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K D Smith

Publications and source records attributed to K D Smith.

At least 37 records · Page 2Linked to original sources
PubMed2000

Therapeutic developments in peroxisome biogenesis disorders.

Clinically, peroxisome biogenesis disorders (PBDs) are a group of lethal diseases with a continuum of severity of clinical symptoms ranging from the most severe form, Zellweger syndrome, to the milder forms, infantile Refsum disease and rhizomelic chondrodysplasia punctata. PBDs are characterised by a number of biochemical abnormalities including impaired degradation of peroxide, very long chain fatty acids, pipecolic acid, phytanic acid and xenobiotics and impaired synthesis of plasmalogens, bile acids, cholesterol and docosahexaenoic acid. Treatment of PBD patients as a group is problematic since a number of patients, especially those with Zellweger syndrome, have significant neocortical alterations in the brain at birth so that full recovery would be impossible even with postnatal therapy. To date, treatment of PBD patients has generally involved only supportive care and symptomatic therapy. However, the fact that some of the milder PBD patients live into the second decade has prompted research into possible treatments for these patients. A number of experimental therapies have been evaluated to determine whether or not correction of biochemical abnormalities through dietary supplementation and/or modification is of clinical benefit to PBD patients. Another approach has been pharmacological induction of peroxisomes in PBD patients to improve overall peroxisomal biochemical function. Well known rodent peroxisomal proliferators were found not to induce human peroxisomes. Recently, our laboratory demonstrated that sodium 4-phenylbutyrate induces peroxisome proliferation and improves biochemical function (very long chain fatty acid beta-oxidation rates and very long chain fatty acid and plasmalogens levels) in fibroblast cell lines from patients with milder PBD phenotypes. Dietary supplementation and/or modification and pharmacological induction of peroxisomes as treatment strategies for PBD patients will be the subject of this review.

Antineoplastic Agents↗
PubMed2000

Pharmacological induction of peroxisomes in peroxisome biogenesis disorders.

Inherited aberrant peroxisome assembly results in a group of neurological diseases termed peroxisome biogenesis disorders (PBDs). PBDs include three major clinical phenotypes that represent a continuum of clinical features from the most severe form, Zellweger syndrome (ZS), through neonatal adrenoleukodystrophy (NALD) to the least severe form, infantile Refsum's disease (IRD). Somatic cell complementation studies have identified 13 PBD complementation groups, each representing a defect in a peroxisomal protein (peroxin) involved in peroxisome biogenesis. Most complementation groups include a range of clinical phenotypes. In this study, peroxisome numbers were determined in fibroblasts from 29 PBD (ZS, NALD, and IRD) patients, with various phenotypes from nine complementation groups, using antibodies against either a peroxisomal membrane protein (anti-Pex14p) or peroxisomal matrix proteins (anti-SKL). A correlation between the number of peroxisomes, determined with either antibody, and PBD phenotype was found, suggesting that induction of peroxisome number might have a favorable effect on PBD. After treatment of PBD fibroblasts with sodium 4-phenylbutyrate, a human peroxisome proliferator, there was an approximate twofold increase in peroxisome number. After 4-phenylbutyrate treatment, an increase in transcription of the adrenoleukodystrophy-related gene and the peroxin gene, PEX11alpha, was found in PBD fibroblasts. In NALD and IRD, but not ZS, fibroblasts there was an increase in very-long-chain fatty acid beta-oxidation and plasmalogen concentrations, and a decrease in very-long-chain fatty acid concentrations. These data suggest that pharmacological agents that induce peroxisome proliferation, such as 4-phenylbutyrate, may have therapeutic potential in the treatment of PBD patients with milder phenotypes (NALD and IRD).

Cells, Cultured↗
PubMed2000

Vertical transtalar Steinmann pin fixation for unstable ankle fractures.

Ankle fractures are common injuries and can usually be managed by either cast immobilisation or open reduction and internal fixation. Occasionally, both of these methods are contra-indicated. In such cases, one solution is the use of a vertical transtalar Steinmann pin to stabilise the fracture. Over the last 7 years, we have managed 8 patients with severe ankle fractures using vertical transtalar Steinmann pin fixation. The median age of these patients was 76 years (range, 35-94 years). This method was used in two patients with open contaminated wounds, in 5 with atrophic and blistered skin, and in one following failure of internal fixation in a patient with atrophic skin. In all patients, a satisfactory reduction was achieved and maintained after removal of the pin. Although all patients began to develop osteo-arthritic changes secondary to their original fractures, no complications were directly attributable to the use of the pin. In unstable ankle fractures where damage and contamination of soft tissues would preclude internal fixation, we recommend the use of vertical transtalar Steinmann pin fixation.

Adult↗
PubMed2000

Co-operative induction of pro-inflammatory signaling by Toll-like receptors.

Toll-like receptors (TLRs) mediate detection of a broad range of pathogens and pathogen-derived products including LPS, peptidoglycan, bacterial lipopeptides, and lipoteichoic acid. Recent evidence indicates that the broad specificity of TLRs may be a consequence of the interactions between different TLRs. In this report, we demonstrate that while a constitutively active TLR4 homodimer can induce the production of pro-inflammatory cytokines, homodimers of TLR2 and TLR6 cannot. However, when co-expressed in the same cell, constitutively active TLR2 and TLR6 strongly induce cytokine production, indicating that these TLRs require partners to productively signal. Since TLR4 signals as a homodimer, while TLR2 and TLR6 do not, it is clear that, despite the conservation of their cytoplasmic signaling domains, the mechanisms by which they initiate signaling are different. We have localized the region of TLR4 that mediates its ability to signal as a homodimer to the membrane-proximal half of the cytoplasmic tail of the receptor.

Animals↗
PubMed1999

Toll-like receptor-2 mediates mycobacteria-induced proinflammatory signaling in macrophages.

The recognition of mycobacterial cell wall components causes macrophages to secrete tumor necrosis factor alpha (TNF-alpha) and other cytokines that are essential for the development of a protective inflammatory response. We show that toll-like receptors are required for the induction of TNF-alpha in macrophages by Mycobacterium tuberculosis. Expression of a dominant negative form of MyD88 (a signaling component required for toll-like receptor signaling) in a mouse macrophage cell line blocks TNF-alpha production induced by M. tuberculosis. We identify toll-like receptor-2 (TLR2) as the specific toll-like receptor required for this induction by showing that expression of an inhibitory TLR2 (TLR2-P681H) blocks TNF-alpha production induced by whole M. tuberculosis. Further, we show that TLR2-dependent signaling mediates responses to mycobacterial cell wall fractions enriched for lipoarrabinomannan, mycolylarabinogalactan-peptidoglycan complex, or M. tuberculosis total lipids. Thus, although many mycobacterial cell wall fractions are identified to be inflammatory, all require TLR2 for induction of TNF-alpha in macrophages. These data suggest that TLR2 is essential for the induction of a protective immune response to mycobacteria.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Peroxisomal very long chain fatty acid beta-oxidation activity is determined by the level of adrenodeukodystrophy protein (ALDP) expression.

Impaired peroxisomal beta-oxidation of saturated very long chain fatty acids (VLCFA, >/=C22:0) results in increased VLCFA levels in the tissues and body fluids of patients with disorders of peroxisomal biogenesis (i.e., Zellweger syndrome and neonatal adrenoleukodystrophy) and single peroxisomal protein defects (i.e., X-linked adrenoleukodystrophy (X-ALD) and acyl-CoA oxidase deficiency). We show that SV40T transformation also results in impaired peroxisomal beta-oxidation and VLCFA accumulation despite the presence of abundant peroxisomes. To explore the mechanism responsible for this observation, we have examined expression of key components of peroxisomal VLCFA beta-oxidation. We found that expression of both acyl-CoA oxidase, the rate limiting enzyme of peroxisomal VLCFA beta-oxidation and the adrenoleukodystrophy protein (ALDP), the defective gene product in X-ALD, are reduced after SV40T transformation. Surprisingly, ALDP overexpression by itself restores peroxisomal VLCFA beta-oxidation in SV40T-transformed control and X-ALD cells. These results demonstrate that ALDP is a fundamental component in VLCFA peroxisomal beta-oxidation and may serve as a "gatekeeper" for VLCFA homeostasis.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed1999

The relationship of serum androgens and ovulatory status to blood pressure in reproductive-age women.

The objective of this cross-sectional study was to determine the relationship between hyperandrogenemia and blood pressure in women with menstrual irregularities seen at an endocrinology clinic. Women with serum testosterone levels (T) > or = 30 ng/dL were more likely to have general obesity (odds ratio [OR] = 6.8, 95% confidence intervals [CI] = 2.2-27.2) and central obesity (OR = 14.5, 95% CI = 6.1-38.7) than euandrogenemic women. Hyperandrogenemic women (HA) had an OR of 2.4 (95% CI = 1.0-6.2) for elevated SBP and an OR of 2.7 (95% CI = 0.8-8.8) for elevated DBP, independent of age and ovulatory status. Obese HA had an OR of 4.7 (95% CI = 2.3-10.4) for elevated SBP and an OR of 2.9 (95% CI = 1.9-9.9) for elevated DBP. In conclusion, T is associated with an increased risk for obesity and central adiposity. T predicts BP elevation independent of age and ovulatory status. There was a synergistic relationship between obesity and androgens in their affect on BP.

Abdomen↗
PubMed1999

X-linked adrenoleukodystrophy: genes, mutations, and phenotypes.

X-linked adrenoleukodystrophy (X-ALD) is a complex and perplexing neurodegenerative disorder. The metabolic abnormality, elevated levels of very long-chain fatty acids in tissues and plasma, and the biochemical defect, reduced peroxisomal very long-chain acyl-CoA synthetase (VLCS) activity, are ubiquitous features of the disease. However, clinical manifestations are highly variable with regard to time of onset, site of initial pathology and rate of progression. In addition, the abnormal gene in X-ALD is not the gene for VLCS. Rather, it encodes a peroxisomal membrane protein with homology to the ATP-binding cassette (ABC) transmembrane transporter superfamily of proteins. The X-ALD protein (ALDP) is closely related to three other peroxisomal membrane ABC proteins. In this report we summarize all known X-ALD mutations and establish the lack of an X-ALD genotype/phenotype correlation. We compare the evolutionary relationships among peroxisomal ABC proteins, demonstrate that ALDP forms homodimers with itself and heterodimers with other peroxisomal ABC proteins and present cDNA complementation studies suggesting that the peroxisomal ABC proteins have overlapping functions. We also establish that there are at least two peroxisomal VLCS activities, one that is ALDP dependent and one that is ALDP independent. Finally, we discuss variable expression of the peroxisomal ABC proteins and ALDP independent VLCS in relation to the variable clinical presentations of X-ALD.

Adrenoleukodystrophy↗
PubMed1999

An Asian-Native American paternal lineage identified by RPS4Y resequencing and by microsatellite haplotyping.

Human paternal population history was studied in 9 populations [three Native American, three Asian, two Caucasian and one African-derived sample(s)] using sequence and short tandem repeat haplotype diversity within the non-pseudoautosegmal region of the Y chromosome. Complete coding and additional flanking sequences (949 base pairs) of the RPS4Y locus were determined in 59 individuals from three of the populations, revealing a nucleotide diversity of 0.0147%, consistent with previous estimates from Y chromosome resequencing studies. One RPS4Y sequence variant, 711C > T, was polymorphic in Asian and Native American populations, but not in African and Caucasian population samples. The RPS4Y 711C > T variant, a second unique sequence variant at DYS287 and nine Y chromosome short tandem repeat (YSTR) loci were used to analyze the evolution of Y chromosome lineages. Three unambiguous lineages were defined in Asian, Native American and Jamaican populations using sequence variants at RPS4Y and DYS287. These lineages were independently supported by the haplotypes defined solely by YSTR alleles, demonstrating the haplotypes constructed from YSTRs can evaluate population diversity, admixture and phylogeny.

Alleles↗
PubMed1999

Cerebral inflammation in X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is an inherited neurodegenerative disease that affects approximately 1 in 25 000 males. It is characterized by elevated levels of saturated very long chain fatty acids (VLCFA), i.e., >C22:0, particularly in ganglioside and cholesterol ester fractions of brain white matter and adrenal cortex. Failure of peroxisomal very long chain fatty acyl-CoA synthetase (VLCS) to activate these VLCFA prevents their degradation by peroxisomal beta-oxidation. X-ALD maps to Xq28 and the gene encodes a peroxisomal membrane protein and not the gene for VLCS. The two most common forms of X-ALD are the cerebral (CER) form, with an inflammatory demyelinating reaction that resembles multiple sclerosis (MS), and adrenomyeloneuropathy (AMN), which involves the spinal cord and in which the inflammatory reaction is mild or absent. Investigations into the nature of the cerebral inflammatory demyelinating reaction in X-ALD will be the subject of this review.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed1998

The t(4;14) translocation in myeloma dysregulates both FGFR3 and a novel gene, MMSET, resulting in IgH/MMSET hybrid transcripts.

Previously we reported that a karyotypically silent t(4;14)(p16. 3;q32.3) translocation is present in about 25% of multiple myeloma (MM) tumors, and causes overexpression of FGFR3, which is 50 to 100 kb telomeric to the 4p16 breakpoints. Frequent FGFR3 kinase activating mutations in MM with t(4;14) translocations substantiate an oncogenic role for FGFR3. We now report that the 4p16 breakpoints occur telomeric to and within the 5' introns of a novel gene, MMSET (Multiple Myeloma SET domain). In normal tissues, MMSET has a complex pattern of expression with a short form (647 amino acids [aa]) containing an HMG box and hath region, and an alternatively spliced long form (1365 aa) containing the HMG box and hath region plus 4 PHD fingers and a SET domain. Although t(4;14) translocation results in IgH/MMSET hybrid transcripts, overexpression of MMSET also occurs from endogenous promoters on 4p16. Given the homology to HRX/MLL1/ALL1 at 11q23 that is dysregulated by translocations in acute leukemia, we hypothesize that dysregulation of MMSET contributes to neoplastic transformation in MM with t(4;14) translocation. This is the first example of an IgH translocation that simultaneously dysregulates two genes with oncogenic potential: FGFR3 on der(14) and MMSET on der(4).

Amino Acid Sequence↗
PubMed1998

Disruption of the Saccharomyces cerevisiae FAT1 gene decreases very long-chain fatty acyl-CoA synthetase activity and elevates intracellular very long-chain fatty acid concentrations.

Activation of fatty acids to their coenzyme A derivatives is necessary for subsequent metabolism. Very long-chain fatty acids, which accumulate in tissues of patients with X-linked adrenoleukodystrophy, are activated by very long-chain acyl-CoA synthetase (VLCS) normally found in peroxisomes and microsomes. We identified a candidate yeast VLCS gene (FAT1), previously identified as encoding a fatty acid transport protein, by its homology to rat liver peroxisomal VLCS. Disruption of this gene decreased, but did not abolish, cellular VLCS activity. Fractionation studies showed that VLCS activity, but not long-chain acyl-CoA synthetase activity, was reduced to about 40% of wild-type level in both 27,000 x g supernatant and pellet fractions. Separation of organelles in the pellet fraction by density gradient centrifugation revealed that VLCS activity was associated with peroxisomes and microsomes but not mitochondria. FAT1 deletion strains exhibited decreased growth on medium containing dextrose, oleic acid, and cerulenin, an inhibitor of fatty acid synthesis. FAT1 deletion strains grown on either dextrose or oleic acid medium accumulated very long-chain fatty acids. Compared with wild-type yeast, C22:0, C24:0, and C26:0 levels were increased approximately 20-, 18-, and 3-fold in deletion strains grown on dextrose, and 2-, 7-, and 5-fold in deletion strains grown on oleate. Long-chain fatty acid levels in wild-type and deletion strains were not significantly different. All biochemical defects in FAT1 deletion strains were restored to normal after functional complementation with the FAT1 gene. The level of VLCS activity measured in both wild-type and deletion yeast strains transformed with FAT1 cDNA paralleled the level of expression of the transgene. The extent of both the decrease in peroxisomal VLCS activity and the very long-chain fatty acid accumulation in the yeast FAT1 deletion model resembles that observed in cells from X-linked adrenoleukodystrophy patients. These studies suggest that the FAT1 gene product has VLCS activity that is essential for normal cellular very long-chain fatty acid homeostasis.

Adrenoleukodystrophy↗
PubMed1998

TAP-independent MHC class I peptide antigen presentation to alloreactive CTL is enhanced by target cell incubation at subphysiologic temperatures.

We investigated the peptide dependency of a group of CD8+ anti-HLA-B7 alloreactive CTL. The CTL killed target cells after acid denaturation of more than 98% of target cell surface peptide/MHC class I complexes. The CTL also killed TAP- HLA-B7-transfected T2 (T2B7) cells. The killing was enhanced by target cell incubation at 26 degrees C. Despite these findings, which suggested peptide-independent allorecognition, CTL-mediated cytolysis was reduced or abolished by several point mutations affecting the HLA-B7 peptide-binding groove. Acid denaturation of HLA complexes on T2B7 cells prohibited CTL recognition. CTL recognition was restored by T2B7 cell incubation with beta2-microglobulin and a single HPLC fraction containing peptides extracted from TAP+HLA-B7+ cells, but not by any of a panel of 17 synthetic HLA-B7-binding peptides. These findings indicated that CTL allorecognition was peptide specific. Sensitizing peptide was extracted from T2B7 cells only after incubation at 26 degrees C. The amount of peptide detected in TAP+ cells was at least 10-fold and 100-fold greater than that detected in TAP- cells incubated at 26 degrees C and at 37 degrees C, respectively. TAP-independent peptide epitope presentation was sensitive to treatment with brefeldin A, but not sensitive to treatment with chloroquine, consistent with an endogenous peptide source. We propose that subphysiologic temperature incubation can enhance peptide/MHC class I presentation in the total absence of TAP function.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

NK cell natural cytotoxicity and IFN-gamma production are not always coordinately regulated: engagement of DX9 KIR+ NK cells by HLA-B7 variants and target cells.

DX9 mAb-binding killer cell-inhibitory receptors (KIR) recognize HLA-B molecules that express the Bw4 public serologic epitope. We assessed DX9+ NK cell fine specificity recognition of HLA-B7 variants and HLA-B27 alleles by 51Cr release natural cytotoxicity assays and by flow cytometry and enzyme-linked immunospot (ELISPOT) IFN-gamma synthesis and release assays. 721.221 target cell expression of Bw4+ HLA-B27 alleles specifically inhibited DX9+ NK cell natural cytotoxicity and IFN-gamma synthesis and release. A triple substitution of HLA-B7 at residues 80, 82, and 83 known to induce expression of the Bw4 serologic epitope also specifically inhibited DX9+ NK cell natural cytotoxicity and IFN-gamma responses. Single HLA-B7 amino acid substitution variants were recognized in the same decreasing rank order by DX9+ NK cells and Bw4-reactive mAbs: G83R > R82L > N80T = HLA-B7. Natural cytotoxicity inhibition was reversed by the presence of blocking DX9 mAb. Natural cytotoxicity and IFN-gamma production were coordinately regulated by a panel of HLA-B7 variants expressed on 721.221 cells, suggesting that these two effector functions are inhibited by the same KIR-mediated signaling mechanisms. In contrast, some NK cell clones killed 721.221 and K562 target cells equally well but released much more IFN-gamma in response to K562 target cells. Differential regulation of natural cytotoxicity and IFN-gamma release shows that NK cell effector functions respond to distinct signals.

Alleles↗
PubMed1998

Gene redundancy and pharmacological gene therapy: implications for X-linked adrenoleukodystrophy.

As more functional redundancy in mammalian cells is discovered, enhanced expression of genes involved in alternative pathways may become an effective form of gene therapy. X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder with impaired very-long-chain fatty acid metabolism. The X-ALD gene encodes a peroxisomal membrane protein (ALDP) that is part of a small family of related peroxisomal membrane proteins. We show that 4-phenylbutyrate treatment of cells from both X-ALD patients and X-ALD knockout mice results in decreased levels of and increased beta-oxidation of very-long-chain fatty acids; increased expression of the peroxisomal protein ALDRP; and induction of peroxisome proliferation. We also demonstrate that ALDP and ALDRP are functionally related, by ALDRP cDNA complementation of X-ALD fibroblasts. Finally, we demonstrate the in vivo efficacy of dietary 4-phenylbutyrate treatment through its production of a substantial reduction of very-long-chain fatty acid levels in the brain and adrenal glands of X-ALD mice.

ATP Binding Cassette Transporter, Subfamily D↗