Expression and secretion of RANTES (CCL5) in granulomatous calcified tissue before and after lipopolysaccharide treatment in vivo

Mycobacterium tuberculosis cell wall released fragments by the action of the human lung mucosa modulate macrophages to control infection in an IL-10-dependent manner

Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis, is a major public health challenge facing the world. During infection, M.tb is deposited in the lung alveolar space where it comes in contact with the lung mucosa, known as alveolar lining fluid (ALF), an environment that M.tb encounters at different stages of the infection and disease. ALF is abundant in homeostatic and antimicrobial hydrolytic enzymes, also known as hydrolases. Here we demonstrate that ALF hydrolases, at their physiological concentrations and upon contact with M.tb, release M.tb cell envelope fragments into the milieu. These released fragments are bioactive, but non-cytotoxic, regulate the function of macrophages, and thus are capable of modulating the immune response contributing to the control of M.tb infection by human macrophages. Specifically, macrophages exposed to fragments derived from the exposure of M.tb to ALF were able to control the infection primarily by increasing phagosome-lysosome fusion and acidification events. This enhanced control was found to be dependent on fragment-induced interleukin-10 (IL-10) production but also involves the STAT3 signaling pathway in an IL-10-independent manner. Collectively our data indicate that M.tb fragments released upon contact with lung mucosa hydrolases participate in the host immune response to M.tb infection through innate immune modulation.

Independent roles of macrophage migration inhibitory factor and endogenous, but not exogenous glucocorticoids in regulating leukocyte trafficking

OBJECTIVES

Macrophage migration inhibitory factor (MIF) promotes leukocyte recruitment and antagonizes the anti-inflammatory effects of glucocorticoids (GC). The aim of this study was to examine whether interaction between MIF and GC underlies the ability of MIF to promote leukocyte-endothelial cell (EC) interactions.

METHODS

Intravital microscopy was used to assess leukocyte-EC interactions in wild-type and MIF(-/-) mice following treatment with lipopolysaccharide (LPS), the GC dexamethasone, and inhibition of endogenous GC, using the GC-receptor antagonist, RU486.

RESULTS

Dexamethasone reduced LPS-induced leukocyte interactions in wild-type mice to levels similar to those observed in MIF(-/-) mice not treated with dexamethasone, whereas in MIF(-/-) mice, leukocyte interactions were not further inhibited by dexamethasone. RU486 increased LPS-induced leukocyte adhesion and emigration to a similar extent in both wild-type and MIF(-/-) mice, indicating that endogenous GC exert a similar inhibitory effect on leukocyte trafficking in wild-type and MIF(-/-) mice. Both MIF deficiency and RU486 treatment reduced VCAM-1 expression, while neither treatment modulated expression of ICAM-1 or chemokines CCL2, KC, and MIP-2.

CONCLUSIONS

These results suggest that endogenous MIF and GC regulate leukocyte-EC interactions in vivo reciprocally but through predominantly independent mechanisms, and that the anti-inflammatory effect of MIF deficiency is comparable to that of exogenous GC.

Human interleukin-10 gene transfer is protective in a rat model of Parkinson's disease

In Parkinson's disease (PD) chronic inflammation occurs in the substantia nigra (SNc) concurrently with dopaminergic neurodegeneration. In models of PD, microglial activation precedes neurodegeneration in the SNc, suggesting that the underlying pathogenesis involves a complex response in the nigrostriatal pathway, and that the innate immune system plays a significant role. We have investigated the neuroprotective effect of an adeno-associated viral type-2 (AAV2) vector containing the complementary DNA (cDNA) for human interleukin-10 (hIL-10) in the unilateral 6-hydroxydopamine (6-OHDA) rat model of PD. AAV2-hIL-10 reduced the 6-OHDA-induced loss of tyrosine hydroxylase (TH)-positive neurons in the SNc, and also reduced loss of striatal dopamine (DA). Pretreatment with AAV2-hIL-10 reduced glial activation in the SNc but did not attenuate striatal release of the inflammatory cytokine IL-1beta. Assessment of rotational behavior in response to apomorphine challenge showed absence of asymmetry, confirming protection of dopaminergic innervation of the lesioned striatum. At baseline, 6-OHDA-lesioned animals displayed a deficit in contralateral forelimb use, but pretreatment with AAV2-hIL-10 reduced this forelimb akinesia. Transcriptional analyses revealed alteration of a few genes by AAV2-hIL-10; these alterations may contribute to neuroprotection. This study supports the need for further investigations relating to gene therapies aimed at reducing neuroinflammation in early PD.