Metallothionein modulates lipopolysaccharide-stimulated tumour necrosis factor expression in mouse peritoneal macrophages

Abstract

Metallothionein (MT) is a low-molecular-mass, cysteine-rich metal binding protein thought to be involved in the detoxification of heavy metals and scavenging of free radicals. MT is directly induced not only by heavy metals, but also by hormones and cytokines. The present study, which uses mice with genetic deletions of the MT proteins (MT(-/-) mice), was designed to evaluate the effects of MT on the expression of pro-inflammatory cytokines in macrophages. We found that the production of tumour necrosis factor (TNF) induced by lipopolysaccharide (LPS) in peritoneal macrophages is up-regulated by MT via the modulation of nuclear factor kappaB (NF-kappaB) activity. This conclusion is supported by the following observations: (1) LPS stimulated the secretion of less TNF activity from MT(-/-) peritoneal exudate macrophages (PEMs) than from wild-type controls (MT(+/+) mice) without a difference in the pattern of kinetics; (2) LPS-stimulated expression of TNF-alpha mRNA was decreased in MT(-/-) PEMs; (3) LPS-stimulated activation of NF-kappaB was decreased in MT(-/-) PEMs; and (4) production of TNF in PEMs of MT(-/-) mice after LPS treatment in vivo was decreased (compared with MT(+/+) PEMs). Expression of other inflammatory cytokines, interleukin (IL)-1alpha and IL-6 mRNA, which were modulated by NF-kappaB, were also down-regulated in MT(-/-) PEMs. Thus MT plays a key role in the LPS-induced activation of PEMs via the modulation of NF-kappaB activity.

Metallothionein Mediates the Level and Activity of Nuclear Factor ΚB in Murine Fibroblasts

“…Several studies support a role for MT in enhanc- ing NF-B activity (Abdel-Mageed and Agrawal, 1998;Kanekiyo et al, 2001Kanekiyo et al, , 2002, whereas others indicate that MTs are inhibitory (Sakurai et al, 1999;Crowthers et al, 2000;Papouli et al, 2002). None of the studies quantitatively assessed total cellular or nuclear NF-B levels, or the capacity of NF-B to induce transcription when MT genes were functionally deleted in, and when an MT expression vector was introduced into, MT knockout cells.…”

“…Previous studies of the relationship between NF-B and MT used indirect measures of NF-B, including NF-B binding to DNA (Abdel-Mageed and Agrawal, 1998;Crowthers et al, 2000;Kanekiyo et al, 2002) and NF-B-dependent expression of reporter (Abdel-Mageed and Agrawal, 1998;Sakurai et al, 1999;Kanekiyo et al, 2002;Papouli et al, 2002) or endogenous genes (Kanekiyo et al, 2001). When we measured the level of the NF-B p65 subunit directly by Western blot, we found that it was reduced in both MT-KO cell lines to less than 20% of the level in MT-WT cells.…”

“…However, reported results are contradictory. On the one hand, MT may positively regulate NF-B: increasing MT by transfection of an MT expression vector into a human breast carcinoma-derived cell line (MCF-7) (Abdel-Mageed and Agrawal, 1998) or zinc induction of L929 cells (Kanekiyo et al, 2001) increased NF-B binding to DNA and reporter gene activity, and NF-B-mediated gene expression was down-regulated in peritoneal macrophages isolated from MT-null mice (Kanekiyo et al, 2002). On the other hand, MT may inhibit NF-B function, since MT has been reported to inhibit TNF-induced degradation of IB␣, and NF-B-dependent gene expression (Sakurai et al, 1999).…”

Expressed Sequence Tag Analysis ofPhysa acuta: A Freshwater Pulmonate in Korea

“…Recently, it has been suggested that ferritin may also be considered an acute-phase protein, and its sequestration may be a component of the invertebrate immune response (Beck et al 2002). The third cluster, metallothionein, is a metal-binding protein thought to be involved in the detoxification of heavy metals, in free radicals scavenging, and also in inflammatory response (Kanekiyo et al 2002). Several studies support the validity of metallothionein as a biomarker for a variety of cellular stress (Pedersen et al 1997, Cosson 2000.…”

Function of Metallothionein in Gene Expression and Signal Transduction: Newly Found Protective Role of Metallothionein

“…75) Zinc-induced expression of macrophage colonystimulating factor in MC3T3-E1 and L929 cells required MT-mediated NF-κB activation. 76) On the other hand, NF-κB is a redox-regulated TF, and MT may control intracellular redox status.…”