Micro magnetic resonance angiography of the finger in systemic sclerosis

OBJECTIVE

To characterize vascular lesions in SSc disease with high-resolution magnetic resonance angiography (Micro-MRA) of the finger.

METHODS

Eight SSc subjects and eight age- and sex-matched healthy controls were recruited for this study. Among the SSc subjects, the mean +/- s.d. age was 54.5 +/- 4.9 yrs, and the mean +/- s.d. duration of disease was 8.3 +/- 8.4 yrs. The numbers of SSc subjects that had telangiectasia, calcinosis and impaired finger flexion were 3, 2 and 3, respectively. The 2D time-of-flight micro-MRA was performed on a 3T clinical MRI scanner using a custom-designed finger coil with an in-plane resolution of 0.16 x 0.21 mm(2) and slice thickness of 1.2 mm. The data for the proper palmar digital artery lumen area, the number of visible dorsal digital veins and a semi-quantitative vascular score, which evaluates the overall integrity of digital vessels, were independently evaluated by two experienced reviewers who were blinded to the status of the subject.

RESULTS

Micro-MRA detected significant differences in the digital vasculature between SSc subjects and healthy volunteers. The SSc subjects had a significantly decreased digital artery lumen area (0.13 +/- 0.06 vs 0.53 +/- 0.26 mm(2), P < 0.001), a reduced number of digital veins (0.63 +/- 1.06 vs 3.13 +/- 0.99, P = 0.001) and a lowered overall vascular score (1.75 +/- 1.04 vs 3.5 +/- 0.53, P = 0.001). The study also found that both the digital artery lumen area (Pearson's; r = -0.72, P = 0.044) and vascular scores (Spearman's; rho = -0.75, P = 0.047) of the SSc subjects were inversely correlated with the duration of the disease.

CONCLUSIONS

Micro-MRA can be used to identify and quantitatively characterize the vascular disease in SSc fingers. The parameters derived from micro-MRA could potentially be used as prospective biomarkers for clinical evaluation.

Human T-cell leukemia virus type I Tax induces expression of the Rel-related family of kappa B enhancer-binding proteins: evidence for a pretranslational component of regulation

The Tax protein of the human T-cell leukemia virus type I (HTLV-I) serves as a potent transcriptional activator of its own long terminal repeat as well as select cellular genes, including interleukin-2 and the alpha subunit of the interleukin-2 receptor. Tax activation of these two growth-related genes appears to involve the induced nuclear expression of DNA-binding proteins that specifically engage related kappa B enhancer elements present in the 5' regulatory regions of these genes. In human T cells, kappa B enhancer-binding activity has been discerned as an unexpectedly large family of UV cross-linked nucleoprotein adducts, termed p50, p55, p75, and p85. The protein components of each of these DNA-protein adducts have been shown to share structural similarity with the v-rel oncogene product. The p55 adduct is composed of the 50-kDa subunit of NF-kappa B derived from a 105-kDa precursor polypeptide, while the p50 adduct contains a smaller protein that is closely related to NF-kappa B p50. The p75 adduct contains the 65-kDa subunit of NF-kappa B, while the p85 adduct is composed of the human c-rel proto-oncogene product. We now demonstrate that HTLV-I Tax, in the absence of other viral pX gene products, is capable of inducing the nuclear expression of all four of these kappa B-binding proteins in human T cells, with most marked effects involving c-Rel and NF-kappa B p65. Tax induction of the nuclear expression of c-Rel and NF-kappa B p50 is regulated, at least in part, at a pretranslational level involving increases in c-rel and NF-kappa B p105 mRNA expression. To study the pattern of expression of these kappa B-specific proteins in cells infected with the whole HTLV-I, seven cloned HTLV-I-infected T-cell lines were established from the peripheral blood of patients with adult T-cell leukemia. Of note, only three of these seven cell lines produced Tax, and c-rel mRNA and nuclear protein expression was confined to these three cell lines. In contrast, NF-kappa B p50 and NF-kappa B p65 were constitutively expressed in the nuclei of all seven of the HTLV-I-infected cell lines, even in the absence of detectable Tax or other viral gene expression. These findings raise the possibility of an alternate, Tax-independent pathway for the induced nuclear expression of NF-kappa B p50 and NF-kappa B p65 following HTLV-I infection.

Kappa B-specific DNA binding proteins are differentially inhibited by enhancer mutations and biological oxidation

Kappa B (kappa B) enhancer binding proteins isolated from the nuclei of activated human T cells produce two distinct nucleoprotein complexes when incubated with the kappa B element from the interleukin-2 receptor-alpha (IL-2R alpha) gene. These two DNA-protein complexes are composed of at least four host proteins (p50, p55, p75, p85), each of which shares structural similarity with the v-rel oncogene product. Nuclear expression of these proteins is induced with distinctly biphasic kinetics following phorbol ester activation of T cells (p55/p75 early and p50/p85 late). DNA-protein crosslinking studies have revealed that the more rapidly migrating B2 complex contains both p50 and p55 while the more slowly migrating B1 complex is composed of p50, p55, p75, and p85. Site-directed mutagenesis of the wild-type IL-2R alpha kappa B enhancer (GGGGAATCTCCC) has revealed that the binding of p50 and p55 (B2 complex) is particularly sensitive to alteration of the 5' triplet of deoxyguanosine residues. In contrast, formation of the B1 complex, reflecting the binding of p75 and p85, critically depends upon the more 3' sequences of this enhancer element. DNA binding by all four of these Rel-related factors is blocked by selective chemical modification of lysine and arginine residues, suggesting that both of these basic amino acids are required for binding to the kappa B element. Similarly, covalent modification of free sulfhydryl groups with diamide (reversible) or N-ethylmaleimide (irreversible) results in a complete loss of DNA binding activity. In contrast, mild oxidation with glucose oxidase selectively inhibits p75 and p85 binding while not blocking p50 and p55 interactions. These findings suggest that reduced cysteine thiols play an important role in the DNA binding activity of this family of Rel-related transcription factors.

NF-kappa B: a family of inducible and differentially expressed enhancer-binding proteins in human T cells

A sensitive DNA-protein crosslinking approach has been used to characterize four inducible T-cell proteins (50 kDa, 55 kDa, 75 kDa, and 85 kDa) that specifically bind to kappa B enhancer elements. Partial proteolytic mapping revealed a distinct cleavage pattern for three of these proteins. These polypeptides are sequestered as inactive precursors in the cytosol of unstimulated T cells but can be converted into active forms in vivo by phorbol ester stimulation or in vitro by detergent treatment. The induction of these proteins by phorbol ester results in a strikingly biphasic pattern of nuclear expression with the 55-kDa and 75-kDa species appearing within minutes, whereas the 50-kDa and 85-kDa species appear only several hours after cellular stimulation. These data suggest that NF-kappa B-binding activity may not correspond to a single polypeptide but rather a family of at least four inducible and differentially regulated DNA-binding proteins that are expressed with distinct kinetics in human T lymphocytes.

The v-rel oncogene encodes a kappa B enhancer binding protein that inhibits NF-kappa B function

Studies of NF-kappa B suggest that this enhancer binding activity corresponds to a family of at least four proteins (p50, p55, p75, and p85) differentially induced with biphasic kinetics during T cell activation. While p55 and p50 are closely related to the 50 kd DNA binding subunit of NF-kappa B, p75 and p85 exhibit DNA binding properties that distinguish them from this 50 kd polypeptide and its regulatory subunits I kappa B and p65. All four members of this kappa B-specific protein family are structurally related to the v-Rel oncoprotein and one, p85, appears identical to human c-Rel. v-Rel, but not nontransforming v-Rel mutants, binds to the kappa B enhancer and inhibits NF-kappa B-activated transcription from the IL-2 receptor alpha promoter and HIV-1 LTR. These findings suggest a Rel-related family of kappa B enhancer binding proteins and raise the possibility that the transforming activity of v-Rel is linked to its inhibitory action on cellular genes under NF-kappa B control.