MC with PGE(2) led to a reciprocal increase in 12/15-LO expression as well as levels of 12(S)-HETE. The 12/15-LO shRNA could significantly attenuate COX-2 protein expression and vice versa. Furthermore, COX-2 expression levels were lower in MC and glomeruli from 12/15-LO knockout mice relative to control. Conversely, mouse MC stably overexpressing 12/15-LO had greater levels of COX-2 expression relative to mock-transfected cells. These new results indicate for the first time that 12/15-LO and COX-2 pathways can cross-talk and activate each other in MC. These novel interactions may amplify their effects on the progression of DN.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Arachidonate 12-Lipoxygenase; Arachidonate 15-Lipoxygenase; Cells, Cultured; Cyclooxygenase 2; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dinoprostone; Enzyme Activation; Gene Expression Regulation, Enzymologic; Glucose; Kidney Cortex; Male; Mesangial Cells; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinase Kinases; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Transfection

The 12/15-lipoxygenase (12/15-LO) pathway is activated in diabetes mellitus (DM), increasing 12(S)-hydroxyeicosatetraenoic acid (12-HETE). We showed that a 12-LO inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC) inhibited 12/15-LO activity in vivo and assessed the efficacy of another 12/15-LO inhibitor, N-benzyl-N-hydroxy-5-phenylpentamidine (BHPP), to diminish urinary 12-HETE and ameliorate diabetic nephropathy (DN) over 4 months. Rats studied were control (C, n=8), DM (n=6), and rats injected with BHPP (C+BHPP, n=4) and (DM+BHPP, n=5). BHPP 3 mg/kg/day decreased urinary (U) 12-HETE/creatinine (cr) by 30-50% after one injection and after 1 week of daily injections in DM rats. U 12-HETE/cr excretion increased paradoxically in controls given BHPP. There was a highly significant relationship between U 12-HETE/cr excretion and U alb/cr (r=0.79, P<10(-5)), demonstrating that renal 12/15-LO pathway activation is associated with albuminuria. BHPP did not inhibit glomerular collagen synthesis or improve histology. More sustained 12-LO inhibition may improve albuminuria in DN.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Albuminuria; Amides; Animals; Benzylamines; Caffeic Acids; Collagen Type IV; Creatinine; Diabetic Nephropathies; Kidney Glomerulus; Lipoxygenase Inhibitors; Male; Rats; Rats, Sprague-Dawley

The lipoxygenase (LO) pathway of arachidonate metabolism and mitogen-activated protein kinases (MAPKs) can mediate cellular growth and ANG II effects in vascular smooth muscle cells. However, their role in renal mesangial cells (MC) is not very clear. ANG II treatment of rat MC significantly increased 12-LO mRNA expression and formation of the 12-LO product 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE; P < 0.03]. ANG II-induced [(3)H]leucine incorporation was blocked by an LO inhibitor, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (P < 0.02). 12(S)-HETE and ANG II directly induced cellular hypertrophy and fibronectin (FN) expression (P < 0.01) to a similar extent. ANG II and 12(S)-HETE led to activation of p38(MAPK) and its target transcription factor cAMP-responsive element-binding protein (CREB). ANG II- and 12(S)-HETE-induced CREB activation and [(3)H]leucine incorporation were blocked by the p38(MAPK) inhibitor SB-202190. A specific molecular inhibitor of rat 12-LO mRNA, namely, a novel ribozyme, could attenuate ANG II-induced FN mRNA. Thus p38(MAPK)-dependent CREB activation may mediate ANG II- and LO product-induced FN expression and cellular growth in rat MC. ANG II effects may be mediated by the LO pathway. These results suggest a novel interaction between LO and p38(MAPK) activation in MC matrix synthesis associated with renal complications.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Angiotensin II; Animals; Arachidonate 12-Lipoxygenase; Cell Division; Cells, Cultured; Cyclic AMP Response Element-Binding Protein; Diabetic Nephropathies; Extracellular Matrix Proteins; Fibronectins; Gene Expression Regulation, Enzymologic; Glomerular Mesangium; Hypertrophy; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Rats; RNA, Messenger; Vasoconstrictor Agents

Earlier studies in diabetic animal models or ex vivo from diabetics suggest a deficiency in prostacyclin (PGI2) production and an increase in an alternate arachidonic acid metabolite, 12-hydroxyeicosatetraenoic acid (12-HETE), which stimulates angiogenesis, mitogenesis, and inhibits renin secretion. We studied the urinary excretion rate of 6-keto-PGF1 alpha (a stable metabolite of PGI2) and 12-HETE in controls and 42 noninsulin-dependent diabetes mellitus (NIDDM) patients with normal renal function and those with micro- or macroalbuminuria/hyporeninemic hypoaldosteronism (HH). The 2 eicosanoids were measured in urine using previously described high pressure liquid chromatography and RIA methods. Normal subjects and patients with NIDDM and microalbuminuria were infused with low dose calcium infusions that stimulate prostacyclin production in normal subjects. The PGI2 excretion rate of NIDDM patients with normal renal function was not different from that of controls (143 +/- 17 vs. 118 +/- 34 ng/g creatinine), but was reduced in those with microalbuminuria (75 +/- 10) and in macroalbuminuria patients (48 +/- 7; P < 0.01). In contrast, 12-HETE was increased in diabetics with normal renal function as well as in those with micro- or macroalbuminuria patients (69 +/- 18 vs. 250 +/- 62 vs. 226 +/- 60 and 404 +/- 131 ng/g creatinine; P < 0.01). Calcium did not stimulate PGI2, but increased 12-HETE in diabetics with microalbuminuria in contrast to levels in normal subjects. HH patients excreted less PGI2 (as previously reported), but had increased 12-HETE. HETE/PGI2 ratios further demonstrated these changes in the various groups. In a nondiabetic hypertensive microalbuminuria group, 12-HETE excretion was normal (73 +/- 28 ng/g creatinine). We conclude that the lipoxygenase product 12-HETE is increased early in the diabetic process, whereas PGI2 production is progressively impaired in NIDDM. These changes may play a role in the vascular disease of diabetes and partially explain the HH syndrome.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Adult; Aged; Albuminuria; Arachidonate 12-Lipoxygenase; Calcium; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Epoprostenol; Female; Humans; Hydroxyeicosatetraenoic Acids; Hypoaldosteronism; Male; Middle Aged; Renin