Expression of receptor for advanced glycosylation end products (AGEP) and inhibition of AGEP-induced cytosolic calcium elevation by diltiazem in cultured rat aortic smooth muscle cells

AIM

To study whether there is a high affinity receptor for advanced glycosylation end product (AGEP) on thoracic aorta smooth muscle cells (ASMC) and to test effect of diltiazem on elevation of cytosolic free calcium induced by AGEP.

METHODS

Interactions of AGEP-bovine serum albumin (BSA) with ASMC were studied with radioligand binding assay and cytosolic free calcium ([Ca2+]i) was examined in cultured ASMC with Fura 2-AM.

RESULTS

AGEP-BSA was specifically bound to cells at 4 degrees C and was taken up and degraded at 37 degrees C. These processes were concentration-dependent and saturable. Scatchard analysis indicated that the receptor was with dissociation constant of 65.3 +/- 1.5 nmol.L-1 and its maximal binding capacity of 1.57 +/- 0.04 nmol/g cell protein. Early glycated low density lipoprotein (LDL) was not recognized by this receptor. AGEP-BSA elevated cytosolic free calcium in a concentration-dependent manner. Pretreatment with diltiazem inhibited AGEP-BSA-induced elevation in concentration- and time-dependent manners.

CONCLUSION

There was a high affinity receptor for AGEP on ASMC, which mediated internalization and degradation of AGEP. Pretreatment with diltiazem inhibited the AGEP-induced elevation of cytosolic free calcium.

Effects of advanced glycosylation end products on proliferation and cytosolic free calcium in cultured rat aortic smooth muscle cells

AIM

To study the effects of advanced glycosylation end products (AGEP) on aortic smooth muscle cell (ASMC) proliferation and its relationship with cytosolic free calcium ([Ca2+]i).

METHODS

The effects of AGEP modified bovine serum albumin (AGEP-BSA) on the incorporation of [3H]TdR and [3H]Leu into cultured ASMC were observed. The [Ca2+]i of cultured ASMC was determined with Fura 2-AM.

RESULTS

AGEP-BSA stimulated the incorporation of [3H]TdR and [3H]Leu into ASMC in concentration and time-dependent manners (P < 0.01), especially [3H]TdR. In AGEP 200 mg.L-1 group, after 12-h exposure, the incorporation of [3H]TdR obviously increased, but DNA synthesis was concentration-dependently decreased in AGEP 300-400 mg.L-1 groups. The peak incorporation of [3H]TdR was 10 times vs control (P < 0.01). The [Ca2+]i of ASMC incubated with AGEP-BSA for 40 min was increased from control groups 121 +/- 4 to 492 +/- 20 nmol.L-1 (P < 0.01). [Ca2+]i induced by AGEP was elevated with the concentration and incubating time of glucose with BSA. [Ca2+]i in BSA incubated with glucose 80 mmol.L-1 for 12 wk was 580 +/- 37 nmol.L-1 (P < 0.01).

CONCLUSION

AGEP stimulated proliferation of ASMC associated with the elevation of [Ca2+]i.

The regulatory effects of cytokines on lymphatic angiogenesis

The effects of fibroblast growth factor basic (bFGF), transforming growth factor alpha (TGF alpha), recombinant human epidermal growth factor (EGF), recombinant human tumor necrosis factor alpha (TNF alpha), and recombinant interleukin 1 alpha (IL-1 alpha) on lymphatic angiogenesis were assessed in cultured newborn bovine lymphatic endothelial cells (NBLEC). bFGF, TGF alpha, and EGF stimulated the proliferation of NBLEC in a dose-dependent manner, but the combination of either two growth factors did not show synergistic effects on NBLEC DNA synthesis. TNF alpha and IL-1 alpha suppressed the multiplication of NBLEC. Treatment with bFGF markedly increased the migration of NBLEC. The tissue plasminogen activator (t-PA) activity was enhanced by bFGF. TNF alpha also promoted NBLEC t-PA activity. These results suggest that bFGF is a major multifunctional lymphatic endothelial cell targeted cytokine, and both growth and pro-inflammatory cytokines exert differential regulatory effects on lymphatic endothelial cell proliferation, migration and t-PA activity.

[Enhancement on expression of LDL receptors in cultured rhesus renal epithelial cells by verapamil]

In order to investigate the anti-atherogenic properties of calcium antagonists, human serum low density lipoproteins (LDL) were isolated by density gradient ultracentrifugation and iodinated with 125I by iodine monochloride method. Effects of verapamil on activity of LDL receptors in cultured rhesus renal epithelial cells were examined by radioligand analysis. The receptor-mediated binding, internalization, and degradation of cultured cells pretreated with verapamil 44 mmol.L-1 for 24 h and cells pretreated for 24 h and incubated for 10 h with verapamil were increased compared with control group (61 +/- 11, 52 +/- 8 vs 20 +/- 3.5, 1006 +/- 106, 579 +/- 124 vs 253 +/- 78, 630 +/- 43, 541 +/- 46 vs 374 +/- 53 125I-LDL/micrograms.g-1 cell protein). In verapamil-treated cells without verapamil pretreatment, increased internalization and degradation were not significant, and binding was not increased. When the cells were pretreated with verapamil 22 mmol.L-1 for 24 h and then incubated with 5, 20, 50 125I-LDL/mg.L-1, binding and internalization were increased, increased degradation was seen only with 50 125I-LDL/mg.L-1. The results indicated that the verapamil enhances expression of LDL receptor in cultured rhesus renal epithelial cells, which might contribute to the protective effects of calcium antagonists in experimental and human atherosclerosis.

The influence of local hyperthermia on lymphedema and lymphedematous skin of the human leg

The influence of microwave and hot water immersion hyperthermia on lymphedema and lymphedematous skin of the leg in 12 patients was studied using circumference and volumetric measurements, immunohistochemistry and "quantitative" lymphoscintigraphy. Whereas heating was associated with a reduction in the girth and volume of the leg, lymph flow as assessed by lymphoscintigraphy was unchanged. Neither absorption of the radiolabeled nanocolloid from the injection site nor the rate of tracer accumulation in the inguinal lymph nodes was significantly altered by heat therapy. Histologically, the lymphedematous skin after heat treatment showed near resolution of perivascular cellular infiltration, disappearance of "lymph lakes" and dilatation of blood capillaries. Labeling of skin migrating immune cells with monoclonal antibodies confirmed subsidence of dermal cellular infiltration; nonetheless, there was nonspecific stimulation of resident epidermal immune cells, endothelial cells, macrophages, lymphocytes and keratinocytes by intense expression of class II and other antigens. There seemed to be a direct relationship between the subsidence of dermal inflammation and a decrease in leg edema. We suspect that subsidence of local inflammation in the lymphedematous limb with alteration in the extracellular protein matrix after regional heating accounts for the reduction in peripheral edema.

Use of tonometry to assess lower extremity lymphedema

Tissue tonometry was used to assess the outcome of microwave hyperthermia in treatment of 9 patients with lower extremity lymphedema. After microwave treatment, tissue tonicity of the lymphedematous leg returned toward normal. This improvement correlated with a reduction of leg volume and circumference, decrease in "inflammation" in the edematous subcutaneous tissue and clinical episodes of cellulitis. Possible factors involved in this shift in tissue tonicity toward normal include mobilization of excess fluid and plasma proteins from the interstitium, reduction in microvascular cellular infiltrate and changes in the elastic and viscoelastic properties of matrix collagen, elastin and ground substance following hyperthermia.

Mesenteric lymph node transplantation in syngeneic rats: changes in cellularity and architecture

The cellular architectural and functional changes of transplanted mesenteric lymph nodes in rats were studied. After lymph nodes were transplanted with interruption of both the afferent and efferent lymphatics, the nodal cellular content gradually became depleted. One month after operation, the recirculating lymphocyte count in the transplanted node was only 3.5% of that in control nodes, whereas the number of mononuclear cells per mg tissue of transplanted node was only 28% of normal. In the transplanted nodal paracortex, the cells of high endothelial venules (HEV) became less prominent and gradually flattened altogether. In the transplanted nodal cortex, germinal centers and follicles also sharply decreased and later disappeared. Three months after transplantation, the normal compartmentalization of the transplanted nodes were no longer distinguishable. Regeneration of afferent lymphatics was not detected in transplanted nodes and the lack of circulating antigen and stimulated lymphocytes was probably responsible for the histological and functional involution of grafted mesenteric lymph nodes.