We have demonstrated that T3 increases the expression of ZAKI-4alpha, an endogenous calcineurin inhibitor. In this study we characterized a T3-dependent signaling cascade leading to ZAKI-4alpha expression in human skin fibroblasts. We found that T3-dependent increase in ZAKI-4alpha was greatly attenuated by rapamycin, a specific inhibitor of a protein kinase, mammalian target of rapamycin (mTOR), suggesting the requirement of mTOR activation by T3. Indeed, T3 activated mTOR rapidly through S2448 phosphorylation, leading to the phosphorylation of p70(S6K), a substrate of mTOR. This mTOR activation is mediated through phosphatidylinositol 3-kinase (PI3K)-Akt/protein kinase B (PKB) signaling cascade because T3 induced Akt/PKB phosphorylation more rapidly than that of mTOR, and these T3-dependent phosphorylations were blocked by both PI3K inhibitors and by expression of a dominant negative PI3K (Deltap85alpha). Furthermore, the association between thyroid hormone receptor beta1 (TRbeta1) and PI3K-regulatory subunit p85alpha, and the inhibition of T3-induced PI3K activation and mTOR phosphorylation by a dominant negative TR (G345R) demonstrated the involvement of TR in this T3 action. The liganded TR induces the activation of PI3K and Akt/PKB, leading to the nuclear translocation of the latter, which subsequently phosphorylates nuclear mTOR. The rapid activation of PI3K-Akt/PKB-mTOR-p70(S6K) cascade by T3 provides a new molecular mechanism for thyroid hormone action.

AST-120 reduces the gene expression of TGF-beta1, TIMP-1 and pro-alpha1(I)collagen in the kidneys, and delays the progression of CRF, at least in part, by alleviating the overload of indoxyl sulphate on remnant proximal tubular epithelial cells.

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Abstract,32-Microglobulin (jB2M) is a major constituent of amyloid fibrils in hemodialysis-associated amyloidosis (HAA), a complication of long-term hemodialysis. However, the pathological role of 62M in HAA remains to be determined. Recently, we demonstrated that ,62M in the amyloid deposits ofHAA is modified with advanced glycation end products (AGEs) of the Maillard reaction. Since AGEs have been implicated in tissue damage associated with diabetic complications and aging, we investigated the possible involvement of AGE-modified j82M (AGE-Ii2M) in the pathogenesis of HAA. AGE-and normalf32M were purified from urine of long-term hemodialysis patients. AGE-,2M enhanced directed migration (chemotaxis) and random cell migration (chemokinesis) of human monocytes in a dose-dependent manner. However, normal-,62M did not enhance any migratory activity. AGE-lB2M, but not normal-#2M, increased the secretion of TNF-a and IL-1,B from macrophages. Similar effects were also induced by in vitro prepared AGE-,32M (normal-B62M incubated with glucose in vitro for 30 d). When TNF-a or IL-1,6 was added to cultured human synovial cells in an amount equivalent to that secreted from macrophages in the presence of AGE-,02M, a significant increase in the synthesis of collagenase and morphological changes in cell shape were observed. These findings suggested that AGE-182M, a major component in amyloid deposits, participates in the pathogenesis of HAA as foci where monocyte /macrophage accumulate and initiate an inflammatory response that leads to bone/joint destruction. (J. Clin. Invest. 1994. 93:521-528.)

VEGF (vascular endothelial growth factor) secreted from tumor cells including breast cancer serves as a potent angiogenic factor which favors tumor growth and metastasis. Indeed, a higher concentration of serum VEGF has been shown to associate with a poorer prognosis in patients with breast cancer. On the other hand, constitutive expression of a transcription factor, NF-kappaB was correlated with progression and metastasis in a number of human breast cancers, suggesting a possible regulation of VEGF expression by NF-kappaB. We thus investigated the relationship between the expression of VEGF and constitutive NF-kappaB activity in three breast cancer cell lines, MCF-7, T47D, and MDA-MB-231. The basal levels of VEGF mRNA expression correlated with those of nuclear NF-kappaB activity in these cell lines. The highest NF-KB activity in MDA-MB-231 cells was associated with the highest expression of VEGF mRNA, while the activity and the mRNA levels were moderate in MCF cells and the lowest in T47D cells. In MDA-MB-231 cells, inhibition of NF-KB by adenovirus-mediated expression of a dominant negative NF-kappaB or by a proteasome inhibitor, MG132, decreased the VEGF mRNA. These results suggest that NF-kappaB is involved in the upregulation of VEGF mRNA and inhibition of the activity could be a new approach for the treatment of breast cancer by preventing angiogenesis.