Prenylated quinolinecarboxylic acid derivative suppresses immune response through inhibition of PAK2

Advances in Innate Immunity to Overcome Immune Rejection during Xenotransplantation

Transplantation is an effective approach for treating end-stage organ failure. There has been a long-standing interest in xenotransplantation as a means of increasing the number of available organs. In the past decade, there has been tremendous progress in xenotransplantation accelerated by the development of rapid gene-editing tools and immunosuppressive therapy. Recently, the heart and kidney from pigs were transplanted into the recipients, which suggests that xenotransplantation has entered a new era. The genetic discrepancy and molecular incompatibility between pigs and primates results in barriers to xenotransplantation. An increasing body of evidence suggests that innate immune responses play an important role in all aspects of the xenogeneic rejection. Simultaneously, the role of important cellular components like macrophages, natural killer (NK) cells, and neutrophils, suggests that the innate immune response in the xenogeneic rejection should not be underestimated. Here, we summarize the current knowledge about the innate immune system in xenotransplantation and highlight the key issues for future investigations. A better understanding of the innate immune responses in xenotransplantation may help to control the xenograft rejection and design optimal combination therapies.

Effect of Monoacylglycerol Lipase Inhibition on Intestinal Permeability of Rats With Severe Acute Pancreatitis

Background: Endocannabinoid 2-arachidonoylglycerol (2-AG) is an anti-nociceptive lipid that is inactivated through cellular uptake and subsequent catabolism by monoacylglycerol lipase (MAGL). In this study, we investigated the effects of MAGL inhibition on intestinal permeability and explored the possible mechanism.

Methods: A rat model of severe acute pancreatitis (SAP) was established. Rats were divided into three groups according to treatment. We analyzed intestinal permeability to fluorescein isothiocyanate-dextran and the levels of inflammatory factors interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) and 2-AG. Hematoxylin and eosin staining was used to assess histological tissue changes. In vivo intestinal permeability was evaluated by transmission electron microscopy. We obtained ileum tissues, extracted total RNA, and applied RNA-sequencing. Sequencing data were analyzed by bioinformatics.

Results: Inflammatory factor levels were higher, while 2-AG levels were lower in the SAP group compared with the control group. Administration of JZL184 to rats with SAP increased the levels of 2-AG and lowered the levels of IL-6 and TNF-α. Notably, intestinal permeability was improved by JZL184 as demonstrated by fluorescein isothiocyanate-dextran measurement, hematoxylin and eosin staining, and transmission electron microscopy. RNA-sequencing showed significant transcriptional differences in SAP and JZL184 groups compared with the control group. KEGG analysis showed that the up- or downregulated genes in multiple comparison groups were enriched in two pathways, focal adhesion and PI3K-Akt signaling pathways. Differential alternative splicing (AS) genes, such as Myo9b, Lsp1, and Git2, have major functions in intestinal diseases. A total of 132 RNA-binding proteins (RBPs) were screened by crossing the identified abnormally expressed genes with the reported RBP genes. Among them, HNRNPDL coexpressed the most AS events as the main RBP.

Conclusion: MAGL inhibition improved intestinal mucosal barrier injury in SAP rats and induced a large number of differentially expressed genes and alternative splicing events. HNRNPDL might play an important role in improving intestinal mucosal barrier injury by affecting alternative splicing events.

A study of the mechanisms responsible for the action of new immunosuppressants and their effects on rat small intestinal transplantation

In a series of studies, using an identical rat intestinal transplantation model, we evaluated the effects of several drugs. FK-506 caused a significant attenuation in the proliferation of allogeneic CD4+ T cells and IFN-γ secreting effector functions. FYT720 resulted in a marked reduction in the numbers of lymphocytes, associated with a reduction of T cell recruitment, in grafts. An anti-MAdCAM antibody was next reported to significantly down-regulate CD4+ T cell infiltration in intestinal grafts by blocking the adhesion molecule, and could be useful as an induction therapy. Concerning TAK-779, this CCR5 and CXCR3 antagonist diminished the number of graft-infiltrating cells by suppressing the expression of their receptors in the graft. As a result, it reduced the total number of recipient T cells involved in graft rejection. As the next step, we focused on the participation of monocytes/ macrophages in this field. PQA-18 has been the focus of a novel immunosuppressant that attenuates not only the production of various cytokines, such as IL-2 & TNF-α, on T cells, but the differentiation of macrophages by inhibiting PAK2 as well. In this report, we summarize our previous studies not only regarding the above drugs, but on an anti-complement drug and a JAK inhibitor as well.

Prenylated quinolinecarboxylic acid compound-18 prevents sensory nerve fiber outgrowth through inhibition of the interleukin-31 pathway

Interleukin-31 (IL-31) is involved in excessive development of cutaneous sensory nerves in atopic dermatitis (AD), leading to severe pruritus. We previously reported that PQA-18, a prenylated quinolinecarboxylic acid (PQA) derivative, is an immunosuppressant with inhibition of p21-activated kinase 2 (PAK2) and improves skin lesions in Nc/Nga mice as an AD model. In the present study, we investigate the effect of PQA-18 on sensory nerves in lesional skin. PQA-18 alleviates cutaneous nerve fiber density in the skin of Nc/Nga mice. PQA-18 also inhibits IL-31-induced sensory nerve fiber outgrowth in dorsal root ganglion cultures. Signaling analysis reveals that PQA-18 suppresses phosphorylation of PAK2, Janus kinase 2, and signal transducer and activator of transcription 3 (STAT3), activated by IL-31 receptor (IL-31R), resulting in inhibition of neurite outgrowth in Neuro2A cells. Gene silencing analysis for PAK2 confirms the requirement for STAT3 phosphorylation and neurite outgrowth elicited by IL-31R activation. LC/MS/MS analysis reveals that PQA-18 prevents the formation of PAK2 activation complexes induced by IL-31R activation. These results suggest that PQA-18 inhibits the IL-31 pathway through suppressing PAK2 activity, which suppresses sensory nerve outgrowth. PQA-18 may be a valuable lead for the development of a novel drug for pruritus of AD.

The novel immunosuppressant prenylated quinolinecarboxylic acid-18 (PQA-18) suppresses macrophage differentiation and cytotoxicity in xenotransplantation

Innate immunity plays a major role in xenograft rejection. However, the majority of immunosuppressants focus on inhibiting acquired immunity and not innate immunity. Therefore, a novel immunosuppressant suitable for use in conjunction with xenografts continues to be needed. It has been reported that prenylated quinolinecarboxylic acid-18 (PQA-18), a p21-activated kinase 2 (PAK2) inhibitor, exerts an immunosuppressive function on T cells. Hence, the possibility exists that PQA-18 might be used in conjunction with xenografts, which prompted us to investigate the efficacy of PQA-18 on macrophages compared with Tofacitinib, a janus kinase (JAK) inhibitor. Initial experiments confirmed that PQA-18 is non-toxic to swine endothelial cells (SECs) and human monocytes. Both PQA-18 and Tofacitinib suppressed macrophage-mediated cytotoxicity in both the differentiation and effector phases. Both PQA-18 and tofacitinib suppressed the expression of HLA-ABC by macrophages. However, contrary to Tofacitinib, PQA-18 also significantly suppressed the expression of CD11b, HLA-DR and CD40 on macrophages. PQA-18 significantly suppressed CCR7 expression on day 3 and on day 6, but Tofacitinib-induced suppression only on day 6. In a mixed lymphocyte reaction (MLR) assay, PQA-18 was found to suppress Interleukin-2 (IL-2)-stimulated T cell proliferation to a lesser extent than Tofacitinib. However, PQA-18 suppressed xenogeneic-induced T cell proliferation more strongly than Tofacitinib on day 3 and the suppression was similar on day 7. In conclusion, PQA-18 has the potential to function as an immunosuppressant for xenotransplantation.

Dictyostelium: An Important Source of Structural and Functional Diversity in Drug Discovery

The cellular slime mold Dictyostelium discoideum is an excellent model organism for the study of cell and developmental biology because of its simple life cycle and ease of use. Recent findings suggest that Dictyostelium and possibly other genera of cellular slime molds, are potential sources of novel lead compounds for pharmacological and medical research. In this review, we present supporting evidence that cellular slime molds are an untapped source of lead compounds by examining the discovery and functions of polyketide differentiation-inducing factor-1, a compound that was originally isolated as an inducer of stalk-cell differentiation in D. discoideum and, together with its derivatives, is now a promising lead compound for drug discovery in several areas. We also review other novel compounds, including secondary metabolites, that have been isolated from cellular slime molds.

Prenylated quinolinecarboxylic acid derivative prevents neuronal cell death through inhibition of MKK4

The development of neuroprotective agents is necessary for the treatment of neurodegenerative diseases. Here, we report PQA-11, a prenylated quinolinecarboxylic acid (PQA) derivative, as a potent neuroprotectant. PQA-11 inhibits glutamate-induced cell death and caspase-3 activation in hippocampal cultures, as well as inhibits N-Methyl-4-phenylpyridinium iodide- and amyloid β_1-42-induced cell death in SH-SY5Y cells. PQA-11 also suppresses mitogen-activated protein kinase kinase 4 (MKK4) and c-jun N-terminal kinase (JNK) signaling activated by these neurotoxins. Quartz crystal microbalance analysis and in vitro kinase assay reveal that PQA-11 interacts with MKK4, and inhibits its sphingosine-induced activation. The administration of PQA-11 by intraperitoneal injection alleviates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced degeneration of nigrostriatal dopaminergic neurons in mice. These results suggest that PQA-11 is a unique MKK4 inhibitor with potent neuroprotective effects in vitro and in vivo. PQA-11 may be a valuable lead for the development of novel neuroprotectants.

Natural Products from Social Amoebae

Natural products are invaluable sources of structural diversity and complexity ideally suited for the development of therapeutic agents. The search for novel bioactive molecules has prompted scientists to explore various ecological niches. Microorganisms have been shown to constitute such an important source. Despite their biosynthetic potential, social amoebae, that is, microorganisms with both a uni- and multicellular lifestyle, are underexplored regarding their secreted secondary metabolome. In this review, we present the structural diversity of amoebal natural products and discuss their biological functions as well as their total syntheses.

Isolation, Synthesis, and Biological Activity of Chlorinated Alkylresorcinols from Dictyostelium Cellular Slime Molds

Eight chlorinated alkylresorcinols, monochasiol A-H (1-8), were isolated from the fruiting bodies of Dictyostelium monochasioides. Compounds 1-8 were synthesized to confirm their structures and to obtain sufficient material for performing biological tests. Monochasiol A (1) selectively inhibited the concanavalin A-induced interleukin-2 production in Jurkat cells, a human T lymphocyte cell line. Monochasiols were biogenetically synthesized by the combination of biosynthetic enzymes relating to the principal polyketides, MPBD and DIF-1, produced by Dictyostelium discoideum.