Activation of human vascular cells decreases their expression of transforming growth factor-beta.

OBJECTIVE: Despite pro-fibrotic effects, transforming growth factor (TGF)-ß prevents arteriosclerosis by suppressing effector leukocytes and promoting smooth muscle differentiation. However, previous observations of increased TGF-ß expression in arteriosclerotic plaques are not consistent with that of an effective protective factor. We investigated the expression, regulation, and responses of TGF-ß in human arterial tissues and cells. METHODS AND RESULTS: The expression of TGF-ß by intrinsic vascular cells was lower in arteriosclerotic than non-diseased coronary arteries. Activation of resident and infiltrating leukocytes did not elicit TGF-ß production from coronary artery segments in organ culture. Instead, the basal expression of TGF-ß by coronary arteries decreased after vessel procurement and ex vivo culture. Activation of cultured smooth muscle cells and endothelial cells with phorbol ester and ionophore also decreased TGF-ß expression. Isolated cell types representing those found in the artery wall were all capable of signaling in response to TGF-ß, however production of the cytoprotective molecule, interleukin-11 was cell type-dependent and restricted to smooth muscle cells and fibroblasts. Interleukin-11 reduced smooth muscle cell apoptosis to T cell effectors. CONCLUSIONS: Inflammation and cellular activation diminish the basal expression of TGF-ß by quiescent human vascular cells. Induction of interleukin-11 may contribute to the anti-arteriosclerotic actions of TGF-ß.

IFN-gamma primes intact human coronary arteries and cultured coronary smooth muscle cells to double-stranded RNA- and self-RNA-induced inflammatory responses by upregulating TLR3 and melanoma differentiation-associated gene 5.

Atherosclerosis of native coronary arteries and graft arteriosclerosis in transplanted hearts are characterized by activation of innate and adaptive immune responses. Nucleic acids generated by infections or cell death have been detected within arteriosclerotic lesions, and it is known that microbial and synthetic nucleic acids evoke inflammatory responses in cultured vascular cells. In this study, we report that model RNA, but not DNA, instigated robust cytokine and chemokine production from intact human coronary arteries containing both intrinsic vascular cells and resident/infiltrating leukocytes. An ssRNA analog induced TNF-alpha and IFN-gamma-induced protein of 10 kDa secretion by isolated human PBMCs, but not vascular cells. Conversely, synthetic dsRNA induced these inflammatory mediators by vascular cells, but not PBMCs. IFN-gamma, a cytokine linked to atherosclerosis and graft arteriosclerosis, potentiated the inflammatory responses of intact arteries and cultured vascular smooth muscle cells (VSMCs) to polyinosinic:polycytidylic acid [poly(I:C)] and was necessary for inflammatory responses of VSMC to self-RNA derived from autologous cells. IFN-gamma also induced the expression of TLR3, melanoma differentiation-associated gene 5, and retinoic acid-inducible gene I dsRNA receptors. Small interfering RNA knockdown revealed that TLR3 mediated VSMC activation by poly(I:C), whereas melanoma differentiation-associated gene 5 was more important for VSMC stimulation by self-RNA. IFN-gamma-mediated induction of dsRNA receptors and priming for inflammatory responses to poly(I:C) was confirmed in vivo using immunodeficient mice bearing human coronary artery grafts. These findings suggest that IFN-gamma, and by inference adaptive immunity, sensitizes the vasculature to innate immune activators, such as RNA, and activation of IFN-gamma-primed vascular cells by exogenous or endogenous sources of RNA may contribute to the inflammatory milieu of arteriosclerosis.