NF-κB in the regulation of epithelial homeostasis and inflammation

The IκB kinase/NF-κB signaling pathway has been implicated in the pathogenesis of several inflammatory diseases. Increased activation of NF-κB is often detected in both immune and non-immune cells in tissues affected by chronic inflammation, where it is believed to exert detrimental functions by inducing the expression of proinflammatory mediators that orchestrate and sustain the inflammatory response and cause tissue damage. Thus, increased NF-κB activation is considered an important pathogenic factor in many acute and chronic inflammatory disorders, raising hopes that NF-κB inhibitors could be effective for the treatment of inflammatory diseases. However, ample evidence has accumulated that NF-κB inhibition can also be harmful for the organism, and in some cases trigger the development of inflammation and disease. These findings suggested that NF-κB signaling has important functions for the maintenance of physiological immune homeostasis and for the prevention of inflammatory diseases in many tissues. This beneficial function of NF-κB has been predominantly observed in epithelial cells, indicating that NF-κB signaling has a particularly important role for the maintenance of immune homeostasis in epithelial tissues. It seems therefore that NF-κB displays two faces in chronic inflammation: on the one hand increased and sustained NF-κB activation induces inflammation and tissue damage, but on the other hand inhibition of NF-κB signaling can also disturb immune homeostasis, triggering inflammation and disease. Here, we discuss the mechanisms that control these apparently opposing functions of NF-κB signaling, focusing particularly on the role of NF-κB in the regulation of immune homeostasis and inflammation in the intestine and the skin.     

STK38 at the crossroad between autophagy and apoptosis

We describe the STK38 protein kinase as a conserved regulator of autophagy. We discovered STK38 as a novel binding partner of Beclin1, a key regulator of autophagy. By combining molecular, cell biological and genetic approaches, we show that STK38 promotes autophagosome formation in human cells and in Drosophila. Furthermore, we also provide evidence demonstrating that STK38 with the small GTPase RalB, assist the co-ordination between autophagic and apoptotic events upon autophagy induction, hence proposing a role for STK38 in determining cellular fate in response to autophagic conditions.     

Pathway and stability of protein folding.

We describe an experimental approach to the problem of protein folding and stability which measures interaction energies and maps structures of intermediates and transition states during the folding pathway. The strategy is based on two steps. First, protein engineering is used to remove interactions that stabilize defined positions in barnase, the RNAse from Bacillus amyloliquefaciens. The consequent changes in stability are measured from the changes in free energy of unfolding of the protein. Second, each mutation is used as a probe of the structure around the wild-type side chain during the folding process. Kinetic measurements are made on the folding and unfolding of wild-type and mutant proteins. The kinetic and thermodynamic data are combined and analysed to show the role of individual side chains in the stabilization of the folded, transition and intermediate states of the protein. The protein engineering experiments are corroborated by nuclear magnetic resonance studies of hydrogen exchange during the folding process. Folding is a multiphasic process in which alpha-helices and beta-sheet are formed relatively early. Formation of the hydrophobic core by docking helix and sheet is (partly) rate determining. The final steps involve the forming of loops and the capping of the N-termini of helices.     

Ferritins: iron/oxygen biominerals in protein nanocages

Ferritin protein nanocages that form iron oxy biominerals in the central nanometer cavity are nature’s answer to managing iron and oxygen; gene deletions are lethal in mammals and render bacteria more vulnerable to host release of antipathogen oxidants. The multifunctional, multisubunit proteins couple iron with oxygen (maxi-ferritins) or hydrogen peroxide (mini-ferritins) at catalytic sites that are related to di-iron sites oxidases, ribonucleotide reductase, methane monooxygenase and fatty acid desaturases, and synthesize mineral precursors. Gated pores, distributed symmetrically around the ferritin cages, control removal of iron by reductants and chelators. Gene regulation of ferritin, long known to depend on iron and, in animals, on a noncoding messenger RNA (mRNA) structure linked in a combinatorial array to functionally related mRNA of iron transport, has recently been shown to be linked to an array of proteins for antioxidant responses such as thioredoxin and quinone reductases. Ferritin DNA responds more to oxygen signals, and ferritin mRNA responds more to iron signals. Ferritin genes (DNA and RNA) and protein function at the intersection of iron and oxygen chemistry in biology.     

Agonist versus antagonist muscle fatigue effects on thigh muscle activity and vertical ground reaction during drop landing

BackgroundAgonist and antagonist co-activation plays an important role for stabilizing the knee joint, especially after fatigue. However, whether selective fatigue of agonists or antagonist muscles would cause different changes in muscle activation patterns is unknown.HypothesisKnee extension fatigue would have a higher influence on landing biomechanics compared with a knee flexion protocol.Study designRepeated-measures design.MethodsTwenty healthy subjects (10 males and 10 females) performed two sets of repeated maximal isokinetic concentric efforts of the knee extensors (KE) at 120° s^?1 until they could no longer consistently produce 30% of maximum torque. On a separate day, a similar knee flexion (KF) fatigue protocol was also performed. Single leg landings from 30 cm drop height were performed before, in the middle and after the end of the fatigue test. The mean normalized electromyographic (EMG) signal of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and gastrocnemius (GAS) at selected landing phases were determined before, during and after fatigue. Quadriceps:hamstrings (Q:H) EMG ratio as well as sagittal hip and knee angles and vertical ground reaction force (GRF) were also recorded.ResultsTwo-way analysis of variance designs showed that KE fatigue resulted in significantly lower GRF and higher knee flexion angles at initial contact while maximum hip and knee flexion also increased (p < 0.05). This was accompanied by a significant decline of BF EMG, unaltered EMG of vastii and GAS muscles and increased Q:H ratio. In contrast, KF fatigue had no effects on vGRFs but it was accompanied by increased activation of VM, BF and GAS while the Q:H increased during before landing and decreased after impact.ConclusionFatigue responses during landing are highly dependent on the muscle which is fatigued.     

Oligodendrocyte-specific FADD deletion protects mice from autoimmune-mediated demyelination

Apoptosis of oligodendrocytes (ODCs), the myelin-producing glial cells in the CNS, plays a central role in demyelinating diseases such as multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. To investigate the mechanism behind ODC apoptosis in EAE, we made use of conditional knockout mice lacking the adaptor protein FADD specifically in ODCs (FADD(ODC-KO)). FADD mediates apoptosis by coupling death receptors with downstream caspase activation. In line with this, ODCs from FADD(ODC-KO) mice were completely resistant to death receptor-induced apoptosis in vitro. In the EAE model, FADD(ODC-KO) mice followed an ameliorated clinical disease course in comparison with control littermates. Lymphocyte and macrophage infiltration into the spinal cord parenchyma was significantly reduced, as was the extent of demyelination and proinflammatory gene expression. Collectively, our data show that FADD is critical for ODC apoptosis and the development of autoimmune demyelinating disease.     

The effects of a twenty-four-week aquatic training program on muscular strength performance in healthy elderly women

The purpose of the present study was to determine the effectiveness of a 24-week aquatic training (AT) program, which included both aerobic and resistance components, on muscle strength (isometric and dynamic), flexibility, and functional mobility in healthy women over 60 years of age. Twenty-two subjects were assigned randomly to either an AT (n = 12) or a control (C, n = 10) group. Volunteers participated in a supervised shallow-water exercise program for 60 minutes a day, 3 days a week; the exercise program consisted of a 10-minute warm-up and stretching, 25 minutes of endurance-type exercise (dancing) at 80% of heart rate (HR)(max), 20 minutes of upper- and lower-body resistance exercises with specialized water-resistance equipment, and a 5-minute cool down. Maximal isometric torque of knee extensors (KEXT) and knee flexors (KFLEX) were evaluated by a Cybex Norm dynamometer, grip strength (HGR) was evaluated using a Jamar hydraulic dynamometer, and dynamic strength was evaluated via the 3 repetition maximum (3RM) test for chest press, knee extension, lat pull down, and leg press. Jumping performance was evaluated using the squat jump (SJ), functional mobility with the timed up-and-go (TUG) test, and trunk flexion with the sit-and-reach test. Body composition was measured using the bioelectrical impedance method. The AT induced significant improvements in KEXT (10.5%) and KFLEX (13.4%) peak torque, HGR strength (13%), 3RM (25.7-29.4%), SJ (24.6%), sit-and-reach (11.6%), and TUG (19.8%) performance. The AT group demonstrated a significant increase in lean body mass (3.4%). No significant changes in these variables were observed in the C group. The results indicate that AT, with both aerobic and resistance components, is an alternative training method for improving neuromuscular and functional fitness performance in healthy elderly women.     

Dipeptides containing the alpha-aminoisobutyric residue (Aib) as ligands: preparation,spectroscopic studies and crystal structures of copper(II) complexes with H-Aib-X-OH (X=Gly,L-Leu,L-Phe)

Synthetic procedures are described that allow access to new copper(II) complexes with dipeptides containing the alpha-aminoisobutyric residue (Aib) as ligands. The solid complexes [Cu(H(-1)L(A))](n).nH(2)O (1) (L(A)H=H-Aib-Gly-OH), [Cu(H(-1)L(B))(MeOH)](n).nMeOH (2) (L(B)H=H-Aib-L-Leu-OH) and [Cu(H(-1)L(C))](n) (3) (L(C)H=H-Aib-L-Phe-OH) have been isolated and characterized by single-crystal X-ray crystallography, solid-state IR spectra and UV-Vis spectroscopy in solution (H(-1)L(2-) is the dianionic form of the corresponding dipeptide). Complexes 1 and 3 are three-dimensional coordination polymers with similar structures. The doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate), O'(carboxylate), O(peptide) mu(3) ligand and binds to one Cu(II) atom at its amino and peptide nitrogens and at one carboxylate oxygen, to a second metal at the other carboxylate oxygen, while a third Cu(II) atom is attached to the peptide oxygen. The geometry around copper(II) is distorted square pyramidal with the peptide oxygen at the apex of the pyramid. The structure of 2 consists of zigzag polymeric chains, where the doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate), O'(carboxylate) mu(2) ligand. The geometry at copper(II) is square pyramidal with the methanol oxygen at the apex. The IR data are discussed in terms of the nature of bonding and known structures. The UV-Vis spectra show that the solid-state structures of 1, 2 and 3 do not persist in H(2)O.