Structure-activity relationships of new N-acylanthranilic acid derivatives as plasminogen activator inhibitor-1 inhibitors.

Novel anthranilic acid derivatives having substituted N-acyl side chains were designed and synthesized for evaluation as plasminogen activator inhibitor-1 (PAI-1) inhibitors. Compounds with a 4-diphenylmethyl-1-piperazinyl moiety on the acyl side chains in general exhibited potent in vitro PAI-1 inhibitory activity and good pharmacokinetic profiles after oral administration in rats. Compound 16f (TM5275) was identified as a promising candidate for further pharmacological evaluation.

Body weight control by a high-carbohydrate/low-fat diet slows the progression of diabetic kidney damage in an obese, hypertensive, type 2 diabetic rat model.

Obesity is one of several factors implicated in the genesis of diabetic nephropathy (DN). Obese, hypertensive, type 2 diabetic rats SHR/NDmcr-cp were given, for 12 weeks, either a normal, middle-carbohydrate/middle-fat diet (MC/MF group) or a high-carbohydrate/low-fat diet (HC/LF group). Daily caloric intake was the same in both groups. Nevertheless, the HC/LF group gained less weight. Despite equivalent degrees of hypertension, hyperglycemia, hyperlipidemia, hyperinsulinemia, and even a poorer glycemic control, the HC/LF group had less severe renal histological abnormalities and a reduced intrarenal advanced glycation and oxidative stress. Mediators of the renoprotection, specifically linked to obesity and body weight control, include a reduced renal inflammation and TGF-beta expression, together with an enhanced level of adiponectin. Altogether, these data identify a specific role of body weight control by a high-carbohydrate/low-fat diet in the progression of DN. Body weight control thus impacts on local intrarenal advanced glycation and oxidative stress through inflammation and adiponectin levels.

Structure-activity relationships of new 2-acylamino-3-thiophenecarboxylic acid dimers as plasminogen activator inhibitor-1 inhibitors.

Small molecule inhibitors of plasminogen activator inhibitor (PAI)-1 have been reported to date but their clinical effects still remain unknown. The present study was undertaken to investigate the structure-activity relationships (SAR) of newly synthesized 2-acylamino-3-thiophenecarboxylic acid dimers based upon a core structure of TM5001 (1) and TM5007 (2) that we have previously identified as orally effective PAI-1 inhibitors. In general, compounds possessing bulky or/and hydrophobic substituents (e.g. phenyl, isobutyl group) on the both thiophene rings showed potent PAI-1 inhibitory activities irrespective of the positions of the substitution. The mono-carboxyl derivative (10) exhibited PAI-1 inhibition comparable to the corresponding dicarboxyl compound (9f).

A novel inhibitor of plasminogen activator inhibitor-1 provides antithrombotic benefits devoid of bleeding effect in nonhuman primates.

Inhibition of plasminogen activator inhibitor (PAI)-1 is useful to treat several disorders including thrombosis. An inhibitor of PAI-1 (TM5275) was newly identified by an extensive study of structure-activity relationship based on a lead compound (TM5007) which was obtained through virtual screening by docking simulations. Its antithrombotic efficacy and adverse effects were tested in vivo in rats and nonhuman primates (cynomolgus monkey). TM5275, administered orally in rats (1 to 10 mg/kg), has an antithrombotic effect equivalent to that of ticlopidine (500 mg/kg) in an arterial venous shunt thrombosis model and to that of clopidogrel (3 mg/kg) in a ferric chloride-treated carotid artery thrombosis model. TM5275 does not modify activated partial thromboplastin time and prothrombin time or platelet activity and does not prolong bleeding time. Combined with tissue plasminogen activator, TM5275 improves the latter's therapeutic efficacy and reduces its adverse effect. Administered to a monkey model of photochemical induced arterial thrombosis, TM5275 (10 mg/kg) has the same antithrombotic effect as clopidogrel (10 mg/kg), without enhanced bleeding. This study documents the antithrombotic benefits of a novel, more powerful, PAI-1 inhibitor in rats and, for the first time, in nonhuman primates. These effects are obtained without adverse effect on bleeding time.

Very high doses of valsartan provide renoprotection independently of blood pressure in a type 2 diabetic nephropathy rat model.

AIM: Angiotensin II type 1 receptor blockers (ARB) retard the progression of hypertensive diabetic kidney disease. Clinical evidence suggests that the dose of ARB required to correct hypertension is suboptimal for renoprotection evaluated by proteinuria. No systematic, prospective study has yet evaluated separately the effect of increasing doses of ARB on blood pressure and proteinuria. METHODS: Over a period of 8 weeks, the effect of seven constant doses of an ARB, valsartan (4-160 mg/kg per day), on blood pressure and proteinuria taken as a surrogate marker of nephropathy in a hypertensive, type 2 diabetic rat model, the spontaneously hypertensive/NIH-corpulent rat (SHR/NDmcr-cp), was assessed. In this spontaneously hypertensive rat strain, a genetic mutation in the leptin receptor gene is associated with hyperphagia leading to obesity with metabolic syndrome and eventually to nephropathy. RESULTS: No additional blood pressure lowering was observed above 120 mg/kg per day of valsartan, suggesting that a dose of 80-120 mg/kg per day had a maximal effect. Nevertheless, higher doses of valsartan further reduced proteinuria in a dose-dependent fashion suggesting the absence of a maximal dose. Obesity, hyperglycaemia and hypercholesterolaemia were unaffected but hypertriglyceridaemia was partially corrected at various ARB doses. CONCLUSION: ARB improve renoprotection at doses above those required for a maximal effect on blood pressure. The mechanism of the renoprotection obtained at high doses of ARB is yet to be elucidated.

A novel Sartan derivative with very low angiotensin II type 1 receptor affinity protects the kidney in type 2 diabetic rats.

BACKGROUND: Antihypertensive angiotensin II receptor blockers (ARBs) protect the kidney, at least in part, independently of blood pressure lowering. Still, the extent to which blood pressure lowering is related to renoprotection remains unclear. METHODS AND RESULTS: 139 newly synthesized ARB-derivatives were assayed for inhibition of advanced glycation (AGEs). The 9 most powerful compounds were then tested for transition metal chelation, angiotensin II type 1 receptor (AT1R) affinity, and pharmacokinetic parameters. R-147176 was eventually selected as it strongly inhibits advanced glycation but is 6700 times less effective than olmesartan in AT1R binding. It is orally bioavailable and toxicologically safe. Despite a minimal blood pressure lowering effect, it provides significant renoprotection in 3 experimental rat models with renal injury, ie, obese, hypertensive, type 2 diabetic rats (SHR/NDmcr-cp), normotensive type 2 diabetic rats (Zucker diabetic fatty), and remnant kidney rats. CONCLUSIONS: R-147176 retains renal protective properties despite a minimal blood pressure-lowering effect. Clearly, the renal benefits of ARBs do not necessarily depend on blood pressure lowering and AT1R affinity, but rather on the inhibition of AGEs and oxidative stress inherent to their chemical structure. R-147176 opens new avenues in the treatment of cardiovascular and kidney diseases.

The role of megsin, a serine protease inhibitor, in diabetic mesangial matrix accumulation.

In diabetic nephropathy decreased activities of matrix metalloproteinase (MMP)-2, MMP-9 and plasmin contribute to mesangial matrix accumulation. Megsin, a novel member of the serine protease inhibitor superfamily, is predominantly expressed in mesangial cells and is up-regulated in diabetic nephropathy and its overexpression spontaneously induces progressive mesangial expansion in mice. High-glucose stimulated megsin mRNA expression in an in vivo model of type II diabetic nephropathy as well as in vitro in cultured mesangial cells. Megsin potentially inhibits total enzymatic activities of MMP-2 and -9 and plasmin, indicating decreased degradation of mesangial matrix. A specific monoclonal anti-megsin neutralizing antibody restored MMP activity in a transforming growth factor-beta independent manner. Our study suggests that the mesangial matrix accumulation caused by hyperglycemia in diabetes might be due at least in part to up-regulation of megsin which can inhibit plasmin and MMP activities.

Inhibition of advanced glycation end products: an implicit goal in clinical medicine for the treatment of diabetic nephropathy?

Several factors have been incriminated in the genesis of diabetic nephropathy. To elucidate their interplay, we have used a hypertensive, obese, diabetic rat model with nephropathy (SHR/NDmcr-cp) that mimics human type 2 diabetes. This model is characterized by hypertension, obesity with the metabolic syndrome, diabetes with insulin resistance, and intrarenal advanced glycation end product (AGE) accumulation. In order to achieve renoprotection, which was evaluated by histology and albuminuria, various therapeutic approaches were used: caloric restriction, antihypertensive agents (angiotensin II receptor blocker [ARB] and calcium channel blocker), lipid- (bezafibrate) or glucose-lowering (insulin and pioglitazone) agents, and cobalt chloride (a hypoxia-inducible factor activator). Altogether, renoprotection is not necessarily associated with blood pressure or glycemic control. By contrast, it is almost always associated with decreased AGE formation, with the exception of insulin, which induces hyperinsulinemia, eventually leading to an overproduction of transforming growth factor-beta. AGE formation is reduced directly by in vitro active compounds (e.g., ARBs) or indirectly by in vitro inactive compounds (e.g., pioglitazone and cobalt). In the latter cases, AGE reduction may reflect a decreased oxidative stress as it is concomitant with a marked reduction of oxidative stress markers. It remains to be seen whether the renoprotection offered by these various approaches may be additive.

Reduction of albuminuria by angiotensin receptor blocker beyond blood pressure lowering: evaluation in megsin/receptor for advanced glycation end products/inducible nitric oxide synthase triple transgenic diabetic nephropathy mouse model.

AIM: Antihypertensive agents inhibiting the renin-angiotensin system (RAS), such as angiotensin II type 1 receptor blockers (ARB), are now part of the standard treatment of patients with diabetic nephropathy, regardless of the presence of systemic hypertension. Whether ARB achieve better renoprotection than other RAS-independent antihypertensive drugs has been an issue of controversy. Several lines of large clinical studies provided better renoprotection of ARB. However, a recent meta-analysis argued against additional benefits of ARB beyond blood pressure. We generated a novel mouse model of diabetic nephropathy; that is, megsin/receptor for advanced glycation end products/inducible nitric oxide synthase triple transgenic mice. This model is normotensive but progressively develops severe diabetic nephropathy that resembles those observed in humans. METHODS: In the present study, we tested whether olmesartan (ARB) achieves better renoprotection than amlodipine (calcium channel blocker). Drug treatment was initiated at the age of 6 weeks and lasted for 12 weeks. RESULTS: This model develops significant glomerular lesions and albuminuria even at the age of 5 weeks. Despite equal blood pressure lowering, only olmesartan suppressed the progression of albuminuria. Neither olmesartan nor amlodipine modified histological lesions. CONCLUSION: Proteinuria and its reduction are known to predict the progression of diabetic nephropathy. Our results support the additional benefit of ARB beyond blood pressure lowering.

Inhibition of plasminogen activator inhibitor-1: its mechanism and effectiveness on coagulation and fibrosis.

OBJECTIVE: Serine protease inhibitors (serpin) play a central role in various pathological processes including coagulation, fibrinolysis, malignancy, and inflammation. Inhibition of serpins may prove therapeutic. As yet, however, only very few small molecule serpin inhibitors have been reported. For the first time, we apply a new approach of virtual screening to discover novel, orally active, small molecule serpin inhibitors and report their effectiveness. METHODS AND RESULTS: We focused on a clinically important serpin, plasminogen activator inhibitor-1 (PAI-1), whose crystal structure has been described. We identify novel, orally active molecules able to enter into the strand 4 position (s4A) of the A beta-sheet of PAI-I as a mock compound. In vitro they specifically inhibit the PAI-1 activity and enhance fibrinolysis activity. In vivo the most effective molecule (TM5007) inhibits coagulation in 2 models: a rat arteriovenous (AV) shunt model and a mouse model of ferric chloride-induced testicular artery thrombosis. It also prevents the fibrotic process initiated by bleomycin in mouse lung. CONCLUSIONS: The present study demonstrates beneficial in vitro and in vivo effects of novel PAI-1 inhibitors. Our methodology proves to be a useful tool to obtain effective inhibitors of serpin activity.

A novel class of advanced glycation inhibitors ameliorates renal and cardiovascular damage in experimental rat models.

BACKGROUND: The reno- and cardiovascular-protective effects of angiotensin II receptor blockers (ARBs), have been ascribed, at least in part, to their ability to inhibit the formation of advanced glycation end products (AGEs), independently of their effect on blood pressure. They act through decreased oxidative stress, unlike previously reported AGE inhibitors which entrap reactive carbonyl (RCOs) precursors of AGEs. The hypotensive effects of ARBs', however, may limit their use. In the present study, we report the synthesis of a new AGE inhibitor, TM2002, and its effects in vitro and in vivo. METHODS: We screened a large chemical library (approximately 1300 compounds) including edaravone, a drug used to treat cerebral infarction, for in vitro AGE inhibitory activity. Based upon the structure-function analysis of edaravone derivatives, we synthesized a novel AGE inhibitor, 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-6-methyl-1,3-dihydro-furo[3,4-c]pyridine-7-ol (TM2002). We delineate in vitro the biological characteristics of TM22002, evaluate in vivo its toxico-pharmacokinetics and document in animal models of rat, their renal and cardiovascular protective effectiveness. RESULTS: Screening of a large chemical library disclosed that edaravone inhibits in vitro AGE formation efficiently. Unfortunately, like most AGE inhibitors, it also traps pyridoxal, limiting its clinical usefulness. We therefore synthesized a novel AGE inhibitor, TM2002, that does not trap pyridoxal. In vitro, TM2002 shows powerful AGE inhibitory activity. Markers of oxidation, i.e. o-tyrosine formation and transition metal chelation, are efficiently inhibited by TM2002-like ARBs. TM2002 does not bind to the angiotensin II type 1 receptor. It is readily bioavailable and non-toxic. In vivo, TM2002, given acutely or for 8 weeks, has no adverse effects. In four different rat models of renal injury (anti-Thy1 and ischaemia-reperfusion) and cardiovascular injury (carotid artery balloon injury and angiotensin II-induced cardiac fibrosis), TM2002 improves renal and cardiovascular lesions without modification of blood pressure. CONCLUSIONS: TM2002 is a novel, non-toxic AGE inhibitor acting through ARB-like mechanisms, able to prevent renal and cardiovascular diseases independently of blood pressure lowering.

Cobalt ameliorates renal injury in an obese, hypertensive type 2 diabetes rat model.

BACKGROUND: Chronic renal hypoxia is suspected to play a pathogenic role in the genesis of diabetic nephropathy (DN). Cobalt enhances the activity of the hypoxia-inducible factor (HIF), a key factor in the defence against hypoxia. Its long-term effect on DN is evaluated. METHODS: Cobalt chloride was given to hypertensive, type 2 diabetic rats with nephropathy (SHR/NDmcr-cp). Treatment was initiated at the age of 13 weeks and continued for 26 weeks. RESULTS: Cobalt did not correct hypertension and metabolic abnormalities (obesity, hyperglycaemia and hyperlipidaemia) but reduced proteinuria as well as histological kidney injury. Cobalt upregulated renal HIF-1alpha and HIF-2alpha expression and increased the expression of HIF-regulated genes, including erythropoietin, vascular endothelial growth factor and heme oxygenase-1. The renal expression of transforming growth factor (TGF)-beta and connective tissue growth factor (CTGF) was significantly reduced by cobalt. The renal expression of NADPH oxidase, a marker of oxidative stress, and the renal content of pentosidine, a marker of advanced glycation, were also significantly reduced by cobalt. CONCLUSIONS: Cobalt achieved renal protection independently of metabolic status and blood pressure. Its effect was attributed to the upregulation of HIF and HIF-regulated genes and to a mitigated advanced glycation and oxidative stress.

A novel inhibitor of advanced glycation and endoplasmic reticulum stress reduces infarct volume in rat focal cerebral ischemia.

We have developed a novel, non-toxic inhibitor of advanced glycation and oxidative stress, TM2002, devoid of effect on blood pressure. In transient focal ischemia, TM2002 significantly decreased infarct volume compared with vehicle (79.5+/-18.7 vs. 183.3+/-22.9 mm3, p<0.01). In permanent focal ischemia, TM2002 (2.79, 5.58, and 11.16 mg/kg twice a day) dose-dependently reduced infarct volume (242.1+/-32.3, 201.3+/-15.1, and 171.3+/-15.2 mm3, respectively), and improved neurological deficits. Reduction of infarct volume is demonstrable, provided that TM2002 was administered within 1.5 h after the occlusion. To unravel TM2002's mechanism of action, we examined its in vitro effect on endoplasmic reticulum (ER) stress, using aortic smooth muscle cells isolated from ORP 150(+/-) mice and F9 Herp null mutated cells. Cell death induced by ER stress (tunicamycin or hypoxia) was dose-dependently prevented by TM2002. In vivo immunohistochemical study demonstrated a significant reduction of ORP- and TUNEL-positive apoptotic cells, especially in the penumbra. Inhibition of advanced glycation and oxidative stress was confirmed by a significantly reduced number of cells positive for advanced glycation end products and heme oxygenase-1. TM2002 reduced the levels of protein carbonyl formation in ischemic caudate. The efficacy of TM2002 is equivalent to that of a known neuroprotective agent, NXY-059. In conclusion, TM2002 significantly ameliorates ischemic cerebral damage through reduction of ER stress, advanced glycation, and oxidative stress, independently of blood pressure lowering.

A novel class of prolyl hydroxylase inhibitors induces angiogenesis and exerts organ protection against ischemia.

OBJECTIVE: Hypoxia inducible factor (HIF) plays a pivotal role in the adaptation to ischemic conditions. Its activity is modulated by an oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHD). METHODS AND RESULTS: We discovered 2 unique compounds (TM6008 and TM6089), which inhibited PHD and stabilized HIF activity in vitro. Our docking simulation studies based on the 3-dimensional structure of human PHD2 disclosed that they preferentially bind to the active site of PHD. Whereas PHD inhibitors previously reported inhibit PHD activity via iron chelation, TM6089 does not share an iron chelating motif and is devoid of iron chelating activity. In vitro Matrigel assays and in vivo sponge assays demonstrated enhancement of angiogenesis by local administration of TM6008 and TM6089. Their oral administration stimulated HIF activity in various organs of transgenic rats expressing a hypoxia-responsive reporter vector. No acute toxicity was observed up to 2 weeks after a single oral dose of 2000 mg/kg for TM6008. Oral administration of TM6008 protected neurons in a model of cerebrovascular disease. The protection was associated with amelioration of apoptosis but independent of enhanced angiogenesis. CONCLUSIONS: The present study uncovered beneficial effects of novel PHD inhibitors preferentially binding to the active site of PHD.

Establishment of a sandwich ELISA for human megsin, a kidney-specific serine protease inhibitor.

BACKGROUND: We previously identified a novel serine protease inhibitor (serpin), megsin, which is predominantly expressed in the kidney. Megsin expression is up-regulated in human and experimental renal diseases associated with mesangial proliferation and expansion, suggesting that urinary megsin may be a novel diagnostic marker for some renal diseases. METHODS: We established a specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) for megsin and measured urinary megsin of patients with various renal diseases. RESULTS: Megsin ELISA specifically detected megsin but not other serpins. The detection limit was 0.04 ng/ml, which allowed detection of urinary megsin in 3.6% of healthy individuals. The antigenic epitope in the urine detected by the ELISA was confirmed as megsin protein by time-of-flight mass spectrometry. Among patients with rapidly progressive glomerulonephritis (n = 18), 55.6% were urinary megsin-positive, while 24.1% in IgA nephropathy (n = 112) and 15.1% in chronic non-IgA glomerulonephritis (n = 245) were urinary megsin-positive, respectively. Among patients with chronic renal failure due to unknown causes (n = 74), 18.9% were positive for urinary megsin. In diabetic patients with or without nephropathy (n = 1073), 12.3% were urinary megsin-positive, while positivity of urinary megsin in patients with non-renal diseases (n = 768) was equivalent (3.3%) to that of healthy individuals. Of note, when urinary megsin-positive patients with diabetic nephropathy (n = 71) were classified into four stages by their proteinuria and estimated glomerular filtration rate, urinary megsin excretion increased as the stage progressed up to stage 3A, suggesting correlation of that with mesangial expansion level. Urinary megsin decreased in the advanced stage, probably reflecting development of glomerulosclerosis. CONCLUSION: We established a high-sensitive megsin ELISA, which detects urinary megsin in some patients with renal diseases and in only a few healthy subjects. Megsin ELISA may be a novel diagnostic tool for renal diseases.

Carbonyl stress reduction in peritoneal dialysis fluid: development of a novel high-affinity adsorption bead.

OBJECTIVE: Heat sterilization of glucose peritoneal dialysis (PD) fluid generates reactive carbonyl compounds (RCOs), which have been implicated in the formation of advanced glycation end products (AGEs) on peritoneal proteins, with an attendant deterioration of peritoneal permeability in PD patients. To reduce their levels in PD fluid, we had previously devised beads coupled with RCO-trapping agents. The hazards linked to the diffusion of RCO-trapping compounds in the systemic circulation are avoided. Hydrazine-epoxy beads proved the most effective. Still, the amount needed to trap all RCOs remained relatively large. METHODS: We developed a novel agent linking a powerful RCO-trapping AGE inhibitor, pyrazolinone-polyethyleneimine, with cellulose beads (PPCBs). We tested its effectiveness to lower RCOs and AGE formation. RESULTS: Mixed with glucose PD fluid, PPCBs markedly lowered RCOs (alpha-dicarbonyls and aldehydes) and inhibited the generation of pentosidine, an AGE, to levels similar to those of filter-sterilized PD fluid. Their effectiveness is more than one order of magnitude above those of previously developed beads. The PPCBs markedly improved PD fluid biocompatibility. Incubation of 1 L commercial glucose PD fluid at 25 degrees C for 24 hours with 10 or 30 g of wet PPCBs reduced RCO content by 75% - 90% and 100% respectively, without altering the pH or glucose and electrolyte contents of the PD fluid. CONCLUSIONS: We developed a high-affinity adsorption bead to reduce the toxic RCO content and AGE formation potential (carbonyl stress) of PD fluid.

Renoprotective properties of angiotensin receptor blockers beyond blood pressure lowering.

Clinical studies have demonstrated that some antihypertensive agents provide renoprotection independent of BP lowering. Recent in vitro and in vivo studies evaluated the mechanisms involved in this protection. First, the in vitro effects of several angiotensin II type 1 receptor blockers (ARB), calcium channel blockers (CCB), and beta blockers (BB) on various mediators were compared: Formation of pentosidine (an advanced glycation end product), hydroxyl radical-induced formation of o-tyrosine, and transition metals-induced oxidation of ascorbic acid (the Fenton reaction). All of the six tested ARB but neither the six CCB nor the nine BB inhibited pentosidine formation. ARB, as well as BB but not CCB, inhibited hydroxyl radicals-mediated o-tyrosine formation. ARB but neither BB nor CCB inhibited efficiently transition metals-catalyzed oxidation of ascorbic acid. Second, the in vivo consequences for the kidney of these various in vitro effects were evaluated. Hypertensive, type 2 diabetic rats with nephropathy, SHR/NDmcr-cp, were given for 20 wk either olmesartan (ARB) or nifedipine (CCB), or atenolol (BB). Despite similar BP reduction, only ARB significantly reduced proteinuria and prevented glomerular and tubulointerstitial damage (mesangial activation, podocyte injury, tubulointerstitial injury, and inflammatory cell infiltration). It is interesting that only ARB prevented abnormal iron deposition in the interstitium, corrected chronic hypoxia, reduced expressions of heme oxygenase and p47phox (a subunit of NADPHoxidase), and inhibited pentosidine formation (which correlates well with proteinuria). These observations confirm unique renoprotective properties of ARB, independent of BP lowering but related to decreased oxidative stress (hydroxyl radicals scavenging and inhibition of the Fenton reaction), correction of chronic hypoxia, and inhibition of advanced glycation end product formation and of abnormal iron deposition. These benefits of ARB may contribute to the renoprotection observed beyond BP lowering.

In a type 2 diabetic nephropathy rat model, the improvement of obesity by a low calorie diet reduces oxidative/carbonyl stress and prevents diabetic nephropathy.

BACKGROUND: The present study has been undertaken to unravel the critical factors involved in the progression of diabetic nephropathy (DN). METHODS: A unique type 2 diabetic rat model with a wide range of metabolic derangements and hypertension has been utilized, the spontaneously hypertensive/NIH-corpulent rat SHR/NDmcr-cp(cp/cp). It develops histologically evident glomerular injury and tubulointerstitial damage, including mesangial activation, podocyte injury, and inflammatory cell infiltration in the tubulointerstitium. RESULTS: A low calorie diet for 22 weeks significantly improves obesity, proteinuria and renal morphological alterations. The correction of renal injury is independent of blood pressure control. Obesity correction, although partial, normalizes the renal content of pentosidine taken as a marker of oxidative stress and advanced glycation end products (AGEs). This occurs despite the fact that, in this model, improvement of glucose control and hyperlipidaemia is limited. Proteinuria and body weight are highly correlated with renal pentosidine content, while proteinuria and body weight are also correlated with each other. Diabetic renal injury is thus inhibited by a low calorie diet with an attendant reduction of oxidative stress and AGE formation, despite sustained hypertension. CONCLUSION: The present findings suggest a direct role of obesity in the generation of a localized oxidative stress and AGE formation, directly responsible for DN.

Pyridoxamine improves functional, structural, and biochemical alterations of peritoneal membranes in uremic peritoneal dialysis rats.

BACKGROUND: We previously suggested that biochemical alterations of peritoneal membrane associated with long-term peritoneal dialysis might be, at least in part, accounted for by reactive carbonyl compounds overload originating both from uremic circulation and heat sterilization of glucose peritoneal dialysis fluid. In the present study, we utilized a uremic rat model on peritoneal dialysis and evaluated the protective effects of pyridoxamine, a recently developed inhibitor of advanced glycation end product (AGE), on structural, functional, and biochemical alterations of peritoneal membrane. METHODS: Uremic rats were generated by subtotal nephrectomy, some of which were undergone peritoneal dialysis with dialysate and/or given intraperitoneal pyridoxamine. Functional [dialysate/plasma ratio (D/P)(urea, creatinine), D/D(0 glucose)], structural (density of blood vessels in peritoneal membrane tissues), and molecular biochemical [formation of pentosidine, an AGE, by high-performance liquid chromatography (HPLC) assay and expressions of vascular endothelial growth factor (VEGF), and fibroblast growth factor 2 (FGF-2), by semiquantitative polymerase chain reaction (PCR) and/or immunohistochemistry] alterations of peritoneal membrane were assessed. RESULTS: Uremic peritoneal membrane was characterized by an increased functional area of exchange for small solutes between blood and dialysate, vascular proliferation, increased AGE genesis, and up-regulated expressions of angiogenic cytokines. The peritoneal membrane alterations associated with peritoneal dialysis are similar but more severe than those in uremia without peritoneal dialysis. Pyridoxamine given in uremic rats with peritoneal dialysis significantly improved functional and structural alterations. This improvement was accompanied by reduction of AGE accumulation and of angiogenic cytokines expressions. CONCLUSION: Peritoneal carbonyl stress derived from uremia as well as peritoneal dialysis procedure might contribute to the vascular proliferation through induction of bioactive molecules and to an increased functional area, eventually leading to ultrafiltration failure. Pyridoxamine may be beneficial in protection of uremic peritoneal membrane on peritoneal dialysis.

From molecular footprints of disease to new therapeutic interventions in diabetic nephropathy.

Proteins are particularly attractive targets for product analysis, which is used to understand pathology. Protein modifications, such as advanced glycation end products (AGEs), serve as footprints of biochemical processes and also help in the search for novel agents that efficiently inhibit protein damage. Interestingly, several medical agents that are used clinically interfere with oxidative protein damage through different mechanisms characteristic of their chemical structures. We recently found that angiotensin II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) lower the in vitro formation of the AGEs pentosidine and carboxymethyllysine. Their inhibition for AGE formation is more striking than aminoguanidine. Unlike aminoguanidine, ARBs and ACEIs do not trap reactive carbonyl precursors of AGEs. Rather, they inhibit AGE formation, possibly as a result of their potent ability to scavenge hydroxyl radicals and to chelate the transition metals necessary for the Fenton reaction. We tested their AGE-lowering ability in vivo in a unique type-2 diabetic model with nephropathic SHR/NDmcr-cp rats, which exhibits the metabolic syndrome (obesity, hyperglycemia, hyperlipidemia, hyperinsulinemia) in addition to hypertension. Obesity and associated metabolic derangements, in addition to hypertension, markedly accelerate renal injury. Expectedly, correction of hyperglycemia and hyperinsulinemia partially but significantly improves renal injury. A low-calorie diet greatly improves renal injury despite persistent hypertension. Among antihypertensive agents, ARBs, unlike nifedipine and atenolol, are renoprotective despite persistent metabolic syndrome, but their action is independent of blood pressure lowering and is observed in a dose-dependent manner despite the complete blockade of angiotensin II receptor. Interestingly, the improvement of renal injury by ARBs as well as a low-calorie diet is associated with a significant reduction in local oxidative stress and AGE formation in the kidney. During the characterization of the AGE-lowering profile of our chemical compound libraries ( approximately 2000), we identified several inhibitors of oxidative stress and advanced glycation. They are indeed renoprotective, independently of correction of hypertension and metabolic syndrome, in experimental diabetic nephropathy and other nephritis models. Altogether, our data are in good agreement with the recent therapeutic concept for diabetic nephropathy that multiple risk factor interventions are critical in the treatment of diabetic renal injury, and further implicate a therapeutic potential of inhibition of oxidative stress and advanced glycation.