While the rat has been used extensively in subarachnoid hemorrhage (SAH)-cerebral vasospasm studies, concerns exist whether this animal represents a usable model because its time course and pattern of cerebral vasospasm following SAH is not comparable to that observed in man. At present, our knowledge of the rat model is based almost exclusively on studies using a 'single hemorrhage' method. Since there is a positive correlation between severity of cerebral vasospasm, and volume of subarachnoid blood, an obvious question is whether the rat will show modifications in vascular responses when insulted by a second SAH. Here, an SAH was produced in rats using a 'double hemorrhage' method. Following SAH, cerebral arteries showed pathological alterations, significant decreases in luminal perimeter, and increases in arterial wall thickness, over a 7-day post-SAH period. The above vascular features are considered to be indicative of cerebral vasospasm and their presence over a 7-day post-SAH period represents a significant time extension when compared to a single hemorrhage. These modified vascular responses made the double hemorrhaged rat a much-improved animal model.

The mRNA upregulation of these proteins indicates that activation of rho A/rho kinase-related signal transduction pathways is involved in the development of long-lasting contraction of cerebral arteries after SAH.

The innate immunity to viral infections induces a potent antiviral response mediated by interferons (IFN). Although IFN-c is detected during the acute stages of illness in the upper respiratory tract secretions and in the serum of influenza A virus-infected individuals, control of influenza A virus is not dependent upon IFN-c as evidenced by studies using anti-IFN-c Ab and IFN-c -/-mice. Thus, we hypothesized that IFN-c is not critical in host survival because influenza A virus has mechanisms to evade the antiviral activity of IFN-c. To test this, A549 cells, an epithelial cell line derived from lung adenocarcinoma, were infected with influenza virus strain A/Aichi/2/68 (H3N2) (Aichi) and/or stimulated with IFN-c to detect IFN-c-stimulated MHC class II expression. Influenza A virus infection inhibited IFN-c-induced up-regulation of HLA-DRa mRNA and the IFN-c induction of class II transactivator (CIITA), an obligate mediator of MHC class II expression. Nuclear translocation of Stat1a upon IFN-c stimulation was significantly inhibited in influenza A virus-infected cells and this was associated with a decrease in Tyr701 and Ser727 phosphorylation of Stat1a. Thus, influenza A virus subverts antiviral host defense mediated by IFN-c through effects on the intracellular signaling pathways. IntroductionInfluenza A viruses are negative-strand RNA viruses that have a segmented genome with a coding capacity for 11 polypeptides. The virus genome is composed of eight different RNA segments, which are tightly associated with the viral nucleoprotein and polymerases in ribonucleoprotein complexes [1]. Influenza A viruses, causing acute infections, continuously escape from recognition by virus neutralizing Ab as a result of accumulation of mutations in their surface glycoproteins hemagglutinin and neuraminidase (antigenic drift) or by introduction of new subtypes of these glycoproteins (antigenic shift) [2,3]. Recent outbreaks of highly pathogenic avian influenza A virus infections in poultry and in humans have raised concerns that a new influenza pandemic will occur in the near future [4]. Thus, prediction of the severity of continuously emerging human influenza virus strains remains a high public health priority, but it is limited by our incomplete understanding of the molecular determinants of pathogenicity in this disease. Although factors dictating the severity of virus disease are complex, interaction between inherent viral properties and host cellular response ultimately determines disease outcome. The first site of viral contact with the host and main target of infection and inflammation is the airway mucosal epithelium. Epithelial cells at the airway mucosal surface have a variety of inflammatory and immune defense mechanisms to deal with virus, including Eur. J. Immunol. 2008. 38: 1559-1573 Immunity to infection expression of cytokines with chemoattractant and proinflammatory functions [5], intercellular adhesion molecule-1 (ICAM-1) [6], IFN regulatory factor 1 (IRF-1) [7], nitric oxide synthase 2 (NOS2) [8], and MHC ...

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Damaged endothelium is one of the pathological changes of the cerebral vasospastic vessels following subarachnoid hemorrhage. Our recent study shows that oxyhemoglobin (OxyHb) induces apoptosis in vascular endothelial cells. Apoptosis generally requires the action of various classes of proteases, including a family of cysteine proteases, known collectively as the caspases. This study was undertaken to investigate the activation of caspases and the ef®cacy of caspase inhibitors, z-IETD-fmk and z-LEHD-fmk, for oxyhemoglobin-induced apoptosis in vascular endothelial cells. Cultured bovine brain microvascular endothelial cells (passages 5±9) were used for this study. OxyHb (10 mmol/L) was added during the 24±72 h incubation with and without caspase-8 or 2 9 inhibitors (z-IETD-fmk and z-LEHD-fmk). Counting surviving cells, DNA laddering, western blotting of poly(ADP-ribose) polymerase, and measurement of caspase activities were employed to con®rm the cytotoxic effects of OxyHb and the protective effects of the caspase inhibitors. OxyHb produced cell detachment in a time-dependent manner and increased caspase-8 and -9 activities in the cells. z-IETDfmk and z-LEHD-fmk (100 mmol/L) attenuated OxyHbinduced cell loss, DNA laddering, and proteolytic cleavage of PARP, although a lower concentration (10 mmol/L) of caspase inhibitors showed partial effects. OxyHb activates caspase-8 and -9 in cultured vascular endothelial cells, and blocking the action of the caspases with the inhibitors ef®ciently prevents loss of vascular endothelial cells from OxyHb-induced apoptosis in vitro. These results suggest that the caspase cascade participates in OxyHb-induced apoptosis.

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