Extracellular nicotinate phosphoribosyltransferasebinds Toll like receptor 4 and mediatesinflammation

Damage-associated molecular patterns (DAMPs) are molecules that can be actively orpassively released by injured tissues and that activate the immune system. Here we showthat nicotinate phosphoribosyltransferase (NAPRT), detected by antibody-mediated assaysand mass spectrometry, is an extracellular ligand for Toll-like receptor 4 (TLR4) and a criticalmediator of inflammation, acting as a DAMP. Exposure of human and mouse macrophages toNAPRT activates the inflammasome and NF-κB for secretion of inflammatory cytokines.Furthermore, NAPRT enhances monocyte differentiation into macrophages by inducingmacrophage colony-stimulating factor. These NAPRT-induced effects are independent ofNAD-biosynthetic activity, but rely on NAPRT binding to TLR4. In line with ourfinding thatNAPRT mediates endotoxin tolerance in vitro and in vivo, sera from patients with sepsiscontain the highest levels of NAPRT, compared to patients with other chronic inflammatoryconditions. Together, these data identify NAPRT as a endogenous ligand for TLR4 and amediator of inflammation

Bidirectional linkage between the B-cell receptor and NOTCH1 in chronic lymphocytic leukemia and in Richter's syndrome: therapeutic implications

NOTCH1 mutations in chronic lymphocytic leukemia (CLL) lead to accumulation of NOTCH1 intracellular domain (NICD) and prolong signaling. These mutations associate with a more aggressive disease compared to wild-type (WT) CLL. In this work we demonstrate a bidirectional functional relationship between NOTCH1 and the B cell receptor (BCR) pathways. By using highly homogeneous cohorts of primary CLL cells, activation of NOTCH1 is shown to increase expression of surface IgM, as well as LYN, BTK, and BLNK, ultimately enhancing BCR signaling responses, including global mRNA translation. Upon BCR cross-linking, NOTCH1 itself is actively translated and increased on cell surface. Furthermore, BCR ligation induces calcium mobilization that can facilitate ligand-independent NOTCH1 activation. These data suggest that the two pathways are functionally linked, providing a rationale for dual inhibition strategies. Consistently, addition of the γ-secretase inhibitor DAPT to ibrutinib significantly potentiates its effects, both in vitro and in a short-term patient-derived xenograft model. While this observation may find limited applications in the CLL field, it is more relevant for Richter's Syndrome (RS) management, where very few successful therapeutic options exist. Treatment of RS-patient-derived xenografts (RS-PDX) with the combination of ibrutinib and DAPT decreases disease burden and increases overall survival.</p

Extracellular nicotinate phosphoribosyltransferase binds Toll like receptor 4 and mediates inflammation

Damage-associated molecular patterns (DAMPs) are molecules that can be actively or passively released by injured tissues and that activate the immune system. Here we show that nicotinate phosphoribosyltransferase (NAPRT), detected by antibody-mediated assays and mass spectrometry, is an extracellular ligand for Toll-like receptor 4 (TLR4) and a critical mediator of inflammation, acting as a DAMP. Exposure of human and mouse macrophages to NAPRT activates the inflammasome and NF-κB for secretion of inflammatory cytokines. Furthermore, NAPRT enhances monocyte differentiation into macrophages by inducing macrophage colony-stimulating factor. These NAPRT-induced effects are independent of NAD-biosynthetic activity, but rely on NAPRT binding to TLR4. In line with our finding that NAPRT mediates endotoxin tolerance in vitro and in vivo, sera from patients with sepsis contain the highest levels of NAPRT, compared to patients with other chronic inflammatory conditions. Together, these data identify NAPRT as a endogenous ligand for TLR4 and a mediator of inflammation

A circulating NAD biosynthetic enzyme is a novel modulator of inflammation

Damage-associated molecular patterns (DAMPs) are molecules that can be actively or passively released by injured tissues and that activate the immune system. Here we show for the first time that the NAD biosynthetic enzyme nicotinate phosphoribosyltransferase (NAPRT), the rate-limiting enzymes in the intracellular synthesis of NAD from nicotinic acid, is physiologically present in human sera, where it acts as a novel DAMP. We detected NAPRT in plasma/sera from human donors by antibody-mediated luminex assays and mass spectrometry. Exposure of human and mouse macrophages to NAPRT triggers activation of ERK1/2, phosphorylation of IKKα/β and nuclear translocation of the p65 subunit of the NF-kB complex, with synthesis and secretion of inflammatory cytokines, including IL-1β, IL-8, TNFα and CCL3. Furthermore, NAPRT enhances monocyte differentiation into macrophages, by inducing macrophage colony-stimulating factor. These effects are independent of the NAPRT catalytic activity, but rely on the protein’s binding to TLR4, as demonstrated by showing direct in vitro interaction and by the in vivo lack of NAPRT effects in TLR4−/− macrophages. In line with the finding that NAPRT mediates endotoxin tolerance, sera from patients with sepsis or septic shock contain the highest levels of circulating NAPRT, compared to other chronic inflammatory conditions, including cancer. Importantly, patients with serum NAPRT >15 ng/ml are characterized by a worse clinical outcome, compared to the counterparts. Together, these data identify NAPRT as a novel endogenous ligand for TLR4 and a critical mediator of inflammation

A circulating NAD biosynthetic enzyme is a novel modulator of inflammation

Damage-associated molecular patterns (DAMPs) are molecules that can be actively or passively released by injured tissues and that activate the immune system. Here we show for the first time that the NAD biosynthetic enzyme nicotinate phosphoribosyltransferase (NAPRT), the rate-limiting enzymes in the intracellular synthesis of NAD from nicotinic acid, is physiologically present in human sera, where it acts as a novel DAMP. We detected NAPRT in plasma/sera from human donors by antibody-mediated luminex assays and mass spectrometry. Exposure of human and mouse macrophages to NAPRT triggers activation of ERK1/2, phosphorylation of IKKα/β and nuclear translocation of the p65 subunit of the NF-kB complex, with synthesis and secretion of inflammatory cytokines, including IL-1β, IL-8, TNFα and CCL3. Furthermore, NAPRT enhances monocyte differentiation into macrophages, by inducing macrophage colony-stimulating factor. These effects are independent of the NAPRT catalytic activity, but rely on the protein’s binding to TLR4, as demonstrated by showing direct in vitro interaction and by the in vivo lack of NAPRT effects in TLR4−/− macrophages. In line with the finding that NAPRT mediates endotoxin tolerance, sera from patients with sepsis or septic shock contain the highest levels of circulating NAPRT, compared to other chronic inflammatory conditions, including cancer. Importantly, patients with serum NAPRT >15 ng/ml are characterized by a worse clinical outcome, compared to the counterparts. Together, these data identify NAPRT as a novel endogenous ligand for TLR4 and a critical mediator of inflammation

Memory CD8+ T cell diversity and B cell responses correlate with protection against SARS-CoV-2 following mRNA vaccination

Understanding immune responses to SARS-CoV-2 messenger RNA (mRNA) vaccines is of great interest, principally because of the poor knowledge about the mechanisms of protection. In the present study, we analyzed longitudinally B cell and T cell memory programs against the spike (S) protein derived from ancestral SARS-CoV-2 (Wuhan-1), B.1.351 (beta), B.1.617.2 (delta) and B.1.1.529 (omicron) variants of concern (VOCs) after immunization with an mRNA-based vaccine (Pfizer). According to the magnitude of humoral responses 3 months after the first dose, we identified high and low responders. Opposite to low responders, high responders were characterized by enhanced antibody-neutralizing activity, increased frequency of central memory T cells and durable S-specific CD8(+) T cell responses. Reduced binding antibodies titers combined with long-term specific memory T cells that had distinct polyreactive properties were found associated with subsequent breakthrough with VOCs in low responders. These results have important implications for the design of new vaccines and new strategies for booster follow-up.Pace and colleagues assessed the antibody titers, B cell and T cell memory response against SARS-COV-2 in mRNA-vaccinated individuals to show that reduced antibody titers combined with a distinctive memory T cell profile in low vaccine responders correlated with breakthrough infection