The Duffy antigen modifies systemic and local tissue chemokine responses following lipopolysaccharide stimulation

The Duffy blood group Ag (dfy) binds selective CXC and CC chemokines at high affinity and is expressed on erythrocytes and endothelial cells. However, it does not transmit a signal via G proteins, as occurs with other seven-transmembrane receptors. We hypothesized that dfy functions as a chemokine reservoir and regulates inflammation by altering soluble chemokine concentrations in the blood and tissue compartments. We determined whether Duffy Ag "loss-of-function" phenotypes (human and murine) are associated with alterations in plasma chemokine concentrations during the innate inflammatory response to LPS. Plasma CXCL8 and CCL2 concentrations from humans homozygous for the GATA-1 box polymorphism, a dfy polymorphism that abrogates erythrocyte chemokine binding, were higher than in heterozygotes following LPS stimulation of their whole blood in vitro. Similarly, dfy(-/-) mice showed higher plasma MIP-2 concentrations than dfy(+/+) mice following LPS stimulation of whole blood in vitro. We then determined the relative contributions of erythrocyte and endothelial Duffy Ag in modifying chemokine concentrations and neutrophil recruitment in the lungs following intratracheal LPS administration in dfy(-/-) and dfy(+/+) mice reconstituted with dfy(-/-) or dfy(+/+) marrow. Mice lacking endothelial dfy expression had higher MIP-2 and keratinocyte chemoattractant concentrations in the airspaces. Mice lacking erythrocyte dfy had higher MIP-2 and keratinocyte chemoattractant concentrations in the lung tissue vascular space, but lower plasma chemokine concentrations associated with attenuated neutrophil recruitment into the airspaces. These data indicate that dfy alters soluble chemokine concentrations in blood and local tissue compartments and enhances systemic bioavailability of chemokines produced during local tissue inflammation.     

Limited life cycle and cost assessment for the bioconversion of lignin-derived aromatics into adipic acid

Lignin is an abundant and heterogeneous waste byproduct of the cellulosic industry, which has the potential of being transformed into valuable biochemicals via microbial fermentation. In this study, we applied a fast-pyrolysis process using softwood lignin resulting in a two-phase bio-oil containing monomeric and oligomeric aromatics without syringol. We demonstrated that an additional hydrodeoxygenation step within the process leads to an enhanced thermochemical conversion of guaiacol into catechol and phenol. After steam bath distillation, Pseudomonas putida KT2440-BN6 achieved a percent yield of cis, cis-muconic acid of up to 95 mol% from catechol derived from the aqueous phase. We next established a downstream process for purifying cis, cis-muconic acid (39.9 g/L) produced in a 42.5 L fermenter using glucose and benzoate as carbon substrates. On the basis of the obtained values for each unit operation of the empirical processes, we next performed a limited life cycle and cost analysis of an integrated biotechnological and chemical process for producing adipic acid and then compared it with the conventional petrochemical route. The simulated scenarios estimate that by attaining a mixture of catechol, phenol, cresol, and guaiacol (1:0.34:0.18:0, mol ratio), a titer of 62.5 (g/L) cis, cis-muconic acid in the bioreactor, and a controlled cooling of pyrolysis gases to concentrate monomeric aromatics in the aqueous phase, the bio-based route results in a reduction of CO₂-eq emission by 58% and energy demand by 23% with a contribution margin for the aqueous phase of up to 88.05 euro/ton. We conclude that the bio-based production of adipic acid from softwood lignins brings environmental benefits over the petrochemical procedure and is cost-effective at an industrial scale. Further research is essential to achieve the proposed cis, cis-muconic acid yield from true lignin-derived aromatics using whole-cell biocatalysts.     

Actin binding by Hip1 (huntingtin-interacting protein 1) and Hip1R (Hip1-related protein) is regulated by clathrin light chain

The huntingtin-interacting protein family members (Hip1 and Hip1R in mammals and Sla2p in yeast) link clathrin-mediated membrane traffic to actin cytoskeleton dynamics. Genetic data in yeast have implicated the light chain subunit of clathrin in regulating this link. To test this hypothesis, the biophysical properties of mammalian Hip1 and Hip1R and their interaction with clathrin light chain and actin were analyzed. The coiled-coil domains (clathrin light chain-binding) of Hip1 and Hip1R were found to be stable homodimers with no propensity to heterodimerize in vitro. Homodimers were also predominant in vivo, accounting for cellular segregation of Hip1 and Hip1R functions. Coiled-coil domains of Hip1 and Hip1R differed in their stability and flexibility, correlating with slightly different affinities for clathrin light chain and more markedly with effects of clathrin light chain binding on Hip protein-actin interactions. Clathrin light chain binding induced a compact conformation of both Hip1 and Hip1R and significantly reduced actin binding by their THATCH domains. Thus, clathrin is a negative regulator of Hip-actin interactions. These observations necessarily change models proposed for Hip protein function.     

The origin of passive force enhancement in skeletal muscle

The aim of the present study was to test whether titin is a calcium-dependent spring and whether it is the source of the passive force enhancement observed in muscle and single fiber preparations. We measured passive force enhancement in troponin C (TnC)-depleted myofibrils in which active force production was completely eliminated. The TnC-depleted construct allowed for the investigation of the effect of calcium concentration on passive force, without the confounding effects of actin-myosin cross-bridge formation and active force production. Passive forces in TnC-depleted myofibrils (n = 6) were 35.0 +/- 2.9 nN/ microm(2) when stretched to an average sarcomere length of 3.4 microm in a solution with low calcium concentration (pCa 8.0). Passive forces in the same myofibrils increased by 25% to 30% when stretches were performed in a solution with high calcium concentration (pCa 3.5). Since it is well accepted that titin is the primary source for passive force in rabbit psoas myofibrils and since the increase in passive force in TnC-depleted myofibrils was abolished after trypsin treatment, our results suggest that increasing calcium concentration is associated with increased titin stiffness. However, this calcium-induced titin stiffness accounted for only approximately 25% of the passive force enhancement observed in intact myofibrils. Therefore, approximately 75% of the normally occurring passive force enhancement remains unexplained. The findings of the present study suggest that passive force enhancement is partly caused by a calcium-induced increase in titin stiffness but also requires cross-bridge formation and/or active force production for full manifestation.     

A potential role of TNFR gene polymorphisms in autoimmune thyroid diseases in the Tunisian population

Autoimmune thyroid diseases (AITDs) including Graves disease (GD) and autoimmune hypothyroidism (AH) are associated with TNF genes polymorphisms. TNF molecules bind to TNFRI and TNFRII. No genetic association was reported between TNFR and AITDs. In this study, we have analysed two polymorphisms in TNFRI gene (TNFRI+36A/G SNP and a microsatellite (GT)₁₇ (GA)_n) and one polymorphism in TNFRII gene (TNFRII +676 T/G). All these polymorphisms were studied in a large Tunisian family with high prevalence of AITDs, and on a case-control sample of 91 GD patients and 165 controls. The present study was undertaken to investigate the genetic association of these polymorphisms with AITDs development. We reported the implication of TNFRIA3 allele in AITDs pathogenesis in familial and case control studies, respectively (χ² = 4.13, p = 0.042; χ² = 9.26, p_c = 0.005). In addition, Case-control study has revealed for the first time that TNFRII+676G allele was associated with GD (χ² = 11.53; p = 0.0007). Two TNFRI haplotypes were found to be associated with GD: TNFRI+36G-A8, TNFRI+36A-A3 (χ² = 88.07; p = 6.32 × 10⁻²¹, χ² = 16.78; p = 4.2 × 10⁻⁵, respectively). Our data showed that TNFRI polymorphisms have an important role in AITDs pathogenesis in both familial and case-control samples and that TNFRII was rather implicated in GD development in the Tunisian population.     

Description of the delayed microbial growth by an extended logistic equation

Logistic equations are suitable for describing microbial growth. By means of VERHULST'S logistic equation, the adaptation to sigmoid-shaped curves of growth improves with a falling ratio C_xo/C_{x, max} < 0.2, if there is no lag-phase. The known logistic equations do not take into account any lag-phase behaviour, so that noticeable deviations in the model adaptation result in this range. Therefore, an extended logistic equation of rate is proposed by which any occuring lag-time is expressed by a 1st-order lag-term. The corresponding time law allows a very good adaptation of curves of delayed growth behaviour, and changes into VERHULST'S logistic equation for a lag-time t_L = 0. Application is facilitated by instructions for the numerical determination.