A newly developed PLD1 inhibitor ameliorates rheumatoid arthritis by regulating pathogenic T and B cells and inhibiting osteoclast differentiation.

Phospholipase D1 (PLD1), which catalyzes the hydrolysis of phosphatidylcholine to phosphatidic acid and choline, plays multiple roles in inflammation. We investigated the therapeutic effects of the newly developed PLD1 inhibitors A2998, A3000, and A3773 in vitro and in vivo rheumatoid arthritis (RA) model. A3373 reduced the levels of LPS-induced TNF-α, IL-6, and IgG in murine splenocytes in vitro. A3373 also decreased the levels of IFN-γ and IL-17 and the frequencies of Th1, Th17 cells and germinal-center B cells, in splenocytes in vitro. A3373 ameliorated the severity of collagen-induced arthritis (CIA) and suppressed infiltration of inflammatory cells into the joint tissues of mice with CIA compared with vehicle-treated mice. Moreover, A3373 prevented systemic bone demineralization in mice with CIA and suppressed osteoclast differentiation and the mRNA levels of osteoclastogenesis markers in vitro. These results suggest that A3373 has therapeutic potential for RA.

PLD1 promotes tumor invasion by regulation of MMP-13 expression via NF-κB signaling in bladder cancer.

Invasion of bladder cancer (BC) cells from the mucosa into the muscle layer is canonical for BC progression while phospholipase D isoform 1 (PLD1) is known to mediate development of cancer through phosphatidic acid (PA) production. We therefore used in silico, in vitro and in vivo approaches to detail the effect of PLD1 on BC invasion. In BC patients, higher levels of PLD1 expression were associated with poor prognoses. PLD1 knockdown significantly suppressed cellular invasion by human BC cells and matrix metalloproteinase-13 (MMP-13) was observed to mediate this effect. In our mouse bladder carcinogenesis model, the development of invasive BCs was suppressed by PLD1 knockout and a global transcriptomic analysis in this model indicated MMP-13 as a potential tumor invasion gene with NF-κB (nuclear factor-kB) as its transcriptional regulator. Furthermore, PA administration increased MMP-13 expression in line with NF-κB p65 phosphorylation levels. Collectively, we demonstrate that PLD1 promotes tumor invasion of BC by regulation of MMP-13 expression through the NF-κB signaling pathway and that PLD1 might be a potential therapeutic target to prevent clinical progression in BC patients.

rhPLD2 inhibits airway inflammation in an asthmatic murine model through induction of stable CD25+ Foxp3+ Tregs.

Our previous studies have shown that recombinant human phospholipase D2 (rhPLD2) plays a modulator role on NF-κB and PKC signaling pathways. It also inhibits IL-5-induced inflammatory response in chronic asthmatic guinea pigs. Additionally, increasing evidence also has revealed that the adoptive transfer of induced regulatory T cells (Tregs) may be a therapeutic solution to airway allergic diseases. To investigate the epigenetic, transcriptomic and phenotypic variability of Treg population in an ovalbumin (OVA)-induced airway inflammation model derived from the induction of rhPLD2, OVA-induced asthmatic murine model is used in this study. The lung inflammation, eosinophil infiltration, the differentiation and proliferation of T helper cells and the amplification of Tregs were examined in this mouse model with and without rhPLD2 induction. Our data showed that rhPLD2 administration in asthmatic mice significantly increases CD4+CD25+ Foxp3+ Treg cell numbers and alleviates lung inflammation. The addition of rhPLD2 in vitro enhanced the demethylation of Treg-specificdemethylated region (TSDR) in iTregs, suggesting that rhPLD2 protein may be involved in improving the quality and quantity of Treg cells that eventually significantly reduces lung inflammation in asthmatic murine model. These results suggest that rhPLD2 could have a clinical impact treating patients with allergic airway inflammation via promoting and stabilizing iTreg differentiation and function.