Regulation of Complement Factor H Expression in L Cells

Vik, D P

doi:10.1006/bbrc.1999.1212

Biochemical and Biophysical Research Communications

1999

DOI: 10.1006/bbrc.1999.1212

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Regulation of Complement Factor H Expression in L Cells

D P Vik

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2002

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“…The primary site of synthesis of FH is the liver (Zipfel and Skerka, 1994). Extrahepatic cell types such as human umbilical vein endothelial cells (HUVEC) (Brooimans et al, 1989(Brooimans et al, , 1990Ripoche et al, 1988b), peripheral blood monocytes (Whaley, 1980), cells of the monocytemacrophage series (De Ceulaer et al, 1980), primary skin fibroblasts (Katz and Strunk, 1988), fibroblast-like L cells (Munoz-Canoves et al, 1989;Vik, 1999), primary myoblasts and rhabdomyosarcoma cell lines (Legoedec et al, 1995), glioma cell lines (Gasque et al, 1992), and glomerular mesangial cells (van den Dobbelsteen et al, 1994) have also been reported to express FH. These cell types may function as local sources of FH and thereby reduce tissue damage caused by local complement activation.…”

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Constitutive Expression and Regulation of Rat Complement Factor H in Primary Cultures of Hepatocytes, Kupffer Cells, and Two Hepatoma Cell Lines

Schlaf

Beisel

Pollok-Kopp

et al. 2002

Laboratory Investigation

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SUMMARY:The 155-kd soluble complement regulator factor H (FH), which consists of 20 short consensus repeats, increases the affinity of complement factor I (FI) for C3b by about 15 times. In addition to its cofactor activity, it prevents factor B from binding to C3b and promotes the dissociation of the C3bBb complex. The primary site of synthesis of FH, as well as of FI, is the liver, but the cell types responsible for the hepatic synthesis of both factors have not yet been clearly identified. In contrast to FI-mRNA, which was detectable only in hepatocytes (HC), FH-specific mRNA was identified in both HC and Kupffer cells (KC). As calculated for equal amounts of mRNA isolated from both cell types, FH-specific mRNA was found to be nearly 10-fold higher in KC than in HC, leading to the conclusion that KC are an abundant source of FH. Of the investigated proinflammatory cytokines IL-6, TNF-␣, IL-1␤, and IFN-␥, only IFN-␥ up-regulated FH-specific mRNA up to 6-fold in both primary HC and KC. This was also demonstrable on the protein level. However, FH-specific mRNA was not inducible in the rat hepatoma cell line H4IIE, which did not express FH-specific mRNA and could not be up-regulated in FAO cells that constitutively expressed FH-specific mRNA. This demonstrates that transformed cell lines do not reflect FH regulation in isolated primary HC. In addition to IFN-␥, the endotoxin lipopolysaccharide (LPS) up-regulated FH-specific mRNA nearly 10-fold in KC after stimulation at concentrations of 10 or 1 ng/ml. In contrast, concentrations of up to 2 g LPS/ml did not show any effect on HC. Our data suggest that LPS does not regulate the expression of FH in HC. (Lab Invest 2002, 82:183-192).T he regulation of complement activation at the level of C3 and C4 is mediated by several receptors and soluble regulatory proteins. These include complement receptor 1 (CD35), complement receptor 2 (CD21), decay-accelerating factor (CD55), membrane cofactor protein (CD46), factor I (FI), and factor H (FH). These proteins, with the exception of FI, form the "regulators of complement activation" family (Hourcade et al, 1989). Their genes are closely linked on chromosome 1 in man and mouse. This illustrates that this region on the long arm of chromosome 1 in humans is analogous to that region in mice (Klickstein et al, 1985). The serine protease FI could be located to chromosome 4 in man (Goldberger et al, 1987) and to chromosome 3 in mouse (Minta et al, 1996).The potentially deleterious complement system is strictly regulated to prevent damage in the absence of pathologic situations Mulligan et al, 1992;Piddlesden et al, 1994;Smith et al, 1993). On some host cell surfaces, membrane-bound complement regulatory factors are expressed only at low levels. Thus, reduced protection against complement attack may be compensated by the soluble regulator FH, which has a critical role in complement inactivation in the fluid phase (Meri and Pangburn, 1990; Pangburn and Müller-Eberhardt, 1978) and acts in concert with FI. FH is a single-chain protein...

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confidence: 99%

Constitutive Expression and Regulation of Rat Complement Factor H in Primary Cultures of Hepatocytes, Kupffer Cells, and Two Hepatoma Cell Lines

Schlaf

Beisel

Pollok-Kopp

et al. 2002

Laboratory Investigation

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Regulation of Complement Factor H Expression in L Cells

Cited by 1 publication

References 10 publications

Constitutive Expression and Regulation of Rat Complement Factor H in Primary Cultures of Hepatocytes, Kupffer Cells, and Two Hepatoma Cell Lines

Constitutive Expression and Regulation of Rat Complement Factor H in Primary Cultures of Hepatocytes, Kupffer Cells, and Two Hepatoma Cell Lines

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