Polymorphisms of sorbitol dehydrogenase (SDH) gene and susceptibility to diabetic retinopathy

The polyol pathway consists of two enzymes aldose reductase (AR) and sorbitol dehydrogenase (SDH); the former is the first enzyme in the polyol pathway, that catalyzes the reduction of glucose to sorbitol, the latter is the second one, that converts sorbitol to fructose using by NAD(+) as a cofactor. We along with others have recently found that SDH activity, the second step in the polyol pathway, might make a greater contribution to the etiology of diabetic retinopathy than does the first step involving AR. In this paper, we propose a novel hypothesis that polymorphisms of SDH gene may be correlated with SDH gene expression levels in diabetic retinas, thus being a valuable genetic marker for diabetic retinopathy.

Can we identify novel angiogenesis inhibitors from cultured embryonic cells?

The first vascular structures in embryos are formed by vasculogensis, the de novo formation of blood vessels from angioblasts. However, angiogenesis, the sprouting of capillaries from pre-existing blood vessels, are also involved in the development of embryonic vascular system in certain organs, such as the kidney or the brain. These facts led us to speculate that embryonic tissues could produce potent angiogenesis inhibitors as well to refine the primitive vascular development. In the present study, we found that two different types of cultured human embryonic cells, 293T and WI-38, produced soluble factors that completely inhibited angiogenic effects of vascular endothelial growth factor on microvascular endothelial cells. Since angiogenesis is related to various pathological states, including tumor growth and metastasis and diabetic retinopathy, to identify novel potent angiogenesis inhibitors from cultured embryonic cells by differential display techniques or DNA microarray technology might be a valuable strategy to develop a novel therapeutic approach.

Pigment epithelium-derived factor prevents advanced glycation end products-induced monocyte chemoattractant protein-1 production in microvascular endothelial cells by suppressing intracellular reactive oxygen species generation

AIMS/HYPOTHESIS

Monocytes and macrophages accumulate in the lesion of the diabetic retina, which are most likely involved in the progression of diabetic retinopathy. The levels of monocyte chemoattractant protein-1 (MCP-1) in vitreous fluids were associated with the severity of proliferative diabetic retinopathy. Recently, pigment epithelium-derived factor has been shown to be involved in the pathogenesis of proliferative diabetic retinopathy. However, a role of pigment epithelium-derived factor in monocyte recruitments in diabetic retinopathy remains to be elucidated. In this study, we investigated effects of purified pigment epithelium-derived factor on AGE-induced reactive oxygen species generation, MCP-1 mRNA up-regulation and protein production in human cultured microvascular endothelial cells.

METHODS

The intracellular formation of reactive oxygen species was measured using the fluorescent probe CM-H(2)DCFDA. MCP-1 gene expression was analysed in quantitative reverse transcription-polymerase chain reaction. Monocyte chemoattractant protein-1 production by microvascular endothelial cells was measured with an ELISA system.

RESULTS

AGE increased intracellular reactive oxygen species generation in microvascular endothelial cells. Pigment epithelium-derived factor inhibited the AGE-induced reactive oxygen species generation in a dose-dependent manner. An anti-oxidant, N-acetylcysteine, or pigment epithelium-derived factor completely prevented the AGE-induced up-regulation of MCP-1 mRNA contents as well as protein production in microvascular endothelial cells.

CONCLUSIONS/INTERPRETATIONS

Pigment epithelium-derived factor inhibits the AGE-induced reactive oxygen species generation and the subsequent increase in MCP-1 production in microvascular endothelial cells. Our study suggests that substitution of pigment epithelium-derived factor could prevent the progression of diabetic retinopathy by attenuating the deleterious effects of AGE.

Angiotensin II-type 1 receptor interaction upregulates vascular endothelial growth factor messenger RNA levels in retinal pericytes through intracellular reactive oxygen species generation

The renin-angiotensin system has been implicated in the development and progression of atherosclerosis, thereby contributing to adverse cardiovascular events. However, its role in diabetic retinopathy remains to be elucidated. Since pericyte loss and dysfunction have been considered as one of the characteristic changes of the early phase of diabetic retinopathy, we investigated the effects of angiotensin II (Ang II) on the growth and function of bovine cultured retinal pericytes. Ang II stimulated intracellular reactive oxygen species (ROS) generation in pericytes in a dose-dependent manner. Telmisartan, a newly developed Ang II type 1 receptor antagonist, completely inhibited ROS generation in pericytes induced by Ang II. Ang II decreased DNA synthesis in pericytes, which was significantly prevented by an antioxidant N-acetylcysteine. Furthermore, telmisartan or N-acetylcysteine were found to completely inhibit the Ang II-induced upregulation of vascular endothelial growth factor messenger RNA levels in pericytes. The present results suggest that Ang II-type 1 receptor interaction could induce pericyte loss and dysfunction through intracellular ROS generation, thus being involved in the development and progression of diabetic retinopathy.

Angiotensin II stimulates platelet-derived growth factor-B gene expression in cultured retinal pericytes through intracellular reactive oxygen species generation

Platelet-derived growth factor-BB (PDGF-BB) is a potent mitogen and chemoattractant for microvascular endothelial cells and glial cells in the retina and is thus involved in the development of proliferative diabetic retinopathy. However, relatively little is known about the regulation of PDGF-B gene expression in retinal cells. In this study, we cloned partial complementary DNAs (cDNAs) encoding bovine PDGF-B and examined the effects of angiotensin II (Ang II), which is also implicated in the pathogenesis of diabetic retinopathy, on PDGF-B gene expression in bovine cultured retinal pericytes. Ang II was found to up-regulate PDGF-B messenger RNA (mRNA) levels in bovine retinal pericytes. Telmisartan, a newly developed Ang II type 1 receptor antagonist, or an antioxidant N-acetylcysteine significantly inhibited PDGF-B gene induction in Ang II-exposed pericytes. The present results suggest that Ang II-type 1 receptor interaction could stimulate PDGF-B gene expression in cultured retinal pericytes through intracellular reactive oxygen species generation and could thus be involved in the progression of diabetic retinopathy.

Nifedipine inhibits apoptotic cell death of cultured endothelial cells induced by tumor necrosis factor-alpha

Impaired endothelial cell (EC) growth and function have been suggested to be an initial event that leads to the development of atherosclerosis. We have very recently found that nifedipine, one of the most popularly used dihydropyridine-based calcium antagonists, prevented EC monocyte chemoattractant protein-1 production elicited by tumor necrosis factor-alpha (TNF-alpha through its antioxidative properties. However, the effects of nifedipine on EC growth and apoptosis are not fully understood. In this study, we investigated whether nifedipine could inhibit tumor necrosis factor (TNF)-alpha-induced growth retardation and apoptotic cell death in human umbilical vein ECs (HUVECs). TNF-alpha inhibited EC proliferation, which was significantly blocked by nifedipine or antioxidant N-acetylcysteine (NAC). Nifedipine or NAC was also found to significantly inhibit apoptotic cell death of TNF-alpha-exposed HUVECs. Our present study suggests that nifedipine may play a protective role against the development and progression of atherosclerosis by promoting EC repair through its antioxidative properties.

Role of advanced glycation end products (AGEs) and their receptor (RAGE) in the pathogenesis of diabetic microangiopathy

Diabetic vascular complication is a leading cause of acquired blindness, end-stage renal failure, a variety of neuropathies and accelerated atherosclerosis, which could account for disabilities and high mortality rates in patients with diabetes. Chronic hyperglycemia is essentially involved in the pathogenesis of diabetic micro- and macrovascular complications via various metabolic derangements. In this review, we discuss the molecular mechanisms of diabetic retinopathy and nephropathy, especially focusing on advanced glycation end products (AGEs) and their receptor (RAGE) system. Several types of AGE inhibitors and their therapeutic implications in diseases, including diabetic microangiopathy, will be discussed in the next review article.

Nifedipine inhibits tumor necrosis factor-alpha-induced monocyte chemoattractant protein-1 overexpression by blocking NADPH oxidase-mediated reactive oxygen species generation

There is a growing body of evidence that dihydropyridine-based calcium antagonists (DHPs) improve endothelial function, thus slowing the development and progression of atherosclerosis. However the molecular mechanisms by which DHPs normalize endothelial dysfunction, an initial step in atherosclerosis, are not fully understood. Monocyte recruitment and firm adhesion to endothelial cells play a central role in the pathogenesis of atherosclerosis. In this study, we investigated whether nifedipine, one of the most popular DHPs, could inhibit tumor necrosis factor-alpha (TNF-alpha)-induced reactive oxygen species (ROS) generation and subsequent monocyte chemoattractant protein-1 (MCP-1) expression in human umbilical vein endothelial cells (HUVEC). TNF-alpha significantly increased intracellular ROS generation in HUVEC, which was completely blocked by nifedipine. Nifedipine completely inhibited TNF-alpha-induced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in HUVEC. Furthermore, nifedipine was found to significantly inhibit upregulation of MCP-1 messenger RNA levels in TNF-alpha-exposed HUVEC. The results demonstrate that nifedipine could inhibit TNF-alpha-induced MCP-1 overexpression in HUVEC by suppressing NADPH oxidase-mediated ROS generation. Our present study suggests that nifedipine may play a protective role in the development and progression of atherosclerosis through its antioxidative properties.

Light-atom location in adsorbed benzene by experiment and theory

Locations of light atoms in C6D6 on Ru[0001] have been determined by low energy electron diffraction (LEED) and density functional theory (DFT). For the favored site/orientation in the p(square root of [7] x square root of [7])-R19 degrees phase, we find alternating outward bowing of the C-D bonds of 24 degrees and 9 degrees via LEED, and 22 degrees and 14 degrees via DFT. This remarkable agreement gives important cross confirmation of the validity of these techniques in describing the subtle contributions of light atoms to adsorbate scattering and energetics. The buckling is explained as a consequence of decreased aromaticity induced by the bonding to the substrate.

Synergistic effects of ATP on oxytocin-induced intracellular Ca2+ response in mouse mammary myoepithelial cells

An increase in intracellular Ca2+ ([Ca2+]i) is essential for mammary myoepithelial cells to contract, leading to milk ejection during lactation. In this study, the intracellular signaling leading to the increase in [Ca2+]i in cultured myoepithelial cells from mouse lactating mammary glands was investigated using fura-2 fluorescence ratiometry. [Ca2+]i increased in cultured myoepithelial cells in response to either oxytocin (1 nM) or ATP (10 microM), and the cells then contracted. These [Ca2+]i responses were diminished by treatment with an inhibitor of phospholipase C (> or = 1 microM U73122). Intracellular application of inositol 1,4,5-trisphosphate (IP3: 10 or 100 microM) increased [Ca2+]i. Pretreatment with pertussis toxin (PTX: 0.1 or 1 microgram/ml) inhibited the [Ca2+]i response to ATP, but had less of an effect on the response to oxytocin. These results indicate that oxytocin and purinergic receptors are coupled to PTX-insensitive and PTX-sensitive G proteins, respectively, and that their activation leads to the increase in [Ca2+]i through the release of Ca2+ from IP3-sensitive intracellular stores via the inositol-phospholipid signaling pathway. Furthermore, we found that the [Ca2+]i responses to oxytocin at physiological doses (0.01-0.1 nM) were augmented in the presence of a sub-responsive dose of ATP (1 microM). The activation of purinergic receptors may facilitate myoepithelial cell contraction in milk-ejection responses.

Brain-derived neurotrophic factor enhances depolarization-evoked glutamate release in cultured cortical neurons

Brain-derived neurotrophic factor (BDNF) has been reported to play an important role in neuronal plasticity. In this study, we examined the effect of BDNF on an activity-dependent synaptic function in an acute phase. First, we found that short-term treatment (10 min) with BDNF enhanced depolarization-evoked glutamate release in cultured cortical neurons. The enhancement diminished gradually according to the length of BDNF treatment. The BDNF-enhanced release did not require the synthesis of protein and mRNA. Both tetanus toxin and bafilomycin abolished the depolarization-evoked glutamate release with or without BDNF, indicating that BDNF acted via an exocytotic pathway. Next, we investigated the effect of BDNF on intracellular Ca(2+). BDNF potentiated the increase in intracellular Ca(2+) induced by depolarization. The Ca(2+) was derived from intracellular stores, because thapsigargin completely inhibited the potentiation. Furthermore, both thapsigargin and xestospongin C inhibited the effect of BDNF. These results suggested that the release of Ca(2+) from intracellular stores mediated by the IP(3) receptor was involved in the BDNF-enhanced glutamate release. Last, it was revealed that the enhancement of glutamate release by BDNF was dependent on the TrkB-PLC-gamma pathway. These results clearly demonstrate that short-term treatment with BDNF enhances an exocytotic pathway by potentiating the accumulation of intracellular Ca(2+) through intracellular stores.

Development and prevention of advanced diabetic nephropathy in RAGE-overexpressing mice

Vascular complications arising from multiple environmental and genetic factors are responsible for many of the disabilities and short life expectancy associated with diabetes mellitus. Here we provide the first direct in vivo evidence that interactions between advanced glycation end products (AGEs; nonenzymatically glycosylated protein derivatives formed during prolonged hyperglycemic exposure) and their receptor, RAGE, lead to diabetic vascular derangement. We created transgenic mice that overexpress human RAGE in vascular cells and crossbred them with another transgenic line that develops insulin-dependent diabetes shortly after birth. The resultant double transgenic mice exhibited increased hemoglobin A(1c) and serum AGE levels, as did the diabetic controls. The double transgenic mice demonstrated enlargement of the kidney, glomerular hypertrophy, increased albuminuria, mesangial expansion, advanced glomerulosclerosis, and increased serum creatinine compared with diabetic littermates lacking the RAGE transgene. To our knowledge, the development of this double transgenic mouse provides the first animal model that exhibits the renal changes seen in humans. Furthermore, the phenotypes of advanced diabetic nephropathy were prevented by administering an AGE inhibitor, (+/-)-2-isopropylidenehydrazono-4-oxo-thiazolidin-5-ylacetanilide (OPB-9195), thus establishing the AGE-RAGE system as a promising target for overcoming this aspect of diabetic pathogenesis.

Extreme endemic radiation of the Malagasy vangas (Aves: Passeriformes)

Phylogenetic relationships of the family Vangidae and representatives of several other passeriform families were inferred from 882 base positions of mitochondrial DNA sequences of 12S and 16S rRNA genes. Results indicated the monophyly of the Vangidae, which includes the genus Tylas, hitherto often placed in the family Pycnonotidae. Our results also revealed the Malagasy endemic Newtonia, a genus never previously assigned to the Vangidae, to be a member of this family. These results suggest the occurrence of an extensive in situ radiation of this family within Madagascar, and that the extant high diversity of this family is not the result of multiple colonizations from outside. The extremely high morphological and ecological diversification of the family seems to have been enhanced through the use and ultimate occupancy of vacant niches in this island.

Enhanced in situ expression of aldose reductase in peripheral nerve and renal glomeruli in diabetic patients

To explore the relationships between polyol pathway-related enzymes and pathologic features, we examined the immunohistochemical expression of aldose reductase (AR) and sorbitol dehydrogenase (SDH) in the peripheral nerve and kidney tissues collected postmortem from diabetic patients and compared it with those from non-diabetic patients. Tissue AR protein concentrations were also quantified. In non-diabetic patients, AR distributed in pericytes, smooth muscle cells of endo- and epi-neurial microvessels, Schwann cells in the sciatic nerve, and tubular cells of the renal medulla. By contrast, positive SDH reactions were observed in tubular cells of the renal cortex but were faint in the sciatic nerve. Diabetic patients frequently showed dense AR expressions in the sciatic nerve. In nephropathic diabetic patients, the glomerular mesangial area showed diffuse positive reactions for AR. The severity of structural changes in glomeruli correlated with the intensity of immunoreactive AR (r2=0.626, P<0.01). AR contents in the renal cortex and sciatic nerve from diabetic patients were 1.5- and 1.8-fold greater than those from non-diabetic patients, respectively (P<0.05 for both). These findings are the first to demonstrate enhanced AR expressions in peripheral nerve and renal glomeruli in diabetic patients and its relevance to the characteristic pathology.

Can we identify genes for susceptibility to diabetic microangiopathies using stroke-prone spontaneously hypertensive rat models?

The aortic biochemical properties are reported to be altered in stroke-prone spontaneously hypertensive rats (SHR-SPs) as a result not only of the accelerated accumulation of advanced glycation end products (AGEs) in thoracic aortae but also of primary defects. There is a growing body of evidence that reactive oxygen species (ROS) are involved in the formation of AGEs. We propose here a novel hypothesis that SHR-SPs are the strain that genetically produce more ROS generations. Since ROS formations and AGE accumulations play central roles in the pathogenesis of diabetic microvascular complications, SHR-SPs might be more susceptible to vascular complications when induced to be diabetic. To reveal new genes involved in susceptibility to diabetic microangiopathies through the study of these animal models might be a valuable strategy to develop novel therapeutic approaches.

p38 mitogen-activated protein kinase regulates low potassium-induced c-Jun phosphorylation and apoptosis in cultured cerebellar granule neurons

Cultured rat cerebellar granule neurons are widely used as a model system for studying neuronal apoptosis. After maturation by culturing in medium containing 26 mm potassium (high K(+)), changing to medium containing 5 mm potassium (low K(+); LK) rapidly induces neuronal apoptosis. Then over 50% of granule cells die within 24 h. However, the molecular mechanisms by which the LK-induced apoptosis occurs in cultured cerebellar granule cells remain unclear. In the present study, we found that p38 MAP kinase (p38) was an important factor for LK-induced apoptosis. Three hours after changing to LK medium, p38 was markedly activated. In addition, SB203580, a specific inhibitor of p38, strongly inhibited the phosphorylation and expression of c-Jun in LK-induced apoptosis of cultured cerebellar granule cells. In vitro kinase assay using glutathione S-transferase-c-Jun as a substrate showed that p38 directly phosphorylated c-Jun. Furthermore, in the presence of SB203580, about 80% of neurons survived. These results indicate that p38 regulates LK-induced apoptosis of cerebellar granule neurons.

Revisiting the roles of mast cells in allergic rhinitis and its relation to local IgE synthesis

Mast cells are important effector cells in the immediate-phase allergic reaction. However, in recent years much evidence has accumulated on the versatile role of mast cells in allergic inflammation. The present article is an overview of the roles of mast cells in allergic inflammation, especially in light of the local production of IgE and the IgE-IgE receptor network. Although both nasal mast cells (NMC) and T cells in allergic rhinitics are important sources of Th2-type cytokines like IL-4 and IL-13, and can induce IgE synthesis, we report here that antigen-activated NMC can secrete greater levels of IL-4/IL-13 and induce increased levels of IgE synthesis than antigen-activated nasal T cells. Furthermore, IgE production can occur locally in the nasal mucosa (target organ) and IgE itself can enhance the Fc epsilon RI expression and subsequent mediator release from NMC, thus contributing to the perpetuation of on-going allergic inflammation. Again, mast cells can contribute to the late-phase allergic reaction not only via the upregulation of adhesion molecules like VCAM-1, but also through the interactions of NMC with the extracellular matrix proteins, and interaction of NMC with nasal epithelial cells (NEC). Thus, it is increasingly evident that mast cells are not only important for the genesis of the allergic reaction, but also contribute to the late-phase allergic reaction and on-going allergic inflammation.