Pathological Features and Pathogenesis of the Endomyocardial Form of Restrictive Cardiomyopathy in Cats.

This study reports pathological and molecular features in 41 cases of feline restrictive cardiomyopathy (RCM). Grossly, there were patchy or diffuse areas of endocardial thickening affecting the left ventricle. The more common patchy endocardial lesions occurred as large trabecular or irregular broad bands of fibrous tissue bridging the left ventricular free wall and ventricular septum. Microscopically, regardless of the gross pattern, the thickened endocardium contained various numbers of stellate, spindle-shaped or elongated mesenchymal cells surrounded by fibrous connective tissue. Immunohistochemical findings were indicative of smooth muscle differentiation in mesenchymal cells. These cells proliferated vigorously and produced alcian blue-positive ground substance and collagen fibres; it was considered that the mesenchymal cells contributed to the formation of the endocardial lesions. In addition, multiple left ventricular 'false tendons' were invariably included within the trabecular or broad fibrous bands, providing a framework for formation of those bands. Evidence of endocarditis or endomyocarditis was lacking in all 41 cases, and no viral genomes were detected in any of the DNA or RNA samples obtained from 14 of the hearts. These observations suggest that any relationship between feline RCM and a virus-induced inflammatory response seems unlikely.

Activation of c-Jun N-terminal kinase by Akabane virus is required for apoptosis.

Akabane virus (AKAV) belongs to the Simbu serogroup of the genus Orthobunyavirus in the family Bunyaviridae. It has been shown that AKAV induces apoptosis in mammalian cells. It is necessary to understand the signaling pathways involved in AKAV-induced apoptosis to further elucidate the molecular virology of AKAV. c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) are mediators of apoptosis; therefore, we investigated the roles of JNK and p38 MAPK cascades in AKAV-infected cells. We found that JNK and p38 MAPK as well as their downstream substrates, c-Jun and heat shock protein 27 (HSP27), were phosphorylated in response to AKAV infection. A JNK inhibitor (SP600125) inhibited AKAV-mediated apoptosis whereas a p38 MAPK inhibitor (SB203580) did not. We conclude that AKAV infection activates the JNK and p38 MAPK signaling pathways, and the JNK cascade plays a crucial role in AKAV-induced apoptosis in vitro.