Treatment strategies for hypertension in patients with type 1 diabetes

ABSTRACT

Introduction

Type 1 diabetes mellitus (T1DM) is a chronic, autoimmune disease that is characterized by total absence of insulin production. Hypertension is a common comorbidity in T1DM with complex pathophysiology, while it is also a well-recognized risk factor for the development of cardiovascular disease (CVD), as well as other microvascular diabetic complications.     

Plasma lipids and lipoproteins and essential hypertension

In recent years there have been many studies demonstrating a correlation between increased arterial blood pressure and altered lipid profiles, and there has been an especially positive correlation between high cholesterol levels and blood pressure. There are differences between the various reports that are important. In our study the lipid distribution in 105 hypertensive patients with mild or moderate arterial hypertension according to WHO criteria without clinically or ultrasonographically apparent atherosclerosis was compared to the lipid distribution in 65 age-matched healthy persons. On the epidemiological level a significant, positive association was found between LDL serum levels (P 0.001), Apo B serum levels (P 0.001), serum triglyceride levels (P 0.05) and VLDL serum levels (P 0.01) and arterial hypertension. However, in contrast to recent reports, no significant difference was found between total serum cholesterol levels in normotensives and hypertensives, and there was no difference in HDL serum levels. No evidence could be found for a significant increase in lipoprotein (a) serum levels in hypertensives.Abbreviations LDL low density lipoprotein - VLDL very low density lipoprotein - HDL high density lipoprotein - Apo B 100 apolipoprotein B 100 - Apo A I apolipoprotein A I Correspondence to: H. Vetter     

Early intracellular signalling pathway of ethanol in vascular smooth muscle cells

1. ERKs belong to MAP kinase family and are activated by several growth and stress factors. Although ethanol has been shown to modulate ERK1 and ERK2 (p44(mapk) and p42(mapk)) activity, it can also act as an antiproliferative agent in various mammalian cells. Since the nature of the antiproliferative effect of ethanol in VSMCs has not been defined, we examined its effects on growth and on early intracellular events normally induced by growth factors in VSMCs. 2. Measurement of cytosolic Ca(2+) and pH in cell monolayers was performed using fura-2/AM and BCECF/AM, respectively. The effect of ethanol on VSMCs growth was assessed by [(3)H]-thymidine incorporation, by cell counting and by determination of the caspase 3 activity. Stimulation of ERK1 and ERK2 was examined by the chemiluminescence Western blotting method. The expression of c-fos was quantitated by Northern blotting. Determination of inositolphosphates was performed after labelling of VSMCs with myo-[2-(3)H]-inositol and separation of inositolphosphates by HPLC. 3. Ethanol (0.3 - 1.0% v v(-1), 17 - 170 mM) induced a dose-dependent maximal stimulation of p44(mapk)/p42(mapk) at 30 min and expression of c-fos mRNA with a maximum at 120 min. Intracellular events upstream to MAP kinase, like an increase in [Ca(2+)](i), activation of the Na(+)/H(+) exchanger and formation of phosphoinositol metabolites were also markedly activated by ethanol. Treatment of VSMCs with ethanol for 3 - 5 min induced an increase in DNA synthesis whereas treatment of the cells for more than 30 min was toxic. Caspase 3 activity was not modulated by ethanol treatment of VSMCs. 4. We may postulate that the activation of these mitogenic signals including the elevation of DNA synthesis reflects a cell effort to protect itself against the toxic effects of ethanol.     

Profiling of drugs and environmental chemicals for functional impairment of neural crest migration in a novel stem cell-based test battery

Developmental toxicity in vitro assays have hitherto been established as stand-alone systems, based on a limited number of toxicants. Within the embryonic stem cell-based novel alternative tests project, we developed a test battery framework that allows inclusion of any developmental toxicity assay and that explores the responses of such test systems to a wide range of drug-like compounds. We selected 28 compounds, including several biologics (e.g., erythropoietin), classical pharmaceuticals (e.g., roflumilast) and also six environmental toxicants. The chemical, toxicological and clinical data of this screen library were compiled. In order to determine a non-cytotoxic concentration range, cytotoxicity data were obtained for all compounds from HEK293 cells and from murine embryonic stem cells. Moreover, an estimate of relevant exposures was provided by literature data mining. To evaluate feasibility of the suggested test framework, we selected a well-characterized assay that evaluates ‘migration inhibition of neural crest cells.’ Screening at the highest non-cytotoxic concentration resulted in 11 hits (e.g., geldanamycin, abiraterone, gefitinib, chlorpromazine, cyproconazole, arsenite). These were confirmed in concentration–response studies. Subsequent pharmacokinetic modeling indicated that triadimefon exerted its effects at concentrations relevant to the in vivo situation, and also interferon-β and polybrominated diphenyl ether showed effects within the same order of magnitude of concentrations that may be reached in humans. In conclusion, the test battery framework can identify compounds that disturb processes relevant for human development and therefore may represent developmental toxicants. The open structure of the strategy allows rich information to be generated on both the underlying library, and on any contributing assay.     

Intracellular free calcium concentration and thromboxane A2 formation of vascular smooth muscle cells are influenced by fish oil and n-3 eicosapentaenoic acid.

The effect of fish oil and n-3 eicosapentaenoic acid (EPA) on intracellular free calcium concentration ([Ca2+]i) and thromboxane B2 (TXB2) formation in resting and stimulated cultured rat vascular smooth muscle cells (VSMC) was examined. In resting control cells [Ca2+]i was 147 +/- 15 nmol l-1 (mean +/- SEM, n = 4). After pretreatment of the cells with fish oil or EPA for 24 days the resting [Ca2+]i was decreased to 126 +/- 10 nmol l-1 and 84 +/- 8 nmol-1, respectively. After stimulation of untreated control cells with either 100 nmol l-1 angiotensin II (AII), 40 micrograms ml-1 low-density lipoprotein (LDL), or 100 ng ml-1 of recombinant platelet-derived growth factor (PDGFAB), [Ca2+]i was (in nmol l-1) 306 +/- 31, 217 +/- 25 and 213 +/- 16. Treatment of cells with fish oil or EPA reduced the stimulatory effect of the agonists, and the following [Ca2+]i values (in nmol l-1) were found: 199 +/- 21, 131 +/- 10, 148 +/- 13; and 175 +/- 11, 98 +/- 12, and 103 +/- 6, respectively. PDGFAB induced a four fold increase in TXB2-generation (270 +/- 28 pg mg-1 cell protein compared with 61 +/- 8.2 pg mg-1 in unstimulated control cells) within 6 min. In cells pretreated with fish oil or EPA, TXB2-formation was reduced by 54% and 44%, respectively. In conclusion: in rat VSMC stimulated by a variety of vasoactive agonist, fish oil and EPA can markedly attenuate intracellular mechanisms related to changes of cytosolic calcium concentration and eicosanoid production.(ABSTRACT TRUNCATED AT 250 WORDS)     

Troglitazone and rosiglitazone inhibit the low density lipoprotein-induced vascular smooth muscle cell growth.

Troglitazone (TRO) and rosiglitazone (RSG) belong to the thiazolidinedione class (insulin-sensitizing agents) and exert many of their metabolic effects as peroxisome proliferator-activated receptor gamma (PPARgamma) ligands. In the present study we examined the effects of TRO and RSG on LDL-induced VSMC growth. Pretreatment of VSMC with 1 microM TRO or 0.1 microM RSG completely blocked the LDL-induced cell proliferation as measured by [3H]thymidine incorporation into DNA and by determination of the cell number. We then examined with Western blotting whether these growth suppressing effects are mediated through the mitogen-activated protein kinase (MAPK) pathway, a common signaling pathway activated by growth factors. TRO and RSG had no effect on the LDL-induced stimulation of the MAP kinases ERK1/2, p38 and SAP/JNK. We conclude that thiazolidinediones are potent inhibitors of LDL-induced VSMC growth acting downstream of the cytoplasmic activation of MAPK.     

The use of suppression subtractive hybridization for the study of SDF-1alpha induced gene-expression in human endothelial cells

Stromal cell-derived factor-1 (SDF-1), the only ligand of the CXCR4 receptor, is mainly known as a chemotactic factor for hematopoietic progenitor cells. However, studies of knock-out mice have shown malformation of different organ-systems suggesting that SDF-1 may have a role in angiogenesis and cardiac and cerebral development. However, the underlying mechanisms of its action are largely unknown. Therefore, we performed suppression subtractive hybridization (SSH) in order to identify genes that are differentially expressed after stimulation of human arterial endothelial cells (HUAEC) with SDF-1. Using SSH we found ten genes, with varied functions, whose mRNA expression is induced by SDF-1alpha in HUAEC. We show that SSH is a reliable method for identifying differentially expressed genes and that SDF-1alpha may have more functions than previously reported.     

Embryonic stem cells produce neurotrophins in response to cerebral tissue extract: Cell line-dependent differences

In the present study, we compare the capacity of two different embryonic stem (ES) cell lines to secrete neurotrophins in response to cerebral tissue extract derived from healthy or injured rat brains. The intrinsic capacity of the embryonic cell lines BAC7 (feeder cell-dependent cultivation) to release brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) exceeded the release of these factors by CGR8 cells (feeder cell-free growth) by factors of 10 and 4, respectively. Nerve growth factor (NGF) was secreted only by BAC7 cells. Conditioning of cell lines with cerebral tissue extract derived from healthy or fluid percussion-injured rat brains resulted in a significant time-dependent increase in BDNF release in both cell lines. The increase in BDNF release by BAC7 cells was more pronounced when cells were incubated with brain extract derived from injured brain. However, differences in neurotrophin release associated with the origin of brain extract were at no time statistically significant. Neutrophin-3 and NGF release was inhibited when cell lines were exposed to cerebral tissue extract. The magnitude of the response to cerebral tissue extract was dependent on the intrinsic capacity of the cell lines to release neurotrophins. Our results clearly demonstrate significant variations in the intrinsic capability of different stem cell lines to produce neurotrophic factors. Furthermore, a significant modulation of neurotrophic factor release was observed following conditioning of cell lines with tissue extract derived from rat brains. A significant modulation of neurotrophin release dependent on the source of cerebral tissue extract used was not observed.