Vascular smooth muscle cell hypertrophy induced by glycosylated human oxyhaemoglobin

Mifepristone is a Vasodilator Due to the Inhibition of Smooth Muscle Cells L-Type Ca2+ Channels

Derived from the estrane progestins, mifepristone was the first synthetic steroid of this class employed as abortifacient in the first months of pregnancy. Mifepristone reduces high potassium-induced contraction and prevents calcium-induced contraction. At the vascular level, mifepristone induces direct relaxation in rat and human arteries, and this effect seems to be endothelium- and NO independent, suggesting that the vascular smooth muscle is its target. Moreover, mifepristone's effect could involve the modulation of different calcium channels. The aim of the present study is to analyze the involvement of calcium channels in the relaxation induced by mifepristone on vascular smooth muscle cells (VSMCs). Planar cell surface area (PCSA) technique was used to analyze the effect of mifepristone on the VSMC contractility, and the whole cell configuration of patch-clamp technique to measure the activity of L-type Ca(2+) channels (LTCC) in A7r5 cells. Regarding the PCSA technique, mifepristone induced relaxation of the VSMC previously contracted by different agents. Also, a rapid inhibitory effect on basal and BAY K8644-stimulated calcium current was observed, which indicates that this drug has the ability to block LTCC. These results suggest that mifepristone induces relaxation on the VSMCs due to the inhibition of the calcium channels.

Sinusoidal constriction and vascular hypertrophy in the diabetes-induced rabbit penis

OBJECTIVE

To assess the morphological changes of penile vascular structures and the corpus cavernosum area in alloxan-induced diabetic rabbits.

MATERIALS AND METHODS

Twenty male rabbits (2 months old) were divided into two groups with 10 rabbits each, the control group (CG) and the diabetic group (DG). The animals from DG received an intravenous injection of alloxan (100mg/kg) to induce the diabetes. Ten weeks after the induction of diabetes, all animals were euthanized. Two fragments of the penile shaft were harvested and samples were processed and paraffin embedded. Sections (5 µm) were cut and stained for histological and immunohistochemical markers.

RESULTS

Nuclear protrusion toward the lumen, and cytoplasmic vacuolization were observed in the tunica intima of the dorsal artery of the penis in DG. The thicknesses of the tunica media increased significantly in DG (p = 0.0350). It was also observed a significant increase in the area of the tunica media (p = 0.0179). There was no significant change in smooth muscle cell density in the tunica media of the dorsal artery of the penis (p = 0.0855). The collagen fiber pattern of the tunica adventitia of the dorsal artery of the penis was different between the control and diabetic groups. There was a significant decrease in the area occupied by the cavernous sinuses in DG (p = 0.0013).

CONCLUSION

Alloxan-induced diabetes mellitus in rabbits promotes important changes in penile vascular structures, thereby decreasing blood supply and affecting penile hemodynamics, leading to erectile dysfunction.

Xanthine oxidase-derived extracellular superoxide anions stimulate activator protein 1 activity and hypertrophy in human vascular smooth muscle via c-Jun N-terminal kinase and p38 mitogen-activated protein kinases

OBJECTIVE

Vascular xanthine oxidase (XO) activity has been found to be elevated in chronic vascular disease. Although a role for XO in endothelial dysfunction has been proposed, little is known about its influence on vascular smooth muscle maladaptive growth.

METHODS

The proliferative and hypertrophic response of human aortic smooth muscle cells (HASMC) stimulated with xanthine/xanthine oxidase (X/XO) was quantified by determining cell number, cell size and protein synthesis. The levels and activity of the growth-related transcription factor activator protein 1 (AP-1) and the activation of mitogen-activated protein kinase (MAPK) by X/XO were determined by either Western blot or transient transfection experiments.

RESULTS

X/XO did not affect HASMC proliferation, but led to enhanced planar cell surface area and protein synthesis. In addition, X/XO enhanced c-jun levels and AP-1 transcriptional activity. Although X/XO did not modify extracellular signal-regulated protein kinases 1/2 MAPK or Akt/PKB activity, it promoted the activation of c-Jun N-terminal kinase and p38 MAPK, which were both necessary for X/XO to increase AP-1 activity and cell size in HASMC cultures. Finally, the effects of X/XO on MAPK activation, AP-1 activity and cell size were dependent on the extracellular release of superoxide anions through the enzymatic activity of XO, as they were prevented by both superoxide dismutase and allopurinol.

CONCLUSION

X/XO exhibits hypertrophic properties for human vascular smooth muscle, which are mediated by redox-sensitive pathways involving MAPK activation. XO can therefore participate in the maladaptive vascular remodeling observed in chronic cardiovascular diseases exhibiting elevated vascular XO activity.

Pro-inflammatory effects of early non-enzymatic glycated proteins in human mesothelial cells vary with cell donor's age

BACKGROUND AND PURPOSE

Diabetes mellitus is prevalent in the elderly population. It is also a disease causing tissue damage through several different mechanisms. Some of these mechanisms are also activated by ageing and this overlap raises questions about how diabetes induces damage in the elderly. Early products of non-enzymatic glycation of proteins (Amadori adducts), and the ageing process share the capacity to induce oxidative stress and inflammation in human peritoneal mesothelial cells (HPMCs). We have evaluated the interactions between the age of the donor of the HPMCs and the pro-inflammatory effects of Amadori adducts in those cells.

EXPERIMENTAL APPROACH

HPMCs were isolated from 20 individuals (age range 21-81 years) and grown in culture. Using different experimental approaches we determined NF-kappaB dependent transcriptional activity and different NF-kappaB-related pro-inflammatory gene and protein expressions in basal (or non-stimulated) conditions and after stimulation with two Amadori adducts; highly-glycated haemoglobin and glycated bovine serum albumin.

KEY RESULTS

Amadori-induced effects on NF-kappaB dependent-transcription and on the activity of NOS, COX and several NF-kappaB-related pro-inflammatory genes (iNOS, COX-2, TNF-alpha, IL-1beta, and IL6) diminished as the donor's age increased, being practically absent in cells from donors more than 65 years old. Such decreased effects were inversely correlated with an increased basal expression and activity of these pro-inflammatory markers with age.

CONCLUSIONS AND IMPLICATIONS

Pro-inflammatory effects of Amadori-adducts in HPMCs were strongly dependent on cell donor's age. This may have significant implications for the mechanisms underlying diabetes-induced tissue damage in patients of different ages.

Amadori adducts activate nuclear factor-kappaB-related proinflammatory genes in cultured human peritoneal mesothelial cells

Diabetes mellitus leads to a high incidence of several so-called complications, sharing similar pathophysiological features in several territories. Previous reports points at early nonenzymatic glycosylation products (Amadori adducts) as mediators of diabetic vascular complications. In the present study, we analysed a possible role for Amadori adducts as stimulators of proinflammatory pathways in human peritoneal mesothelial cells (HPMCs). Cultured HPMCs isolated from 13 different patients (mean age 38.7+/-16 years) were exposed to different Amadori adducts, that is, highly glycated haemoglobin (10 nM) and glycated bovine serum albumin (0.25 mg ml(-1)), as well as to their respective low glycosylation controls. Amadori adducts, but not their respective controls, elicited a marked increase of NF-kappaB activation, as determined by electromobility shift assays and transient transfection experiments. Additionally, Amadori adducts significantly increased the production of NF-kappaB-related proinflammatory molecules, including cytokines, such as TNF-alpha, IL-1beta or IL-6, and enzymes, such as cyclooxygenase-2 and inducible nitric oxide (NO) synthase, this latter leading to the release of NO by HPMCs. The effects of Amadori adducts were mediated by different reactive oxygen and nitrosative species (e.g. superoxide anions, hydroxyl radicals, and peroxynitrite), as they were blunted by coincubation with the appropriate scavengers. Furthermore, NO generated upon exposure to Amadori adducts further stimulated NF-kappaB activation, either directly or after combination with superoxide anions to form peroxynitrite. We conclude that Amadori adducts can favour peritoneal inflammation by exacerbating changes in NO synthesis pathway and triggering NF-kappaB-related proinflammatory signals in human mesothelial cells.

Iron Chelation Suppresses Ferritin Upregulation and Attenuates Vascular Dysfunction in the Aorta of Angiotensin II–Infused Rats

Objective— We have investigated whether long-term administration of angiotensin (Ang) II causes ferritin induction and iron accumulation in the rat aorta, and their possible relation to regulatory effects on gene expression and vascular function in Ang II-infused animals.

Methods and Results— Sprague-Dawley rats were given Ang II for 7 days via subcutaneously implanted osmotic minipumps. Ang II infusion caused a >20-fold increase in ferritin protein expression over control values. Immunohistochemistry showed that Ang II infusion markedly increased the ferritin expression in the aortic endothelial and adventitial cells, with some of the latter being identified as monocytes/macrophages. Prussian blue staining showed that stainable iron was observed in the adventitial layer of aorta from Ang II-infused animals, but not in the endothelial layer. Chelation of iron suppressed aortic induction of ferritin and also the oxidative stress markers, heme oxygenase-1 and 4-hydroxynonenal-modified protein adducts. In addition, iron chelation attenuated Ang II-induced impairment of aortic relaxations in response to acetylcholine and sodium nitroprusside and suppressed upregulation of mRNA levels of monocyte chemoattractant protein-1. Iron chelation also partially attenuated the medial thickening and perivascular fibrosis induced by Ang II infusion for 4 weeks.

Conclusion— Ang II infusion caused ferritin induction and iron deposition in the aortas. These phenomena might have a role in the regulation of gene expression, impairment of vascular function, and arterial remodeling induced by Ang II, which are presumably mediated in part by enhancement of oxidative stress.

Glycosylated human oxyhaemoglobin activates nuclear factor-kappaB and activator protein-1 in cultured human aortic smooth muscle

Diabetic vessels undergo structural changes that are linked to a high incidence of cardiovascular diseases. Reactive oxygen species (ROS) mediate cell signalling in the vasculature, where they can promote cell growth and activate redox-regulated transcription factors, like activator protein-1 (AP-1) or nuclear factor-kappaB (NF-kappaB), which are involved in remodelling and inflammation processes. Amadori adducts, formed through nonenzymatic glycosylation, can contribute to ROS formation in diabetes. In this study, we analysed whether Amadori-modified human oxyhaemoglobin, glycosylated at either normal (N-Hb) or elevated (E-Hb) levels, can induce cell growth and activate AP-1 and NF-kappaB in cultured human aortic smooth muscle cells (HASMC). E-Hb (1 nm-1 x microm), but not N-Hb, promoted a concentration-dependent increase in cell size from nanomolar concentrations, although it failed to stimulate HASMC proliferation. At 10 nm, E-Hb stimulated both AP-1 and NF-kappaB activity, as assessed by transient transfection, electromobility shift assays or immunofluorescence staining. The effects of E-Hb resembled those of the proinflammatory cytokine tumour necrosis factor-alpha (TNF-alpha). E-Hb enhanced intracellular superoxide anions content and its effects on HASMC were abolished by different ROS scavengers. In conclusion, E-Hb stimulates growth and activates AP-1 and NF-kappaB in human vascular smooth muscle by redox-sensitive pathways, thus suggesting a possible direct role for Amadori adducts in diabetic vasculopathy.

Erythema measurements may allow early diagnosis of diabetes mellitus in adult psoriatics

BACKGROUND

We have observed that the erythema in subjects with psoriasis vulgaris associated with non-insulin-dependent diabetes mellitus (NIDDM) presents a mostly deep-red to purple hue instead of the typical pink to red tones. We carried out a descriptive clinical study, including 141 patients with psoriasis vulgaris to quantify these colour differences.

METHODS

Mean erythema index values were established for the psoriatic plaques of adult subjects using an optoelectronic method. Non-diabetic psoriatics underwent an oral glucose tolerance test (OGTT), and based on the results of the oral OGTTs, the subjects were divided into three groups: 18 psoriatics with NIDDM, 16 psoriatics with impaired glucose tolerance (IGT) and 107 psoriatics with normal glucose tolerance. The mean erythema index value was calculated for each group and the findings were compared.

RESULTS

The differences in the erythema were found to be highly significant between the group of subjects with psoriasis having normal glucose tolerance and both those with IGT and those with NIDDM (P < 0.01 and P < 0.01). The differences in the erythema were also highly significant between the psoriatic group with normal glucose tolerance and the group of 34 psoriatics with IGT and NIDDM all together (P < 0.01).

CONCLUSIONS

Individuation of the various hues of erythema in psoriatics by careful dermatological examination or routine measurements of lesional erythema may alert the physician to possible IGT in the presenting subject, and this may affect disease severity.

High glucose induces cell death of cultured human aortic smooth muscle cells through the formation of hydrogen peroxide

Alterations of the vessel structure, which is mainly determined by smooth muscle cells through cell growth and/or cell death mechanisms, are characteristic of diabetes complications. We analysed the influence of high glucose (22 mM) on cultured human aortic smooth muscle cell growth and death, as hyperglycaemia is considered one of the main factors involved in diabetic vasculopathy. Growth curves were performed over 96 h in medium containing 0.5% foetal calf serum. Cell number increased by 2 - 4 fold over the culture period in the presence of 5.5 mM (low) glucose, while a 20% reduction in final cell number was observed with high glucose. Under serum-free conditions, cell number remained constant in low glucose cultures, but a 40% decrease was observed in high glucose cultures, suggesting that high glucose may induce increased cell death rather than reduced proliferation. Reduced final cell number induced by high glucose was also observed after stimulation with 5 or 10% foetal calf serum. The possible participation of oxidative stress was investigated by co-incubating high glucose with different reactive oxygen species scavengers. Only catalase reversed the effect of high glucose. Intracellular H(2)O(2) content, visualized with 2',7'-dichlorofluorescein and quantified by flow cytometry, was increased after high glucose treatment. To investigate the cell death mechanism induced by high glucose, apoptosis and necrosis were quantified. No differences were observed regarding the apoptotic index between low and high glucose cultures, but lactate dehydrogenase activity was increased in high glucose cultures. In conclusion, high glucose promotes necrotic cell death through H(2)O(2) formation, which may participate in the development of diabetic vasculopathy.

Pharmacological interference of vascular smooth muscle cell hypertrophy induced by glycosylated human oxyhaemoglobin

Nonenzymatically glycosylated human oxyhaemoglobin induces vascular smooth muscle cell hypertrophy by releasing reactive oxygen species. We analysed the ability of drugs with antihypertrophic properties for the vascular wall and/or antioxidant activity, such as captopril, losartan, and nifedipine, or gliclazide, carvedilol, and ascorbic acid, to interfere with 10 nM glycosylated human oxyhaemoglobin-induced increase in vascular smooth muscle cell size (118+/-0.5% of basal). Vascular smooth muscle cell hypertrophy was abolished concentration-dependently, with pD(2) values over a 100-fold interval: 6.4+/-0.3, 7.7+/-0.4, 7.3+/-0.4, 7.4+/-0.6, 8. 8+/-0.2, and 9.0+/-0.2 for captopril, losartan, nifedipine, ascorbic acid, carvedilol and gliclazide, respectively. Drugs with powerful antioxidant properties, especially carvedilol and gliclazide, are particularly effective in preventing glycosylated human oxyhaemoglobin-induced vascular smooth muscle cell hypertrophy.