The 'novel' 'uncoupling' proteins UCP2 and UCP3: what do they really do? Pros and cons for suggested functions

The scientifically novel, but evolutionarily ancient, so-called uncoupling proteins 2 and 3 (UCP2, UCP3) are structurally similar to the archetypical uncoupling protein UCP1. A series of suggestions have been forwarded for their physiological function. We discuss systematically here the pros and cons for these suggestions. We conclude that the novel UCPs do not seem to be physiologically relevant uncoupling proteins; the uncoupling property was apparently a late introduction into the subfamily through the evolution of UCP1. Physiological functions ascribed to UCP2 and UCP3 based on their purported uncoupling property may have to be revised (i.e. any type of thermogenesis, including protection against obesity, protection against the formation of reactive oxygen species and thermogenic involvement in the fever response). The presence of a mixed genetic background in most published studies of UCP2 or UCP3 gene-ablated mice also means that data concerning marked differences in diabetes propensity, infection sensitivity and production of reactive oxygen species may require confirmation in backcrossed mice. The increased expression of UCP2 and UCP3 under conditions of increased fatty acid metabolism implies an as yet undefined role in lipid metabolism. Thus, the novel UCPs should probably be considered as mitochondrial carriers, and the challenge now is to identify the transported molecule.     

Levels of analysis in etiological research on schizophrenia

Etiological research spanning domains of inquiry as diverse as social psychology and molecular genetics has identified a number of potential factors that likely contribute to the development and clinical manifestation of schizophrenia. In this article, we first highlight the challenges inherent in developing cogent etiological models that represent both the diversity of suspected causal influences and their mechanisms of action. Then, using our own research program as a heuristic context, we present a general analytical framework for identifying and integrating multiple types of etiologic factors across different levels of analysis in the prediction of schizophrenia. In recognition of the myriad complexities of multifactorial causation, we argue that a multilevel causal perspective is required for the development and advancement of a fully nuanced theory of schizophrenia etiology and pathophysiology.     

Identification of diversified genes that contain immunoglobulin-like variable regions in a protochordate

The evolutionary origin of adaptive immune receptors is not understood below the phylogenetic level of the jawed vertebrates. We describe here a strategy for the selective cloning of cDNAs encoding secreted or transmembrane proteins that uses a bacterial plasmid (Amptrap) with a defective beta-lactamase gene. This method requires knowledge of only a single target motif that corresponds to as few as three amino acids; it was validated with major histocompatibility complex genes from a cartilaginous fish. Using this approach, we identified families of genes encoding secreted proteins with two diversified immunoglobulin-like variable (V) domains and a chitin-binding domain in amphioxus, a protochordate. Thus, multigenic families encoding diversified V regions exist in a species lacking an adaptive immune response.     

Genetic dissection of a rat model for rheumatoid arthritis: significant gender influences on autosomal modifier loci

Rheumatoid arthritis (RA) is a common, chronic, autoimmune, inflammatory disease that is influenced by genetic factors including gender. Many studies suggest that the genetic risk for RA is determined by the MHC, in particular class II alleles with a 'shared epitope' (SE), and multiple non-MHC loci. Other studies indicate that RA and other autoimmune diseases, in particular insulin-dependent diabetes mellitus (IDDM) and autoimmune thyroid disease (ATD), share genetic risk factors. Rat collagen-induced arthritis (CIA) is an experimental model with many features that resemble RA. The spontaneous diabetes-resistant bio-breeding rat, BB(DR), is of interest because it is susceptible to experimentally induced CIA, IDDM and ATD, and it has an SE in its MHC class II allele. To explore the genetics of CIA, including potential gender influences and the genetic relationships between CIA and other autoimmune diseases, we conducted a genome-wide scan for CIA regulatory loci in the F(2) progeny of BB(DR) and CIA-resistant BN rats. We identified 10 quantitative trait loci (QTLs), including 5 new ones (Cia15, Cia16*, Cia17, Cia18* and Cia19 on chromosomes 9, 10, 18 and two on the X chromosome, respectively), that regulated CIA severity. We also identified four QTLs, including two new ones (Ciaa4* and Ciaa5* on chromosomes 4 and 5, respectively), that regulated autoantibody titer to rat type II collagen. Many of these loci appeared to be gender influenced, and most co-localized with several other autoimmune trait loci. Our data support the view that multiple autoimmune diseases may share genetic risk factors, and suggest that many of these loci are gender influenced.     

Effects of gold sodium thiomalate,cyclosporin A,cyclophosphamide, and placebo on collagen-induced arthritis in rats

The prophylactic and therapeutic effects of gold sodium thiomalate, cyclosporin A, cyclophosphamide, and placebo on collagen-induced arthritis (CIA) were evaluated in DA rats. Prophylactic treatment with cyclosporin A and cyclophosphamide suppressed the arthritis incidence, clinical inflammation, destructive bone changes, and development of anti-collagen antibody in DA rats subsequently injected with porcine type-II collagen. Therapeutic treatment with cyclosporin A and cyclophosphamide had a definite suppression on established CIA when started 21 days after the initial collagen injection, but the suppression was less marked than that of prophylactic treatment. Gold had no impact on CIA in DA rats when administered either prophylactically or therapeutically.     

The stability of methacrylate biomaterials when enzyme challenged: kinetic and systematic evaluations

This study addressed whether methacrylate monomers and polymers used in dentistry might degrade from enzymolysis by acetylcholinesterase (ACHE), cholesterol esterase (CHE), porcine liver esterase (PRLE), and a pancreatic lipase (PNL). Short (hour) and long-term (day) exposures were performed. Product ratios were used to determine surface hydrolysis of the polymeric materials. Enzyme kinetics were studied for the monomers when challenged by ACHE, CHE, and PRLE. In the case of PRLE, the V(max) for the dimethacrylate substrates varied slightly, but amounted to as much as 10% of that of p-nitrophenylacetate. The K(m) for triethylene glycol dimethacrylate (TEGDMA) was 197 microM for ACHE and 1107 microM for CHE. The V(max) was 2.7 nmol/min for ACHE and 3.5 nmol/min for CHE. TEGDMA was converted by CHE at 2% the rate of cholesteryl oleate. Long-term incubations of monomers with CHE and ACHE produced degrees of hydrolysis that evidenced structure dependency in the ability of the enzymes to effect hydrolysis. Particularly resistant were aromativ derivatives and those with branching in methacrylate linkages. Overall, the study confirms the ability of physiologically important esterases to catalyze the hydrolysis of biomaterial methacrylates.     

Targeted disruption of fibronectin-integrin interactions in human gingival fibroblasts by the RI protease of Porphyromonas gingivalis W50

Cell surface integrins mediate interactions between cells and their extracellular matrix and are frequently exploited by a range of bacterial pathogens to facilitate adherence and/or invasion. In this study we examined the effects of Porphyromonas gingivalis proteases on human gingival fibroblast (HGF) integrins and their fibronectin matrix. Culture supernatant from the virulent strain W50 caused considerably greater loss of the beta1 integrin subunit from HGF in vitro than did that of the beige-pigmented strain W50/BE1. Prior treatment of the W50 culture supernatant with the protease inhibitor Nalpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) blocked its effects on cultured cells, indicating that this process is proteolytically mediated. Purified arginine-specific proteases from P. gingivalis W50 were able to mimic the effects of the whole-culture supernatant on loss of beta1 integrin expression. However purified RI, an alpha/beta heterodimer in which the catalytic chain is associated with an adhesin chain, was 12 times more active than RIA, the catalytic monomer, in causing loss of the alpha5beta1 integrin (fibronectin receptor) from HGF. No effect was observed on the alphaVbeta3 integrin (vitronectin receptor). The sites of action of RI and RIA were investigated in cells exposed to proteases pretreated with TLCK to inactivate the catalytic component. Use of both monoclonal antibody 1A1, which recognizes only the adhesin chain of RI, and a rabbit antibody against P. gingivalis whole cells indicated localization of RI on the fibroblasts in a clear, linear pattern typical of that seen with fibronectin and alpha5beta1 integrin. Exact colocalization of RI with fibronectin and its alpha5beta1 receptor was confirmed by double labeling and multiple-exposure photomicroscopy. In contrast, RIA bound to fibroblasts in a weak, patchy manner, showing only fine linear or granular staining. It is concluded that the adhesin component of RI targets the P. gingivalis arginine-protease to sites of fibronectin deposition on HGF, contributing to the rapid loss of both fibronectin and its main alpha5beta1 integrin receptor. Given the importance of integrin-ligand interactions in fibroblast function, their targeted disruption by RI may represent a novel mechanism of damage in periodontal disease.     

In vitro production of IL 1 beta, IL 1 alpha, TNF and IL2 in healthy subjects: distribution, effect of cyclooxygenase inhibition and evidence of independent gene regulation

Numerous studies have reported altered in vitro cytokine production in various diseases. In the present study we used specific immunoassays to quantitate production of interleukin 1 beta (IL 1 beta), IL 1 alpha, tumor necrosis factor (TNF) and IL 2 from human peripheral blood mononuclear cells (PBMC). The distribution of cell-associated and secreted cytokines was studied in PBMC of 21 individuals; in response to lipopolysaccharide (LPS) the proportion of cell-associated IL 1 beta ranged from 13% to 56%, for IL 1 alpha 29% to 98%, and for TNF 2% to 17%. In a larger cohort of 32 subjects, the total amount of immunoreactive cytokines produced in response to LPS or phytohemagglutinin was normally distributed within the study group. Mean production of IL 1 alpha in response to LPS was 10.1 ng/ml and exceeded production of IL 1 beta (5.6 ng/ml) and TNF (2.2 ng/ml). The distribution pattern was characterized by high intersubject variability extending over two orders of magnitude and the presence of high and low "producers". Production of IL 1 alpha and IL 1 beta correlated (R = 0.69). In contrast, production of IL 1 beta did not correlate with production of TNF or IL 2. Indomethacin present during stimulation of PBMC increased the amount of IL 1 beta produced and showed a high correlation (R = 0.83) compared to cultures without indomethacin. Thus, low production of IL 1 beta in certain subjects appears not to be due to inhibitable levels of cyclooxygenase products. In a retrospective study, PBMC from 12 subjects who had taken oral cyclooxygenase inhibitors during the preceding 7 days produced 43% more IL 1 beta than subjects who did not take these drugs (p less than 0.05). These studies demonstrate that the amount of cytokine synthesized by PBMC (a) is regulated independently for IL 1, TNF and IL 2; (b) correlates for IL 1 beta and IL 1 alpha; (c) is intrinsic for low and high "producers", and (d) production of IL 1 beta increases with the use of oral cyclooxygenase inhibitors.