LRRK2 negatively regulates glucose tolerance via regulation of membrane translocation of GLUT4 in adipocytes

Epidemiological studies have shown that abnormalities of glucose metabolism are involved in leucine-rich repeat kinase 2 (LRRK2)-associated Parkinson's disease (PD). However, the physiological significance of this association is unclear. In the present study, we investigated the effect of LRRK2 on high-fat diet (HFD)-induced glucose intolerance using Lrrk2-knockout (KO) mice. We found for the first time that HFD-fed KO mice display improved glucose tolerance compared with their wild-type (WT) counterparts. In addition, high serum insulin and leptin, as well as low serum adiponectin resulting from HFD in WT mice were improved in KO mice. Using western blotting, we found that Lrrk2 is highly expressed in adipose tissues compared with other insulin-related tissues that are thought to be important in glucose tolerance, including skeletal muscle, liver, and pancreas. Lrrk2 expression and phosphorylation of its kinase substrates Rab8a and Rab10 were significantly elevated after HFD treatment in WT mice. In cell culture experiments, treatment with a LRRK2 kinase inhibitor stimulated insulin-dependent membrane translocation of glucose transporter 4 (Glut4) and glucose uptake in mouse 3T3-L1 adipocytes. We conclude that increased LRRK2 kinase activity in adipose tissue exacerbates glucose tolerance by suppressing Rab8- and Rab10-mediated GLUT4 membrane translocation.

Facilitation of colonic T cell immune responses is associated with an exacerbation of dextran sodium sulfate-induced colitis in mice lacking microsomal prostaglandin E synthase-1

Background

Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme that acts downstream of cyclooxygenase and plays a major role in inflammation by converting prostaglandin (PG) H₂ to PGE₂. The present study investigated the effect of genetic deletion of mPGES-1 on the development of immunologic responses to experimental colitis induced by dextran sodium sulfate (DSS), a well-established model of inflammatory bowel disease (IBD).

Methods

Colitis was induced in mice lacking mPGES-1 (mPGES-1^−/− mice) and wild-type (WT) mice by administering DSS for 7 days. Colitis was assessed by body weight loss, diarrhea, fecal bleeding, and histological features. The colonic expression of mPGES-1 was determined by real-time PCR, western blotting, and immunohistochemistry. The impact of mPGES-1 deficiency on T cell immunity was determined by flow cytometry and T cell depletion in vivo.

Results

After administration of DSS, mPGES-1^−/− mice exhibited more severe weight loss, diarrhea, and fecal bleeding than WT mice. Histological analysis further showed significant exacerbation of colonic inflammation in mPGES-1^−/− mice. In WT mice, the colonic expression of mPGES-1 was highly induced on both mRNA and protein levels and colonic PGE₂ increased significantly after DSS administration. Additionally, mPGES-1 protein was localized in the colonic mucosal epithelium and infiltrated inflammatory cells in underlying connective tissues and the lamina propria. The abnormalities consistent with colitis in mPGES-1^−/− mice were associated with higher expression of colonic T-helper (Th)17 and Th1 cytokines, including interleukin 17A and interferon-γ. Furthermore, lack of mPGES-1 increased the numbers of Th17 and Th1 cells in the lamina propria mononuclear cells within the colon, even though the number of suppressive regulatory T cells also increased. CD4⁺ T cell depletion effectively reduced symptoms of colitis as well as colonic expression of Th17 and Th1 cytokines in mPGES-1^−/− mice, suggesting the requirement of CD4⁺ T cells in the exacerbation of DSS-induced colitis under mPGES-1 deficiency.

Conclusions

These results demonstrate that mPGES-1 is the main enzyme responsible for colonic PGE₂ production and deficiency of mPGES-1 facilitates the development of colitis by affecting the development of colonic T cell–mediated immunity. mPGES-1 might therefore impact both the intestinal inflammation and T cell–mediated immunity associated with IBD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-021-00188-1.

LRRK2 Inhibition Ameliorates Dexamethasone-Induced Glucose Intolerance via Prevents Impairment in GLUT4 Membrane Translocation in Adipocytes

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with Parkinson's disease. LRRK2 is a large protein with multiple functional domains, including a guanosine 5'-triphosphate (GTP)-binding domain and a protein kinase domain. Recent studies indicated that the members of the Rab GTPase family, Rab8a and Rab10, which are involved in the membrane transport of the glucose transporter type 4 (GLUT4) during insulin-dependent glucose uptake, are phosphorylated by LRRK2. However, the physiological role of LRRK2 in the regulation of glucose metabolism is largely unknown. In the present study, we investigated the role of LRRK2 using dexamethasone (DEX)-induced glucose intolerance in mice. LRRK2 knockout (KO) mice exhibited suppressed glucose intolerance, even after treatment with DEX. The phosphorylation of LRRK2, Rab8a and Rab10 was increased in the adipose tissues of DEX-treated wild-type mice. In addition, inhibition of the LRRK2 kinase activity prevented the DEX-induced inhibition of GLUT4 membrane translocation and glucose uptake in cultured 3T3-L1 adipocytes. These results suggest that LRRK2 plays an important role in glucose metabolism in adipose tissues.

Panton-Valentine Leukocidin Induces Cytokine Release and Cytotoxicity Mediated by the C5a Receptor on Rabbit Alveolar Macrophages

Necrotizing pneumonia caused by Panton-Valentine leukocidin (PVL)-positive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has high mortality rates and is currently a serious clinical issue. PVL is a two-component toxin (LukS-PV and LukF-PV). It can cause necrosis in target cells by forming pores consisting of an octamer comprised of LukS-PV and LukF-PV. However, considering the specificity of PVL towards several target cells and species, the specific effect of PVL remains controversial. Therefore, we focused on necrotizing pneumonia caused by PVL-positive S. aureus and clarified the effect of PVL on alveolar macrophages, which play a central role in innate immunity in the alveolar space. We constructed recombinant PVL (rPVL) components and stimulated alveolar macrophages isolated from rabbits to evaluate cytotoxicity and pro-inflammatory cytokine release. Recombinant LukS-PV (rLukS-PV), but not recombinant LukF-PV (rLukF-PV), induced pro-inflammatory cytokine release. Specifically, tumor necrosis factor (TNF)-α release was mediated by the C5a receptor (C5aR) expressed on rabbit alveolar macrophages, and the toxicity of rPVL, consisting of rLukS-PV and rLukF-PV, towards rabbit alveolar macrophages was mediated by the same receptor. Overall, our findings shed light on the C5aR-mediated cytotoxic effect of PVL on alveolar macrophages, which may be useful for understanding the mechanism of necrotizing pneumonia caused by PVL.

Complete genome sequencing and comparative plasmid analysis of KPC-2-producing Klebsiella pneumoniae isolated from hospital sewage water in Japan

OBJECTIVES

The Klebsiella pneumoniae carbapenemase (bla_KPC) gene is one of the most widespread carbapenemase genes in the world. However, there are few reports on KPC-producing bacteria in Japan. The aim of this study was therefore to investigate KPC-producing K. pneumoniae in Japan.

METHODS

A KPC-2-producingK. pneumoniae strain (KAM260) was isolated from hospital sewage water in Japan in 2018. The complete genome was determined by whole-genome sequencing. Subsequent comparative sequence analysis of the bla_KPC-2-carrying plasmid was performed.

RESULTS

Klebsiella pneumoniae KAM260, belonging to sequence type 3026 (ST3026), harboured the bla_KPC-2 gene in 114.6-kbp plasmid pKAM260_2 with IncFIB(pQIL) and IncFII(K) replicons. pKAM260_2 was highly identical to pKpQIL-like plasmids, which carry bla_KPC genes and have spread worldwide. pKAM260_2 had functional conjugation-associated genes and was transferable to Escherichia coli.

CONCLUSION

pKAM260_2, the self-transmissible plasmid carrying thebla_KPC-2 gene, was detected from hospital sewage water in Japan and was characterised as a pKpQIL-like plasmid. This plasmid needs to be monitored in Japan in the future owing to its high diffusivity.

Real-time visualization of intratumoral necrosis using split-luciferase reconstitution by protein trans-splicing

Necrosis, a form of cell death, occurs not only with the development of various diseases but also with a tumor tissue response to cancer treatment. Therefore, pursuing progress for cancer therapy through induction of necrosis may be one of the most effective approaches for cancer eradication. We herein describe the development of a real-time imaging system to visualize intratumoral necrosis. The system is composed of two types of cells expressing either one of two necrosis imaging reporters that consist of a DnaE intein sequence linking to one of two split-luciferase fragments. When necrosis occurs in a tumor composed of both of the cells, the two types of leaked reporters can reconstitute the enzymatic activity as a result of protein trans-splicing and thereby emit bioluminescence in the presence of the substrate. This system, which was constructed with shrimp-derived luciferase, allowed in vitro imaging of necrosis. We further confirmed real-time imaging of intratumoral necrosis caused by physical or chemical tissue disruption, validating its application in in vivo necrosis imaging. Thus, the constructed imaging system could be a powerful tool for the optimization of the therapeutic condition for cancer therapy and for the evaluation of novel anticancer drugs targeting necrosis.

Histamine depolarizes rat intracardiac ganglion neurons through the activation of TRPC non-selective cation channels

The cardiac plexus, which contains parasympathetic ganglia, plays an important role in regulating cardiac function. Histamine is known to excite intracardiac ganglion neurons, but the underlying mechanism is obscure. In the present study, therefore, the effect of histamine on rat intracardiac ganglion neurons was investigated using perforated patch-clamp recordings. Histamine depolarized acutely isolated neurons with a half-maximal effective concentration of 4.5 μM. This depolarization was markedly inhibited by the H₁ receptor antagonist triprolidine and mimicked by the H₁ receptor agonist 2-pyridylethylamine, thus implicating histamine H₁ receptors. Consistently, reverse transcription-PCR (RT-PCR) and Western blot analyses confirmed H₁ receptor expression in the intracardiac ganglia. Under voltage-clamp conditions, histamine evoked an inward current that was potentiated by extracellular Ca²⁺ removal and attenuated by extracellular Na⁺ replacement with N-methyl-D-glucamine. This implicated the involvement of non-selective cation channels, which given the link between H₁ receptors and G_q/11-protein-phospholipase C signalling, were suspected to be transient receptor potential canonical (TRPC) channels. This was confirmed by the marked inhibition of the inward current through the pharmacological disruption of either G_q/11 signalling or intracellular Ca²⁺ release and by the application of the TRPC blockers Pyr3, Gd³⁺ and ML204. Consistently, RT-PCR analysis revealed the expression of several TRPC subtypes in the intracardiac ganglia. Whilst histamine was also separately found to inhibit the M-current, the histamine-induced depolarization was only significantly inhibited by the TRPC blockers Gd³⁺ and ML204, and not by the M-current blocker XE991. These results suggest that TRPC channels serve as the predominant mediator of neuronal excitation by histamine.

Interleukin-24 Transduction Modulates Human Prostate Cancer Malignancy Mediated by Regulation of Anchorage Dependence

BACKGROUND

Hormone therapy and chemotherapy are not effective for castrate-resistant prostate cancer, thus development of novel treatment strategies is required. Gene therapy involving transient high-copy transfection of interleukin (IL)-24 with an adenoviral vector can exert antitumor activity; however, the effects of stable IL-24 transfection are not fully understood. The aim of this study was to investigate the effects of IL-24 overexpression in prostate cancer cells, in vitro.

MATERIALS AND METHODS

DU145 cells were transfected the IL-24 gene using a retroviral vector. Apoptosis induction was investigated by the cell death detection ELISA, and the gene expression was analyzed by real time RT-PCR.

RESULTS

IL-24 transduction suppressed the growth of prostate cancer and induced tumor cell apoptosis. In addition, up-regulation of epithelial markers and down-regulation of mesenchymal markers were noted, suggesting that tumor aggressiveness was reduced.

CONCLUSION

Introduction of IL-24 displays antitumor activity both by induction of apoptosis and regulation of anchorage dependence.

Prostaglandin F2α Facilitates Platelet Activation by Acting on Prostaglandin E2 Receptor Subtype EP3 and Thromboxane A2 Receptor TP in Mice

Platelets play an important role in both physiological hemostasis and pathological thrombosis. Thromboxane (TX) A₂ and prostaglandin (PG) I₂ are well known as a potent stimulator and an inhibitor of platelet function, respectively. Recently, PGE₂ has also been reported to regulate platelet function via PGE₂ receptor subtypes. However, the effect of PGF₂α on platelet function remains to be determined. The aim of the present study was to clarify the effect of PGF₂α on murine platelet function both in vitro and in vivo. Platelets prepared from wild-type mice (WT platelets) expressed several types of prostanoid receptors, including the PGE₂ receptor subtype EP₃ and the TXA₂ receptor TP, while expression of the PGF₂α receptor FP was not detected. In WT platelets, PGF₂α potentiated adenosine diphosphate-induced aggregation in a concentration-dependent manner, while PGF₂α alone did not induce aggregation. In platelets prepared from mice lacking FP, however, PGF₂α-induced potentiation was not significantly different from that in WT platelets. Interestingly, the potentiation was significantly blunted in platelets lacking EP₃ or TP and disappeared completely in platelets lacking both EP₃ and TP. Accordingly, PGF₂α decreased the cyclic adenosine monophosphate level via EP₃ and increased the inositol triphosphate level via TP in WT platelets. Intravenously administered PGF₂α significantly shortened the bleeding time and aggravated arachidonic acid-induced acute thromboembolism in WT mice, suggesting that PGF₂α works as a platelet stimulator also in vivo. In conclusion, PGF₂α potentiates platelet aggregation in vitro via EP₃ and TP but not FP. Accordingly, PGF₂α facilitates hemostasis and thromboembolism in vivo.

Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice

Nonalcoholic steatohepatitis (NASH) is a hepatic manifestation of metabolic syndrome. Although the prostaglandin (PG)I₂ receptor IP is expressed broadly in the liver, the role of PGI₂-IP signaling in the development of NASH remains to be determined. Here, we investigated the role of the PGI₂-IP system in the development of steatohepatitis using mice lacking the PGI₂ receptor IP [IP-knockout (IP-KO) mice] and beraprost (BPS), a specific IP agonist. IP-KO and wild-type (WT) mice were fed a methionine- and choline-deficient diet (MCDD) for 2, 5, or 10 wk. BPS was administered orally to mice every day during the experimental periods. The effect of BPS on the expression of chemokine and inflammatory cytokines was examined also in cultured Kupffer cells. WT mice fed MCDD developed steatohepatitis at 10 wk. IP-KO mice developed steatohepatitis at 5 wk with augmented histologic derangements accompanied by increased hepatic monocyte chemoattractant protein-1 (MCP-1) and TNF-α concentrations. After 10 wk of MCDD, IP-KO mice had greater hepatic iron deposition with prominent oxidative stress, resulting in hepatocyte damage. In WT mice, BPS improved histologic and biochemical parameters of steatohepatitis, accompanied by reduced hepatic concentration of MCP-1 and TNF-α. Accordingly, BPS suppressed the LPS-stimulated Mcp-1 and Tnf-α mRNA expression in cultured Kupffer cells prepared from WT mice. PGI₂-IP signaling plays a crucial role in the development and progression of steatohepatitis by modulating the inflammatory response, leading to augmented oxidative stress. We suggest that the PGI₂-IP system is an attractive therapeutic target for treating patients with NASH.-Kumei, S., Yuhki, K.-I., Kojima, F., Kashiwagi, H., Imamichi, Y., Okumura, T., Narumiya, S., Ushikubi, F. Prostaglandin I₂ suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

mPGES1-Dependent Prostaglandin E2 (PGE2) Controls Antigen-Specific Th17 and Th1 Responses by Regulating T Autocrine and Paracrine PGE2 Production

The integration of inflammatory signals is paramount in controlling the intensity and duration of immune responses. Eicosanoids, particularly PGE₂, are critical molecules in the initiation and resolution of inflammation and in the transition from innate to acquired immune responses. Microsomal PGE synthase 1 (mPGES1) is an integral membrane enzyme whose regulated expression controls PGE₂ levels and is highly expressed at sites of inflammation. PGE₂ is also associated with modulation of autoimmunity through altering the IL-23/IL-17 axis and regulatory T cell (Treg) development. During a type II collagen-CFA immunization response, lack of mPGES1 impaired the numbers of CD4⁺ regulatory (Treg) and Th17 cells in the draining lymph nodes. Ag-experienced mPGES1^-/- CD4⁺ cells showed impaired IL-17A, IFN-γ, and IL-6 production when rechallenged ex vivo with their cognate Ag compared with their wild-type counterparts. Additionally, production of PGE₂ by cocultured APCs synergized with that of Ag-experienced CD4⁺ T cells, with mPGES1 competence in the APC compartment enhancing CD4⁺ IL-17A and IFN-γ responses. However, in contrast with CD4⁺ cells that were Ag primed in vivo, exogenous PGE₂ inhibited proliferation and skewed IL-17A to IFN-γ production under Th17 polarization of naive T cells in vitro. We conclude that mPGES1 is necessary in vivo to mount optimal Treg and Th17 responses during an Ag-driven primary immune response. Furthermore, we uncover a coordination of autocrine and paracrine mPGES1-driven PGE₂ production that impacts effector T cell IL-17A and IFN-γ responses.

Selective activation of the prostaglandin E2 receptor subtype EP2 or EP4 leads to inhibition of platelet aggregation

The effect of selective activation of platelet prostaglandin (PG) E2 receptor subtype EP2 or EP4 on platelet aggregation remains to be determined. In platelets prepared from wild-type mice (WT platelets), high concentrations of PGE2 inhibited platelet aggregation induced by U-46619, a thromboxane receptor agonist. However, there was no significant change in the inhibitory effect of PGE2 on platelets lacking EP2 (EP2 –/– platelets) and EP4 (EP4 –/– platelets) compared with the inhibitory effect on WT platelets. On the other hand, AE1–259 and AE1–329, agonists for EP2 and EP4, respectively, potently inhibited U-46619 -induced aggregation with respective IC50 values of 590 ± 14 and 100 ± 4.9 nM in WT platelets, while the inhibition was significantly blunted in EP2 –/– and EP4 –/– platelets. In human platelets, AE1–259 and AE1–329 inhibited U-46619-induced aggregation with respective IC50 values of 640 ± 16 and 2.3 ± 0.3 nM. Notably, the inhibitory potency of AE1–329 in human platelets was much higher than that in murine platelets, while such a difference was not observed in the inhibitory potency of AE1–259. AE1–329 also inhibited adenosine diphosphate-induced platelet aggregation, and the inhibition was almost completely blocked by AE3–208, an EP4 antagonist. In addition, AE1–329 increased intracellular cAMP concentrations in a concentration- and EP4-dependent manner in human platelets. These results indicate that selective activation of EP2 or EP4 can inhibit platelet aggregation and that EP4 agonists are particularly promising as novel anti-platelet agents.

Cigarette Smoke Extract Inhibits Platelet Aggregation by Suppressing Cyclooxygenase Activity

The results of studies that were performed to determine whether cigarette smoking affects platelet function have been controversial, and the effects of nicotine- and tar-free cigarette smoke extract (CSE) on platelet function remain to be determined. The aim of this study was to determine the effect of CSE on platelet aggregation and to clarify the mechanism by which CSE affects platelet function. CSE inhibited murine platelet aggregation induced by 9,11-dideoxy-9α,11α-methanoepoxy-prosta-5Z,13E-dien-1-oic acid (U-46619), a thromboxane (TX) A ₂ receptor agonist, and that induced by collagen with respective IC ₅₀ values of 1.05 ± 0.14% and 1.34 ± 0.19%. A similar inhibitory action of CSE was also observed in human platelets. CSE inhibited arachidonic acid–induced TXA ₂ production in murine platelets with an IC ₅₀ value of 7.32 ± 2.00%. Accordingly, the inhibitory effect of CSE on collagen-induced aggregation was significantly blunted in platelets lacking the TXA ₂ receptor compared with the inhibitory effect in control platelets. In contrast, the antiplatelet effects of CSE in platelets lacking each inhibitory prostanoid receptor, prostaglandin (PG) I ₂ receptor and PGE ₂ receptor subtypes EP ₂ and EP ₄ , were not significantly different from the effects in respective control platelets. Among the enzymes responsible for TXA ₂ production in platelets, the activity of cyclooxygenase (COX)-1 was inhibited by CSE with an IC ₅₀ value of 1.07 ± 0.15% in an uncompetitive manner. In contrast, the activity of TX synthase was enhanced by CSE. The results indicate that CSE inhibits COX-1 activity and thereby decreases TXA ₂ production in platelets, leading to inhibition of platelet aggregation.

Suppression of lymphangiogenesis by soluble vascular endothelial growth factor receptor-2 in a mouse lung cancer model

The vascular endothelial growth factor (VEGF) family has a key role in the formation of blood vessels and lymphatics. Among the members of this family, VEGF-C is one of the most important factors involved in lymphangiogenesis via binding with two receptors (vascular endothelial growth factor receptor-2 and -3: VEGFR-2 and VEGFR-3). Soluble VEGFR-2 (sVEGFR-2) has a role in maintaining the alymphatic state of the cornea associated with binding to VEGF-C, and selectively inhibits lymphangiogenesis but not angiogenesis. In this study, we introduced sVEGFR-2 into lung cancer cells and evaluated the influence on tumor progression and on genes regulating lymphatic formation and metastasis in vivo. A retroviral vector was used to introduce the sVEGFR-2 gene into Lewis lung carcinoma cells (LLC), which were designated as LLC-sVEGFR-2 cells. Proteins secreted into the culture supernatant by these cells were detected by western blotting using specific antibodies. To examine lymphangiogenesis by primary lung cancer in vivo, LLC-sVEGFR-2 cells were subcutaneously injected into C57BL/6 mice. At 14days after injection, immunohistochemistry was performed using an antibody directed against lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), a marker of lymphatics. Expression of mRNA for VEGFR-2, VEGFR-3 and matrix metalloproteinases (MMPs) was also determined by real-time PCR. Furthermore, LLC-sVEGFR-2 cells were directly inoculated into the left lung in C57BL/6 mice and the number of micro-metastases in pulmonary lymph nodes was determined. Introduction of sVEGFR-2 into LLC cells resulted in secretion of sVEGFR-2 protein into the culture supernatant. There were fewer LYVE-1 positive lymphatics after inoculation of LLC-sVEGFR-2 into mice compared with the control group. In addition, VEGFR-2, VEGFR-3, and MMPs gene expression was suppressed in the primary tumors of the LLC-sVEGFR-2 group compared with the control group. Furthermore, there were fewer micro-metastases in the pulmonary lymph nodes of the LLC-sVEGFR-2 group compared with the control group after cells were directly inoculated into the lung. These findings indicate that introduction of sVEGFR-2 suppressed lymphangiogenesis in primary lung cancer and also suppressed lymphogenic metastasis by inhibiting VEGF-C, followed by down-regulation of VEGFR-2, VEGFR-3 and MMPs. Accordingly, sVEGFR-2 might be a promising target for treatment of cancer by regulating lymphangiogenesis and lymphogenic metastasis.

The novel prostaglandin I2 mimetic ONO-1301 escapes desensitization in an antiplatelet effect due to its inhibitory action on thromboxane A2 synthesis in mice

ONO-1301 [(E)-[5-[2-[1-phenyl-1-(3-pyridyl)methylidene-aminooxy]ethyl]-7,8-dihydronaphthalene-1-yloxy]acetic acid] is a novel prostaglandin (PG) I2 mimetic with inhibitory activity on the thromboxane (TX) A2 synthase. Interestingly, ONO-1301 retains its inhibitory effect on platelet aggregation after repeated administration, while beraprost, a representative agonist for the PGI2 receptor (IP), loses its inhibitory effect after repeated administration. In the present study, we intended to clarify the mechanism by which ONO-1301 escapes desensitization of an antiplatelet effect. In platelets prepared from wild-type mice, ONO-1301 inhibited collagen-induced aggregation and stimulated cAMP production in an IP-dependent manner. In addition, ONO-1301 inhibited arachidonic acid-induced TXA2 production in platelets lacking IP. Despite the decrease in stimulatory action on cAMP production, the antiplatelet effect of ONO-1301 hardly changed after repeated administration for 10 days in wild-type mice. Noteworthy, beraprost could retain its antiplatelet effect after repeated administration in combination with a low dose of ozagrel, a TXA2 synthase inhibitor. Therefore, we hypothesized that chronic IP stimulation by beraprost induces an increase in TXA2 production, leading to reduction in the antiplatelet effect. As expected, repeated administration of beraprost increased the plasma and urinary levels of a TXA2 metabolite, while ONO-1301 did not increase them significantly. In addition, beraprost could retain the ability to inhibit platelet aggregation after repeated administration in mice lacking the TXA2 receptor (TP). These results indicate that TP-mediated signaling participates in platelet desensitization against IP agonists and that simultaneous inhibition of TXA2 production confers resistance against desensitization on IP agonists.

Reduced T cell-dependent humoral immune response in microsomal prostaglandin E synthase-1 null mice is mediated by nonhematopoietic cells

Microsomal PGE synthase-1 (mPGES-1) is an inducible enzyme that specifically catalyzes the conversion of PGH2 to PGE2. We showed that mPGES-1 null mice had a significantly reduced incidence and severity of collagen-induced arthritis compared with wild-type (WT) mice associated with a marked reduction in Abs to type II collagen. In this study, we further elucidated the role of mPGES-1 in the humoral immune response. Basal levels of serum IgM and IgG were significantly reduced in mPGES-1 null mice. Compared with WT mice, mPGES-1 null mice exhibited a significant reduction of hapten-specific serum Abs in response to immunization with the T cell-dependent (TD) Ag DNP-keyhole limpet hemocyanin. Immunization with the T cell-independent type 1 Ag trinitrophenyl-LPS or the T cell-independent type 2 Ag DNP-Ficoll revealed minimal differences between strains. Germinal center formation in the spleen of mPGES-1 null and WT mice were similar after immunization with DNP-keyhole limpet hemocyanin. To determine whether the effect of mPGES-1 and PGE2 was localized to hematopoietic or nonhematopoietic cells, we generated bone marrow chimeras. We demonstrated that mPGES-1 deficiency in nonhematopoietic cells was the critical factor for reduced TD Ab production. We conclude that mPGES-1 and PGE2-dependent phenotypic changes of nonhematopoietic/mesenchymal stromal cells play a key role in TD humoral immune responses in vivo. These findings may have relevance to the pathogenesis of rheumatoid arthritis and other autoimmune inflammatory diseases associated with autoantibody formation.

Fluid overload deteriorate chylothorax: evaluation in a canine model

No conservative treatments for chylothorax have yet been established, and surgical ligation of the thoracic duct is required in many cases. In the present study, we investigated the management of body fluid in a canine chylothorax model. Twelve beagle dogs were divided evenly into three groups: A, B, and C. Under general anesthesia, the thoracic duct was cut and opened, and the amount of lymph fluid leakage was measured. Intravenous extracellular fluid infusion was started at 5mL/kg/h for the first 2h, and then between 2 and 4h, the infusion rate was increased to 10 mL/kg/h in group A and to 20mL/kg/h in group B. During the first 2h after cutting the thoracic duct, the mean lymph fluid leakage rates in groups A, B, and C were 0.466, 0.635, and 0.575 mL/kg/h, respectively. The rates of leakage did not differ significantly among the groups. Between 2 and 4h, the mean rates of leakage were 0.750, 1.43, and 0.544mL/kg/h, respectively, being significantly higher in groups A and B than in group C. The amount of lymph fluid ascending the thoracic duct correlates with the amount of intravenous fluid infusion. For the management of chylothorax, it is important to avoid fluid overload.

Cathepsin K expression in basal cell carcinoma

BACKGROUND

Cathepsin K is a cysteine protease with strong collagenolytic and elastolytic properties. Recently, cathepsin K expression in tumour cells of malignant melanoma and in the stromal cells of squamous cell carcinoma of the skin has been reported to play an important role in tumour progression. However, its expression profile in basal cell carcinoma (BCC) has not yet been clarified.

OBJECTIVE

The aim of this study is to examine the expression profile of cathepsin K in both the tumour cells and the peritumoural stromal cells of BCC in comparison with its expression in normal skin.

METHODS

Fifty consecutive operative cases of BCC, 10 cases of actinic keratosis, 10 cases of Bowen's disease and five normal skin tissues were assessed for cathepsin K expression by immunohistochemical methods.

RESULTS

In normal skin, cathepsin K expression was observed in the stratum corneum, mature sebaceous cells and outer root sheath of the hair follicles. Cathepsin K was expressed in the tumour cells of all BCC cases, in which 90% showed diffuse expression (>51% of tumour cells), as well as in the peritumoural stromal cells in all BCC cases. Focal cathepsin K expression was observed in the tumour cells of Bowen's disease (2/10 cases), but not in any of actinic keratosis (0/10 cases).

CONCLUSION

Cathepsin K expression may contribute to tumour invasion and peculiar histopathological features, such as fibromucinous stroma around the tumour nests by mediating extracellular matrix degradation in BCC.

Genetic deletion of mPGES-1 abolishes PGE2 production in murine dendritic cells and alters the cytokine profile, but does not affect maturation or migration

We undertook this study to determine the role of Microsomal PGE Synthase-1 (mPGES-1), and mPGES-1-generated Prostaglandin (PG) E2 on Dendritic Cell (DC) phenotype and function. Using mPGES-1 KnockOut (KO) mice, we generated bone marrow derived DCs and determined their eicosanoid production profile, cell surface marker expression, and cytokine production. We also assessed DC migratory and functional capacity in vivo. Compared to wild-type, mPGES-1 deficient DCs exhibited a markedly attenuated increase in PGE2 production upon LPS stimulation, and displayed preferential shunting towards PGD2 production. mPGES-1 KO DCs did not display deficiencies in maturation, migration or ability to sensitize T cells. However, mPGES-1 deficient DCs generated reduced amounts of the Th1 cytokine IL-12, which may in part be due to increased PGD2 rather than decreased PGE2. These findings provide useful information on the effects of inducible PGE2 on the innate immune system, and have important implications regarding potential consequences of pharmacologic mPGES-1 inhibition.

mPGES-1 null mice are resistant to bleomycin-induced skin fibrosis

Introduction

Microsomal prostaglandin E2 synthase-1 (mPGES-1) is an inducible enzyme that acts downstream of cyclooxygenase (COX) to specifically catalyze the conversion of prostaglandin (PG) H₂ to PGE₂. mPGES-1 plays a key role in inflammation, pain and arthritis; however, the role of mPGES-1 in fibrogenesis is largely unknown. Herein, we examine the role of mPGES-1 in a mouse model of skin scleroderma using mice deficient in mPGES-1.

Methods

Wild type (WT) and mPGES-1 null mice were subjected to the bleomycin model of cutaneous skin scleroderma. mPGES-1 expressions in scleroderma fibroblasts and in fibroblasts derived from bleomycin-exposed mice were assessed by Western blot analysis. Degree of fibrosis, dermal thickness, inflammation, collagen content and the number of α-smooth muscle actin (α-SMA)-positive cells were determined by histological analyses. The quantity of the collagen-specific amino acid hydroxyproline was also measured.

Results

Compared to normal skin fibroblasts, mPGES-1 protein expression was elevated in systemic sclerosis (SSc) fibroblasts and in bleomycin-exposed mice. Compared to WT mice, mPGES-1-null mice were resistant to bleomycin-induced inflammation, cutaneous thickening, collagen production and myofibroblast formation.

Conclusions

mPGES-1 expression is required for bleomycin-induced skin fibrogenesis. Inhibition of mPGES-1 may be a viable method to alleviate the development of cutaneous sclerosis and is a potential therapeutic target to control the onset of fibrogenesis.

Potential roles of microsomal prostaglandin E synthase-1 in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease which primarily affects the synovial joints leading to inflammation, pain and joint deformities. Nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids, both of which inhibit cyclooxygenase (COX), have been extensively used for treating RA patients. Prostaglandin E synthase (PGES) is a specific biosynthetic enzyme that acts downstream of COX and converts prostaglandin (PG) H(2) to PGE(2). Among PGES isozymes, microsomal PGES-1 (mPGES-1) has been shown to be induced in a variety of cells and tissues under inflammatory conditions. The induction of mPGES-1 in the synovial tissue of RA patients is closely associated with the activation of the tissue by proinflammatory cytokines. Although selective mPGES-1 inhibitors have not yet been widely available, mice lacking mPGES-1 (mPGES-1(-/-) mice) have been generated to evaluate the physiological and pathological roles of mPGES-1 in vivo. Recent studies utilizing mPGES-1(-/-) mice have demonstrated the significance of mPGES-1 in the process of chronic inflammation and evocation of humoral immune response in autoimmune arthritis models. These recent findings highlight mPGES-1 as a novel therapeutic target for the treatment of autoimmune inflammatory diseases, including RA. Currently, both natural and synthetic chemicals are being tested for inhibition of mPGES-1 activity to produce PGE(2). The present review focuses on the recent advances in understanding the role of mPGES-1 in the pathophysiology of RA.

Somatic cell plasticity and Niemann-Pick type C2 protein: fibroblast activation

A growing body of evidence points toward activated fibroblasts, also known as myofibroblasts, as one of the leading mediators in several major human pathologies including proliferative fibrotic disorders, invasive tumor growth, rheumatoid arthritis, and atherosclerosis. Niemann-Pick Type C2 (NPC2) protein has been recently identified as a product of the second gene in NPC disease. It encodes ubiquitous, highly conserved, secretory protein with the poorly defined function. Here we show that NPC2 deficiency in human fibroblasts confers their activation. The activation phenomenon was not limited to fibroblasts as it was also observed in aortic smooth muscle cells upon silencing NPC2 gene by siRNA. More importantly, activated synovial fibroblasts isolated from patients with rheumatoid arthritis were also identified as NPC2-deficient at both the NPC2 mRNA and protein levels. The molecular mechanism responsible for activation of NPC2-null cells was shown to be a sustained phosphorylation of ERK 1/2 mitogen-activated protein kinase (MAPK), which fulfills both the sufficient and necessary fibroblast activation criteria. All of these findings highlight a novel mechanism where NPC2 by negatively regulating ERK 1/2 MAPK phosphorylation may efficiently suppress development of maladaptive tissue remodeling and inflammation.

Adiponectin stimulates prostaglandin E(2) production in rheumatoid arthritis synovial fibroblasts

OBJECTIVE

Adipokines may influence inflammatory and/or immune responses. This study was undertaken to examine whether adiponectin affects the production of prostaglandin E(2) (PGE(2)) by rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Synovial tissue was obtained from patients with RA who were undergoing joint replacement surgery. Fibroblast-like cells from the third or fourth passage were used as RASFs. Expression of adiponectin receptor messenger RNA (mRNA) and protein was detected. PGE(2) (converted from arachidonic acid) was measured by enzyme-linked immunosorbent assay (ELISA). Expression of mRNA and protein for cyclooxygenase 2 (COX-2) and membrane-associated PGE synthase 1 (mPGES-1), key enzymes involved in PGE(2) synthesis, was detected in RASFs. The effects of RNA interference (RNAi) targeting the adiponectin receptor genes and the receptor signal inhibitors were examined. The influence of adiponectin on NF-kappaB activation in RASFs was measured with an ELISA kit.

RESULTS

Adiponectin receptors were detected in RASFs. Adiponectin increased both COX-2 and mPGES-1 mRNA and protein expression by RASFs in a time- and concentration-dependent manner. PGE(2) production by RASFs was also increased by the addition of adiponectin, and this increase was inhibited by RNAi for the adiponectin receptor gene, or coincubation with the receptor signal inhibitors. Enhancement of NF-kappaB activation by adiponectin as well as by interleukin-1beta was observed in RASFs.

CONCLUSION

Our findings indicate that adiponectin induces COX-2 and mPGES-1 expression, resulting in the enhancement of PGE(2) production by RASFs. Thus, adiponectin may play a role in the pathogenesis of synovitis in RA patients.

Roles of prostanoids in the pathogenesis of cardiovascular diseases

The roles of prostanoids in the pathogenesis of cardiovascular diseases and in the development of pathological conditions have been examined using mice lacking the individual, specific prostanoid receptor. Prostaglandin (PG) I2 protected the heart from ischemia-reperfusion injury in a model of acute myocardial infarction. In addition, PGI2 suppressed the development of pressure overload-induced cardiac hypertrophy. Aside from its potent vasodilatory action, PGI2 contributed critically to the development of renovascular hypertension via the activation of the renin-angiotensin-aldosterone system. Thromboxane (TX) A2 and PGF2alpha were found to be the mediators of inflammatory tachycardia under a systemic inflammatory condition induced by lipopolysaccharide. Under a septic condition leading to a vascular hypo-responsive state, TXA2 worked to maintain vascular tone by inhibiting the induction of inducible nitric oxide synthase in vascular smooth muscle cells. Mice lacking the PGE2 receptor subtype EP3 had a bleeding tendency and were resistant to thromboembolism, due to a defective activation of platelets. From these studies, the important and novel roles of prostanoids in the pathogenesis of cardiovascular diseases have been clarified.

Prostaglandin E2 differentially modulates proinflammatory/prodestructive effects of TNF-alpha on synovial fibroblasts via specific E prostanoid receptors/cAMP

The present study investigated the influence of PGE(2), E prostanoid (EP) receptors, and their signaling pathways on matrix metalloproteinase (MMP)-1 and IL-6 expression in synovial fibroblasts (SFs) from rheumatoid arthritis (RA) patients. RASFs expressed all four EP receptors, with selective induction of EP2 by TNF-alpha. TNF-alpha time-dependently increased intracellular cAMP/protein kinase A signaling (maximum, 6-12 h) and PGE(2) secretion (maximum, 24 h). PGE(2) and the EP2 agonists butaprost or ONO-AE1-259 ((16)-9-deoxy-9beta-chloro-15-deoxy-16-hydroxy-17,17-trimethylene-19,20-didehydro PGE(1)), in turn, induced a rapid, time-dependent (maximum, 15-30 min) increase of cAMP. Additionally, cyclooxygenase-2 inhibition by NS-398 (N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulfonamide) reduced the TNF-alpha-induced increase in IL-6 mRNA/protein, which was restored by stimulation with PGE(2) or EP2, EP3, and EP4 agonists. In contrast, TNF-alpha-induced MMP-1 secretion was not influenced by NS-398 and diminished by PGE(2) via EP2. Finally, 3-isobutyl-1-methylxanthine enhanced the effects of PGE(2) on MMP-1, but not on IL-6 mRNA. In conclusion, PGE(2) differentially affects TNF-alpha-induced mRNA expression of proinflammatory IL-6 and prodestructive MMP-1 regarding the usage of EP receptors and the dependency on cAMP. Although specific blockade of EP2 receptors is considered a promising therapeutic strategy in RA, opposite regulation of proinflammatory IL-6 and prodestructive MMP-1 by PGE(2) via EP2 may require more complex approaches to successfully inhibit the cyclooxygenase-1/2 cAMP axis.

Prostaglandin E2 activates Rap1 via EP2/EP4 receptors and cAMP-signaling in rheumatoid synovial fibroblasts: involvement of Epac1 and PKA

The small GTPase Rap1 is implicated in a variety of cellar functions. In this study, we investigated the effect of prostaglandin E(2) (PGE(2)) on Rap1 activation in rheumatoid synovial fibroblasts (RSF). Rap1 was expressed in RSF, and GTP-bound active Rap1 (GTP-Rap1) was rapidly increased by PGE(2). The effect of PGE(2) was mimicked by an EP2 receptor agonist, an EP4 agonist and a cAMP-elevating agent forskolin with association to the increase of cAMP, but not by an EP1 or an EP3 agonist. RSF expressed the downstream signaling partners of cAMP, exchange protein directly activated by cAMP (Epac1) and protein kinase A (PKA). Both 8-pCPT-2-O-Me-cAMP (an Epac-specific cAMP analog) and 6-Bnz-cAMP (a PKA-specific cAMP analog) activated Rap1 in RSF. Activation of Rap1 by PGE(2) via cAMP-signaling may play an important role in the articular pathology of rheumatoid arthritis (RA).

Defective generation of a humoral immune response is associated with a reduced incidence and severity of collagen-induced arthritis in microsomal prostaglandin E synthase-1 null mice

Microsomal PGE synthase-1 (mPGES-1) is an inducible enzyme that acts downstream of cyclooxygenase and specifically catalyzes the conversion of PGH(2) to PGE(2). The present study demonstrates the effect of genetic deletion of mPGES-1 on the developing immunologic responses and its impact on the clinical model of bovine collagen-induced arthritis. mPGES-1 null and heterozygous mice exhibited decreased incidence and severity of arthritis compared with wild-type mice in a gene dose-dependent manner. Histopathological examination revealed significant reduction in lining hyperplasia and tissue destruction in mPGES-1 null mice compared with their wild-type littermates. mPGES-1 deficient mice also exhibited attenuation of mechanical nociception in a gene dose-dependent manner. In addition, mPGES-1 null and heterozygous mice showed a marked reduction of serum IgG against type II collagen, including subclasses IgG1, IgG2a, IgG2b, IgG2c, and IgG3, compared with wild-type mice, which correlated with the reduction in observed inflammatory features. These results demonstrate for the first time that deficiency of mPGES-1 inhibits the development of collagen-induced arthritis, at least in part, by blocking the development of a humoral immune response against type II collagen. Pharmacologic inhibition of mPGES-1 may therefore impact both the inflammation and the autoimmunity associated with human diseases such as rheumatoid arthritis.

Microsomal prostaglandin E synthase-1 genetic deletion results in reduced incidence and severity of collagen-induced arthritis associated with a marked reduction of anti-collagen antibodies (130.47)

Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible enzyme that acts downstream of cyclooxygenase and specifically catalyzes the conversion of prostaglandin (PG)H2 to PGE2, most prominently in inflammatory conditions. However, the role of mPGES-1 in the immune response has not yet been full elucidated. In this study, we demonstrate the effect of genetic deletion of mPGES-1 on initiating immune responses as well as clinical arthritis development in bovine collagen-induced arthritis (CIA), a well established model to study pathogenic mechanisms relevant to rheumatoid arthritis. mPGES-1 null and heterozygous mice exhibited decreased paw edema, arthritis severity and incidence compared to wild-type mice in a gene dose-dependent manner. Histopathological changes further showed a significant reduction in lining hyperplasia and tissue destruction in mPGES-1 null mice compared to their wild-type littermates. In addition, mPGES-1 genetic deletion showed attenuated mechanical allodynia in a gene dose-dependent manner. The reduction of inflammatory features observed in mPGES-1 null mice were associated with significantly lower levels of IgG including IgG1, IgG2a, IgG2b, IgG2c and IgG3 against type II collagen (CII). These results suggest that deficiency of mPGES-1 inhibits the development of CIA, at least in part, by blocking development of the anti-CII antibody response.

Grant Support: Arthritis Foundation Biomedical Sciences Grant and NIH/NIAMS AR49010.