Toll-like receptors and cytokines in the brain and in spleen of dogs with visceral leishmaniosis.

Visceral leishmaniosis (VL) is a multisystem disease that affects domestic dogs and can have several clinical manifestations, including some rare reports of neurological clinical signs, or it may remain asymptomatic, depending on the individual immune response against the Leishmania parasite. VL involves immune system sensors, such as the Toll-like receptors (TLRs), that are related to innate immunity and inflammation. Previously, we have reported the presence of brain inflammation in infected dogs. Here, we investigated the gene expression profile of TLRs 1-10 in the brain and the spleen of infected dogs, along with the production of proinflammatory cytokines (TNF-α, IFN-γ, IL-1ß and IL-6) with the aim of explaining the origin of brain inflammation. The gene expression of TLRs has varied according to the tissue evaluated. In the brain, TLR-4 was only up-regulated in a small subpopulation of infected dogs, while in the spleen, we detected an increase in TLR-5 and TLR-9 transcripts, as well as a reduction in TLRs 2-4 and TLR-10. All cytokines except IL-6 were detected in infected dogs. Moreover, we detected Leishmania DNA in all infected dogs in both tissues evaluated. In the histopathological analysis, we observed a predominance of lymphoplasmacytic infiltrate, mainly in leptomeninges and choroid plexuses, ranging from mild to intense. This study provides the first insight into the TLRs profile in the brain and the spleen during canine VL and provides support to confirm the involvement of sensors of the innate immune system sensors against L. infantum parasites.

Zymographic patterns of MMP-2 and MMP-9 in the CSF and cerebellum of dogs with subacute distemper leukoencephalitis.

Distemper leukoencephalitis is a disease caused by the canine distemper virus (CDV) infection. It is a demyelinating disease affecting mainly the white matter of the cerebellum and areas adjacent to the fourth ventricle; the enzymes of the matrix metalloproteinases (MMPs) group, especially MMP-2 and MMP-9 have a key role in the myelin basic protein fragmentation and in demyelination, as well as in leukocyte traffic into the nervous milieu. To evaluate the involvement of MMPs during subacute distemper leukoencephalitis, we measured the levels of MMP-2 and MMP-9 by zymography in the cerebrospinal fluid (CSF) and in the cerebellum of 14 dogs naturally infected with CDV and 10 uninfected dogs. The infected dogs presented high levels of pro-MMP-2 in the CSF and elevated levels of pro-MMP-2 and pro-MMP-9 in the cerebellar tissue. Active MMP-2 was detected in the CSF of some infected dogs. As active MMP-2 and MMP-9 are required for cellular migration across the blood-brain barrier and any interference between MMPs and their inhibitors may result in an amplification of demyelination, this study gives additional support to the involvement of MMPs during subacute distemper leukoencephalitis and suggests that MMP-2 and MMP-9 may take part in the brain inflammatory changes of this disease.

Differential alterations in the activity of matrix metalloproteinases within the nervous tissue of dogs in distinct manifestations of visceral leishmaniasis.

Canine visceral leishmaniasis is an important emerging disease with a multitude of clinical symptoms, including neurological alterations. Matrix metalloproteinases (MMP) are proteases implicated with the extracellular matrix remodelling and, within the central nervous system, these enzymes are involved with blood-brain-barrier disruption and inflammation. To establish the involvement of MMP-2 and -9 within the nervous tissue of dogs with spontaneous visceral leishmaniasis, fragments of nervous tissue from oligosymptomatic (n=9), symptomatic (n=8), neurological (n=12) and normal dogs (n=8) were subjected to zymographic and to immunohistochemical analysis. Immunohistochemistry evidenced MMP-2 staining in inflammatory cells inside and outside blood vessels. MMP-9 was found in endothelial cells and in the ependyma. Zymographic evaluation revealed only the latent forms of MMP-2 and -9 within the nervous tissue. ProMMP-9 activity in the infected animals was found higher than the normal dogs, but with no difference among the infected dogs. Oligosymptomatic dogs presented the highest proMMP-2 activity, followed by the symptomatic and then, by the neurological and the normal dogs. In summary, the nervous tissue compartment seems to be preserved in dogs with VL, due to the absence of active MMPs, even though the elevated levels of proMMP-2 and -9 would indicate a pro-inflammatory state in the brain.