Low Bone Mineral Density in Hemophiliacs.

OBJECTIVE: To review the current knowledge on bone health in patients with hemophilia A and the underlying pathogenetic mechanisms. DATA SOURCES: Original research articles, meta-analyses, and scientific reviews. DATA SYNTHESIS: Already in childhood, patients with hemophilia A are prone to low bone mineral density, leading to osteopenia and/or osteoporosis. Initially associated with the life style of hemophilia, today we are faced with accumulating evidence that coagulation factor VIII is involved directly or indirectly in bone physiology. CONCLUSION: Understanding the role of factor VIII and the mechanisms of decreased bone mineral density in hemophilia A is critically important, especially as non-factor replacement therapies are available, and treatment decisions potentially impact bone health.

vWDI is inherited in an autosomal dominant manner with incomplete penetrance, in the Kromfohrländer breed.

BACKGROUND: Von Willebrand disorder type I (vWDI) is known as an inherited bleeding disorder in different dog breeds following an autosomal recessive inheritance. The Kromfohrländer is a rare dog breed with an increased incidence of unclear bleeding episodes and prolonged coagulation time during/after surgery or injuries, indicating a defect in one or more critical proteins of the coagulation cascade. OBJECTIVE: The objective of this study was to determine whether the c.7437G > A mutation in the VWF gene previously shown to cause von Willebrand disorder type I in Doberman Pinscher is also linked to this disease in the Kromfohrländer breed and to serum concentrations of vWF. Furthermore, establish a possible link between bleeding phenotype, vWF serum concentrations and VWF mutation status. RESULTS: Eighty-seven Kromfohrländer were genotyped for the G > A von Willebrand type I mutation. For detection of the associated mutation we used an endpoint genotyping method. We identified the G > A von Willebrand type I mutation in 80.5% of our study population. 65.5% were heterozygous (WT/MUT) and 15.0% were homozygous for the mutation (MUT/MUT). 21% of the overall study population exhibited bleeding symptoms. 45.5% of all homozygous dogs (MUT/MUT) showed bleeding symptoms. In contrast, wild-type homozygotes exhibited no bleeding symptoms, whereas 23.2% of the heterozygotes did. VWF serum concentrations varied from 28 to 137% in wild-type dogs while in heterozygous and homozygous dogs the concentration ranged from 3 to 77% and 1 to 23%, respectively (p < 0.05). CONCLUSION: Based on our data, we found the G > A mutation in the VWF gene in the Kromfohrländer breed and the subsequent vWDI as the underlying cause for the bleeding episodes and delayed coagulation in heterozygous and homozygous dogs. Since both, heterozygotes and homozygotes show reduced vWF serum concentrations and exhibit to a certain percentage the vWD syndrome phenotype, we postulate that, in contrast to most other vWDI affected breeds, inheritance follows an autosomal dominant mode with incomplete penetrance.

Rac1 and PAK1 are upstream of IKK-epsilon and TBK-1 in the viral activation of interferon regulatory factor-3.

The anti-viral type I interferon (IFN) response is initiated by the immediate induction of IFN beta, which is mainly controlled by the IFN-regulatory factor-3 (IRF-3). The signaling pathways mediating viral IRF-3 activation are only poorly defined. We show that the Rho GTPase Rac1 is activated upon virus infection and controls IRF-3 phosphorylation and activity. Inhibition of Rac1 leads to reduced IFN beta promoter activity and to enhanced virus production. As a downstream mediator of Rac signaling towards IRF-3, we have identified the kinase p21-activated kinase (PAK1). Furthermore, both Rac1 and PAK1 regulate the recently described IRF-3 activators, I kappa B kinase- and TANK-binding kinase-1, establishing a first canonical virus-induced IRF-3 activating pathway.

Acetylsalicylic acid (ASA) blocks influenza virus propagation via its NF-kappaB-inhibiting activity.

Influenza is still one of the major plagues worldwide. The statistical likeliness of a new pandemic outbreak highlights the urgent need for new and amply available antiviral drugs. We and others have shown that influenza virus misuses the cellular IKK/NF-kappaB signalling pathway for efficient replication suggesting that this module may be a suitable target for antiviral intervention. Here we examined acetylsalicylic acid (ASA), also known as aspirin, a widely used drug with a well-known capacity to inhibit NF-kappaB. We show that the drug efficiently blocks influenza virus replication in vitro and in vivo in a mechanism involving impaired expression of proapoptotic factors, subsequent inhibition of caspase activation as well as block of caspase-mediated nuclear export of viral ribonucleoproteins. As ASA showed no toxic side-effects or the tendency to induce resistant virus variants, existing salicylate-based aerosolic drugs may be suitable as anti-influenza agents. This is the first demonstration that specific targeting of a cellular factor is a suitable approach for anti-influenza virus intervention.

NF-kappaB-dependent induction of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas/FasL is crucial for efficient influenza virus propagation.

Activation of the transcription factor NF-kappaB is a hallmark of infections by viral pathogens including influenza viruses. Because gene expression of many proinflammatory and antiviral cytokines is controlled by this factor, the concept emerged that NF-kappaB and its upstream regulator IkappaB kinase are essential components of the innate antiviral immune response to infectious pathogens. In contrast to this common view we report here that NF-kappaB activity promotes efficient influenza virus production. On a molecular level this is due to NF-kappaB-dependent viral induction of the proapoptotic factors tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and FasL, which enhance virus propagation in an autocrine and paracrine fashion. Thus, NF-kappaB acts both proapoptotically and provirally in the context of an influenza virus infection.

Caspase 3 activation is essential for efficient influenza virus propagation.

Apoptosis is a hallmark event observed upon infection with many viral pathogens, including influenza A virus. The apoptotic process is executed by a proteolytic system consisting of a family of cysteinyl proteases, termed caspases. Since the consequences of apoptosis induction and caspase activation for the outcome of an influenza virus infection are not clear, we have addressed this issue by interfering with expression or function of a major virus-induced apoptosis effector, caspase 3. Surprisingly, influenza virus propagation was strongly impaired in the presence of an inhibitor that blocks caspase 3 and in cells where caspase 3 was partially knocked down by small interfering RNAs. Consistent with these findings, poor replication efficiencies of influenza A viruses in cells deficient for caspase 3 could be boosted 30-fold by ectopic expression of the protein. Mechanistically, the block in virus propagation appeared to be due to retention of the viral RNP complexes in the nucleus, preventing formation of progeny virus particles. Our findings indicate that caspase 3 activation during the onset of apoptosis is a crucial event for efficient influenza virus propagation.