Objectives To analyse the prevalence of CECR1 mutations in patients diagnosed with early onset livedo reticularis and/or haemorrhagic/ischaemic strokes in the context of inflammation or polyarteritis nodosa (PAN). Forty-eight patients from 43 families were included in the study. Methods Direct sequencing of CECR1 was performed by Sanger analysis. Adenosine deaminase 2 (ADA2) enzymatic activity was analysed in monocyte isolated from patients and healthy controls incubated with adenosine and with or without an ADA1 inhibitor. Results Biallelic homozygous or compound heterozygous CECR1 mutations were detected in 15/48 patients. A heterozygous disease-associated mutation (p.G47V) was observed in two affected brothers. The mean age of onset of the genetically positive patients was 24 months (6 months to 7 years). Ten patients displayed one or more cerebral strokes during their disease course. Low immunoglobulin levels were detected in six patients. Thalidomide and anti-TNF (tumour necrosis factor) blockers were the most effective drugs. Patients without CECR1 mutations had a later age at disease onset, a lower prevalence of neurological and skin manifestations; one of these patients displayed all the clinical features of adenosine deaminase 2deficiency (DADA2) and a defective enzymatic activity suggesting the presence of a missed mutation or a synthesis defect. Conclusions DADA2 accounts for paediatric patients diagnosed with PAN-like disease and strokes and might explain an unrecognised condition in patients followed by adult rheumatologist. Timely diagnosis and treatment with anti-TNF agents are crucial for the prevention of severe complications of the disease. Functional assay to measure ADA2 activity should complement genetic testing in patients with non-confirming genotypes.

Abscisic acid (ABA) is a phytohormone involved in fundamental physiological processes of higher plants, such as response to abiotic stress (temperature, light, drought), regulation of seed dormancy and germination, and control of stomatal closure. Here, we provide evidence that ABA stimulates several functional activities [phagocytosis, reactive oxygen species and nitric oxide (NO) production, and chemotaxis] of human granulocytes through a signaling pathway sequentially involving a pertussis toxin (PTX)-sensitive G protein/receptor complex, protein kinase A activation, ADP-ribosyl cyclase phosphorylation, and consequent cyclic-ADP-ribose overproduction, leading to an increase of the intracellular Ca ²⁺ concentration. The increase of free intracellular ABA and its release by activated human granulocytes indicate that ABA should be considered as a new pro-inflammatory cytokine in humans. This discovery is an intriguing example of conservation of a hormone and its signaling pathway from plants to humans and provides insight into the molecular mechanisms of granulocyte activation, possibly leading to the development of new antiinflammatory drugs.

NAD⁺ is mainly synthesized in human cells via the “salvage” pathways starting from nicotinamide, nicotinic acid, or nicotinamide riboside (NR). The inhibition with FK866 of the enzyme nicotinamide phosphoribosyltransferase (NAMPT), catalyzing the first reaction in the “salvage” pathway from nicotinamide, showed potent antitumor activity in several preclinical models of solid and hematologic cancers. In the clinical studies performed with FK866, however, no tumor remission was observed. Here we demonstrate that low micromolar concentrations of extracellular NAD⁺ or NAD⁺ precursors, nicotinamide mononucleotide (NMN) and NR, can reverse the FK866-induced cell death, this representing a plausible explanation for the failure of NAMPT inhibition as an anti-cancer therapy. NMN is a substrate of both ectoenzymes CD38 and CD73, with generation of NAM and NR, respectively. In this study, we investigated the roles of CD38 and CD73 in providing ectocellular NAD⁺ precursors for NAD⁺ biosynthesis and in modulating cell susceptibility to FK866. By specifically silencing or overexpressing CD38 and CD73, we demonstrated that endogenous CD73 enables, whereas CD38 impairs, the conversion of extracellular NMN to NR as a precursor for intracellular NAD⁺ biosynthesis in human cells. Moreover, cell viability in FK866-treated cells supplemented with extracellular NMN was strongly reduced in tumor cells, upon pharmacological inhibition or specific down-regulation of CD73. Thus, our study suggests that genetic or pharmacologic interventions interfering with CD73 activity may prove useful to increase cancer cell sensitivity to NAMPT inhibitors.

Human mesenchymal stem cells (MSC) are immunosuppressive and poorly immunogenic but may act as antigen-presenting cells (APC) for CD4+ T-cell responses; here we have investigated their ability to serve as APC for in vitro CD8+ T-cell responses. MSC pulsed with peptides from viral antigens evoked interferon (IFN)-γ and Granzyme B secretion in specific cytotoxic T lymphocytes (CTL) and were lysed, although with low efficiency. MSC transfected with tumor mRNA or infected with a viral vector carrying the Hepatitis C virus NS3Ag gene induced cytokine release but were not killed by specific CTL, even following pretreatment with IFN-γ. To investigate the mechanisms involved in MSC resistance to CTL-mediated lysis, we analyzed expression of human leukocyte antigen (HLA) class I-related antigen-processing machinery (APM) components and of immunosuppressive HLA-G molecules in MSC. The LMP7, LMP10, and ERp57 components were not expressed and the MB-1 and zeta molecules were downregulated in MSC either unmanipulated or pretreated with IFN-γ. Surface HLA-G was constitutively expressed on MSC but was not involved in their protection from CTL-mediated lysis. MSC supernatants containing soluble HLA-G (sHLA-G) inhibited CTL-mediated lysis, whereas those lacking sHLA-G did not. The role of sHLA-G in such inhibition was unambiguously demonstrated by partial restoration of lysis following sHLA-G depletion from MSC supernatants. In conclusion, human MSC can process and present HLA class I-restricted viral or tumor antigens to specific CTL with a limited efficiency, likely because of some defects in APM components. However, they are protected from CTL-mediated lysis through a mechanism that is partly sHLA-G-dependent.Disclosure of potential conflicts of interest is found at the end of this article.