Role of calcium-activated potassium channels in the genesis of 3,4-diaminopyridine-induced periodic contractions in isolated canine coronary artery smooth muscles

We found that 3,4-diaminopyridine (3,4-DAP), a voltage-gated potassium channel (K(V)) inhibitor, elicits pH-sensitive periodic contractions (PCs) of coronary smooth muscles. Underlying mechanisms of PCs, however, remained to be elucidated. The present study was performed to examine the roles of ion channels in the genesis of PCs. To determine the electromechanical changes of smooth muscles, isolated coronary arterial rings from beagles were suspended in organ chambers filled with Krebs-Henseleit solution, and 10(-2) M 3,4-DAP was added to elicit PCs. 3,4-DAP caused periodic spike-and-plateau depolarization accompanied by contraction. PCs were not produced when the CaCl(2) concentration in the chamber was ≤ 0.3 × 10(-3) or ≥ 10(-2) M. PCs were eliminated by a CaCl(2) concentration ≥ 5 × 10(-3) M or by lowering pH below 7.20 with HCl and recovered by the addition of iberiotoxin or charybdotoxin, which inhibit large-conductance calcium-activated potassium channels (K(Ca)), or by elevating pH above 7.35 with NaOH. PCs, as well as the spike-and-plateau depolarization, were eliminated by nifedipine, which inhibits L-type voltage-gated calcium channels (Ca(V)). Influx of Ca(2+) through L-type Ca(V), which was opened because closing of K(Ca), secondary to 3,4-DAP-induced closing of K(V), resulted in contraction; the intracellular Ca(2+) increased by this influx opened K(Ca), leading to closure of Ca(V) and consequent cessation of Ca(2+) influx with resultant relaxation. These processes were repeated spontaneously to cause PCs. H(+) and OH(-) were considered to act as the opener and closer of K(Ca), respectively.

The roles of transforming growth factor-β and Smad3 signaling in adipocyte differentiation and obesity

We aimed at elucidating the roles of transforming growth factor (TGF)-β and Smad3 signaling in adipocyte differentiation (adipogenesis) and in the pathogenesis of obesity. TGF-β/Smad3 signaling in white adipose tissue (WAT) was determined in genetically obese (ob/ob) mice. The effect of TGF-β on adipogenesis was evaluated in mouse embryonic fibroblasts (MEF) isolated both from WT controls and Smad3 KO mice by Oil red-O staining and gene expression analysis. Phenotypic analyses of high-fat diet (HFD)-induced obesity in Smad3 KO mice compared to WT controls were performed. TGF-β/Smad3 signaling was elevated in WAT from ob/ob mice compared to the controls. TGF-β significantly inhibited adipogenesis in MEF, but the inhibitory effects of TGF-β on adipogenesis were partially abolished in MEF from Smad3 KO mice. TGF-β inhibited adipogenesis independent from the Wnt and β-catenin pathway. Smad3 KO mice were protected against HFD-induced insulin resistance. The size of adipocytes from Smad3 KO mice on the HFD was significantly smaller compared to the controls. In conclusion, the TGF-β/Smad3 signaling pathway plays key roles not only in adipogenesis but also in development of insulin resistance.

Functional medial thickening and folding of the internal elastic lamina in coronary spasm

Although there are a number of studies on vasospastic angina, the structural changes at the cellular level that occur in the coronary arterial wall during spasm are not well known. Coronary spasm was induced by brushing the coronary adventitia in nine anesthetized beagles, and structural changes in the spastic coronary segments were examined by light and electron microscopy, making comparisons with the adjacent nonspastic segments. The % diameter stenosis of the spastic segments as measured angiographically was 79.4±12% (mean±SD). Light microscopic changes in the spastic and nonspastic segments were as follows: medial thickness 1,512 vs. 392 μm (P<0.0001) and % diameter and % area stenoses of spastic segment 81.0% and 96.5%, respectively, indicating that spasm was induced by medial thickening. Circular smooth muscle cells (SMCs) in the media were arranged in parallel with the internal (IEL) and external (EEL) elastic lamina in nonspastic segments but radially rearranged in spastic segments. SMCs were classified by their patterns of connection to IEL into six types by electron microscopy. Of these, three contracted and pulled the IEL toward the EEL, causing folding of the IEL and waving of EEL resulting in thickening of the media and narrowing of the lumen. We conclude that coronary spasm was elicited by radial rearrangement of the medial SMCs due to their own contraction and resultant medial thickening and folding of IEL, creating a piston effect to narrow the lumen, i.e., spasm.

Insulin signaling to the glomerular podocyte is critical for normal kidney function

Diabetic nephropathy (DN) is the leading cause of renal failure in the world. It is characterized by albuminuria and abnormal glomerular function and is considered a hyperglycemic "microvascular" complication of diabetes, implying a primary defect in the endothelium. However, we have previously shown that human podocytes have robust responses to insulin. To determine whether insulin signaling in podocytes affects glomerular function in vivo, we generated mice with specific deletion of the insulin receptor from their podocytes. These animals develop significant albuminuria together with histological features that recapitulate DN, but in a normoglycemic environment. Examination of "normal" insulin-responsive podocytes in vivo and in vitro demonstrates that insulin signals through the MAPK and PI3K pathways via the insulin receptor and directly remodels the actin cytoskeleton of this cell. Collectively, this work reveals the critical importance of podocyte insulin sensitivity for kidney function.

Halofuginone prevents extracellular matrix deposition in diabetic nephropathy

Transforming growth factor-beta (TGF-beta) is known to promote the accumulation of extracellular matrix (ECM) and the development of diabetic nephropathy. Halofuginone, an analog of febrifugine, has been shown to block TGF-beta(1) signaling and subsequent type I collagen production. Here, the inhibitory effect of halofuginone on diabetic nephropathy was examined. Halofuginone suppressed Smad2 phosphorylation induced by TGF-beta(1) in cultured mesangial cells. In addition, the expression of TGF-beta type 2 receptor decreased by halofuginone. Halofuginone showed an inhibitory effect on type I collagen and fibronectin expression promoted by TGF-beta(1). An in vivo experiment using db/db mice confirmed the ability of halofuginone to suppress mesangial expansion and fibronectin overexpression in the kidneys. Moreover, an analysis of urinary 8-OHdG level and dihydroethidium fluorescence revealed that halofuginone reduced oxidative stress in the glomerulus of db/db mice. These data indicate that halofuginone prevents ECM deposition and decreases oxidative stress, thereby suppressing the progression of diabetic nephropathy.

Influence of C-peptide on early glomerular changes in diabetic mice

BACKGROUND

C-peptide has been shown to ameliorate diabetes-induced functional and structural renal changes in animal models as well as in patients with type 1 diabetes. This study aims to examine the molecular effects of C-peptide on early glomerular changes in a mouse model of type 1 diabetes.

METHODS

Fourteen days after induction of diabetes by streptozotocin (STZ), the animals received rat C-peptide for either 24 h or 7 days. Urinary albumin excretion was measured by ELISA. Glomerular mRNA expression of the transforming growth factor (TGF)-beta(1) and type IV collagen was quantified by real-time PCR. The effect of C-peptide on type IV collagen gene expression in cultured murine podocytes was also examined.

RESULTS

C-peptide decreased urinary albumin excretion from 0.29 to 0.18 microg/min (-40.7%, P < 0.01). The transcript level of (alpha3)IV collagen in glomeruli was up-regulated 2.2-fold in diabetic mice and was inhibited by 45-70% (P < 0.05) upon C-peptide treatment. C-peptide suppressed glomerular expression of TGF-beta(1) by 36.6% after 7 days (P < 0.05) but not 24 h after injection. In vitro studies using cultured podocytes revealed that C-peptide dose-dependently inhibited TGF-beta-induced up-regulation of type IV collagen. Moreover, both pertussis toxin (PTX) and a specific inhibitor for extracellular signal-regulated kinase (ERK) pathway reversed the inhibitory effect of C-peptide on TGF-beta. Finally, C-peptide was shown to up-regulate the activity of ERK in podocytes.

CONCLUSIONS

These findings indicate that C-peptide suppresses specific aspects of early glomerular changes in a mouse model of diabetes and that the effect is at least in part mediated via interaction with the TGF-beta signal in glomerular podocytes.

[A case of an elderly type 2 diabetes who had severe diabetic nephropathy without retinopathy]

We encountered a man who developed severe diabetic nephropathy without progression of diabetic retinopathy. He had a 14-year history of diabetes, and had been treated with sulfonylurea, and his HbA1c remained around 6.5%. He was admitted because of systemic edema and dyspnea on effort Laboratory data revealed renal failure and nephrotic syndrome, whereas there was no symptom of diabetic retinopathy. Since diabetic nephropathy usually progresses in parallel with retinopathy, it is atypical to develop severe nephropathy without retinopathy. In this case, longstanding hypertension and his genetic background including angiotensin converting enzyme D/I polymorphism might have played an important role in development of diabetic nephropathy.

Targeted disruption of TGF-beta-Smad3 signaling leads to enhanced neointimal hyperplasia with diminished matrix deposition in response to vascular injury

The role of transforming growth factor (TGF)-beta and its signal in atherogenesis is not fully understood. Here, we examined mice lacking Smad3, a major downstream mediator of TGF-beta, to clarify the precise role of Smad3-dependent signaling in vascular response to injury. Femoral arteries were injured in wild-type and Smad3-null (null) male mice on C57Bl/6 background. Histopathological evaluation of the arteries 1 to 3 weeks after the injury revealed significant enhancement of neointimal hyperplasia in null compared with wild-type mice. Transplantation of null bone marrow to wild-type mice did not enhance neointimal thickening, suggesting that vascular cells in situ play a major role in the response. Null intima contained more proliferating smooth muscle cells (SMC) with less amount of collagen compared with wild-type intima. TGF-beta caused significant inhibition of cellular proliferation in wild-type aortic SMC, whereas the growth of null SMC was only weakly inhibited by TGF-beta in vitro, indicating a crucial role of Smad3 in the growth inhibitory function. On the other hand, Smad3-deficiency did not attenuate chemotaxis of SMC toward TGF-beta. TGF-beta increased transcript level of alpha2 type I collagen and tissue inhibitor of metalloproteinases-1, and suppressed expression and activity of matrix metalloproteinases in wild-type SMC. However, these effects of TGF-beta were diminished in null SMC. Our findings altogether show that the loss of Smad3 pathway causes enhanced neointimal hyperplasia on injury through modulation of growth and matrix regulation in vascular SMC. These results indicate a vasculoprotective role of endogenous Smad3 in response to injury.

IgE-dependent enhancement of Th2 cell-mediated allergic inflammation in the airways

T helper 2 (Th2) cell-derived cytokines, including interleukin (IL)-4, IL-5 and IL-13, play important roles in causing allergic airway inflammation. In contrast to Th2 cells, however, the role of IgE and mast cells in inducing allergic airway inflammation is not understood fully. In the present study, we addressed this point using transgenic mice expressing trinitrophenyl (TNP)-specific IgE (TNP-IgE mice), which enable us to investigate the role of IgE without the influence of antigen-specific T cell activation and other immunoglobulins. When the corresponding antigen, TNP-BSA, was administered intranasally to TNP-IgE mice, a large number of CD4+ T cells were recruited into the airways. In contrast, TNP-BSA administration did not induce eosinophil recruitment into the airways or airway hyperreactivity. Furthermore, when ovalbumin (OVA)-specific Th2 cells were transferred to TNP-IgE mice and the mice were challenged with inhaled OVA, TNP-BSA administration increased OVA-specific T cell recruitment and then enhanced Th2 cell-mediated eosinophil recruitment into the airways. These results indicate that IgE-induced mast cell activation principally induces CD4+ T cell recruitment into the airways and thus plays an important role in enhancing Th2 cell-mediated eosinophilic airway inflammation by recruiting Th2 cells into the site of allergic inflammation.

High glucose-induced upregulation of osteopontin is mediated via Rho/Rho kinase pathway in cultured rat aortic smooth muscle cells

OBJECTIVE

Osteopontin is upregulated in the diabetic vascular wall and in vascular smooth muscle cells cultured under high glucose concentration. In the present study, we analyzed the mechanism of high glucose-induced upregulation of osteopontin in cultured rat aortic smooth muscle cells.

METHODS AND RESULTS

We found that an inhibitor of Rho-associated protein kinase, Y-27632, suppressed osteopontin mRNA expression under high glucose concentration. Transfection of cells with a constitutive active Rho mutant, pSRalpha-myc-RhoDA, enhanced osteopontin mRNA expression. Furthermore, incubation of cells under high glucose concentration activated Rho, indicating that Rho/Rho kinase pathway mediates high-glucose-stimulated osteopontin expression. Treatment of cells with an inhibitor of protein kinase C, GF109203X, and azaserine, an inhibitor of the hexosamine pathway, suppressed high glucose-induced Rho activation. Glucosamine treatment was shown to activate Rho. Treatment of cells with an inhibitor of MEK1, PD98059, suppressed osteopontin mRNA expression under high glucose concentration. Incubation of cells under high glucose concentration activated ERK. Finally, transfection of cells with pSRalpha-myc-RhoDA also activated ERK.

CONCLUSIONS

In conclusion, our present findings support a notion that Rho/Rho kinase pathway functions downstream of protein kinase C and the hexosamine pathways and upstream of ERK in mediating high-glucose-induced upregulation of osteopontin expression.

Mice lacking Smad3 are protected against streptozotocin-induced diabetic glomerulopathy

Transforming growth factor-beta (TGF-beta) has been implicated in the development of diabetic glomerulopathy. In order to evaluate a role of Smad3, one of the major signaling molecules downstream of TGF-beta, in the pathogenesis of diabetic glomerulopathy, Smad3-null mice were made diabetic with streptozotocin injection and analyzed 4 weeks after induction of diabetes. Electron microscopy revealed that the thickness of glomerular basement membrane (GBM) in wild-type diabetic mice was significantly higher than that in non-diabetic mice, whereas no appreciable GBM thickening was found in Smad3-null diabetic mice. Urinary albumin excretion was dramatically increased in wild-type diabetic mice, whereas Smad3-null diabetic mice did not show any overt albuminuria. Northern blotting revealed that mRNA levels of fibronectin and alpha 3 chain of type IV collagen (alpha 3Col4) in renal cortex of wild-type diabetic mice were approximately twice as much as those of non-diabetic mice, whereas their mRNA levels were not increased in Smad3-null diabetic mice. Real-time polymerase chain reaction (PCR) also confirmed diabetes-induced upregulation of fibronectin and alpha 3Col4 in glomeruli of wild-type mice. Glomerular expression of TGF-beta 1, as assessed by real-time PCR, was enhanced to a similar degree in wild-type and smad3-null diabetic mice, indicating that the observed differences between wild-type and Smad3-null mice are not attributable to difference in the expression of TGF-beta 1. These data clearly demonstrate a critical role of Smad3 in the early phase of diabetic glomerulopathy. This may be due at least partly to the present findings that diabetes-induced upregulation of fibronectin and alpha 3Col4 is dependent on Smad3 function.

[A report of a case with Werner's syndrome suffering from end-stage renal failure]

A 54-year-old man was found to have hypertension at age 32, and a diagnosis of Werner's Syndrome was made at age 36 when he was examined for hyperlipidemia. Diabetes mellitus was found at age 42. Proteinuria appeared at age 49, and microscopic hematuria was seen at age 50. At age 51, serum creatinin level began to rise and atrophy of bilateral kidneys was observed by abdominal CT. There after, the renal function gradually worsened. At age 53, the serum creatinin level rose to 8.3 mg/dl, and systemic edema as well as loss of appetite appeared, resulting in the initiation of hemodialysis. In Werner's syndrome, though arteriosclerosis arises frequently, case reports with chronic renal failure are extremely rare. To investigate the cause of the renal dysfunction, renal biopsy was performed and the samples were histologically examined, revealing the presence of hypertensive glomerular changes. It is, thus, conceivable that hypertension had played a major role in the progression of renal failure in this case.

Bone Marrow-derived Vascular Cells in Response to Injury

Intimal hyperplasia is a key lesion for various vascular disorders such as atherosclerosis, postangioplasty restenosis and transplant arteriopathy. It has widely been accepted that intimal smooth muscle cells (SMC) originate from the medial layer in the same artery. However, recent studies suggest that bone marrow can also provide circulating progenitors for vascular SMC. Bone marrow-derived SMC participate in neointimal formation in animal models of allotransplantation, severe mechanical injury and hyperlipidemia-induced atherosclerosis. In human, transplantation arteriopathy also seems to involve circulating SMC, but their role in atherosclerosis and restenosis remains to be elucidated. Mobilization, differentiation and proliferation steps of SMC progenitors will provide promising targets for novel therapeutic approaches against proliferative vascular diseases.

Successful treatment of listerial brain abscess: a case report and literature review

Listerial brain abscess is extremely rare; only two cases have been reported in Japan. We encountered a female patient with immunoblastic lymphadenopathy, who developed listerial brain abscess after 8 years of treatment with antineoplastic agents and corticosteroids. Brain MRI revealed multiple space occupying lesions, suggesting abscesses which were possibly caused by hematogenous spread of the bacteria. Immediate blood culture enabled early diagnosis, and she entered into complete remission with high-dose ampicillin. Blood culture and brain imaging seem to play a crucial role in making an early diagnosis, and the administration of high dose of antibiotics is recommended for improvement of this disease.

Gait analysis of spastic walking in patients with cervical compressive myelopathy

To assess neurological status and to evaluate the effect of surgical decompression in patients with cervical myelopathy, we performed computerized gait analysis in 24 patients with cervical compressive myelopathy who showed spastic walking. Gait analysis was repeated during neurological follow-up that averaged 32.4 months. The gait pattern in patients with severe myelopathy was characterized by hyperextension of the knee in the stance phase without plantar flexion of the ankle in the swing phase, significantly reduced walking speed and step length, prolonged stance phase duration and decreased single-stance phase duration, and increased step width. The angle of flexion of the knee joint in the stance phase was significantly correlated with the Japanese Orthopaedic Association (JOA) score. Postoperative neurological improvement was associated with increased walking speed and decreased extension angle of the knee joint (single-stance phase and swing phase). Postoperatively, 12 patients had normalized extension of the knee in stance phase and their walking speed, cadence, stance phase duration, and single-stance phase duration, as well as step length and width, showed nonsignificant differences from these parameters in healthy controls. Our results show that kinesiological gait analysis is clinically useful for the functional assessment of the severity of spastic walking in cervical myelopathy.

Ligamentum flavum hematoma in the thoracic spine

We report a case of a hematoma of ligamentum flavum at T11-12 in a 66-year-old man who presented with progressive weakness of the right foot and numbness of both legs. Past history was negative and no precipitating episode of lower back sprain or trauma. The resected T11 and T12 laminas showed old hematoma with degenerative changes in the ligamentum flavum. Hematoma occurring in the thoracic spine has never been reported previously.

Expression of various growth factors for cell proliferation and cytodifferentiation during fracture repair of bone

We examined immunohistochemically the fracture repair process in rat tibial bone using antibodies to PCNA, BMP2, TGF-beta 1,-2,-3, TGF-beta R1,-R2, bFGF, bFGFR, PDGF, VEGF, and S-100. The peak level of cell proliferation as revealed by PCNA labelling appeared first in primitive mesenchymal cells and inflammatory cells at the fracture edges and neighboring periosteum at 2-days after fracture, followed by the peaks of periosteal primitive fibroblasts and chondroblasts, which appeared at fracture edges at 3- and 4-days after fracture, respectively. BMP2 was weakly positive in primitive mesenchymal cells, osteoblasts and chondroblasts. At 3-days post-fracture, periosteal osteoblasts produced osteoid tissue and callus with marrow spaces lined by osteoblasts and osteoclasts, and all primitive mesenchymal cells and osteoblasts were positive for TGF-beta 1,-2,-3, and TGF-beta R1,-R2. They were also positive for vascular growth factors bFGF, FGFR and PDGF, but negative for VEGF, and the peak of PCNA labelling of vascular endothelial cells in the marrow space was delayed to 4-days after fracture. Chondroblasts at fracture edges produced hypertrophic chondrocytes at 5-days after fracture and they were positive for TGF-beta 1,-2,-3, and TGF-beta R1,-R2. Primitive chondroblasts were positive for vascular growth factors VEGF as well as bFGF, FGFR, and the peak of PCNA labelling of vascular endothelial cells in the cartilage was at 5-days after fracture. Hypertrophic chondrocytes were also positive for these growth factors but negative for bFGF and bFGFR. S-100 protein-induced calcification was only positive on chondroblasts and hypertrophic chondrocytes. At 7-days after fracture, bone began to be formed from the cartilage at fracture edges, by a process similar to bone formation in the growth plate. Enchondral ossification established a bridge between both fracture edges and periosteal membranous ossification encompassed the fracture site like a sheath at 14 day after fracture. Our study of fracture repair of bone indicates that this process is complex and occurs through various steps involving various growth factors.