A case of palisaded neutrophilic and granulomatous dermatitis associated with systemic lupus erythematosus presenting with pustules

Palisaded neutrophilic and granulomatous dermatitis (PNGD) is a relatively rare skin disease that is characterized by a reactive granulomatous histopathological pattern and is often associated with systemic autoimmune diseases. We encountered a case of PNGD that presented with pustules, although the prototypical clinical presentation of PNGD is mainly erythema and papules. Here, this rare case of PNGD with pustules is presented and discussed in relation to the relevant literature.

Decreased peripheral basophil counts in urticaria and mouse model of oxazolone-induced hypersensitivity, the latter suggesting basopenia reflecting migration to skin

A decrease in the number of basophils in the peripheral blood, or basopenia, has been noted, reflecting the activity of chronic spontaneous urticaria (CSU). Infiltration of basophils into the skin has also been reported, but the mechanism of basopenia in CSU has not been clarified. The phenomenon of basopenia during the active phase of urticaria was confirmed, and basophil numbers increased following symptom improvement in 15 out of 17 patients treated with omalizumab and in 13 of 15 patients treated with antihistamines. Our examination by immunostaining also revealed basophil infiltration of the CSU lesions, as in previous reports, but since most of our patients were already taking oral steroids, it was not considered appropriate to examine the relationship between basophil numbers in tissue and peripheral blood. Then, we used mouse model of contact hypersensitivity with a single application of oxazolone, which is known to stimulate basophil infiltration, and investigated basophil counts in the skin, peripheral blood, and bone marrow. In this model, a decrease in peripheral blood basophil numbers was observed one day after challenge, but not after 2 days, reflecting supplementation from the bone marrow. Indeed, when cultured basophils expressing GFP were transplanted into the peripheral blood, GFP-positive basophil numbers in the peripheral blood remained low even after 2 days of challenge. Despite differences among species and models, these results suggest that one reason for the decrease of basophils in the peripheral blood in CSU may involve migration of circulating basophils into the skin.

The Potential Role of Basophils in Urticaria

Urticaria is a symptom of acute skin allergies that is not clearly understood, but mast cell histamine is hypothesized to cause swelling and itching. Omalizumab, an anti-human IgE antibody that traps IgE and prevents its binding to high-affinity IgE receptors, is effective in treating urticaria. We recently experienced a case of urticaria refractory to antihistamine therapy in which the peripheral-blood basophil count responded to omalizumab therapy and its withdrawal. Furthermore, the peripheral-blood basophils showed an unexpected increase in the expression of a cell surface activation marker. This phenomenon has been reported by other analyses of basophil and mast cell dynamics during omalizumab treatment. Here, we analyze these observations and formulate a hypothesis for the role of basophils in urticaria. Specifically, that activated basophils migrate to the local skin area, lowering peripheral-blood counts, omalizumab therapy alters basophilic activity and causes their stay in the peripheral blood. We hope that our analysis will focus urticaria research on basophils and reveal new aspects of its pathogenesis.

Imbalance toward TFH 1 cells playing a role in aberrant B cell differentiation in systemic sclerosis

OBJECTIVE

SSc is a connective tissue disease with multisystem disorder induced by the inflammation and fibrosis following T and B cell abnormalities. Follicular helper CD4+ T (TFH) cells play a crucial role in the formation of germinal centres and specialize in interacting to aid B cell differentiation. We aimed to investigate TFH cells and their subsets to evaluate their involvement with B cell alteration in SSc.

METHOD

Circulating TFH cells (cTFH), B cells and their subsets were assessed by flow cytometry. The concentration of serum cytokines was measured by cytokine array assay. Immunohistochemistry and IF were performed to evaluate the migration of TFH cells in SSc skin lesions.

RESULTS

The proportion of cTFH cells did not differ from controls, but their subsets were imbalanced in SSc patients. The frequency of TFH 1 was increased and correlated with ACA titre, serum IgM or CRP levels of patients, and cytokine concentrations of IL-21 and IL-6 that induce B cell differentiation in SSc. cTFH cells from SSc showed activated phenotype with expressing higher cytokine levels compared with controls. The frequency of TFH 17 was also increased, but was not correlated with a high level of Th17 cytokines in patients' sera. Furthermore, infiltration of TFH cells was found in skin lesion of SSc patients.

CONCLUSION

We here describe an imbalance of cTFH toward TFH 1 that may induce B cell alteration through IL-21 and IL-6 pathways and promote inflammation, contributing to the pathogenesis of SSc disease.

TARC expression in the circulation and cutaneous granulomas correlates with disease severity and indicates Th2-mediated progression in patients with sarcoidosis

BACKGROUND

Sarcoidosis is a systemic disorder characterized by the accumulation of lymphocytes and monocyte/macrophage lineage cells that results in the formation of non-caseating granulomas. Thymus- and activation-regulated chemokine (TARC)/CCL17 is an important chemokine in the amplification of Th2 responses, which are achieved by recruiting CCR4-expressing CD4⁺ T lymphocytes. TARC concentrations are known to increase in the serum of sarcoidosis patients; however, its role in the assessment of severity and prognosis of sarcoidosis remains unknown. The objective of this study is to elucidate the role of TARC in sarcoidosis by investigating its expression in peripheral blood and at inflammatory sites. We also examined its relationship with clinical features.

METHODS

Serum levels of TARC, soluble interleukin 2 receptor, angiotensin-converting enzyme, and lysozyme were measured in 82 sarcoidosis patients. The Th1 and Th2 balance in circulating CD4⁺ T cells was evaluated by flow cytometry. The immunohistochemical staining of TARC and CCR4 was performed in order to identify the source of TARC in affected skin tissues.

RESULTS

TARC serum levels were elevated in 78% of patients and correlated with disease severity. The percentage of CCR4⁺ cells and the CCR4⁺/CXCR3⁺ cell ratios were significantly higher in sarcoidosis patients than in normal subjects (P = 0.002 and P = 0.015, respectively). Moreover, TARC was expressed by monocyte/macrophage lineage cells within granulomas. The abundancy as well as distribution of TARC staining correlated with its serum levels.

CONCLUSIONS

The present results suggest that elevations in TARC drive an imbalanced Th2- weighted immune reaction and might facilitate prolonged inflammatory reactions in sarcoidosis.

Cytochrome P450 2A6 Phenotyping Using Dietary Caffeine Salivary Metabolite Ratios and Genotyping Using Blood on Storage Cards in Non-smoking Japanese Volunteers

BACKGROUND

A simple method of genotyping and phenotyping cytochrome P450 2A6 (CYP2A6) was previously reported using individual blood samples and urinary caffeine metabolite ratios of 1,7-dimethyluric acid (17U) to 1-methylxanthine (1X).

OBJECTIVE

Blood spotted onto storage cards and salivary caffeine metabolites were analyzed in 27 healthy non-smoking Japanese volunteers with no prior abstention from dietary caffeine intake.

METHODS

1,7-Dimethylxanthine (17X), 17U, 1X, and caffeine levels in spot saliva samples were determined in Japanese non-smokers by high-performance liquid chromatography under normal dietary caffeine consumption.

RESULTS

17U/17X ratios in saliva were almost constant over time, but those of 17U/1X were variable in two subjects tested before and 1-2.5 h after caffeine treatment (a cup of black tea). In seven subjects, 17U/17X ratios in saliva were highly correlated with those in plasma (r = 0.98, p < 0.01) and well correlated with those in urine samples (r = 0.78, p < 0.05). The average 17U/17X ratios, but not 17U/1X ratios, in saliva under dietary caffeine consumption obtained from subjects with CYP2A6*1/*4 (n=11) and CYP2A6*4/*4 (whole-gene deletion, n=2) genotypes were significantly lower than those from subjects with wild-type CYP2A6*1/*1 (n=14). Genotyping was done by a multiplex real-time polymerase chain reaction method using blood spotted onto storage cards.

CONCLUSION

The present results suggest that the decreased CYP2A6 function associated with the whole-gene deletion genotype (determined using blood samples) could be detected using 17U/17X ratios, but not 17U/1X ratios, in spot saliva samples under normal dietary caffeine consumption in Japanese non-smokers, just as it could be detected using urinary 17U/1X ratios.

Up-regulated expression of CD86 on circulating intermediate monocytes correlated with disease severity in psoriasis

BACKGROUND

The number of intermediate monocytes (CD14⁺⁺CD16⁺) increases in many inflammatory conditions. However, it is not yet known which functional markers expressed by these populations are linked to the pathogenesis of psoriasis.

OBJECTIVES

We evaluated the expression of functional markers on circulating intermediate monocytes. Our goal was to correlate specific populations and their markers with the clinical severity of psoriasis.

METHODS

A cohort of 43 psoriatic patients was subjected to analysis. The proportion of intermediate monocytes with CD86 expression was evaluated by flow cytometry. Serum beta defensin-2 levels were measured by ELISA. Immunofluorescent staining was performed in order to identify the presence of CD14⁺CD16⁺ cells that co-expressed CD86 in affected skin tissues.

RESULTS

Upregulated expression of CD86 on the intermediate subset (but not the number of intermediate monocytes) correlated with clinical severity as measured by PASI scores and serum beta defensin-2 levels. Immunostaining also showed the presence of CD86⁺CD14⁺CD16⁺ cells in the epidermis and dermis of psoriatic plaques, which was associated with increased epidermal proliferation.

CONCLUSION

These results suggest that the expression of CD86 on circulating intermediate monocytes could be used as an index in clinical practice and provide novel insights into how these cells join a complex immune network under the pathological conditions of psoriasis.

Effect of basal insulin therapy on vascular endothelial function and adipokine profiles in people with Type 2 diabetes

AIM

To compare the effects of the basal insulin analogues glargine and detemir on endothelial function and adipocytokine levels in people with Type 2 diabetes.

METHODS

We studied 32 people with Type 2 diabetes whose blood glucose control was unsatisfactory while receiving only oral hypoglycaemic drugs. Participants were randomized to either insulin glargine or detemir for 24 weeks and then crossed over to the other treatment without a washout period. Flow-mediated vasodilatation, adipocytokine levels (plasminogen activator inhibitor-1 and leptin/adiponectin ratio), and fasting ghrelin levels were monitored.

RESULTS

HbA_1c levels were significantly decreased by both basal insulin therapies. Body weight was significantly increased by glargine but not by detemir. The proportion of flow-mediated vasodilatation was significantly increased by detemir but not glargine (glargine: from 5.17 ± 0.69 to 5.94 ± 0.83%; detemir: from 4.89 ± 0.78 to 7.92 ± 0.69%). Plasminogen activator inhibitor-1 level was significantly decreased by only detemir (glargine: from 16.4 ± 1.8 to 17.3 ± 2.1; detemir: from 19.2 ± 2.8 to 16.0 ± 1.6 ng/ml). The leptin/adiponectin ratio was significantly increased only by glargine. Acyl ghrelin level was significantly decreased by glargine but not detemir.

CONCLUSIONS

These results suggest that the effect on endothelial function and adipocytokine profiles may differ between glargine and detemir in people with diabetes (Trial registration ID: UMIN000004973).

Impact of B-type natriuretic peptide (BNP) on development of atrial fibrillation in people with Type 2 diabetes

AIMS

To examine if a simple biomarker can identify people with diabetes who are at high risk of atrial fibrillation.

METHODS

A retrospective cohort study was conducted at a single centre in people with Type 2 diabetes referred to our department between January 2000 and December 2007. In 517 consecutive people without any history, signs or symptoms of atrial fibrillation at baseline, the association between baseline B-type natriuretic peptide level and future atrial fibrillation incidence was examined, with adjustments for other potentially confounding factors.

RESULTS

A total of 28 people were diagnosed with new-onset atrial fibrillation during a median 6-year follow-up. When people were categorized into three groups according to B-type natriuretic peptide clinical thresholds (20 and 100 pg/ml), hazard ratios for the development of atrial fibrillation in the middle and highest B-type natriuretic peptide groups were 2.8 and 9.4, respectively, compared with the lowest B-type natriuretic peptide group. Time-dependent receiver-operating curve analysis identified a threshold for B-type natriuretic peptide to detect atrial fibrillation development of 52.8 pg/ml (sensitivity 75.2%, specificity 68.8%). The B-type natriuretic peptide predictive value was independent of and similar to that of left atrial size and ventricular dimension.

CONCLUSION

In people with Type 2 diabetes, high baseline B-type natriuretic peptide levels were significantly associated with future atrial fibrillation development.

Dataset for genotyping validation of cytochrome P450 2A6 whole-gene deletion (CYP2A6*4) by real-time polymerase chain reaction platforms

This data article contains a supplementary figure and validation data relating to the research article entitled “Genotyping of wild-type cytochrome P450 2A6 and whole-gene deletion using human blood samples and a multiplex real-time polymerase chain reaction method with dual-labeled probes” (Shimizu et al., Clinica Chimica Acta 441, 71–74, 2015), which presents a multiplex real-time polymerase chain reaction method with dual-labeled probes for human P450 2A6 wild-type and whole-gene deletion. Real-time methods have dramatically improved the speed of complex genetic diagnostics compared to conventional assays based on restriction enzyme digestion. Here, we show the basic assay validation data by single and multiplex determinations in comparison with commercial TaqMan copy number assays for P450 2A6.

Germline deletion and a somatic mutation of the PRKAR1A gene in a Carney complex-related pituitary adenoma

OBJECTIVE

The objective was to assess involvement of loss of the PRKAR1A gene encoding a type 1α regulatory subunit of cAMP-dependent protein kinase A located on 17q24 in a Carney complex (CNC)-related pituitary adenoma.

DESIGN

We investigated aberrations of the PRKAR1A gene in a CNC patient with a GH-producing pituitary adenoma, whose family has three other members with probable CNC.

METHODS

A gene mutation was identified by a standard DNA sequencing method based on PCR. DNA copy number was measured to evaluate allelic loss on 17q24 by quantitative PCR. The breakpoints of deletion were determined by cloning a rearranged region in the deleted allele.

RESULTS

A PRKAR1A mutation of c.751_758del8 (p.S251LfsX16) was found in genomic DNA obtained from a pituitary adenoma, but not leukocytes from the patient. Reduced DNA copy number at loci including the PRKAR1A gene on 17q24 was detected in both the tumor and leukocytes, suggesting a deletion at the loci at the germline level. The deletion size was determined to be ∼ 0.5 Mb and this large deletion was also found in two other family members.

CONCLUSION

This is the first case showing a CNC-related pituitary adenoma with the combination of somatic mutation and a large inherited deletion of the PRKAR1A gene. Biallelic inactivation of PRKAR1A appears to be necessary for the development of CNC-related pituitary adenoma.

Induced pluripotent stem cells generated from diabetic patients with mitochondrial DNA A3243G mutation

AIMS/HYPOTHESIS

The aim of this study was to generate induced pluripotent stem (iPS) cells from patients with mitochondrial DNA (mtDNA) mutation.

METHODS

Skin biopsies were obtained from two diabetic patients with mtDNA A3243G mutation. The fibroblasts thus obtained were infected with retroviruses encoding OCT4 (also known as POU5F1), SOX2, c-MYC (also known as MYC) and KLF4. The stem cell characteristics were investigated and the mtDNA mutation frequencies evaluated by Invader assay.

RESULTS

From the two diabetic patients we isolated four and ten putative mitochondrial disease-specific iPS (Mt-iPS) clones, respectively. Mt-iPS cells were cytogenetically normal and positive for alkaline phosphatase activity, with the pluripotent stem cell markers being detectable by immunocytochemistry. The cytosine guanine dinucleotide islands in the promoter regions of OCT4 and NANOG were highly unmethylated, indicating epigenetic reprogramming to pluripotency. Mt-iPS clones were able to differentiate into derivatives of all three germ layers in vitro and in vivo. The Mt-iPS cells exhibited a bimodal degree of mutation heteroplasmy. The mutation frequencies decreased to an undetectable level in six of 14 clones, while the others showed several-fold increases in mutation frequencies (51-87%) compared with those in the original fibroblasts (18-24%). During serial cell culture passage and after differentiation, no recurrence of the mutation or no significant changes in the levels of heteroplasmy were seen.

CONCLUSIONS/INTERPRETATION

iPS cells were successfully generated from patients with the mtDNA A3243G mutation. Mutation-rich, stable Mt-iPS cells may be a suitable source of cells for human mitochondrial disease modelling in vitro. Mutation-free iPS cells could provide an unlimited, disease-free supply of cells for autologous transplantation therapy.

Vasodilator therapy with hydralazine induces angiotensin AT receptor-mediated cardiomyocyte growth in mice lacking guanylyl cyclase-A

BACKGROUND AND PURPOSE

Recent clinical guidelines advocate the use of the isosorbide dinitrate/hydralazine combination in treatment for heart failure. However, clinical and laboratory evidence suggest that some vasodilators may induce cardiac hypertrophy under uncertain conditions. This study investigated the effects and underlying mechanism of action of the vasodilator hydralazine on cardiac growth.

EXPERIMENTAL APPROACH

Wild-type mice and animals deficient in guanylyl cyclase-A (GCA) and/or angiotensin receptors (AT(1) and AT(2) subtypes) were treated with hydralazine ( approximately 24 mg.kg(-1).day(-1) in drinking water) for 5 weeks. Cardiac mass and/or cardiomyocyte cross-sectional area, fibrosis (van Giessen-staining) and cardiac gene expression (real-time RT-PCR) were measured.

KEY RESULTS

Hydralazine lowered blood pressure in mice of all genotypes. However, this treatment increased the heart and left ventricular to body weight ratios, as well as cardiomyocyte cross-sectional area, and cardiac expression of atrial natriuretic peptide mRNA in mice lacking GCA. Hydralazine did not affect cardiac hypertrophy in wild-type mice and mice lacking either AT(1) or AT(2) receptors alone. However, the pro-hypertrophic effect of hydralazine was prevented in mice lacking both GCA and AT(2), but not GCA and AT(1) receptors. However, hydralazine did decrease cardiac collagen deposition and collagen I mRNA (signs of cardiac fibrosis) in mice that were deficient in GCA, or both GCA and AT(2) receptors.

CONCLUSIONS AND IMPLICATIONS

The vasodilator hydralazine induced AT(2) receptor-mediated cardiomyocyte growth under conditions of GCA deficiency. However, attenuation of cardiac fibrosis by hydralazine could be beneficial in the management of cardiac diseases.

Decreased circulating CD34+ cells are associated with progression of diabetic nephropathy

AIMS

Circulating progenitor cells such as CD34+ cells play a key role in maintenance of vascular endothelial function and neovascularization, and a decrease in the number of CD34+ cells is associated with cardiovascular disease. However, the contribution of circulating progenitor cells to microvascular disease, such as diabetic nephropathy, is unclear. This study was therefore designed to clarify the association between diabetic nephropathy and circulating CD34+ cells.

METHODS

We measured circulating CD34+ cell numbers in 85 Type 2 diabetic patients aged 40-70 years with normo- and microalbuminuria and determined the association with urinary albumin excretion rate (UAER).

RESULTS

The number of circulating CD34+ cells significantly correlated with log UAER (r = -0.289, P = 0.008). Furthermore, in patients with low numbers of CD34+ cells (0.68 > cells/microl, lowest quartile of CD34+ cell number) UAER increased significantly after 12 months compared with baseline [from 34.3 +/- 7.0 to 53.6 +/- 10.8 mg/g creatinine (gCr), P < 0.05], whereas in patients with a high number of CD34+ cells (1.0 < cells/microl, highest quartile of CD34+ cell number) UAER did not change (from 16.7 +/- 4.8 to 20.1 +/- 3.0 mg/gCr).

CONCLUSIONS

These results suggest that a decreased number of circulating CD34+ cells is involved in the progression of diabetic nephropathy and may be a predictor of the disease.

C-type natriuretic peptide is a Schwann cell-derived factor for development and function of sensory neurones

Cyclic GMP (cGMP) is known to play important roles for neuronal development and neurite pathfinding. However, the regulatory mechanism that governs the synthesis of cGMP in the nervous system is not well defined. In the present study, we examined the role of C-type natriuretic peptide (CNP), which increases intracellular cGMP upon binding to its receptor, guanylyl cyclase (GC)-B, in the peripheral nervous system. Immunohistochemistry revealed that CNP is demonstrated in Schwann cells, whereas GC-B mRNA is highly expressed in dorsal root ganglion (DRG) neurones. In cultured DRG neurones, GC-B was demonstrated in dendrites of TrkA-positive cells, where it co-exists with cGMP-dependent protein kinase I (cGKI), the major intracellular mediator of cGMP actions. Addition of CNP in the culture medium increased the density of fine neurites, which was accompanied by the increase in phosphorylation of vasodilator-stimulated phosphoprotein, a cGKI substrate. Furthermore, in mice deficient for the CNP gene (CNP-KO), the numbers of TrkA-positive DRG neurones were diminished. Likewise, there were much less cGKI-positive neurones in DRG and cGKI-positive fibres in the dorsal spinal cord of CNP-KO than wild-type mice. Finally, the bone deformity-rescued CNP-KO mice displayed a decreased response to formalin-induced pain compared to wild-type. Taken together, these results suggest that CNP is derived from Schwann cells and plays an important role for the development and function of nociceptive sensory neurones.

Tumour budding at invasive margins and outcome in colorectal cancer

OBJECTIVE

Tumour budding, defined as small clusters of undifferentiated cancer cells at invasive margins, has been shown to reflect biologic aggressiveness of colorectal cancers. We therefore examined the prognostic significance of tumour budding in patients with colorectal carcinoma, particularly focusing on comparisons with other clinicopathological findings.

METHOD

Tumour budding was investigated in surgically resected specimens from 159 patients with colorectal carcinoma. With haematoxylin and eosin stained slides containing the entire invasive margin, the degree of tumour budding was classified into three grades: mild, <1/3 of the entire invasive margin; moderate, 1/3-2/3; marked, >2/3.

RESULTS

Mild tumour budding was found in 54 (34%) cases, moderate in 59 (37%) cases and marked in 46 (29%) cases. The degree of budding was linked with poor tumour differentiation, lymph node metastasis and advanced TNM stage (P < 0.001). In univariate analysis, patients with marked tumour budding [5-year cancer-related survival (CRS)/recurrence-free survival (RFS), 39%/53%] had significantly worse survival [CRS, hazard ratio (HR), 4.561; 95% confidence interval (CI), 2.265-9.184; P < 0.001; RFS, HR, 3.240; 95% CI, 1.430-7.342; P = 0.005] than those with mild (5-year CRS/RFS, 80%/82%) or moderate (63%/66%) budding. In the Cox regression model, marked tumour budding (HR, 3.137; 95% CI, 1.517-6.487; P = 0.002) and advanced tumour stage (stage III, HR, 3.226; 95% CI, 1.475-7.053; P = 0.003; stage IV, HR, 24.443; 95% CI, 10.843-55.100; P < 0.001) proved to be an independent predictor of short CRS.

CONCLUSION

Tumour budding is a practical and significant histological index for identification of high malignant potential and poor outcome in patients with colorectal carcinoma.

SIRT2, a tubulin deacetylase, acts to block the entry to chromosome condensation in response to mitotic stress

We previously identified SIRT2, an nicotinamide adenine dinucleotide (NAD)-dependent tubulin deacetylase, as a protein downregulated in gliomas and glioma cell lines, which are characterized by aneuploidy. Other studies reported SIRT2 to be involved in mitotic progression in the normal cell cycle. We herein investigated whether SIRT2 functions in the mitotic checkpoint in response to mitotic stress caused by microtubule poisons. By monitoring chromosome condensation, the exogenously expressed SIRT2 was found to block the entry to chromosome condensation and subsequent hyperploid cell formation in glioma cell lines with a persistence of the cyclin B/cdc2 activity in response to mitotic stress. SIRT2 is thus a novel mitotic checkpoint protein that functions in the early metaphase to prevent chromosomal instability (CIN), characteristics previously reported for the CHFR protein. We further found that histone deacetylation, but not the aberrant DNA methylation of SIRT2 5'untranslated region is involved in the downregulation of SIRT2. Although SIRT2 is normally exclusively located in the cytoplasm, the rapid accumulation of SIRT2 in the nucleus was observed after treatment with a nuclear export inhibitor, leptomycin B and ionizing radiation in normal human fibroblasts, suggesting that nucleo-cytoplasmic shuttling regulates the SIRT2 function. Collectively, our results suggest that the further study of SIRT2 may thus provide new insights into the relationships among CIN, epigenetic regulation and tumorigenesis.

Apparent B-type natriuretic peptide selectivity in the kidney due to differential processing

Two natriuretic peptides, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), are found principally in the heart. In preliminary experiments with mouse kidney cells or slices, we found mouse BNP1-45 much more potent than ANP1-28 in causing elevations of cGMP (>50-fold). The guanylyl cyclase-A (GC-A) receptor has been suggested to represent the primary means by which both peptides signal. In cultured cells overexpressing GC-A, BNP and ANP were almost equivalent in potency, suggesting that a receptor unique for BNP exists in the kidney. However, in mice lacking the GC-A gene, neither BNP nor ANP significantly elevated cGMP in kidney slices. Phosphoramidon, a neutral endopeptidase inhibitor, shifted the apparent potency of ANP to values equivalent to that of BNP, suggesting these kidney cell/slices rapidly degrade ANP but not BNP. Mass spectroscopic analysis confirmed that ANP is rapidly cleaved at the first cysteine of the disulfide ring, whereas BNP is particularly stable to such cleavage. Other tissues (heart, aorta) failed to significantly degrade ANP or BNP, and therefore the kidney-specific degradation of ANP provides a mechanism for preferential regulation of kidney function by BNP independent of peripheral ANP concentration.

Blockade of the natriuretic peptide receptor guanylyl cyclase-A inhibits NF-kappaB activation and alleviates myocardial ischemia/reperfusion injury

Acute myocardial infarction (AMI) remains the leading cause of death in developed countries. Although reperfusion of coronary arteries reduces mortality, it is associated with tissue injury. Endothelial P-selectin-mediated infiltration of neutrophils plays a key role in reperfusion injury. However, the mechanism of the P-selectin induction is not known. Here we show that infarct size after ischemia/reperfusion was significantly smaller in mice lacking guanylyl cyclase-A (GC-A), a natriuretic peptide receptor. The decrease was accompanied by decreases in neutrophil infiltration in coronary endothelial P-selectin expression. Pretreatment with HS-142-1, a GC-A antagonist, also decreased infarct size and P-selectin induction in wild-type mice. In cultured endothelial cells, activation of GC-A augmented H2O2-induced P-selectin expression. Furthermore, ischemia/reperfusion-induced activation of NF-kappaB, a transcription factor that is known to promote P-selectin expression, is suppressed in GC-A-deficient mice. These results suggest that inhibition of GC-A alleviates ischemia/reperfusion injury through suppression of NF-kappaB-mediated P-selectin induction. This novel, GC-A-mediated mechanism of ischemia/reperfusion injury may provide the basis for applying GC-A blockade in the clinical treatment of reperfusion injury.

Induction of JAB/SOCS-1/SSI-1 and CIS3/SOCS-3/SSI-3 is involved in gp130 resistance in cardiovascular system in rat treated with cardiotrophin-1 in vivo

CIS (cytokine-inducible SH2 protein), SOCS (suppressor of cytokine signaling), or SSI (signal transducers and activators of transcription [STAT]-induced STAT inhibitor) proteins are a family of cytokine-inducible negative regulators of cytokine signaling via Janus kinase (JAK)-STAT pathways. Given the evidence that the JAK-STAT pathway plays a critical role in the cardiovascular system, the primary objective of this study was to assess the effects of the CIS family on JAK-STAT signaling in the cardiovascular system in rats treated with cardiotrophin-1 (CT-1), an interleukin-6 family of cytokines. Intravenous injection of 20 microgram/kg body weight of CT-1 induced a transient, marked increase in STAT3 activation in various tissues, including heart and lung, and subsequent upregulation of 2 members of the CIS family, JAK-binding protein (JAB)/SOCS-1/SSI-1 and CIS3/SOCS-3/SSI-3, in the same tissues. It was also observed that CIS3 was directly associated with JAK2 in vivo. Pretreatment with the same dose of CT-1 60 minutes before significantly attenuated the STAT3 activation induced by a second injection of CT-1. We previously reported that intravenous injection of CT-1 results in the nitric oxide (NO)-dependent hypotension accompanied by the induction of inducible NO synthase mRNA. In rats pretreated with CT-1, the induction of inducible NO synthase mRNA or hypotension by subsequent CT-1 injection was not observed. Forced expression of JAB or CIS3, but not other CISs, directly blocked CT-1-induced STAT3 activation in 293 cells. These results suggest that JAB and CIS3 serve as endogenous inhibitors of CT-1-mediated JAK-STAT signaling in the cardiovascular system in vivo.

The neuron-restrictive silencer element-neuron-restrictive silencer factor system regulates basal and endothelin 1-inducible atrial natriuretic peptide gene expression in ventricular myocytes

Induction of the atrial natriuretic peptide (ANP) gene is a common feature of ventricular hypertrophy. A number of cis-acting enhancer elements for several transcriptional activators have been shown to play central roles in the regulation of ANP gene expression, but much less is known about contributions made by transcriptional repressors. The neuron-restrictive silencer element (NRSE), also known as repressor element 1, mediates repression of neuronal gene expression in nonneuronal cells. We found that NRSE, which is located in the 3' untranslated region of the ANP gene, mediated repression of ANP promoter activity in ventricular myocytes and was also involved in the endothelin 1-induced increase in ANP gene transcription. The repression was conferred by a repressor protein, neuron-restrictive silencer factor (NRSF). NRSF associated with the transcriptional corepressor mSin3 and formed a complex with histone deacetylase (HDAC) in ventricular myocytes. Trichostatin A (TSA), a specific HDAC inhibitor, relieved NRSE-mediated repression of ANP promoter activity, and chromatin immunoprecipitation assays revealed the involvement of histone deacetylation in NRSE-mediated repression of ANP gene expression. Furthermore, in myocytes infected with recombinant adenovirus expressing a dominant-negative form of NRSF, the basal level of endogenous ANP gene expression was increased and a TSA-induced increase in ANP gene expression was apparently attenuated, compared with those in myocytes infected with control adenovirus. Our findings show that an NRSE-NRSF system plays a key role in the regulation of ANP gene expression by HDAC in ventricular myocytes and provide a new insight into the role of the NRSE-NRSF system outside the nervous system.

A genetic model provides evidence that the receptor for atrial natriuretic peptide (guanylyl cyclase-A) inhibits cardiac ventricular myocyte hypertrophy

Guanylyl cyclase-A (NPR-A; GC-A) is the major and possibly the only receptor for atrial natriuretic peptide (ANP) or B-type natriuretic peptide. Although mice deficient in GC-A display an elevated blood pressure, the resultant cardiac hypertrophy is much greater than in other mouse models of hypertension. Here we overproduce GC-A in the cardiac myocytes of wild-type or GC-A null animals. Introduction of the GC-A transgene did not alter blood pressure or heart rate as a function of genotype. Cardiac myocyte size was larger (approximately 20%) in GC-A null than in wild-type animals. However, introduction of the GC-A transgene reduced cardiac myocyte size in both wild-type and null mice. Coincident with the reduction in myocyte size, both ANP mRNA and ANP content were significantly reduced by overexpression of GC-A, and this reduction was independent of genotype. This genetic model, therefore, separates a regulation of cardiac myocyte size by blood pressure from local regulation by a GC-mediated pathway.

The heart is a source of circulating cardiotrophin-1 in humans

Cardiotrophin-1 (CT-1) is a new member of the interleukin (IL)-6 family of cytokines and one of the endogenous ligands for gp130 signaling pathways in the heart, which has potent hypertrophic and survival effects on cardiac myocytes. However, the clinical significance of CT-1 is poorly understood, mainly because there is no widely applicable specific and sensitive assay system for measuring plasma levels of circulating CT-1. We therefore developed a competitive radioimmunoassay (RIA) for human CT-1 with rabbit antiserum recognizing the N-terminus region of human CT-1 and using recombinant human CT-1 as a calibrator. The assay displays no cross-reactivities with any of the IL-6 family of cytokines including IL-11, leukemia inhibitory factor, ciliary neurotrophic factor, and oncostatin M. The lower detection limit in buffer was found to be 43 fmol/ml, and the working range was 120-8300 fmol/ml (CV < 15%). This RIA directly recognizes CT-1-like immunoreactivity in human plasma with a mean value of 571 +/- 75 fmol/ml (mean +/- SD) in healthy volunteers. The RIA coupled with gel filtration chromatographic analyses showed that the major molecular form of circulating CT-1 corresponds to recombinant full-length human CT-1. Moreover, there is a significant increase in the plasma CT-1 concentration from the aorta and coronary sinus, which clearly indicates that the heart secretes CT-1 via the coronary sinus into the peripheral circulation. This RIA should serve as a powerful tool for investigating the clinical significance of CT-1.

Replication protein A1 reduces transcription of the endothelial nitric oxide synthase gene containing a -786T-->C mutation associated with coronary spastic angina

We recently reported that a mutation (-786T-->C) in the promoter region of the endothelial nitric oxide synthase (eNOS) gene reduced transcription of the gene and was strongly associated with coronary spastic angina and myocardial infarction. To elucidate the molecular mechanism for the reduced eNOS gene transcription, we have now purified a protein that specifically binds to the mutant allele in nuclear extracts from HeLa cells. The purified protein was identical to replication protein A1 (RPA1), known as a single-stranded DNA binding protein essential for DNA repair, replication and recombination. In human umbilical vein endothelial cells, inhibition of RPA1 expression using antisense oligonucleotide restored transcription driven by the mutated promoter sequence, whereas, conversely, overexpression of RPA1 further reduced it. RPA1 was similarly detected in placenta and eNOS mRNA levels in placentas carrying the -786T-->C mutation were significantly lower than in placentas without it. The functional importance of the diminished eNOS expression was revealed by the finding that serum nitrite/nitrate levels among individuals carrying the -786T-->C mutation were significantly lower than among those without the mutation. RPA1 thus apparently functions as a repressor protein in the -786T-->C mutation-related reduction of eNOS gene transcription associated with the development of coronary artery disease.

Lack of association between T-786-->C mutation in the 5'-flanking region of the endothelial nitric oxide synthase gene and essential hypertension

Accumulating evidence strongly suggests that an alteration in nitric oxide metabolism is involved in the pathogenesis of hypertension. We recently found 2 polymorphisms in the endothelial nitric oxide synthase (eNOS) gene, a Glu298Asp missense variant in exon 7 and a T-786-->C variant in the 5'-flanking region, which are not linked to each other. In our previous reports, we showed a positive association between the Glu298Asp variant and essential hypertension, myocardial infarction, and coronary spastic angina. We also revealed that the T-786-->C variant is strongly associated with coronary spastic angina and leads to the reduction of the eNOS gene promoter activity. To further investigate the genetic involvement of the eNOS gene in essential hypertension, we examined the frequency of T-786-->C variant in two independent populations of persons with essential hypertension in Kyoto (n=215) and Kumamoto (n=186) and compared the frequency with that in each age- and gender-matched control (233 controls in Kyoto and 223 controls in Kumamoto). In both groups, the frequency of T-786-->C variant was similar in patients with hypertension and normal controls. In conclusion, the T-786-->C variant was not positively associated with essential hypertension. Given the evidence of positive association of another polymorphism in the eNOS gene, the Glu298Asp polymorphism, with essential hypertension, special attention will be required to interpret the results of a case-control study for genetic risk factors.

Genetic models reveal that brain natriuretic peptide can signal through different tissue-specific receptor-mediated pathways

Brain natriuretic peptide (BNP), a hormone produced primarily by the cardiac ventricle, is thought to be involved in a variety of homeostatic processes through its cognate receptor, guanylyl cyclase A (GC-A). We previously created transgenic mice overexpressing BNP under the control of the liver-specific human serum amyloid P component promoter (BNP-transgenic mice) and demonstrated that they exhibit reduced blood pressure and cardiac weight accompanied by an elevation of plasma cGMP concentrations and marked skeletal overgrowth through the activation of endochondral ossification. To address whether BNP exerts its biological effects solely through GC-A, we produced BNP-transgenic mice lacking GC-A (BNP-Tg/GC-A-/- mice) and examined their cardiovascular and skeletal phenotypes. The GC-A-/- mice are hypertensive with cardiac hypertrophyrelative to wild-type littermates, which is not alleviated by overexpression of BNP in BNP-Tg/GC-A-/- mice. The BNP-Tg/GC-A-/- mice, however, continue to exhibit marked longitudinal growth of vertebrae and long bones comparably to BNP-Tg mice. This study provides genetic evidence that BNP reduces blood pressure and cardiac weight through GC-A, whereas it dramatically alters endochondral ossification in the absence of this receptor. Therefore, the BNP-Tg/GC-A-/- mice provide the first experimental model demonstrating that this natriuretic peptide can signal in a tissue-specific manner through a receptor other than GC-A.

Cardiotrophin-1 phosphorylates akt and BAD, and prolongs cell survival via a PI3K-dependent pathway in cardiac myocytes

Growth factors and cytokines trigger survival signaling in a wide variety of cell systems, including cardiac myocytes. Participation of the phosphatidylinositol 3-OH kinase (PI3K)/Akt pathway in survival signaling has already been described in some cell types, but its involvement in the survival of cardiac myocytes is as yet unknown. Recently, CT-1, an interleukin 6-related cytokine, was shown to have survival-promoting, anti-apoptotic effects on cultured cardiac myocytes. However, roles of PI3K-dependent pathways in this signaling have not been elucidated. In the present study, therefore, we examined the participation of the PI3K/Akt pathway in CT-1-induced, survival-promoting signaling in cultured ventricular myocytes. It was found that CT-1 phosphorylated and activated Akt, and the effect was blocked by the PI3K inhibitors LY294002 and wortmannin. CT-1 also phosphorylated the pro-apoptotic factor, BAD, and the BAD phosphorylation was inhibited by LY294002, suggesting that phosphorylation of BAD is one of the key events by which the PI3K/Akt pathway mediates CT-1-induced survival signaling. Further, CT-1 PI3K-dependently prolonged the survival of serum-starved ventricular myocytes by preventing apoptosis. In summary, our findings show that PI3K-dependent survival signals contribute to CT-1-mediated ventricular myocyte survival. In vivo, the death of ventricular myocytes leads to heart failure, and downregulation of survival signals and/or augmentation of pro-apoptotic signals are likely to be important components of disease processes. Thus, the extent to which CT-1 and the PI3K/Akt pathway mitigate such pathological processes, in vivo, is an important question for the future.

Effects of cardiotrophin-1 on hemodynamics and endocrine function of the heart

Cardiotrophin-1 (CT-1), a member of the interleukin-6 superfamily of cytokines, possesses hypertrophic actions and atrial natriuretic peptide (ANP)-producing activity in vitro. The goal of our study is to elucidate whether CT-1 affects the cardiovascular system in vivo. Intravenous injection of CT-1 (4-100 microg/kg) in conscious rats evoked significant declines in blood pressure and reflex increases in heart rate (HR) in a dose-dependent manner. CT-1 induced no significant change in cardiac output (from 260.7 +/- 11.0 to 264.7 +/- 26.6 ml. min(-1). kg(-1), P = not significant), which was compatible with the results from isolated perfused rat hearts; HR, change in pressure over time, left ventricular developed pressure, and perfusion pressure were unaffected. Northern blot and RT-PCR analyses revealed that CT-1 increased expression of inducible nitric oxide synthase (iNOS) in lung and aorta but not in heart or liver. Pretreatment with aminoguanidine, a specific iNOS inhibitor, inhibited both iNOS mRNA production and the depressor effect of CT-1. Interestingly, CT-1 increased ventricular expression of ANP and brain natriuretic peptide (BNP). The data demonstrate that CT-1 elicits its hypotensive effect via a nitric oxide-dependent mechanism and that CT-1 induces ANP and BNP mRNA expression in vivo.

Outside-in signalling of fibronectin stimulates cardiomyocyte hypertrophy in cultured neonatal rat ventricular myocytes

Cardiac hypertrophy involves the accumulation of extracellular matrix proteins, such as fibronectin, leading to increasing myocardial stiffness, ventricular dysfunction and heart failure. To better understand the possible role of extracellular matrix-evoked intracellular signalling in ventricular myocytes, we investigated the effect of fibronectin on myocyte hypertrophic responses using cell culture models. Cell size in myocytes cultured on fibronectin-coated dishes was three times larger than that grown on non-coated dishes. However, the number of cells on fibronectin-coated dishes was not changed throughout the experiment. Protein synthesis was significantly increased by fibronectin, as were synthesis of atrial and brain natriuretic peptides. Fibronectin also elicited actin reorganization, co-localization of beta 1 integrin and vinculin, formation of focal adhesions and tyrosine phosphorylation of focal adhesion kinase in myocytes. These fibronectin-mediated effects were inhibited in a dose-dependent manner by GRGDSP, a competitive antagonist of the fibronectin receptors; GRGDSP had no effect on cell number or viability. Blocking antibody for beta 1 and beta 3 integrin significantly suppressed fibronectin-induced secretion of natriuretic peptides. Myocyte hypertrophy was observed in myocyte-nonmyocyte co-culture that reflects more closely the myocyte environment in vivo. GRGDSP may also suppress the myocyte hypertrophic response in the co-culture. These findings demonstrate that the interaction of fibronectin and RGD-dependent integrins is involved in the hypertrophic responses of myocyte in vitro, and suggest that extracellular matrix proteins such as fibronectin are not merely passive adhesive molecules but are active participants in processes leading to myocyte hypertrophy.

A genetic model defines the importance of the atrial natriuretic peptide receptor (guanylyl cyclase-A) in the regulation of kidney function

Disruption of the atrial natriuretic peptide (ANP) receptor [guanylyl cyclase-A (GC-A)] gene yields mice with a salt-resistant form of hypertension, raising fundamental questions on the role of ANP in acute regulation of the kidney. Here, we show that water intake, food consumption, stool weight, urine volume, and sodium excretion are not significantly different between wild-type and GC-A null mice on standard rodent chow (0.7% NaCl) or a high-salt diet (8% NaCl). In conscious mice with an indwelling catheter, the infusion of a physiological saline solution containing 4% BSA resulted in a marked natriuresis/diuresis in wild-type mice but no response in GC-A null animals. When physiological saline was given by gavage, however, the kidney response of wild-type and null mice was equivalent, raising the possibility that the gastrointestinal tract can directly regulate kidney function. However, administration of 0.9% saline through an intraperitoneal route also resulted in equal kidney responses in wild-type and null mice. When 0.9% NaCl lacking protein was infused i.v., wild-type and null mice both responded at the kidney level. Thus, GC-A appears dispensable for regulation of sodium/water excretion in response to changes in dietary sodium concentration, but likely becomes critical in volume expansions where the isooncotic pressure remains constant, such as head-out immersion or the initial and correctable stages of congestive heart failure.

The effects of the selective ROCK inhibitor, Y27632, on ET-1-induced hypertrophic response in neonatal rat cardiac myocytes--possible involvement of Rho/ROCK pathway in cardiac muscle cell hypertrophy

A small GTPase, Rho, participates in agonist-induced cytoskeletal organization and gene expression in many cell types including cardiac myocytes. However, little is known about the functions of Rho's downstream targets in cardiac myocytes. We examined the role of ROCK, a downstream target of Rho, in ET-1-induced hypertrophic response. Y27632, a selective ROCK inhibitor, inhibited ET-1-induced increases in natriuretic peptide production, cell size, protein synthesis, and myofibrillar organization. In addition, a dominant-negative mutant of p160ROCK suppressed ET-1-induced transcription of the BNP gene. These findings suggest that the Rho/ROCK pathway is an important component of ET-1-induced hypertrophic signals in cardiac myocytes.

Cloacal inoculation with the Connecticut strain of avian infectious bronchitis virus: an attempt to produce nephropathogenic virus by in vivo passage using cloacal inoculation

Avian infectious bronchitis virus (IBV) strain Connecticut A-5968 isolated from respiratory tissue of chickens in USA in the 1960s, is considered as representative of respiratory disease causing IBV strains. Specific pathogen free chicks inoculated with the strain via the cloaca replicated the virus more rapidly in their kidneys than did chicks inoculated with the same virus intratracheally. Virus passaged thirteen-times via the cloaca caused stronger nephrotropism and nephropathogenicity than the parent virus. It is suggested that cloacal inoculation of IBV provides new and interesting information concerning the mechanisms of nephropathogenicity of IBV which has became increasingly important worldwide during the last ten years.

Physiological regulation of blood pressure and kidney function by guanylyl cyclase isoforms

Guanylyl cyclase isoforms can serve as receptors for various molecules including atrial natriuretic peptide, brain natriuretic peptide, C-type natriuretic peptide and nitric oxide. It has been speculated these signaling pathways are important regulators of cardiovascular and renal physiology. Within the past year, gene targeting in particular has strengthened this speculation, suggesting critical roles of guanylyl cyclase receptors in both the chronic and acute regulation of blood pressure.

The heart communicates with the kidney exclusively through the guanylyl cyclase-A receptor: acute handling of sodium and water in response to volume expansion

Disruption of guanylyl cyclase-A (GC-A) results in mice displaying an elevated blood pressure, which is not altered by high or low dietary salt. However, atrial natriuretic peptide (ANP), a proposed ligand for GC-A, has been suggested as critical for the maintenance of normal blood pressure during high salt intake. In this report, we show that infusion of ANP results in substantial natriuresis and diuresis in wild-type mice but fails to cause significant changes in sodium excretion or urine output in GC-A-deficient mice. ANP, therefore, appears to signal through GC-A in the kidney. Other natriuretic/diuretic factors could be released from the heart. Therefore, acute volume expansion was used as a means to cause release of granules from the atrium of the heart. That granule release occurred was confirmed by measurements of plasma ANP concentrations, which were markedly elevated in both wild-type and GC-A-null mice. After volume expansion, urine output as well as urinary sodium and cyclic GMP excretion increased rapidly and markedly in wild-type mice, but the rapid increases were abolished in GC-A-deficient animals. These results strongly suggest that natriuretic/diuretic factors released from the heart function exclusively through GC-A.

Regulation of secretion and clearance of C-type natriuretic peptide in the interaction of vascular endothelial cells and smooth muscle cells

OBJECTIVE

To clarify the significance of C-type natriuretic peptide in the interaction between endothelial cells and vascular smooth muscle cells by investigating the endothelial production of C-type natriuretic peptide and the clearance mechanism of C-type natriuretic peptide using the endothelial cells-smooth muscle cells co-culture system.

RESULTS

Secretion of C-type natriuretic peptide in the direct co-culture of endothelial cells with smooth muscle cells elicited as much as a 60-fold increase compared with endothelial cells alone. The accumulation of intracellular cyclic GMP in the co-culture was consequently increased and the elevation of cyclic GMP level in the co-culture was abolished by the anti-C-type natriuretic peptide monoclonal antibody. The elevated cyclic GMP production in the co-culture was abolished by the anti-transforming growth factor-beta neutralizing antibody. Candoxatrilat (10(-6)-10(-4) mol/l), a neutral endopeptidase inhibitor, dose-dependently increased the concentrations of C-type natriuretic peptide in the culture medium with endothelial cells alone, but not in the endothelial cells-smooth muscle cells co-culture. The transcript of neutral endopeptidase messenger RNA was detected in endothelial cells but not in smooth muscle cells by reverse transcriptase polymerase chain reaction. Treatment with C-atrial natriuretic factor4-23 (10(-9)-10(-6) mol/l), the specific ligand for the clearance receptor of the natriuretic peptides, resulted in dose-dependent augmentation of C-type natriuretic peptide concentration and concomitant intracellular cyclic GMP production in the endothelial cells-smooth muscle cells co-culture but not in endothelial cells alone.

CONCLUSION

The present study demonstrated that direct interaction between endothelial cells and smooth muscle cells augments C-type natriuretic peptide secretion from endothelial cells through transforming growth factor-beta activation, and revealed that the enzymatic degradation is responsible for the steady state level of C-type natriuretic peptide in endothelial cells alone and that the receptor-mediated clearance mainly determines the augmented level of C-type natriuretic peptide in the interaction between endothelial cells and smooth muscle cells. The results taken together raise the possibility that endothelial C-type natriuretic peptide might play a role in regulation of vascular tone and remodelling.

Regulation of endothelial production of C-type natriuretic peptide in coculture with vascular smooth muscle cells. Role of the vascular natriuretic peptide system in vascular growth inhibition

Recently, we have demonstrated that C-type natriuretic peptide (CNP) is produced in vascular endothelial cells (ECs). In the present study, we investigated the interaction of ECs and vascular smooth muscle cells (SMCs) for endothelial production of CNP and its action on vascular growth, using the EC/SMC coculture system. The concentration of CNP-like immunoreactivity in the medium was increased 60-fold within 48 hours in the EC/SMC coculture with direct contact compared with that in EC alone. Northern blot analysis revealed the augmented expression of CNP mRNA in the EC/SMC coculture. The accumulation of intracellular cGMP in the coculture was concomitantly increased, and this response was blocked by anti-CNP monoclonal antibody and HS-142-1, a nonpeptide atrial natriuretic peptide receptor antagonist. The concentration of biologically active transforming growth factor-beta (TGF-beta) in the culture medium of the coculture with direct contact of ECs and SMCs was elevated to the level to stimulate endothelial production of CNP. Actually, the neutralizing antibody against TGF-beta abrogated the cGMP accumulation in the coculture. These results show that endothelial production of CNP in the EC/SMC coculture is at least in part regulated by TGF-beta. Furthermore, the conditioned medium from ECs stimulated by TGF-beta was demonstrated to have a growth-inhibitory effect on SMCs, which was abolished by anti-CNP monoclonal antibody and HS-142-1. The treatment with anti-CNP monoclonal antibody and HS-142-1 also significantly increased the cell number of the EC/SMC coculture. The present study reveals the pathophysiological significance of endothelial CNP as a paracrine/autocrine vascular regulator for vascular growth in the interaction of ECs and SMCs.

Altered gene expression of natriuretic peptide receptor subtypes in the kidney of stroke-prone spontaneously hypertensive rats

1. To elucidate the physiological and pathophysiological role of the natriuretic peptide system in the progression of hypertensive renal disease, we examined the gene expression of natriuretic peptide receptor subtypes, guanylate cyclase-A (GC-A), guanylate cyclase-B (GC-B) and clearance receptor (C receptor), in the kidney of stroke-prone spontaneously hypertensive rats (SHRSP) at 8 and 20 weeks of age, and compared them with their gene expression in age-matched Wistar-Kyoto (WKY) rats. 2. Northern blot analyses revealed that messages for three natriuretic peptide receptor subtypes were expressed in the kidney, and their expressions were higher in the glomeruli than in the whole kidney in each strain. 3. In 20 week old rats with established hypertension, the glomerular concentration of GC-A mRNA was significantly higher in SHRSP than in WKY. The concentrations of GC-B and C receptor mRNA in the glomeruli tended to increase and decrease, respectively, but they were not statistically significant in SHRSP. 4. In 8 week old rats, the glomerular concentrations of GC-A, GC-B and C receptor mRNA were not significantly different between SHRSP and WKY. 5. This study demonstrates that in the progression of hypertension, the expression of GC-A, which mediates biological actions of natriuretic peptides, is enhanced in the kidney of SHRSP compared to that of WKY. Together with the augmented secretion of the ligands previously revealed, altered expression of natriuretic peptide receptor subtypes in SHRSP may have a deterrent role in the development of hypertension and its renal complications.

Endothelin-induced activation of mitogen-activated protein kinases in glomerular mesangial cells from normotensive and stroke-prone spontaneously hypertensive rats

1. Kinase assay in myelin basic protein (MBP) containing polyacrylamide gels revealed that endothelin-1 (ET-1) and ET-3 increased MBP kinase activities in glomerular mesangial cells (MC) from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rat (SHRSP). ET-1 stimulated MBP kinase activities more potently than ET-3. 2. Immunoprecipitation with anti-41-kDa MAPK antiserum showed that the MBP kinases activated by ET-1 correspond to 43- and 41-kDa MAPK. 3. Since Phorbol 12-myristate 13-acetate, a direct activator of protein kinase C, also activated MAPK, protein kinase C was suggested to mediate ET-induced activation of MAPK. 4. These results suggest that MAPK may mediate the ET actions in glomerular mesangial cells from normotensive rats as well as spontaneously hypertensive rats. Since ET is produced by vascular endothelial cells of the kidney and glomerular mesangial cells, the ET signalling pathway may have some physiological and pathophysiological significance in vivo glomerulus.

Salt-resistant hypertension in mice lacking the guanylyl cyclase-A receptor for atrial natriuretic peptide

Around half of all humans with essential hypertension are resistant to salt (blood pressure does not change by more than 5 mm Hg when salt intake is high), and although various inbred strains of rats display salt-insensitive elevated blood pressure, a gene defect to account for the phenotype has not been described. Atrial natriuretic peptide (ANP) is released from the heart in response to atrial stretch and is thought to mediate its natriuretic and vaso-relaxant effects through the guanylyl cyclase-A receptor (GC-A). Here we report that disruption of the GC-A gene results in chronic elevations of blood pressure in mice on a normal salt diet. Unexpectedly, the blood pressure remains elevated and unchanged in response to either minimal or high salt diets. Aldosterone and ANP concentrations are not affected by the genotype. Therefore, mutations in the GC-A gene could explain some salt-resistant forms of essential hypertension and, coupled with previous work, further suggest that the GC-A signaling pathway dominates at the level of peripheral resistance, where it can operate independently of ANP.