Autoantibody reaction to myelin basic protein by plasma parvovirus B19 IgG in MS patients

The etiology of multiple sclerosis (MS) remains unclear. To determine if autoantibodies to myelin basic protein (MBP) are produced during parvovirus B19 infection, a competitive ELISA was performed using plasma from MS patients exhibiting high IgG titers for parvovirus. Our results showed the addition of MBP decreased the binding of IgG to B19 antigen in a dose dependent fashion suggesting a possible link between parvovirus B19 and a subset of patients with clinical MS.     

Similar transition states mediate the Q-cycle and superoxide production by the cytochrome bc1 complex

The cytochrome bc complexes found in mitochondria, chloroplasts and many bacteria play critical roles in their respective electron transport chains. The quinol oxidase (Q(o)) site in this complex oxidizes a hydroquinone (quinol), reducing two one-electron carriers, a low potential cytochrome b heme and the "Rieske" iron-sulfur cluster. The overall electron transfer reactions are coupled to transmembrane translocation of protons via a "Q-cycle" mechanism, which generates proton motive force for ATP synthesis. Since semiquinone intermediates of quinol oxidation are generally highly reactive, one of the key questions in this field is: how does the Q(o) site oxidize quinol without the production of deleterious side reactions including superoxide production? We attempt to test three possible general models to account for this behavior: 1) The Q(o) site semiquinone (or quinol-imidazolate complex) is unstable and thus occurs at a very low steady-state concentration, limiting O(2) reduction; 2) the Q(o) site semiquinone is highly stabilized making it unreactive toward oxygen; and 3) the Q(o) site catalyzes a quantum mechanically coupled two-electron/two-proton transfer without a semiquinone intermediate. Enthalpies of activation were found to be almost identical between the uninhibited Q-cycle and superoxide production in the presence of antimycin A in wild type. This behavior was also preserved in a series of mutants with altered driving forces for quinol oxidation. Overall, the data support models where the rate-limiting step for both Q-cycle and superoxide production is essentially identical, consistent with model 1 but requiring modifications to models 2 and 3.     

Rheology of passive and adhesion-activated neutrophils probed by atomic force microscopy

The rheology of neutrophils in their passive and activated states plays a key role in determining their function in response to inflammatory stimuli. Atomic force microscopy was used to study neutrophil rheology by measuring the complex shear modulus G*(omega) of passive nonadhered rat neutrophils on poly(HEMA) and neutrophils activated through adhesion to glass. G*(omega) was measured over three frequency decades (0.1-102.4 Hz) by indenting the cells 500 nm with a spherical tip and then applying a 50-nm amplitude multi-frequency signal. G*(omega) of both passive and adhered neutrophils increased as a power law with frequency, with a coupling between elastic (G') and loss (G') moduli. For passive neutrophils at 1.6 Hz, G' = 380 +/- 121 Pa, whereas G' was fourfold smaller and the power law coefficient was of x = 1.184. Adhered neutrophils were over twofold stiffer with a lower slope (x = 1.148). This behavior was adequately described by the power law structural damping model but not by liquid droplet and Kelvin models. The increase in stiffness with frequency may modulate neutrophil transit, arrest, and transmigration in vascular microcirculation.     

ACE inhibitors reduce fecundity in the mosquito,Anopheles stephensi

Angiotensin-converting enzyme (ACE) is a dipeptidyl carboxypeptidase, which cleaves dipeptides and, in some instances, dipeptide or tripeptide amides from the C-terminus of regulatory peptides (e.g. angiotensin I, bradykinin and substance P). The expression of ACE is highly regulated in insects, where it is thought to have a role in the metabolism of peptide hormones involved in regulating reproduction. After a blood meal, ACE activity in the female mosquito Anopheles stephensi, increases four-fold with much of the enzyme finally accumulating in the ovary. In the present study, we have studied the effect on reproduction of adding two selective inhibitors of ACE, captopril and lisinopril, to the blood meal. Both ACE inhibitors reduced the size of the batch of eggs laid by females in a dose-dependent manner, with no observable effects on the behaviour of the adult insect. The almost total failure to lay eggs after feeding on either 1 mM captopril or 1 mM lisinopril, did not result from interference with the development of the primary follicle, but was due to the inhibition of egg-laying. Since very similar effects on the size of the egg-batch were observed with two selective ACE inhibitors, belonging to different chemical classes, we suggest that these effects are mediated by the selective inhibition of the induced mosquito ACE, a peptidase probably involved in the activation/inactivation of a peptide regulating egg-laying activity in A. stephensi.     

Mitochondrial-targeted antioxidants represent a promising approach for prevention of cisplatin-induced nephropathy

Cisplatin is a widely used antineoplastic agent; however, its major limitation is the development of dose-dependent nephrotoxicity whose precise mechanisms are poorly understood. Here we show not only that mitochondrial dysfunction is a feature of cisplatin nephrotoxicity, but also that targeted delivery of superoxide dismutase mimetics to mitochondria largely prevents the renal effects of cisplatin. Cisplatin induced renal oxidative stress, deterioration of mitochondrial structure and function, an intense inflammatory response, histopathological injury, and renal dysfunction. A single systemic dose of mitochondrially targeted antioxidants, MitoQ or Mito-CP, dose-dependently prevented cisplatin-induced renal dysfunction. Mito-CP also prevented mitochondrial injury and dysfunction, renal inflammation, and tubular injury and apoptosis. Despite being broadly renoprotective against cisplatin, Mito-CP did not diminish cisplatin's antineoplastic effect in a human bladder cancer cell line. Our results highlight the central role of mitochondrially generated oxidants in the pathogenesis of cisplatin nephrotoxicity. Because similar compounds seem to be safe in humans, mitochondrially targeted antioxidants may represent a novel therapeutic approach against cisplatin nephrotoxicity.     

Mice expressing T4826I-RYR1 are viable but exhibit sex- and genotype-dependent susceptibility to malignant hyperthermia and muscle damage

Mutation T4825I in the type 1 ryanodine receptor (RYR1(T4825I/+)) confers human malignant hyperthermia susceptibility (MHS). We report a knock-in mouse line that expresses the isogenetic mutation T4826I. Heterozygous RYR1(T4826I/+) (Het) or homozygous RYR1(T4826I/T4826I) (Hom) mice are fully viable under typical rearing conditions but exhibit genotype- and sex-dependent susceptibility to environmental conditions that trigger MH. Hom mice maintain higher core temperatures than WT in the home cage, have chronically elevated myoplasmic[Ca(2+)](rest), and present muscle damage in soleus with a strong sex bias. Mice subjected to heat stress in an enclosed 37°C chamber fail to trigger MH regardless of genotype, whereas heat stress at 41°C invariably triggers fulminant MH in Hom, but not Het, mice within 20 min. WT and Het female mice fail to maintain euthermic body temperature when placed atop a bed whose surface is 37°C during halothane anesthesia (1.75%) and have no hyperthermic response, whereas 100% Hom mice of either sex and 17% of the Het males develop fulminant MH. WT mice placed on a 41°C bed maintain body temperature while being administered halothane, and 40% of the Het females and 100% of the Het males develop fulminant MH within 40 min. Myopathic alterations in soleus were apparent by 12 mo, including abnormally distributed and enlarged mitochondria, deeply infolded sarcolemma, and frequent Z-line streaming regions, which were more severe in males. These data demonstrate that an MHS mutation within the S4-S5 cytoplasmic linker of RYR1 confers genotype- and sex-dependent susceptibility to pharmacological and environmental stressors that trigger fulminant MH and promote myopathy.     

Mitochondrial reactive oxygen species generation triggers inflammatory response and tissue injury associated with hepatic ischemia-reperfusion: Therapeutic potential of mitochondrially targeted antioxidants

Mitochondrial reactive oxygen species generation has been implicated in the pathophysiology of ischemia-reperfusion (I/R) injury; however, its exact role and its spatial-temporal relationship with inflammation are elusive. Herein we explore the spatial-temporal relationship of oxidative/nitrative stress and inflammatory response during the course of hepatic I/R and the possible therapeutic potential of mitochondrial-targeted antioxidants, using a mouse model of segmental hepatic ischemia-reperfusion injury. Hepatic I/R was characterized by early (at 2h of reperfusion) mitochondrial injury, decreased complex I activity, increased oxidant generation in the liver or liver mitochondria, and profound hepatocellular injury/dysfunction with acute proinflammatory response (TNF-α, MIP-1α/CCL3, MIP-2/CXCL2) without inflammatory cell infiltration, followed by marked neutrophil infiltration and a more pronounced secondary wave of oxidative/nitrative stress in the liver (starting from 6h of reperfusion and peaking at 24h). Mitochondrially targeted antioxidants, MitoQ or Mito-CP, dose-dependently attenuated I/R-induced liver dysfunction, the early and delayed oxidative and nitrative stress response (HNE/carbonyl adducts, malondialdehyde, 8-OHdG, and 3-nitrotyrosine formation), and mitochondrial and histopathological injury/dysfunction, as well as delayed inflammatory cell infiltration and cell death. Mitochondrially generated oxidants play a central role in triggering the deleterious cascade of events associated with hepatic I/R, which may be targeted by novel antioxidants for therapeutic advantage.     

Thalamocortical inputs show post-critical-period plasticity

Experience-dependent plasticity in the adult brain has clinical potential for functional rehabilitation following central and peripheral nerve injuries. Here, plasticity induced by unilateral infraorbital (IO) nerve resection in 4-week-old rats was mapped using MRI and synaptic mechanisms were elucidated by slice electrophysiology. Functional MRI demonstrates a cortical potentiation compared to thalamus 2 weeks after IO nerve resection. Tracing thalamocortical (TC) projections with manganese-enhanced MRI revealed circuit changes in the spared layer 4 (L4) barrel cortex. Brain slice electrophysiology revealed TC input strengthening onto L4 stellate cells due to an increase in postsynaptic strength and the number of functional synapses. This work shows that the TC input is a site for robust plasticity after the end of the previously defined critical period for this input. Thus, TC inputs may represent a major site for adult plasticity in contrast to the consensus that adult plasticity mainly occurs at cortico-cortical connections.     

Bone marrow stromal cells stimulate an angiogenic program that requires endothelial MT1-MMP

Bone marrow-derived stromal/stem cells (BMSCs) have recently been characterized as mediators of tissue regeneration after injury. In addition to preventing fibrosis at the wound site, BMSCs elicit an angiogenic response within the fibrin matrix. The mechanistic interactions between BMSCs and invading endothelial cells (ECs) during this process are not fully understood. Using a three-dimensional, fibrin-based angiogenesis model, we sought to investigate the proteolytic mechanisms by which BMSCs promote vessel morphogenesis. We find that BMSC-mediated vessel formation depends on the proteolytic ability of membrane type 1-matrix metalloproteinase (MT1-MMP). Knockdown of the protease results in a small network of vessels with enlarged lumens. Contrastingly, vessel morphogenesis is unaffected by the knockdown of MMP-2 and MMP-9. Furthermore, we find that BMSC-mediated vessel morphogenesis in vivo follows mechanisms similar to what we observe in vitro. Subcutaneous, cellular fibrin implants in C.B-17/SCID mice form aberrant vasculature when MMPs are inhibited with a broad-spectrum chemical inhibitor, and a very minimal amount of vessels when MT1-MMP proteolytic activity is interrupted in ECs. Other studies have debated the necessity of MT1-MMP in the context of vessel invasion in fibrin, but this study clearly demonstrates its requirement in BMSC-mediated angiogenesis.