The immunomodulatory molecule pidotimod induces the expression of the NOD-like receptor NLRP12 and attenuates TLR-induced inflammation.

Pidotimod (3-L-pyroglutamyl-L-thiaziolidine-4-carboxylic acid) (PDT) is a synthetic dipeptide with in vitro and in vivo immunomodulatory properties that is largely used for treatment and prevention of infections in paediatric and disease-prone patients. However, the effects of PDT on cellular immune responses are still poorly characterized and there is little information on the mechanism of action of this compound. It has been speculated that PDT action may be exerted through the interaction with a Pattern Recognition Receptor (PRR). Therefore, to gain a further understanding of the immune pathways involved by PDT, we first decided to investigate whether PDT could modify the immune response triggered by TLR ligands. Monocytic cells were exposed to PDT then stimulated with a panel of TLR agonists. Under these experimental conditions, we observed a significant decrease in the synthesis of key proinflammatory mediators in comparison to the production observed in TLR-stimulated cells that were not treated with PDT. Using RT² Profiler PCR Array we have observed that PDT specifically up-regulates the expression of the NOD-like receptor NLRP12 mRNA in the absence of any further costimulation. Increase of NLRP12 in cells treated with PDT was confirmed using specifically designed real-time quantitative PCR and western blotting assays where a clear increase in the amount of NLRP12 protein was detected. Furthermore, in myeloid/monocytic cells we demonstrated that PDT treatment counteracts the NLRP12 reduction induced by TLR agonists. Finally, the results obtained using NLRP12 silenced cells showed that down-regulation of the proinflammatory function occurring in PDT-treated cells upon interaction with TLRs is associated with the increased levels of NLRP12 induced by PDT. To our knowledge this is the first evidence of an immunomodulatory peptide that upregulates NLRP12 and, through this molecule, antagonizes the TLR-induced inflammatory response. These results pave the way for the development of innovative therapeutic approaches aimed at controlling different pathological settings such as tumorigenesis, systemic inflammatory processes and autoimmunity, where NLRP12 plays a crucial role.

8-Iso-PGF2 alpha induces beta 2-integrin-mediated rapid adhesion of human polymorphonuclear neutrophils: a link between oxidative stress and ischemia/reperfusion injury.

F(2)-Isoprostanes are generated from a cyclooxygenase-independent oxidative modification of arachidonic acid. They are present in atherosclerotic plaques and are platelet activators as well as potent vasoconstrictors. Polymorphonuclear neutrophils are major players in ischemia/reperfusion injury and in restenosis after PTCA. The effects of 8-isoprostaglandin (PG) F(2alpha) on very rapid beta(2)-integrin-dependent adhesion was evaluated in human neutrophils in vitro by use of purified integrin as ligand. 8-Iso-PGF(2alpha) (1 nmol/L to 20 micromol/L) triggers a dose-dependent, very rapid neutrophil adhesion to human fibrinogen but not to the endothelial ligand intercellular adhesion molecule-1. Pretreatment with anti-ss(2)-integrin subtypes showed activation of CD11b/CD18 and CD11c/CD18. Adhesion triggering was completely prevented by pertussis toxin. SQ29,548, a specific antagonist of thromboxane A2 receptor, also dose-dependently prevented 8-iso-PGF(2alpha)-triggered neutrophil adhesion. 8-Iso-PGF(2alpha) did not trigger adhesion in human monocytes and lymphocytes and did not induce neutrophil chemotaxis or activation of the oxygen free-radical-forming enzyme NADPH-oxidase. These data highlight the role of 8-iso-PGF(2alpha) as a specific activator of rapid neutrophil adhesion and suggest its involvement in the pathogenesis of ischemia/reperfusion injury and in restenosis after PTCA. The effect is transduced via activation of the receptor for thromboxane A2.

Detection of KI WU and Merkel cell polyomavirus in respiratory tract of cystic fibrosis patients.

In the last few years, many reports have confirmed the presence of WU, KI and Merkel cell (MC) polyomaviruses (PyV) in respiratory samples wordwide, but their pathogenic role in patients with underlying conditions such as cystic fibrosis is still debated. To determine the prevalence of MCPyV, WUPyV and KIPyV, we conducted a 1-year-long microbiological testing of respiratory specimens from 93 patients with cystic fibrosis in Brescia, Italy. We detected PyV DNA in 94 out of 337 analysed specimens. KIPyV was the most common virus detected (12.1%), followed by WUPyV (8.9%) and MCPyV (6.8%). We found an intriguing association between the presence of MCPyV and the concurrent isolation of Pseudomonas aeruginosa, as well as with the patient status, classified as chronically colonized with P. aeruginosa. Our study adds perspective on the prevalence and the potential pathogenic role of PyV infections.

Chemokines trigger immediate beta2 integrin affinity and mobility changes: differential regulation and roles in lymphocyte arrest under flow.

Chemokines trigger rapid integrin-dependent lymphocyte arrest to vascular endothelium. We show that the chemokines SLC, ELC, and SDF-1alpha rapidly induce lateral mobility and transient increase of affinity of the beta2 integrin LFA-1. Inhibition of phosphatidylinositol 3-OH kinase (PI(3)K) activity blocks mobility but not affinity changes and prevents lymphocyte adhesion to ICAM-1 immobilized at low but not high densities, suggesting that mobility enhances the frequency of encounters between high-affinity integrin and ligand but that at higher ligand density affinity changes are sufficient for arrest. Thus, chemokines trigger, through distinct signaling pathways, both a high-affinity state and lateral mobility of LFA-1 that can coordinately determine the vascular arrest of circulating lymphocytes under physiologic conditions.