Glucose control with insulin results in reduction of NF-kappaB-binding activity in mononuclear blood cells of patients with recently manifested type 1 diabetes

AIM

Chronic elevated blood glucose levels are associated with the formation of advanced glycation end products (AGEs). Hyperglycaemia and AGEs have been shown to induce activation of the redox-sensitive transcription factor nuclear factor-kappaB (NF-kappaB). To validate the hypothesis that the maintenance of normal glucose levels results in the reduction of NF-kappaB-binding activity in vivo, the redox-sensitive transcription factor NF-kappaB was used as marker of hyperglycaemia-induced mononuclear cell activation in patients who recently developed type 1 diabetes.

METHODS

Twelve patients with recently manifested type 1 diabetes mellitus were examined in our study. After sampling blood for determination of baseline glucose values, the 12 patients were treated with insulin, and blood samples were taken 4 and 12 weeks later. Mononuclear cells were isolated and assayed in a tissue culture-independent electrophoretic mobility shift assay (EMSA)-based detection system for NF-kappaB-binding activity. Western blot analysis was used to determine nuclear and cytoplasmic localization of NF-kappaB-p65 and cytoplasmic content of inhibitor of kappa B-alpha (IkappaB-alpha). In addition, we determined the concentration of heme oxygenase-1 (HO-1) from cytoplasmic extract as a marker of oxidative stress.

RESULTS

Normalization of blood glucose levels resulted in a highly significant reduction of NF-kappaB activation in EMSA. Before and after glucose normalization, there were no differences in binding by the members of the NF-kappaB family to the NF-kappaB consensus sequence oligonucleotide. Similar data were obtained by Western blot analysis showing NF-kappaB-p65 localization in the nucleus, while p65 levels increased in the cytoplasm. IkappaB-alpha increased in the cytoplasm after glucose normalization. HO-1 antigen consistently decreased, as expected from the decrease in NF-kappaB activation.

CONCLUSION

Thus, we conclude that normalization of blood glucose levels results in the reduction of NF-kappaB activation and gene products controlled by this transcription factor.

HSP47 expression by smooth muscle cells is increased during arterial development and lesion formation and is inhibited by fibrillar collagen

HSP47 is a heat-shock protein that interacts with intracellular procollagen. It has been found in fibrous atherosclerotic plaque, but its involvement in acute vascular restructuring is unknown. We analyzed the expression of HSP47 and its regulation in the developing rat aorta and after balloon injury to the adult rat carotid artery. HSP47 was strongly expressed in each layer of the maturing fetal aorta (embryonic day 17 to birth). Expression declined during the first 4 postnatal days but persisted at low abundance into adulthood. HSP47 expression was substantially upregulated in the injured carotid artery, with intense immunostaining in neointimal smooth muscle cells (SMCs). HSP47 expression in SMCs was correlated with the emergence of a less mature phenotype and with expression of type I procollagen. Interestingly, a precipitous decline in HSP47 expression was evident during aortic development and after carotid artery injury, in association with the appearance of collagen fibrils in the local extracellular matrix. Furthermore, type I collagen fibrils, but not collagen monomers, inhibited expression of HSP47 by SMCs. These findings indicate that upregulation of HSP47 is a feature of vascular restructuring, including acute neointimal formation, and that the constituents of the extracellular matrix regulate the duration of expression. This feedback control may be important for self-termination of vascular development and lesion growth.

Heat shock protein 47 is expressed in fibrous regions of human atheroma and Is regulated by growth factors and oxidized low-density lipoprotein

BACKGROUND

Heat shock protein 47 (Hsp47) is a stress protein that may act as a chaperone for procollagen. Its involvement in atherosclerosis is unknown.

METHODS AND RESULTS

Hsp47 expression in human coronary arteries was assessed by immunostaining. Strong focal expression was evident in atherosclerotic, but not normal, arteries and was prevalent in the collagenous regions. Double immunostaining revealed that all cells expressing type I procollagen also expressed Hsp47. Moreover, parallel regulation of proalpha1(I)collagen and Hsp47 mRNA expression occurred with cultured human smooth muscle cells stimulated with transforming growth factor-beta1 or fibroblast growth factor-2. However, a proportion of Hsp47-expressing cells in plaque did not express type I procollagen, and this pattern could be reproduced in culture. Heat shock and oxidized LDL stimulated the expression of Hsp47 mRNA by smooth muscle cells, without a concomitant rise in proalpha1(I)collagen expression.

CONCLUSIONS

These findings identify Hsp47 as a novel constituent of human coronary atheroma. Its localization to the fibrous cap, regulation by growth factors in parallel with type I procollagen, and selective upregulation by stress raise the possibility that Hsp47 is a determinant of plaque stability.