Growth factors increase pericellular proteoglycans independently of their mitogenic effects on A10 rat vascular smooth muscle cells

How Structure, Mechanics, and Function of the Vasculature Contribute to Blood Pressure Elevation in Hypertension

Large conduit arteries and the microcirculation participate in the mechanisms of elevation of blood pressure (BP). Large vessels play roles predominantly in older subjects, with stiffening progressing after middle age leading to increases in systolic BP found in most humans with aging. Systolic BP elevation and increased pulsatility penetrate deeper into the distal vasculature, leading to microcirculatory injury, remodelling, and associated endothelial dysfunction. The result is target organ damage in the heart, brain, and kidney. In younger individuals genetically predisposed to high BP, increased salt intake or other exogenous or endogenous risk factors for hypertension, including overweight and excess alcohol intake, lead to enhanced sympathetic activity and vasoconstriction. Enhanced vasoconstrictor responses and myogenic tone become persistent when embedded in an increased extracellular matrix, resulting in remodelling of resistance arteries with a narrowed lumen and increased media-lumen ratio. Stimulation of the renin-angiotensin-aldosterone and endothelin systems and inflammatory and immune activation, to which gut microbiome dysbiosis may contribute as a result of salt intake, also participate in the injury and remodelling of the microcirculation and endothelial dysfunction. Inflammation of perivascular fat and loss of anticontractile factors play roles as well in microvessel remodelling. Exaggerated myogenic tone leads to closure of terminal arterioles, collapse of capillaries and venules, functional rarefaction, and eventually to anatomic rarefaction, compromising tissue perfusion. The remodelling of the microcirculation raises resistance to flow, and accordingly raises BP in a feedback process that over years results in stiffening of conduit arteries and systo-diastolic or predominantly systolic hypertension and, more rarely, predominantly diastolic hypertension. Thus, at different stages of life and the evolution of hypertension, large vessels and the microcirculation interact to contribute to BP elevation.

Inflammasome Activation Aggravates Cutaneous Xanthomatosis and Atherosclerosis in ACAT1 (Acyl-CoA Cholesterol Acyltransferase 1) Deficiency in Bone Marrow

Objective- ACAT1 (Acyl-CoA cholesterol acyltransferase 1) esterifies cellular free cholesterol, thereby converting macrophages to cholesteryl ester-laden foam cells in atherosclerotic lesions and cutaneous xanthoma. Paradoxically, however, loss of ACAT1 in bone marrow causes the aggravation of atherosclerosis and the development of severe cutaneous xanthoma in hyperlipidemic mice. Recently, it has been reported that cholesterol crystals activate NLRP3 (NACHT, LRR [leucine-rich repeats], and PYD [pyrin domain] domain-containing protein 3) inflammasomes, thereby contributing to the development of atherosclerosis. The present study aimed to clarify the role of NLRP3 inflammasomes in the worsening of atherosclerosis and cutaneous xanthoma induced by ACAT1 deficiency. Approach and Results- Ldlr-null mice were transplanted with bone marrow from WT (wild type) mice and mice lacking ACAT1, NLRP3, or both. After the 4 types of mice were fed high-cholesterol diets, we compared their atherosclerosis and skin lesions. The mice transplanted with Acat1-null bone marrow developed severe cutaneous xanthoma, which was filled with numerous macrophages and cholesterol clefts and had markedly increased expression of inflammatory cytokines, and increased atherosclerosis. Loss of NLRP3 completely reversed the cutaneous xanthoma, whereas it improved the atherosclerosis only partially. Acat1-null peritoneal macrophages showed enhanced expression of CHOP (C/EBP [CCAAT/enhancer binding protein] homologous protein) and TNF-α (tumor necrosis factor-α) but no evidence of inflammasome activation, after treatment with acetylated LDL (low-density lipoprotein). Conclusions- Elimination of ACAT1 in bone marrow-derived cells aggravates cutaneous xanthoma and atherosclerosis. The development of cutaneous xanthoma is induced mainly via the NLRP3 inflammasome activation.

Loss of ACAT1 Attenuates Atherosclerosis Aggravated by Loss of NCEH1 in Bone Marrow-Derived Cells

AIM

Acyl-CoA cholesterol acyltransferase 1 (ACAT1) esterifies free cholesterol to cholesteryl esters (CE), which are subsequently hydrolyzed by neutral cholesterol ester hydrolase 1 (NCEH1). The elimination of ACAT1 in vitro reduces the amounts of CE accumulated in Nceh1-deficient macrophages. The present study aimed at examining whether the loss of ACAT1 attenuates atherosclerosis which is aggravated by the loss of NCEH1 in vivo.

METHODS

Low density lipoprotein receptor (Ldlr)-deficient mice were transplanted with bone marrow from wild-type mice and mice lacking ACAT1, NCEH1, or both. The four types of mice were fed a high-cholesterol diet and, then, were examined for atherosclerosis.

RESULTS

The cross-sectional lesion size of the recipients of Nceh1-deficient bone marrow was 1.6-fold larger than that of the wild-type bone marrow. The lesions of the recipients of Nceh1-deficient bone marrow were enriched with MOMA2-positive macrophages compared with the lesions of the recipients of the wild-type bone marrow. The size and the macrophage content of the lesions of the recipients of bone marrow lacking both ACAT1 and NCEH1 were significantly smaller than the recipients of the Nceh1-deficient bone marrow, indicating that the loss of ACAT1 decreases the excess CE in the Nceh1-deficient lesions. The collagen-rich and/or mucin-rich areas and en face lesion size were enlarged in the recipients of the Acat1^－/－ bone marrow compared with those of the recipients of the WT bone marrow.

CONCLUSION

The loss of ACAT1 in bone marrow-derived cells attenuates atherosclerosis, which is aggravated by the loss of NCEH1, corroborating the in vitro functions of ACAT1 (formation of CE) and NCEH1 (hydrolysis of CE).

A synthetic glycosaminoglycan mimetic (RGTA) modifies natural glycosaminoglycan species during myogenesis

Crucial events in myogenesis rely on the highly regulated spatiotemporal distribution of cell surface heparan sulfate proteoglycans to which are associated growth factors, thus creating a specific microenvironment around muscle cells. Most growth factors involved in control of myoblast growth and differentiation are stored in the extracellular matrix through interaction with specific sequences of glycosaminoglycan oligosaccharides, mainly heparan sulfate (HS). Different HS subspecies revealed by specific antibodies, have been shown to provide spatiotemporal regulation during muscle development. We have previously shown that glycosaminoglycan (GAG) mimetics called RGTA (ReGeneraTing Agent), stimulate muscle precursor cell growth and differentiation. These data suggest an important role of GAGs during myogenesis; however, little is yet known about the different species of GAGs synthesized during myogenesis and their metabolic regulation. We therefore quantified GAGs during myogenesis of C2.7 cells and show that the composition of GAG species was modified during myogenic differentiation. In particular, HS levels were increased during this process. In addition, the GAG mimetic RGTA, which stimulated both growth and differentiation of C2.7 cells, increased the total amount of GAG produced by these cells without significantly altering their rate of sulfation. RGTA treatment further enhanced HS levels and changed its sub-species composition. Although mRNA levels of the enzymes involved in HS biosynthesis were almost unchanged during myogenic differentiation, heparanase mRNA levels decreased. RGTA did not markedly alter these levels. Here we show that the effects of RGTA on myoblast growth and differentiation are in part mediated through an alteration of GAG species and provide an important insight into the role of these molecules in normal or pathologic myogenic processes.

Glycosaminoglycan mimetics (RGTA) modulate adult skeletal muscle satellite cell proliferation in vitro

Muscle regeneration occurs through the activation of satellite cells, which are stimulated to proliferate and to fuse into myofibers that will reconstitute the damaged muscle. We have previously reported that a family of new compounds called "regenerating agents" (RGTAs), which are polymers engineered to mimic heparan sulfates, stimulate in vivo tissue repair. One of these agents, RG1192, a dextran derivative substituted by CarboxyMethyl, Benzylamide, and Sulfate (noted CMBS, RGTA type), was shown to improve greatly the regeneration of rat skeletal muscle after severe crushing, denervation, and acute ischemia. In vitro, these compounds mimic the protecting and stabilizing properties of heparin or heparan sulfates toward heparin-binding growth factors (HBGFs). We hypothesized that RGTA could act by increasing the bioavailability of some HBGF involved in myoblast growth and thus asked whether RGTA would alter the ability of satellite cells to proliferate. Its effect was tested on primary cultures of rat satellite cells. The RG1192 stimulated the proliferation of satellite cells in vitro in a dose-dependent manner. It appeared to be as efficient as natural glycosaminoglycans (GAGs; heparan sulfate, dermatan sulfate, or keratan sulfate) in stimulating satellite cell proliferation but was about 100 times more efficient than heparin. RG1192 stimulated satellite cell proliferation by increasing the potency of fibroblast growth factor 2 and scatter factor-hepatocyte growth factor. It also partially restored myoblast proliferation of satellite cells with chlorate-induced hyposulfation. Taken together, our results explain to some extent the improving effect of RGTA with a CMBS structure, such as the RG1192, on muscle regeneration in vivo by providing support for the hypothesis that RGTA may act by increasing the potency of some HBGFs during the proliferation phase of the regenerating muscle.

Effect of transforming growth factor-beta1, insulin-like growth factor-I, and hepatocyte growth factor on proteoglycan production and regulation in canine melanoma cell lines

OBJECTIVE

To identify extracellular proteoglycans produced by canine melanoma cell lines and analyze the effect of transforming growth factor-beta1 (TGF-beta1), insulin-like growth factor-I (IGF-I), and hepatocyte growth factor (HGF) on these proteoglycans.

SAMPLE POPULATION

3 canine melanoma cell lines (ie, CML-1, CML-6M, and CML-10c2).

PROCEDURE

Extracellular proteoglycans were analyzed by use of metabolic labeling and western immunoblot analysis. The effect of TGF-beta1 on cell proliferation was determined by incorporation of 5-bromo-2'-deoxyuridine.

RESULTS

The CML-1 and CML-6M melanoma cell lines produced 2 main extracellular proteoglycans. One of them was identified as versican, a proteoglycan found in undifferentiated human melanoma cell lines. The CML-10c2 cells produced a small amount of extracellular proteoglycans. Addition of TGF-beta1 (1.25 to 6.25 ng/ml) increased the release of sulfated proteoglycans into the medium. The TGF-beta1 had mainly a posttranslational effect, because it increased the molecular mass of the sulfated bands. Addition of IGF-I (50 ng/ml) slightly increased production of proteoglycans in the CML-6M cell line, whereas HGF (50 ng/ml) did not have any effect on proteoglycan production.

CONCLUSIONS AND CLINICAL RELEVANCE

The proteoglycan content and response toTGF-beta1 treatment for CML-1 and CML-6M canine melanoma cell lines are similar to that for undifferentiated human melanoma cell lines. In contrast, CML-10c2 cells produced a low amount of proteoglycans with high molecular weight. Because these extracellular proteoglycans are involved in the control of cell adhesion, proliferation, and migration, they may play an important role in the progression of melanomas in dogs.

Early changes in proteoglycans production by resistance arteries smooth muscle cells of hypertensive rats

Several functional and structural modifications at the vascular level have been described in spontaneously hypertensive rats (SHR) during the early development of hypertension. In this study, we hypothesize that changes in the extracellular matrix (ECM) could precede the development of hypertension. Synthesis of secreted and membrane-bound sulfated proteoglycans (S-PG) by cultured vascular smooth muscle cells (VSMC) obtained from young spontaneously hypertensive rats (pSHR) mesenteric resistance arteries, during the period preceding the elevation of blood pressure (BP) was tested. After 24 h of stimulation with angiotensin II (Ang II), 10% fetal calf serum (FCS), or 0.1% FCS as control, medium and cell layer S-PG synthesis was evaluated by labeling sulfated disaccharides with [35S] sodium sulfate. To relate this variable with cell proliferation, DNA synthesis was measured by incorporation of [3H]thymidine in the cell lysate. The VSMC from pSHR synthesized more secreted and membrane-bound S-PG than age-matched Wistar rat (pW) cells in the nonstimulated (0.1% FCS) and stimulated (Ang II or 10% FCS) experimental groups. When data were expressed as percent of their own control value, both Ang II and 10% FCS lowered basal secreted and cell-associated S-PG content in VSMC from pSHR, whereas in pW rat cells, these agents produced a small increase or no change. An inverse relationship between proliferation and total S-PG production (secreted plus membrane-bound) was found in pSHR cells, but not in pW cells. In conclusion, the present study demonstrates that changes in S-PG synthesis by VSMC of resistance arteries precede the vascular dysfunction associated with the development of hypertension in SHR.

Preferential binding of polyethylene glycol-coated liposomes containing a novel cationic lipid, TRX-20, to human subendthelial cells via chondroitin sulfate

PURPOSE

To design novel cationic liposomes, polyethylene glycol (PEG)-coated cationic liposomes containing a newly synthesized cationic lipid, 3,5-dipentadecyloxybenzamidine hydrochloride (TRX-20) were formulated and their cellular binding and uptake investigated in vitro in the following cells: human subendothelial cells (aortic smooth muscle cells and mesangial cells) and human endothelial cells.

METHODS

Three different PEG-coated cationic liposomes were prepared by the extrusion method, and their mean particle size and zeta potential were determined. Rhodamine-labeled PEG-coated cationic liposomes were incubated with smooth muscle cells, mesangial cells, and endothelial cells at 37 degrees C for 24 h. The amounts of cellular binding and uptake of liposomes were estimated by measuring the cell-associated fluorescence intensity of rhodamine. To investigate the binding property of the liposomes, the changes of the binding to the cells pretreated by various kinds of glycosaminoglycan lyases were examined. Fluorescence microscopy-is used to seek localization of liposomes in the cells.

RESULTS

The cellular binding and uptake of PEG-coated cationic liposomes to smooth muscle cells was depended strongly on the chemical species of cationic lipids in these liposomes. Smooth muscle cells bound higher amount of PEG-coated TRX-20 liposomes than other cationic liposomes containing N-(1-(2.3-dioleoyloxy) propyl)-N, N, N-trimethylammonium salts or N-(alpha-(trimethylammonio)acetyl)-D-glutamate chloride. Despite of the higher affinity of PEG-coated TRX-20 liposomes for subendothelial cells, their binding to endothelial cells was very small. The binding to subendothelial cells was inhibited when cells were pretreated by certain kinds of chondroitinase, but not by heparitinase. These results suggest that PEG-coated TRX-20 liposomes have strong and selective binding property to subendothelial cells by interacting with certain kinds of chondroitin sulfate proteoglycans (not with heparan sulfate proteoglycans) on the cell surface and in the extracellular matrix of the cells. This binding feature was different from that reported for other cationic liposomes.

CONCLUSIONS

PEG-coated TRX-20 liposomes can strongly and selectively bind to subendothelial cells via certain kinds of chondroitin sulfate proteoglycans and would have an advantage to use as a specific drug delivery system.

A subpopulation of fibroblast growth factor-2-binding heparan sulfate is lost in human papillary thyroid carcinomas

We hypothesized that a change in composition of proteoglycans can regulate the bioactivity of fibroblast growth factor (FGF)-2 in the thyroid. In order to test this hypothesis, we established a simple and sensitive method for detecting FGF-2-binding heparan sulfates and characterized them in papillary thyroid carcinomas and normal thyroids. The thyroid extracts were applied to a Q-Sepharose anion exchange column. After the column was washed with 10 mM of phosphate buffer, 1 microgram of human recombinant FGF-2 was added onto the column. The column was eluted with a gradient of NaCl (0.3-1.5 M). Each fraction was blotted onto nitrocellulose membrane. Immunoreactivity of heparan sulfate and FGF-2 was revealed by the incubation of membranes with the specific antibodies, and quantitatively estimated by measuring the density of the color product. In normal thyroids, immunoreactivity of heparan sulfate was detected as two peaks at 0.7 and 0.9 M of NaCl. Heparan sulfate-containing fractions also showed FGF-2 immunoreactivity, indicating the complex formation of FGF-2 and heparan sulfate. In papillary thyroid carcinomas, immunoreactivity of heparan sulfate showed various elution profiles on Q-Sepharose chromatography, including single peak at 0.7 M of NaCl and the one similar to that of the normal thyroids. However, FGF-2 immunoreactivity was detected only in the fractions eluting at 0.7 M of NaCl. This loss of a subpopulation of FGF-2-binding heparan sulfate in human papillary thyroid carcinomas may lead to the increase of free FGF-2 bioavailable in extracellular matrix.

Structure and mechanical properties of resistance arteries in hypertension: role of adhesion molecules and extracellular matrix determinants

Abnormalities of resistance arteries may play a role in the pathogenesis and pathophysiology of hypertension in experimental animals and humans. Vessels that, when relaxed, measure <400 microm in lumen diameter act as the major site of vascular resistance and include a network of small arteries (lumen approximately 100 to 400 microm) and arterioles (<100 microm). Because increased peripheral resistance is generated by a narrowed lumen diameter, significant effort has been focused on determining the mechanisms that reduce lumen size. Three important vascular components are clearly involved, including alterations of vascular structure, mechanics (stiffness), and function. Structural abnormalities comprise a reduced lumen diameter and thickening of the vascular media, resulting in an increased media-lumen ratio. Changes in the mechanical properties of an artery, particularly increased stiffness, may also result in a reduced lumen diameter. These vascular abnormalities may be caused or influenced by the expression and/or topographic localization of extracellular matrix components, such as collagen and elastin, and by changes in cell-extracellular fibrillar attachment sites, such as adhesion molecules like integrins. This article discusses the abnormalities of resistance arteries in hypertension and reviews the evidence suggesting an important role for adhesive and extracellular matrix determinants.

Proteoglycan production by vascular smooth muscle cells from resistance arteries of hypertensive rats

Extracellular matrix (ECM) modifications in the vascular wall contribute to the narrowing of arteries in hypertension. Because direct evidence for the role of proteoglycans (PGs) in the pathological process of resistance-sized arteries has not already been demonstrated, we examined the effect of growth factors on secreted and membrane-bound PG synthesis by cultured mesenteric vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) and Wistar rats. After 48 hours of stimulation with angiotensin II (Ang II), platelet-derived growth factor (PDGF-BB), and 10% fetal calf serum (FCS) or 0.1% FCS as control, PG synthesis (in dpm/ng DNA) was evaluated in the medium (M-ECM) and in the cell layer (P-ECM) by a double-isotopic label method with both [(3)H]-glucosamine and [(35)S]-sodium sulfate, which are incorporated into all complex carbohydrates or only into sulfated disaccharides, respectively. VSMC from SHR displayed a significantly lower level of synthesis of M-ECM [(3)H]-PGs than those of Wistar rats in all the experimental groups, including the control group (0. 1% FCS), but no differences in M-ECM [(35)S] uptake were found in any case. In the P-ECM, Ang II was the only factor that produced a lesser effect on [(3)H]-glucosamine and a greater effect on [(35)S]-sodium sulfate uptakes in VSMC from SHR than from Wistar rats. The most prominent change seen in VSMC from SHR was an increased sulfation, assessed by [(35)S]/[(3)H] ratio, in nonstimulated cells and in response to 10% FCS and Ang II but not to PDGF-BB compared with VSMC from Wistar rats. These data indicate the existence of changes in PG modulation in the resistance vessels of SHR, which suggests that PGs may contribute to the development of structural and functional modifications in hypertensive states.

Modulatory proteins and processes in alliance with immune cells, mediators, and extracellular proteins in renal interstitial fibrosis

A synopsis of the many aspects and factors that contribute to renal tubulo-interstitial fibrosis is presented. The role of fibrogenic cytokines and the conversion of fibroblasts to myofibroblasts are described. It is emphasized that oxygen radicals cause fibroblasts to generate collagen. The properties of those accessory modulatory proteins that affect the behavior of cells in the interstitium are considered and how matrix for ensuing fibrosis is laid down. Understanding the extracellular matrix proteins and these modulatory proteins is important because their behavior can now be modified by means of antisense oligonucleotides.