Expression of Id-1 mRNA and protein in the post-ischemic regenerating rat kidney

Evidence of a novel antiapoptotic factor: role of inhibitor of differentiation or DNA binding (Id-1) in anticancer drug-induced apoptosis

Id-1 (inhibitor of differentiation or DNA binding), a member of the basic helix-loop-helix transcription factor family, is up-regulated in many types of human cancer and its expression levels are correlated with poor treatment outcome and shorter survival. In this study, we provided evidence to suggest that Id-1 is a universal survival factor that plays a key role in protection against anticancer drug-induced apoptosis. Using nine anticancer drugs and five cancer cell lines derived from nasopharyngeal carcinoma (CNE1), cervical carcinoma (HeLa), breast cancer (MCF7), hepatocarcinoma (Huh7) and prostate cancer (PC3), we found that down-regulation of Id-1 expression at both transcriptional and protein levels was associated with increased apoptosis rates and increased cleaved PARP after exposure to all anticancer agents. Treatment with a caspase 9 inhibitor, Z-LEHD-FMK, protected cancer cells from drug-induced PARP cleavage. However, overexpression of Id-1 in a p53 mutated cell line, CNE1, was able to suppress PARP cleavage in response to all anticancer drugs examined. In contrast, down-regulation of Id-1 through small RNA technology in CNE1 cells led to increased sensitivity to all six types of chemotherapeutic drugs. Our results demonstrate that Id-1 may be a general negative regulator of anticancer drug-induced apoptosis and suggest a novel therapeutic target in inducing chemosensitization in cancer cells. Our evidence also provides a possible underlying mechanism responsible for the positive role of Id-1 in the progression of human cancer.

Down-regulation of Id-1 expression is associated with TGF beta 1-induced growth arrest in prostate epithelial cells

Transforming growth factor beta1 (TGF beta 1) plays important roles in the regulation of cell growth and differentiation in both normal and malignant prostate epithelial cells. Although certain pathways have been suggested, the mechanisms responsible for the action of TGF beta 1 are not well understood. In the present study, using a human papilloma virus 16 E6/E7 immortalized prostate epithelial cell line, HPr-1, we report that TGF beta 1 was able to suppress the expression of Id-1, a helix-loop-helix (HLH) protein, which plays important roles in the inhibition of cell differentiation and growth arrest. In addition, a decrease at both Id-1 mRNA and protein expression levels was associated with TGF beta 1-induced growth arrest and differentiation, indicating that Id-1 may be involved in TGF beta 1 signaling pathway. The fact that up-regulation of p21(WAF1), one of the downstream effectors of Id-1, was observed after exposure to TGF beta 1 further indicates the involvement of Id-1 in the TGF beta 1-induced growth arrest in HPr-1 cells. However, increased expression of p27(KIP1) was also observed in the TGF beta 1-treated cells, suggesting that in addition to down-regulation of Id-1, other factors may be involved in the TGF beta 1-induced cell growth arrest and differentiation in prostate epithelial cells. Our results provide evidence for the first time that TGF beta 1 may be one of the upstream regulators of Id-1.

cDNA array analysis of pineal gene expression reveals circadian rhythmicity of the dominant negative helix-loop-helix protein-encoding gene, Id-1

The pineal gland is a major output of the endogenous vertebrate circadian clock, with melatonin serving as the output signal. In many species, elevated nocturnal melatonin production is associated with changes in pineal gene expression. In the current study, cDNA array analysis was used in an attempt to identify additional genes that exhibit day/night differential expression in the rat pineal gland. This revealed 38 candidate genes, including Id-1 (inhibitor of DNA binding and differentiation). Id-1 encodes a helix-loop-helix (HLH) protein that lacks a basic DNA binding domain and could affect pineal physiology via a dominant negative trans-acting regulatory activity. For this reason Id-1 was selected for further analysis. Id-1 was expressed in a major population of pineal cells and the Id-1 protein was associated with a nuclear complex. The levels of Id-1 mRNA and protein exhibit approximately six-fold day/night rhythms. In contrast, the related genes Id-2 and Id-3 do not exhibit marked day/night differences in pineal expression. Rhythmic Id-1 expression is primarily limited to a C-terminally extended splice variant of Id-1, which would restrict the functional output of the rhythm to protein binding partners of this isoform of Id-1. Our findings add to the body of evidence indicating that transcriptional regulators play a role in neuroendocrine rhythms, and extend this by introducing the concept of a dominant negative HLH involvement. The rhythm in Id-1 in the pineal gland provides an experimental opportunity to identify Id-1-binding partners which may also be involved in Id-1 activity in other functional contexts.

BMP-7 regulates chemokine, cytokine, and hemodynamic gene expression in proximal tubule cells

BACKGROUND

Proximal tubule epithelial cells (PTEC) play a central role in the response of the kidney to insult by virtue of their production of chemokines and cytokines that signal an inflammatory response. Bone morphogenic protein-7 (BMP-7/OP-1), a member of the transforming growth factor-beta (TGF-beta) superfamily, has previously been demonstrated to reduce macrophage infiltration and tissue damage in animal models of acute and chronic renal failure. The present study was designed to define the molecular mechanism of BMP-7 action in human PTEC.

METHODS

Expression of BMP-7 in the adult mouse kidney was determined indirectly through X-gal staining of heterozygous BMP-7/lacZ mice in combination with cell-type specific markers. Primary human PTEC were cultured in the presence of the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), with and without BMP-7. RNA isolated from these two populations was then used to identify differentially regulated genes via gene-array analysis. Modulation of potential target genes was subsequently confirmed through ELISA and/or quantitative PCR.

RESULTS

Expression from the BMP-7/lacZ transgene was detected in the collecting duct, thick ascending limb, distal convoluted tubule, and podocytes within glomeruli. No expression was detected within PTEC; however, these cells were found to express mRNA for BMP receptors including, ActR-I, BMPR-IA, ActR-II, ActR-IIB, and BMPR-II. BMP-7 significantly reduced TNF-alpha stimulated increases in mRNA for the pro-inflammatory genes, interleukin-6 (IL-6) and interleukin-1beta (IL-1beta), and the chemoattractants monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) in primary human PTEC. In addition, BMP-7 also reduced the expression of mRNA for endothelin-2 (ET-2), a vasoconstrictor, and increased the expression of mRNA for heme oxygenase-1 (HO-1), a vasodilator, although the latter was not statistically significant. In experiments designed to examine MCP-1 and IL-6 protein levels in response to additional TGF-beta superfamily members, TGF-beta1 was unable to mimic the effects of BMP-7 in reducing IL-6 production. However, the closely related BMP-6 exhibited similar properties to those of BMP-7. Each of the factors reduced MCP-1 expression.

CONCLUSIONS

BMP-7 represses the basal and TNF-alpha-stimulated expression of the pro-inflammatory cytokines IL-6 and IL-1beta, the chemokines MCP-1 and IL-8, and the vasoconstrictor ET-2 in PTEC. This data are consistent with the in vivo observations that BMP-7 administration in a model of chronic and acute renal failure results in a reduction in the infiltration of macrophages in the renal interstitium. Taken together, these observations suggest that BMP-7 may be a novel therapeutic agent for kidney disorders involving inflammation and ischemic damage of PTEC.

The koniocellular pathway in primate vision

A neurochemically distinct population of koniocellular (K) neurons makes up a third functional channel in primate lateral geniculate nucleus. As part of a general pattern, K neurons form robust layers through the full representation of the visual hemifield. Similar in physiology and connectivity to W cells in cat lateral geniculate nucleus, K cells form three pairs of layers in macaques. The middle pair relays input from short-wavelength cones to the cytochrome-oxidase blobs of primay visual cortex (V1), the dorsal-most pair relays low-acuity visual information to layer I of V1, and the ventral-most pair appears closely tied to the function of the superior colliculus. Throughout each K layer are neurons that innervate extrastriate cortex and that are likely to sustain some visual behaviors in the absence of V1. These data show that several pathways exist from retina to V1 that are likely to process different aspects of the visual scene along lines that may remain parallel well into V1.