Deferoxamine preconditioning to restore impaired HIF-1α-mediated angiogenic mechanisms in adipose-derived stem cells from STZ-induced type 1 diabetic rats

OBJECTIVES

Both excessive and insufficient angiogenesis are associated with progression of diabetic complications, of which poor angiogenesis is an important feature. Currently, adipose-derived stem cells (ADSCs) are considered to be a promising source to aid therapeutic neovascularization. However, functionality of these cells is impaired by diabetes which can result from a defect in hypoxia-inducible factor-1 (HIF-1), a key mediator involved in neovascularization. In the current study, we sought to explore effectiveness of pharmacological priming with deferoxamine (DFO) as a hypoxia mimetic agent, to restore the compromised angiogenic pathway, with the aid of ADSCs derived from streptozotocin (STZ)-induced type 1 diabetic rats ('diabetic ADSCs').

MATERIALS AND METHODS

Diabetic ADSCs were treated with DFO and compared to normal and non-treated diabetic ADSCs for expression of HIF-1α, VEGF, FGF-2 and SDF-1, at mRNA and protein levels, using qRT-PCR, western blotting and ELISA assay. Activity of matrix metalloproteinases -2 and -9 were measured using a gelatin zymography assay. Angiogenic potential of conditioned media derived from normal, DFO-treated and non-treated diabetic ADSCs were determined by in vitro (in HUVECs) and in vivo experiments including scratch assay, three-dimensional tube formation testing and surgical wound healing models.

RESULTS

DFO remarkably enhanced expression of noted genes by mRNA and protein levels and restored activity of matrix metalloproteinases -2 and -9. Compromised angiogenic potential of conditioned medium derived from diabetic ADSCs was restored by DFO both in vitro and in vivo experiments.

CONCLUSION

DFO preconditioning restored neovascularization potential of ADSCs derived from diabetic rats by affecting the HIF-1α pathway.

Protective effect of 17β-estradiol on serum deprivation-induced apoptosis and oxidative stress in bone marrow-derived mesenchymal stem cells

Stem cell transplantation has indicated great promise for cell therapy in a wide range of diseases, but poor and insufficient viability of cells within damaged tissues has limited its potential therapeutic effects. 17 β-Estradiol (E2) is a steroid hormone that plays an important role in expression of many genes and regulating proliferation, viability, and intracellular redox status in different cell types. In this study, we aimed to assess the effect of E2 on bone marrow-derived mesenchymal stem cells (BM-MSCs). Apoptosis was induced by serum deprivation (SD), and cells were exposed to E2 in the presence or absence of serum for varying periods of time, after which cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Expression of proapoptotic and antiapoptotic proteins after exposure to E2 was examined by Western blotting. The ability of E2 to prevent reactive oxygen species (ROS) production was also measured. The results indicated that E2 significantly enhanced the viability of the cells and protected BM-MSCs against SD-induced overproduction of ROS. It could reduce lipid peroxidation, total antioxidant power, and also Bax/Bcl-2 ratio as well as expression of caspase-3. Taken together, our data support that E2 treatment protects BM-MSCs against SD-induced damage by regulating ROS production and upregulation of antiapoptotic/proapoptotic proteins ratio.

Investigating the protective effect of lithium against high glucose-induced neurotoxicity in PC12 cells: involvements of ROS, JNK and P38 MAPKs, and apoptotic mitochondria pathway

Hyperglycemia that occurs under the diabetic condition is a major cause of diabetic complications such as diabetic neuropathy, one of the most common diabetes-related complications. It is well known that hyperglycemia could result in generation of reactive oxygen species (ROS). Over production of ROS recommended as an important mediator for apoptotic signaling pathway as well as a key early event in the development of diabetic neuropathy. Recently, many studies have indicated that lithium has robust neuroprotective effect in relation to several neurodegenerative diseases. The present study aimed to examine effects of lithium on high glucose (HG)-induced neurotoxicity and to determine some of the underlying molecular mechanisms involved in this response in PC12 cells as a neuronal culture model for diabetic neuropathy. PC12 cells were pretreated with different concentrations of lithium for 7 days, exposed to HG for 24 h. Cell viability was measured by MTT assay. ROS and lipid peroxidation levels as well as superoxide dismutase activity were measured. In order to examine the underlying molecular mechanisms, the expressions of Bax, Bcl-2, Caspase-3, total and phosphorylated JNK and P38 MAPK were also analyzed by Western blotting. The present results indicated that pretreatment with 1 mM lithium has protected PC12 cells against HG-induced apoptotic cell death. It could reduce ROS generation, Bax/Bcl-2 ratio, Caspase-3 activation, and JNK and P38 MAPK phosphorylation. It may be concluded that in HG condition, lithium pretreatment could prevent mitochondrial apoptosis as well as JNK and P38 MAPK pathway in PC12 cells.

Apoptosis in vasculature of spontaneously hypertensive rats: effect of an angiotensin converting enzyme inhibitor and a calcium channel antagonist

Increased apoptosis has been demonstrated in various forms of human and experimental cardiovascular disease. The role of this phenomenon in the vasculature in different models of hypertension is unclear. In hypertension, regression of vessel wall hypertrophy/hyperplasia or remodeling in response to various antihypertensive drugs may be mediated in part by apoptosis. This study examined vascular smooth muscle apoptosis in spontaneously hypertensive rats (SHR), in which it may presumably counterbalance vascular wall growth. Angiotensin converting enzyme (ACE) inhibitors and calcium channel blockers induce regression of the vascular wall in hypertension. Therefore, we investigated the effect of the ACE inhibitor enalapril and the dihydropyridine calcium channel blocker amlodipine on apoptosis in blood vessels of SHR to determine whether part of the growth inhibitory effect of these drugs is mediated by apoptosis. This was performed by detection and measurement of DNA fragmentation using DNA laddering and examining aortic histologic sections with in situ end-labeling (terminal deoxynucleotide transferase-mediated dUTP-nick labeling [TUNEL]). Ten-week-old SHR were treated for 12 weeks with 10 mg/kg per day of enalapril and 20 mg/kg per day of amlodipine. Blood pressure was significantly reduced by enalapril and amlodipine (P < .01). Cross-sectional area of aorta was significantly increased (3.34+/-0.15 mm2) in SHR compared to that of Wistar-Kyoto (WKY) control rats (1.17+/-0.07 mm2, P < .01). The cross-sectional area of the aorta was significantly smaller in enalapril-treated SHR (2.42+/-0.12 mm2, P < .05) compared to untreated SHR, and almost normalized by amlodipine (1.65+/-0.31 mm2, P < .01). Apoptosis characterized using terminal deoxynucleotidyl transferase to radiolabel 3'-OH ends of fragmented DNA extracted from aorta, showed presence of fragmented labeled DNA as "DNA laddering," a hallmark of apoptosis. SHR had increased apoptosis (341+/-25 pixels/microg DNA) compared to WKY controls (206+/-13 pixels/microg DNA, P < .01). Apoptosis was six- to eightfold greater in aorta of enalapril and amlodipine-treated SHR (P < .01). These results were confirmed by in situ end-labeling of fragmented DNA in aortic histologic sections. Western blot quantification of Bax and Bcl-2 (pro- and antiapoptotic gene products, respectively) showed higher Bax and lower Bcl-2 expression, and accordingly increased the Bax-to-Bcl-2 ratio in aorta from SHR treated with enalapril or amlodipine in comparison to untreated SHR. In conclusion, enhanced apoptosis is present in aorta of SHR, possibly as a homeostatic mechanism counterbalancing growth. Antihypertensive agents such as the ACE inhibitor enalapril and the calcium antagonist amlodipine may cause regression or inhibition of vascular wall growth in SHR partly through enhanced apoptosis, which may contribute to the antihypertensive effects of these drugs.

Vascular endothelin-1 expression and effect of an endothelin ETA antagonist on structure and function of small arteries from stroke-prone spontaneously hypertensive rats

There is some evidence that the endothelin (ET) system may participate in blood pressure elevation and in vascular hypertrophy in stroke-prone spontaneously hypertensive rats (SHR-SP). To further understand the involvement of the ET system in this hypertensive model, we examined preproendothelin-1 (preproET-1) mRNA abundance in blood vessels of 5-week and 18-week SHR-SP in comparison to SHR, and treated 12-week old SHR-SP with the ETA-selective receptor antagonist A-127722.5 (30 mg/kg/day in the drinking water) for 10 weeks. Abundance of preproET-1 mRNA by Northern blot analysis was increased more than twofold in aorta and mesenteric arteries of SHR-SP relative to SHR at 18 weeks but not at 5 weeks of age. SHR-SP treated with A-127722.5 had a tail-cuff systolic blood pressure at 22 weeks of age of 241 +/- 2 mm Hg vs. 251 +/- 3 mm Hg in untreated SHR-SP (p < 0.05). Heart:body weight ratio was no different in both groups, but aortic segment:body weight ratio was slightly but significantly smaller in treated SHR-SP (p < 0.05). Pressurized mesenteric small arteries from treated SHR-SP had a smaller media width (12.6 +/- 0.6 microns vs. 14.9 +/- 0.5 microns; p < 0.05) and media:lumen ratio (5.8 +/- 0.2% vs. 7.3 +/- 0.3%; p < 0.01), whereas media cross-sectional area and lumen diameter tended to decrease and increase, respectively, without achieving statistical significance. Acetylcholine-induced relaxation was improved in treated SHR-SP (99.6 +/- 0.6% vs. 90.0 +/- 3.6%; p < 0.05), whereas relaxation responses to sodium nitroprusside were similar in both groups. These results show increases of preproET-1 expression in blood vessels that appear to be secondary to blood pressure elevation. There is a small ET-dependent component in blood pressure elevation and in conduit and resistance artery changes in adult stroke-prone SHR.

Effects of enalapril and amlodipine on small-artery structure and composition, and on endothelial dysfunction in spontaneously hypertensive rats

OBJECTIVES

To determine whether an angiotensin converting enzyme inhibitor, enalapril, and a dihydropyridine calcium channel antagonist, amlodipine, regress the altered structure, media composition, and vascular relaxation of small arteries of spontaneously hypertensive rats.

METHODS

Spontaneously hypertensive rats aged 10 weeks were treated for 12 weeks with 10 mg/kg per day enalapril or 10-20 mg/kg per day amlodipine and compared with age-matched untreated spontaneously hypertensive rats. Small coronary, renal, mesenteric, and femoral arteries (lumen diameter 200-250 microm) were studied isometrically on a wire myograph, and mesenteric arteries isobarically as pressurized vessels. The composition of the vascular media of the latter was studied by electron microscopy.

RESULTS

Blood pressure, and cardiac and aortic hypertrophy were reduced in treated spontaneously hypertensive rats. Treatment significantly decreased media thickness and media: lumen ratio of coronary, renal, mesenteric, and femoral small arteries studied isometrically and of pressurized mesenteric small arteries. Media cross-sectional area was smaller for coronary arteries studied isometrically and mesenteric arteries studied isobarically. Electron microscopic analysis revealed an increase in collagen: elastin ratio in the media of spontaneously hypertensive rat vessels, and a decrease under treatment to levels found in Wistar-Kyoto rats, with no significant changes detected in smooth muscle cells. The amplitude of contractions induced by acetylcholine on wire-myograph-mounted mesenteric arteries from spontaneously hypertensive rats were decreased by treatment, and relaxation of pressurized arteries induced by acetylcholine was normalized.

CONCLUSION

Treatment of spontaneously hypertensive rats with enalapril or with amlodipine resulted in regression of cardiovascular hypertrophy and amelioration of endothelial dysfunction. Morphometric results obtained using an isometric myograph and a pressurized preparation to study rat small arteries were closely correlated. Regression of structural remodeling in small arteries was outward hypotrophic, with a reduction in the collagen: elastin ratio, and without net change in the absolute and relative volumes of smooth muscle and number of smooth muscle layers.

Apoptosis in aorta of deoxycorticosterone acetate-salt hypertensive rats: effect of endothelin receptor antagonism

BACKGROUND

Apoptosis or programmed cell death could be greater than normal in various cardiovascular disorders, particularly in the heart. Apoptosis might contribute to remodeling of blood vessels in hypertension and could participate in regulation of vascular hypertrophy/hyperplasia.

OBJECTIVE

To investigate apoptosis in deoxycorticosterone acetate (DOCA)-salt hypertension and to determine whether endothelin-1, whose expression is enhanced in these rats, plays a role in apoptosis.

METHODS

We administered two orally active endothelin-A (ET[A])-selective receptor antagonists, A-127,722.5 (30 mg/kg per day) and LU 135,252 (50 mg/kg per day), to establish whether antigrowth effects of these ET(A) antagonists are in part mediated through apoptosis. Apoptosis was evaluated by radiolabeling of 3' OH ends of fragmented DNA, extracted from aortas, using terminal deoxynucleotidyl transferase, to show the presence of internucleosomal DNA splicing as 'DNA laddering'. Its presence was confirmed by in-situ end-labeling.

RESULTS

Systolic blood pressure was slightly but significantly lower in treated than it was in untreated DOCA-salt hypertensive rats by a mean of 26 mmHg (P < 0.01) after 4 weeks of treatment with A-127,722.5 and by 19 mmHg (P < 0.01) in rats treated with LU 135,252. Aortic cross-sectional area (CSA) was significantly greater (P < 0.001) in DOCA-salt rats than it was in uninephrectomized controls. This increased CSA was normalized by both ET(A) antagonists. DOCA-salt rats exhibited a greater degree of apoptosis (evaluated by DNA 'laddering') in aorta (353 +/- 14 pixels/microg DNA) than did control rats (232 +/- 10 pixels/microg DNA, P < 0.01). The magnitude of apoptosis was significantly greater (P < 0.01) in aorta of endothelin-antagonist-treated than it was in aorta of untreated DOCA-salt hypertensive rats. In-situ end-labeling confirmed that more apoptosis had occurred in the media of aorta from DOCA-salt hypertensive rats and the further increase found after treatment with the ET(A) antagonists.

CONCLUSION

An increase in apoptosis occurs in aorta of DOCA-salt hypertensive rats, probably as a physiologic counterpart of growth in this hypertensive model. ET(A) antagonists may act in part by accentuating the apoptosis, thereby inducing a blunting of vascular growth, which could also contribute to their antihypertensive effects.

Effect of AT1 angiotensin-receptor blockade on structure and function of small arteries in SHR

The structure and function of small arteries of different vascular beds in spontaneously hypertensive rats (SHRs) are altered relative to Wistar-Kyoto (WKY) control rats, and these differences may be blunted under treatment with angiotensin-converting enzyme inhibitors. To determine whether this effect of angiotensin-converting enzyme inhibitors was caused by the interruption of the renin-angiotensin system, our experiments were conducted with an AT1 angiotensin-receptor antagonist to evaluate its ability to induce regression of hypertrophy of resistance arteries in SHRs. The result of treatment of SHRs with losartan, an orally active selective angiotensin AT1 receptor antagonist was examined at a low (20 mg/kg/day) and a high (60 mg/kg/day) oral dose in SHRs once blood pressure had been elevated for some time. SHRs were treated for 12 weeks with losartan. Blood pressure was significantly reduced by losartan treatment from 210 +/- 2 mm Hg in untreated SHRs to 181 +/- 1 mm Hg (low dose) and 156 +/- 4 mm Hg (high dose) (p < 0.01). Cardiac and aortic hypertrophy were dose-dependently reduced in treated SHRs. Coronary, renal, mesenteric, and femoral small arteries (luminal diameter, 200-250 microm) studied on an isometric wire myograph and pressurized mesenteric small arteries examined under isobaric conditions exhibited significant hypertrophy and inward remodeling in SHRs in comparison to WKY rats. Losartan treatment resulted in a dose-dependent reduction in the media thickness and mediato-lumen ratio in small arteries from the four vascular beds studied on the wire myograph and in pressurized mesenteric small arteries. Endothelium-dependent relaxation studied in pressurized arteries was enhanced, and acetylcholine-induced endothelium-dependent contractions studied on the wire myograph were abolished in losartan-treated SHRs relative to untreated SHRs. In WKY rats, treatment had no effect. These results demonstrate that treatment with the selective angiotensin II receptor antagonist losartan, even at doses that reduce blood pressure only moderately, induces regression of cardiovascular hypertrophy and of endothelial dysfunction in genetic hypertension in the rat.

Endothelin receptors mediating vasoconstriction in rat pressurized small arteries

The effects of endothelin-1 (ET-1), a nonselective ETA and ETB receptor agonist, and sarafotoxin S6c, a selective ETB agonist, were investigated in the presence and absence of BQ123 and BQ788, ETA- and ETB-selective antagonists, respectively, in rat mesenteric small arteries, using a perfusion pressurized arteriograph in which segments of vessels were cannulated and exposed to constant pressure and flow. ET-1 (10(-13)-10(-7) M) induced vasoconstriction in both intact and endothelium-denuded arteries in a concentration-dependent manner. BQ123 (10(-7) and 10(-6) M) inhibited the effect of ET-1, displacing the concentration-response curve to the right in a concentration-dependent manner. The effect of ET-1 was not significantly affected by BQ788 (10(-7) and 10(-6) M), a selective antagonist of ETB receptors. Sarafotoxin S6c (10(-11)-10(-7) M) also induced a slight concentration-dependent vasoconstriction. The effect of sarafotoxin S6c (10(-8) M) was inhibited by the ETB-selective antagonist BQ788 (10(-7) M), but was not significantly changed by BQ123 (10(-7) M). Vasoconstriction induced by sarafotoxin S6c (10(-8) M) in a single bolus concentration was significantly greater than the contraction induced by the same concentration as part of a cumulative concentration-response curve, indicating desensitization or downregulation of ETB receptors during the latter. Repeated application of single concentrations of sarafotoxin S6c (10(-8) M) caused progressively smaller contraction of arteries. These results show the existence of both ETA and ETB vasoconstrictor receptors located on smooth muscle of small arteries. They also show that ETB receptors induce a smaller constrictor effect, and rapidly undergo desensitization after sustained or repeated activation.