Tumor Necrosis Factor-α Induces Interleukin-6 Production and Integrin Ligand Expression by Distinct Transduction Pathways

Abstract

Tumor necrosis factor-␣ (TNF-␣) is a pleiotropic cytokine that elicits a large number of biological effects. However, the intracellular signaling mechanisms that are responsible for the TNF-␣ effects remain largely unknown. We have previously demonstrated that cultured mouse Sertoli cells, after TNF-␣ treatment, increase the surface expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and interleukin-6 (IL-6) production (Riccioli, A., Filippini, A., De Cesaris, P., Barbacci, E., Stefanini, M., Starace, G., and Ziparo, E. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 5808 -5812). Here, we show that, in cultured Sertoli cells, TNF-␣ activates the mitogen-activated protein kinase pathway (p38, cJun N-terminal protein kinase/stress-activated protein kinase, and the p42/p44 mitogen-activated protein kinases) as revealed by an increased phosphorylation of p38, activating transcription factor-2, c-Jun, and Elk-1. Furthermore, our data indicate that the biological effects induced by TNF-␣ in Sertoli cells (enhancement of ICAM-1, VCAM-1, and IL-6 expression) depend on the activation of different signaling pathways. SB203580, a highly specific p38 inhibitor, does not affect ICAM-1 and VCAM-1 expression, but strongly inhibits IL-6 production. Moreover, interferon-␥, which up-regulates adhesion molecule expression and reduces IL-6 production, does not induce phosphorylation of p38. Our data strongly support the hypothesis that, in response to TNF-␣, activation of p38 leads to IL-6 production, whereas ICAM-1 and VCAM-1 expression could be induced by activation of the c-Jun N-terminal protein kinase/stress-activated protein kinase pathway.

Intercellular adhesion molecule-1 is a regulator of blood–testis barrier function

“…A protein band corresponding to ICAM-1 was seen in lysates from Sertoli and germ cells, as well as in the testis, and these data were in agreement with RT-PCR results (Fig. 1C), as well as with previous reports from other laboratories (De Cesaris et al, 1998;Riccioli et al, 1995).…”

“…expressed by several cell types, including Sertoli and germ cells in the testis (De Cesaris et al, 1998;Wong et al, 2000), and it is well known to function in the transendothelial migration of leukocytes (Lawson and Wolf, 2009;Long, 2011;Mamdouh et al, 2009;Muller, 2011). Immunolocalization studies showed ICAM-1 to be present at the site of the BTB, where its level was highest at stage VIII of the seminiferous epithelial cycle, coinciding with two critical cellular events that occur at this stage: the movement of preleptotene/leptotene spermatocytes across the BTB and the release of elongated spermatids into the tubule lumen (de Kretser and Kerr, 1988;Mruk and Cheng, 2004;Russell, 1993b).…”

Mapping of Early Signaling Events in Tumor Necrosis Factor-α-mediated Lipolysis in Human Fat Cells

“…We obtained well characterized inhibitors specific for the three different MAPK pathways, SB203580 for p38 (25), PD98059 for p44/42 (an inhibitor of MAP/ERK kinase 1/2, the kinase immediately upstream of p44/42) (26), and dimethylaminopurine (DMAP) for JNK/SAPK (27). These were initially added to the cells at concentrations known to be effective in other cell systems (25)(26)(27). To minimize background activity, cells were incubated for 2 h in the presence of the inhibitor prior to stimulation with 100 ng/ml TNF-␣.…”

FLIP is expressed in mouse testis and protects germ cells from apoptosis

“…51 After 3 days culture at 321C in 5% CO 2 , in serum-free (MEM), Sertoli cell monolayers were incubated at room temperature with 20 mM Tris-HCl buffer (pH 7.4) for 2 min to remove residual germ cells present in the culture. 52 After 4 days culture, Sertoli cell monolayers were processed for Western and Northern blotting as described below.…”