Influence of losartan intake on the circadian rhythm of melatonin secretion in humans.

It has been reported that losartan, an angiotensin II receptor blocker, alters the circadian rhythm of melatonin secretion and significantly reduces melatonin production. However, this finding has been confirmed at the animal experiment level only, and there are no reports of studies in humans. Therefore, we performed this study to confirm the reproducibility of the aforementioned findings of animal experiments in humans. Ten male subjects who were in good general health and free from any medical condition were recruited for this study. After a preliminary observation period of 7 days, the subjects received oral losartan treatment, 50 mg daily for 7 days. Blood samplings for measurement of the plasma melatonin concentrations were performed on day 7 of the preliminary observation period and day 7 of the losartan treatment period. The circadian rhythm of melatonin secretion after the 7-day treatment with losartan showed no significant difference from that recorded before the losartan administration. The significant decrease of the home blood pressure was observed on the afternoons. The blood samples showed significant decrease of the serum sodium and uric acid levels, along with a significant increase of the serum potassium level. The pharmacological actions of losartan at the ordinarily used clinical dose level were confirmed in humans, however, no significant inhibitory effect of the drug on melatonin secretion could be confirmed. These results are expected to be useful for guiding the proper use of angiotensin II receptor blockers.

[Angina pectoris in patients who underwent stent implantations for severe atherosclerotic coronary lesions 16 years after heart transplantation].

The case was a 56-year-old male who underwent heart transplantation due to dilated cardiomyopathy abroad in 1990. In 2006, he suffered from anginal chest pain on effort. The coronary angiogram showed severe atherosclerotic lesions in the middle of left descending artery. A drug eluting stent, Cypher 3.5 x 23 mm was deployed, followed by balloon dilatations (4 x 8 mm). The procedure was successful without any complications. Furthermore, the 8-month follow-up angiogram showed no significant restenosis in the target vessel. There have been several reports on the outcomes of percutaneous coronary intervention (PCI) for cardiac allograft vasculopathy. According to them, the drug eluting stent, as is used in the present case, might be a promising procedure after further evaluations.

High salt diet enhances cardiovascular responses from the nucleus tractus solitarius and ventrolateral medulla of Sprague-Dawley rats.

High salt intake has been shown to augment the sensitivity of rostral ventrolateral medulla (RVLM) sympathoexcitatory neurons. We examined the effects of 4 weeks of high dietary salt (8%) on the sensitivity of nucleus tractus solitarius (NTS) and caudal ventrolateral medulla (CVLM) in controlling RVLM. In chloralose-anesthetized Sprague-Dawley rats, high salt intake did not elevate baseline arterial pressure or heart rate (HR). In high-salt group, NTS, CVLM, and RVLM responses to glutamate were greater. NTS responses to acetylcholine or serotonin, which is independent of baroreflex, also were greater. Phenylephrine or nitroprusside (i.v.) elicited similar changes in arterial pressure and heart rate, the baroreflex sensitivity also was similar in both groups of rats. These results suggest that high salt intake augments the sensitivity of NTS and CVLM sending inhibitory input to RVLM. This presumably may inhibit the RVLM, thereby inhibiting the elevation of arterial pressure.

The microsatellite alleles on chromosome 1 associated with essential hypertension and blood pressure levels.

Essential hypertension (EH) is thought to be a polygenic disease. Several candidate genes of this disease have been investigated in studies using polymorphic genetic markers, but some studies have failed to show any association of EH with these genes. In this experiment, we used microsatellite markers on chromosome 1, and performed an association study between EH and control subjects. Genomic DNA was amplified with fluorescently labelled primers from the Applied Biosystems PRISM linkage mapping set HD-5 comprising 63 highly polymorphic microsatellite markers with an average spacing of 4.5 cM. We isolated three loci showing significant differences: D1S507, D1S2713 and D1S2842. The P-values of the allele with the greatest post hoc contributions in D1S507, D1S2713 and D1S2842 were 0.0008, 0.0062 and 0.0084, respectively. All these values were significant after Bonferroni correction. Furthermore, we found that the three microsatellite alleles were associated with the levels of systolic blood pressure. These data suggest that there are at least the three susceptibility loci for EH on chromosome 1, and that a case-control study using microsatellite markers on genomewide basis is a useful method for isolating the susceptibility loci of multifactorial disorders.

Interleukin-17 stimulates the release of pro-inflammatory cytokines by blood monocytes in patients with IgA nephropathy.

OBJECTIVE: Interleukin-17 (IL-17) is a newly discovered cytokine implicated in the regulation of inflammation. The present study was designed to explore whether IL-17 is involved in the immunoregulatory response in IgA nephropathy (IgAN). MATERIAL AND METHODS: We examined the in vitro effect of recombinant human IL-17 (rhIL-17) on pro-inflammatory cytokine release by peripheral blood monocytes (PBM) from patients with IgAN. Measurement of IL-1beta and tumor necrosis factor-alpha (TNF-alpha) was performed by means of a sandwich enzyme-linked immunosorbent assay. RESULTS: IL-1beta and TNF-alpha release were upregulated by rhIL-17 in a dose- and time-dependent fashion. Treatment of PBM from patients with IgAN with lipopolysaccharide and rhIL-17 resulted in significant activation and release of IL-1beta and TNF-alpha protein. Levels of IL-1beta and TNF-alpha were significantly higher in IgAN patients with the nephrotic syndrome (NS) than in patients without NS or in healthy subjects. We also provide information indicating that there is excessive production of IL-17 in IgAN patients. When IL-17-activated PBM were incubated in the presence of IL-10, IL-10 exerted a significant suppressive effect on IL-1beta and TNF-alpha release in vitro. CONCLUSION: IL-17 can stimulate the release of pro-inflammatory cytokines from PBM in patients with IgAN.

Hammerhead ribozyme targeting human platelet-derived growth factor A-chain mRNA inhibited the proliferation of human vascular smooth muscle cells.

Platelet-derived growth factor (PDGF) A-chain contributes to the pathogenesis of cardiovascular proliferative diseases, such as hypertensive vascular disease, atherosclerosis, and re-stenosis of an artery after angioplasty. To develop a ribozyme against human PDGF A-chain mRNA as a gene therapy for human arterial proliferative diseases, we designed and synthesized a 38-base hammerhead ribozyme to cleave human PDGF A-chain mRNA at the GUC sequence at nucleotide 591. In the presence of MgCl(2), synthetic hammerhead ribozyme to human PDGF A-chain mRNA cleaved the synthetic target RNA to two RNA fragments at a predicted size. Doses of 0.01-1.0 microM hammerhead ribozyme to human PDGF A-chain mRNA significantly inhibited angiotensin II (Ang II) and transforming growth factor (TGF)-beta(1)-induced DNA synthesis in vascular smooth muscle cells (VSMC) from human in a dose-dependent manner. One micromolor of hammerhead ribozyme to human PDGF A-chain mRNA significantly inhibited Ang II-induced PDGF A-chain mRNA and PDGF-AA protein expressions in VSMC from humans. These results indicate that the designed hammerhead ribozyme to human PDGF A-chain mRNA effectively inhibited growth of human VSMC by cleaving the PDGF A-chain mRNA and inhibiting the PDGF-AA protein expression in human VSMC. This suggests that the designed hammerhead ribozyme to PDGF A-chain mRNA is a feasible gene therapy for treating arterial proliferative diseases.

[Usefulness of combination post-stress dysfunction and perfusion imaging in technetium-99m-tetrofosmin myocardial scintigraphy].

OBJECTIVES: Myocardial perfusion imaging has lower sensitivity for the diagnosis of coronary artery disease in patients with three-vessel disease. The presence of post-stress dysfunction of the left ventricle, evaluated by electrocardiography(ECG) gated single photon emission computed tomography(SPECT) with a quantitative gated SPECT program, was investigated in patients with coronary artery disease, and also whether combining post-stress dysfunction and myocardial perfusion imaging improved the diagnosis of coronary artery disease. METHODS: ECG gated technetium-99m-tetrofosmin SPECT was performed using a one day, stress and rest, protocol in 139 patients. SPECT and coronary angiography were performed within 1 month. The coronary artery disease group consisted of 89 patients: 43 with one-vessel disease(1VD), 28 with two-vessel disease(2VD), and 18 with three-vessel disease(3VD). The group with zero-vessel disease(0VD) consisted of 50 patients. According to post-stress and rest ejection fraction(EF) and end-systolic volume (ESV), post-stress dysfunction is defined as follows: rest EF--post-stress EF > or = 5% and post-stress ESV--rest ESV > or = 5 ml. RESULTS: In the coronary artery disease group, post-stress ESV was larger than rest ESV(37.8 +/- 26.4, 34.0 +/- 24.2 ml, p < 0.001), and post-stress EF was lower than rest EF (61.5 +/- 11.1%, 64.2 +/- 10.8%, p < 0.001). In the 0VD group, ESV and EF were the same for post-stress and rest (25.7 +/- 20.8, 26.2 +/- 21.6 ml, NS; 70.4 +/- 9.5%, 70.0 +/- 9.6%, NS). Post-stress dysfunction was 6.0% in the 0VD group and 30.3% in the coronary artery disease group(p < 0.001). Furthermore, post-stress dysfunction in the 2VD (35.7%) and 3VD(38.9%) groups was higher than that in the 0VD group(p < 0.01, p < 0.01). Sensitivity of coronary artery disease diagnosis by myocardial perfusion imaging was 75%. The combination of post-stress dysfunction and myocardial perfusion imaging improved sensitivity from 75% to 82%(p < 0.05), but reduced the specificity from 92% to 86%(p = 0.08). CONCLUSIONS: Post-stress dysfunction is a useful parameter for clinical diagnosis of coronary artery disease.

Endogenous angiotensin II suppresses insulin signaling in vascular smooth muscle cells from spontaneously hypertensive rats.

BACKGROUND: Angiotensin II (Ang II) has been reported to inhibit insulin signaling at multiple levels in vascular smooth muscle cells (VSMC) in vitro. We have demonstrated that VSMC from spontaneously hypertensive rats (SHR) produce Ang II in a homogeneous culture. OBJECTIVE: In the current study, we investigated influences of endogenous Ang II on insulin signaling in VSMC from SHR. DESIGN AND METHODS: Phosphatidylinositol 3-kinase (PI3-kinase) activity, insulin receptor substrate-1 (IRS-1) associated tyrosine phosphorylation, and p85 subunit of PI3-kinase were measured in VSMC from SHR and normotensive Wistar-Kyoto (WKY) rats in the absence and presence of Ang II type 1 receptor antagonist RNH6270 and mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) inhibitor U0126. RESULTS: Insulin treatment increased PI3-kinase activity in VSMC from WKY rats in a dose-dependent manner. In contrast, insulin treatment of VSMC from SHR did not affect PI3-kinase activity. However, co-treatment of VSMC from SHR with RNH6270 and insulin, increased PI3-kinase activity. PI3-kinase activity, IRS-1-associated tyrosine phosphorylation and p85 subunit of PI3-kinase in VSMC from WKY rats decreased in response to treatment with Ang II and returned to control levels upon co-treatment with U0126. Basal levels of PI3-kinase activity, IRS-1-associated tyrosine phosphorylation, and p85 subunit of PI3-kinase were significantly lower in VSMC from SHR than in cells from WKY rats. U0126 treatment of VSMC from SHR significantly increased levels of PI3-kinase activity, IRS-1-associated tyrosine phosphorylation, and p85 subunit of PI3-kinase. CONCLUSION: These results indicate that endogenous Ang II suppresses insulin signaling in VSMC from SHR by activating extracellular signal-regulated kinase. These findings suggest that tissue Ang II may play a role in insulin resistance in hypertension.

Effects of the L- and N-type calcium channel blocker cilnidipine on growth of vascular smooth muscle cells from spontaneously hypertensive rats.

Cultured vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) show exaggerated growth compared with cells from Wistar-Kyoto (WKY) rats. Calcium antagonists have recently been reported to have an in vivo antiproliferative effect on hypertensive cardiovascular organs. We investigated the effects of the calcium antagonist cilnidipine that blocks both L- and N-type calcium channels on the growth of VSMC from SHR. Cilnidipine (1 and 10 microM) significantly inhibited basal DNA synthesis in VSMC from both rat strains; the inhibition was significantly larger in VSMC from SHR than in cells from WKY rats, and was significantly greater than effects of nifedipine. Cilnidipine (1 microM) significantly inhibited serum-stimulated DNA synthesis in VSMC from both rat strains. The inhibition was more marked in VSMC from SHR than in cells from WKY rats. Angiotensin II, platelet-derived growth factor (PDGF)-AA, and phorbol-12-myristate-13-acetate dose-dependently increased DNA synthesis in VSMC from SHR but not in cells from WKY rats. Cilnidipine (1 microM) significantly suppressed this increase in DNA synthesis in VSMC from SHR. Expression of basic fibroblast growth factor (bFGF), transforming growth factor-beta1, and PDGF A-chain mRNAs was markedly greater in VSMC from SHR than in cells from WKY rats. Cilnidipine (1 microM) significantly inhibited the expression of TGF-beta1 mRNA in VSMC from SHR but not in cells from WKY rats. These findings suggest that cilnidipine exerts its antiproliferative effects through the inhibition of DNA synthesis induced by growth-promoting factors and by inhibiting the expression of TGF-beta1 mRNA in VSMC from SHR.

Intracoronary electrocardiogram for early detection of myocardial viability during coronary angioplasty in acute myocardial infarction.

PURPOSE: The clinical value of the intracoronary electrocardiogram (ECG) for detecting myocardial viability in acute myocardial infarction was evaluated by thallium-201 scintigraphy and left ventriculogram at the chronic stage. METHODS: Intracoronary ECGs, recorded from the tip of a guidewire during emergency coronary angioplasty, were obtained in 65 patients with reperfused anterior myocardial infarction. Further ST segment elevation of greater than 0.2 mV detected during the balloon inflation was taken as significant. The left ventricular segmental shortening was measured from left ventriculograms recorded at acute and chronic stages. The infarct area was defined as viable when a thallium uptake of more than 50% was detected on thallium-201 myocardial scintigraphy at the chronic stage. RESULTS: During emergency coronary angioplasty, significant ST segment elevation was noted in 45 patients (Group A); however, the ST segment was not significantly elevated in the other 20 patients (Group B). The infarct area of 42 patients in Group A and three patients in Group B was viable on scintigraphy. Improvement left ventricular wall motion of the infarct area was observed in 39 of the 42 patients in Group A and the three patients in Group B. Therefore, intracoronary ECG can predict reversible dysfunction with excellent sensitivity (92.9%) and specificity (73.9%). CONCLUSIONS: The myocardium within an infarct area can be regarded as viable when a further ST segment elevation occurs on intracoronary ECG during emergency coronary angioplasty. It is useful, therefore, to monitor the intracoronary ECG during coronary angioplasty balloon inflation to assess the myocardial viability of the infarct area.

Systematic screening of type B human natriuretic peptide receptor gene polymorphisms and association with essential hypertension.

C-type natriuretic peptide (CNP) dilates arteries, lowers blood pressure and inhibits proliferation of vascular smooth muscle cells via the type B natriuretic peptide receptor (NPRB). The CNP-NPRB system may play a crucial role in the development of cardiovascular disease. We recently determined the structure of the human NPRB gene. In the present study, our objectives are to identify the polymorphisms of the NPRB gene and investigate the association of this gene with essential hypertension (EH). We used the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique to study the NPRB gene polymorphism, and conducted an association study using a novel polymorphic marker. PCR-SSCP analysis of all 22 exons was done in 90 subjects, and abnormally-migrating bands were observed in the analyses of exon 11 and intron 18. Direct sequencing of these DNA fragments revealed the following sequence alterations: a C to T transition at nucleotide (nt) 2077 in exon 11 and a 9-bp insertion/deletion (I/D) in intron 18. PCR-restriction fragment length polymorphism analysis (PCR-RFLP) was developed to detect the C2077T transition. PCR-RFLP analyses of healthy subjects revealed that the C2077T polymorphism had complete linkage to GT repeats in intron 2 reported previously. The I/D polymorphism was identified by polyacrylamide gel electrophoresis, and it was not linked to any known polymorphic alleles of this gene. Therefore, the possible association between the I/D polymorphism and EH was investigated. A total of 123 individuals with EH and 123 age-matched normotensive control subjects were studied. Overall distributions of allele frequencies in the two groups were not significantly different. Although the I/D polymorphism in intron 18 of the NPRB gene was not associated with EH, the results of this study, which identified two novel polymorphisms in the human NPRB gene, will facilitate further genetic analysis of this gene and cardiovascular disease.

Elevated interleukin-18 levels in the urine of nephrotic patients.

BACKGROUND/AIM: The etiology of minimal-change nephritic syndrome (MCNS) is obscure. It has been speculated that T cells play a role in the pathogenesis of MCNS. Interleukin (IL)-18, a novel immunoregulatory cytokine with potent inferon-gamma-inducing activities, may play an important role in T-helper type 1-mediated immune responses. To examine further the possible role of IL-18 in nephrotic syndrome (NS), in the present study we measured IL-18 levels in the urine in different clinical stages of MCNS. The aim of this study was to investigate the involvement of IL-18 in MCNS. METHODS: Urine samples were obtained from 20 MCNS patients. The disease controls included 20 patients with IgA nephropathy. The samples were assayed for IL-18 protein by a sandwich enzyme-linked immunosorbent assay. RESULTS: Compared with normal controls, significantly increased urinary levels of IL-18 were detected in MCNS patients with the NS. The urinary IL-18 (uIL-18) levels correlated with the degree of proteinuria in MCNS patients. Moreover, when individual MCNS patients were followed through their clinical illness, uIL-18 levels were increased during the active phase and decreased as the patients went into remission. CONCLUSIONS: These results indicate that uIL- 18 is detectable in a subgroup of patients with active NS and correlates to their disease activity in patients with MCNS. Our findings support the notion that IL-18 may play a role in the pathophysiology of NS.

Relationship between insulin resistance and uremic toxins in the gastrointestinal tract.

The relationship between insulin resistance and local uremic toxins was examined using an oral adsorbent. Fourteen rats demonstrating a diabetic state underwent two-thirds, nephrectomy and were divided into two groups. The control group was fed standard rat chow, and the test group was fed standard rat chow containing 5% AST-120. The target level of blood glucose was achieved by controlling the dosage of exogenous insulin. All rats were sacrificed at week 6. Body weight, blood glucose level, and renal function at week 6 were not significantly different between both groups. However, the mean blood glucose level and the mean dose of exogenous insulin in the AST-120-fed group were significantly reduced as compared with the control group. The results of the present study indicate that administration of an oral adsorbent in diabetic nephropathy decreases the doses of exogenous insulin and improves insulin resistance, and that uremic toxins which exist in the gastrointestinal tract play important roles.

Association study between the variants of the human ANP gene and essential hypertension.

Variants of atrial natriuretic peptide (ANP) are reported to be more common in blacks with hypertension than in normotensive controls and constitute an independent risk factor for cerebral infarction. The purpose of the present study was to investigate the role of ANP in the pathogenesis of essential hypertension (EH) in the Japanese. We investigated 2 previously reported ANP gene markers, G1837A and T2238C, for their possible associations with EH. A total of 233 individuals with EH and 213 age-matched normotensive (NT) control subjects were studied. The frequencies of the G and A alleles were 0.09 (42/466) and 0.91 (424/466), respectively, for the NT group and 0.11 (47/426) and 0.89 (379/426), respectively, for the EH group. These frequencies did not differ significantly between the two groups. The frequencies of the T and C alleles were 0.024 (11/466) and 0.97 (455/466), respectively, for the NT group and 0.03 (13/426) and 0.97 (413/426), respectively, for the EH group. These frequencies also did not differ significantly between the two groups. Neither G1837A nor the T2238C polymorphism of the ANP gene was associated with EH. Our findings do not support the hypothesis that the G1837A and T2238C polymorphisms of the ANP gene are markers for EH in the Japanese.

Isolation of the 5'-flanking region of genes by thermal asymmetric interlaced polymerase chain reaction.

BACKGROUND: Isolation of the 5'-flanking region of gene segments adjacent to known sequences is a tedious task. Thermal asymmetric interlaced (TAIL)-PCR developed in 1995 uses nested sequence-specific primers together with a shorter arbitrary degenerate primer so that the relative amplification efficiencies of specific and nonspecific products can be thermally controlled. In the present study, we modified the TAIL-PCR method to isolate the 5'-flanking region of two human genes, human natriuretic peptide receptor type A (NPRA) and type B (NPRB) genes. MATERIAL AND METHODS: We improved upon the original TAIL-PCR method in some aspects: three different series of eight AD primers were used simultaneously; a high denaturing temperature was used; and a Taq DNA polymerase developed for long and accurate PCR was used. RESULTS: We succeeded in isolating the 5'-flanking region of the NPRA and NPRB genes directly from human genomic DNA. CONCLUSION: Our TAIL-PCR method is applicable not only to be human genome but also to the genome of other life forms.

Polymorphism of the promoter region of prostacyclin synthase gene is not related to essential hypertension.

An impaired synthesis of prostacyclin has been implicated in the development of essential hypertension (EH). We therefore investigated whether there is an association between the prostacyclin synthase (PGIS) gene and EH using a variable number of tandem repeats (VNTR) polymorphism in the promoter region that influences transcriptional activity of this gene. A total of 125 patients with EH and 125 age-matched subjects with normal blood pressure were studied. The number of VNTR of the five alleles ranged from 3 to 7 repeats in the 250 unrelated Japanese subjects. The allele frequency distribution in the two groups were not significantly different. Thus, this VNTR polymorphism in the PGIS gene is not associated with EH.

Effects of PDGF A-chain antisense oligodeoxynucleotides on growth of cardiovascular organs in stroke-prone spontaneously hypertensive rats.

We examined the effects of the platelet-derived growth factor (PDGF) A-chain antisense oligodeoxynucleotides (ODN) on cardiovascular organ growth in stroke-prone spontaneously hypertensive rats (SHR-SP) in vivo. Expression of PDGF A-chain mRNA was higher in the aorta and kidney in 9-week-old SHR-SP than in Wistar-Kyoto (WKY) rats. A phosphorothioate-linked 15-mer antisense ODN complementary to the initiation codon region of rat PDGF A-chain mRNA and a control sense ODN were infused subcutaneously into SHR-SP/Izumo at a dose of 90 ng/g body weight/day for 28 days using an implanted ALZET pump. The PDGF A-chain antisense ODN did not affect blood pressure or body weight. The antisense ODN significantly inhibited [3H]thymidine incorporation into the DNA in the aorta and kidney but not in the heart. Infusion of the antisense ODN considerably reduced production of PDGF A-chain protein but did not affect expression of PDGF A-chain mRNA. Infusion of the antisense ODN considerably improved the arterial and renal tissue damage in SHR-SP morphologically. From these findings, it can be confirmed that suppression of PDGF A-chain by the antisense DNA is useful as a gene therapy for treating cardiovascular organ damage in hypertension.

Elevated vascular endothelial growth factor levels in the urine of patients with minimal-change nephrotic syndrome.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a selective endothelial mitogen and vascular permeability factor (VPF), that is mainly produced by activated monocytes/macrophages and T cells. To our knowledge, very little is known about the involvement of VEGF in minimal-change nephrotic syndrome (MCNS). The aim here was to define further the involvement of VEGF in MCNS. PATIENTS AND METHODS: Urine samples were obtained from 20 MCNS patients. The disease controls included 20 patients with IgA nephropathy (IgAN). The samples were assayed for VEGF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: Compared with normal controls, markedly increased urinary levels of VEGF were detected in both MCNS and IgAN patients with the nephrotic syndrome (NS). The urinary VEGF (uVEGF) levels correlated with the degree ofproteinuria in MCNS and IgAN patients. Moreover, when individual MCNS patients were followed through their clinical illness, uVEGF levels were increased during the active phase and decreased as the patients went into remission. Our main concern is to distinguish between two possibilities: Increases in uVEGF excretion might indeed relate to specific glomerular pathology and thus have a pathophysiological role. Alternatively, uVEGF may be derived from the circulation and as such may be nothing more than an assay for proteinuria. In fact, given the strict correlation between uVEGF excretion and the amount of proteinuria, the second possibility appears quite conceivable. CONCLUSION: Therefore, this may be a coincidental finding which has no bearing on the pathophysiology of MCNS.

Regulation of in situ complement activation via the lectin pathway in patients with IgA nephropathy.

The lectin pathway, which is initiated by mannose-binding lectin (MBL) and MBL-associated serine protease (MASP), is one of the possible routes to activate the complement cascade in immunoglobulin A (IgA) nephropathy. The purpose of this study was to elucidate the regulatory mechanism of the pathway. Levels of complement activation products and regulatory proteins were measured in sera from 27 patients with IgA nephropathy, and generation of fluid-phase complement activation products in the presence of pooled normal human serum was quantified to evaluate activation in vitro. Although there were no significant differences in the serum levels and in vitro activation between the MBL-MASP positive (n = 14) and negative (n = 13) groups, there were positive correlations between complement activation products (Bb fragment and C4d fragment) and regulatory proteins (factor H, C4-binding protein, and C1 inhibitor) in the MBL-MASP-positive group. Furthermore, immunohistochemical studies demonstrated glomerular deposition of the regulatory protein (C4-binding protein, alpha2-macroglobulin, and factor H) in all patients in the MBL-MASP-positive group. These findings suggest that the regulatory proteins control in situ complement activation via the lectin pathway immediately, and continuous activation due to inadequate control will lead to the advanced glomerular injury.