Peroxisome Proliferator Activated Receptor-γ Agonistic Compounds from the Jellyfish-Derived Fungus Cladosporium oxysporum.

In our search for peroxisome proliferator-activated receptor (PPAR) agonists, five undescribed compounds, namely two acyclic diterpenes (1 and 2; cladopsol A and cladopsol B), two sesquiterpenes (3 and 4; cladopsol C and cladopsol D), and one C21-ecdysteroid (5; cladopsol E), and 15 known compounds were isolated from the jellyfish-derived fungus - Cladosporium oxysporum. The structures of the undescribed compounds were defined using UV, NMR, HR-ESI-MS, and electronic circular dichroism (ECD) spectroscopy and a modified Mosher's method. Luciferase reporter assay and docking analysis suggested that cladopsol B may function as a PPAR-γ partial agonist with a potential antidiabetic lead which may evade the side effects of full agonists. Moreover, cladopsol B stimulated glucose uptake in HepG2 cells with an efficacy comparable to that of rosiglitazone, but with less side effect induced by lipid accumulation in 3T3-L1 cells. Therefore, cladopsol B could serve as a molecular skeleton in a study of advanced antidiabetic lead with less side effect.

Atractylodin Ameliorates Colitis via PPARα Agonism.

Atractylodin is a major compound in the rhizome of Atractylodes lancea, an oriental herbal medicine used for the treatment of gastrointestinal diseases, including dyspepsia, nausea, and diarrhea. Recent studies have shown that atractylodin exerts anti-inflammatory effects in various inflammatory diseases. Herein, we investigated the anti-colitis effects of atractylodin and its molecular targets. We determined the non-cytotoxic concentration of atractylodin (50 µM) using a cell proliferation assay in colonic epithelial cells. We found that pretreatment with atractylodin significantly inhibits tumor necrosis factor-α-induced phosphorylation of nuclear factor-κ-light-chain-enhancer of activated B in HCT116 cells. Through docking simulation analysis, luciferase assays, and in vitro binding assays, we found that atractylodin has an affinity for peroxisome proliferator-activated receptor alpha (PPARα). Daily administration of atractylodin (40 mg/kg) increased the survival rate of mice in a dextran sodium sulfate-induced colitis mouse model. Thus, atractylodin can be a good strategy for colitis therapy through inducing PPARα-dependent pathways.

A New Fungal Triterpene from the Fungus Aspergillus flavus Stimulates Glucose Uptake without Fat Accumulation.

Through activity-guided fractionation, a new triterpene (asperflagin, 1) was isolated as a PPAR-γ agonist from the jellyfish-derived fungus Aspergillus flavus. Asperflagin displayed selective and moderate transactivation effects on PPAR-γ in Ac2F rat liver cells. Based on further biological evaluation and molecular docking analysis, we postulated that asperflagin might function as a PPAR-γ partial agonist. This compound was calculated to display a typical PPAR-γ ligand-receptor interaction that is distinct from that of full agonistic antidiabetics such as rosiglitazone, and may retain the antidiabetic effect without accompanying weight gain. Weight gain and obesity are typical side effects of the PPAR-γ full agonist rosiglitazone, and lead to suboptimal outcomes in diabetic patients. Compared to rosiglitazone, asperflagin showed higher glucose uptake in HepG2 human liver cells at concentrations of 20 and 40 µM but induced markedly lower adipogenesis and lipid accumulation in 3T3-L1 preadipocytes. These results suggest that asperflagin may be utilized for further study on advanced antidiabetic leads.

Neuroprotective Effect of Cyclo-(L-Pro-L-Phe) Isolated from the Jellyfish-Derived Fungus Aspergillus flavus.

Peroxisome proliferator-activated receptor (PPAR) expression has been implicated in pathological states such as cancer, inflammation, diabetes, and neurodegeneration. We isolated natural PPAR agonists-eight 2,5-diketopiperazines-from the jellyfish-derived fungus Aspergillus flavus. Cyclo-(L-Pro-L-Phe) was the most potent PPAR-γ activator among the eight 2,5-DKPs identified. Cyclo-(L-Pro-L-Phe) activated PPAR-γ in Ac2F rat liver cells and SH-SY5Y human neuroblastoma cells. The neuroprotective effect of this partial PPAR-γ agonist was examined using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, lactate dehydrogenase release, and the Hoechst 33342 staining assay in SH-SY5Y cells. Our findings revealed that cyclo-(L-Pro-L-Phe) reduced hydrogen peroxide-induced apoptosis as well as the generation of reactive oxygen species. Rhodamine 123 staining and western blotting revealed that cyclo-(L-Pro-L-Phe) prevented the loss of mitochondrial membrane potential and inhibited the activation of mitochondria-related apoptotic proteins, such as caspase 3 and poly (ADP-ribose) polymerase. Moreover, cyclo-(L-Pro-L-Phe) inhibited the activation and translocation of nuclear factor-kappa B. Thus, the partial PPAR-γ agonist cyclo-(L-Pro-L-Phe) demonstrated potential neuroprotective activity against oxidative stress-induced neurodegeneration in SH-SY5Y cells.

Cyclooxygenase-2 Inhibitor Parecoxib Was Disclosed as a PPAR-γ Agonist by In Silico and In Vitro Assay.

In a search for effective PPAR-γ agonists, 110 clinical drugs were screened via molecular docking, and 9 drugs, including parecoxib, were selected for subsequent biological evaluation. Molecular docking of parecoxib to the ligand-binding domain of PPAR-γ showed high binding affinity and relevant binding conformation compared with the PPAR-γ ligand/antidiabetic drug rosiglitazone. Per the docking result, parecoxib showed the best PPAR-γ transactivation in Ac2F rat liver cells. Further docking simulation and a luciferase assay suggested parecoxib would be a selective (and partial) PPAR-γ agonist. PPAR-γ activation by parecoxib induced adipocyte differentiation in 3T3-L1 murine preadipocytes. Parecoxib promoted adipogenesis in a dose-dependent manner and enhanced the expression of adipogenesis transcription factors PPAR-γ, C/EBPα, and C/EBPß. These data indicated that parecoxib might be utilized as a partial PPAR-γ agonist for drug repositioning study.

Nitric Oxide-Releasing Thermoresponsive Pluronic F127/Alginate Hydrogel for Enhanced Antibacterial Activity and Accelerated Healing of Infected Wounds.

Nitric oxide (NO), a highly reactive and lipophilic molecule, is one of the molecules present in the wound environment and implicated as an important regulator in all phases of wound healing. Here, we developed an NO-releasing thermoresponsive hydrogel (GSNO-PL/AL) composed of S-nitrosoglutathione (GSNO), pluronic F127 (PL), and alginate (AL) for the treatment of infected wounds. The GSNO was incorporated into the thermoresponsive PL/AL hydrogel, and differential scanning calorimetry techniques were used for the hydrogel characterization. The hydrogel was assessed by in vitro NO release, antibacterial activity, cytotoxicity, and wound-healing activity. The GSNO-PL/AL hydrogel demonstrated thermal responsiveness and biocompatibility, and it showed sustained NO release for 7 days. It also exhibited potent bactericidal activity against Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative multidrug-resistant Pseudomonas aeruginosa (MRPA). Moreover, the GSNO-PL/AL treatment of MRPA-infected wounds accelerated healing with a reduced bacterial burden in the wounds. The GSNO-PL/AL hydrogel would be a promising option for the treatment of infected wounds.

Viriditoxin Stabilizes Microtubule Polymers in SK-OV-3 Cells and Exhibits Antimitotic and Antimetastatic Potential.

Microtubules play a crucial role in mitosis and are attractive targets for cancer therapy. Recently, we isolated viriditoxin, a cytotoxic and antibacterial compound, from a marine fungus Paecilomyces variotii. Viriditoxin has been reported to inhibit the polymerization of bacterial FtsZ, a tubulin-like GTPase that plays an essential role in bacterial cell division. Given the close structural homology between FtsZ and tubulin, we investigated the potential antimitotic effects of viriditoxin on human cancer cells. Viriditoxin, like paclitaxel, enhanced tubulin polymerization and stabilized microtubule polymers, thereby perturbing mitosis in the SK-OV-3 cell line. However, the morphology of the stabilized microtubules was different from that induced by paclitaxel, indicating subtle differences in the mode of action of these compounds. Microtubule dynamics are also essential in cell movement, and viriditoxin repressed migration and colony formation ability of SK-OV-3 cells. Based on these results, we propose that viriditoxin interrupts microtubule dynamics, thus leading to antimitotic and antimetastatic activities.

Anti-inflammatory effects of an optimized PPAR-γ agonist via NF-κB pathway inhibition.

In our previous study, a PPAR-γ agonist (+)-(R,E)-6a1 was elaborated as an anti-inflammatory lead. However, in silico analysis showed that (+)-(R,E)-6a1 lacks key hydrogen bonding with Tyr473 of PPAR-γ LBD (ligand binding domain). To facilitate additional hydrogen bonding with Tyr473, a more polar head group was introduced to the structure of (+)-(R,E)-6a1, and we also attempted to synthesize enzymatically stable derivatives. Of the synthetic derivatives, compound (+)-(R,E)-5f showed highest PPAR-γ transcriptional activity and reasonable metabolic stability. Compound (+)-(R,E)-5f suppressed the expression of pro-inflammatory mediators such as inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α). Reduction of nitric oxide (NO), and ROS was also observed. Compound (+)-(R,E)-5f was found to suppress the NF-κB pathway by inhibiting phosphorylation of IKK (IκB kinase), and this may lead to subsequent inhibition of IκBα (inhibitor of NF-κBα) phosphorylation and inhibition of NF-κB activation. These results indicate that (+)-(R,E)-5f exerts anti-inflammatory activity via NF-κB pathway inhibition, and may serve as a potential anti-inflammatory lead.

Design of balanced COX inhibitors based on anti-inflammatory and/or COX-2 inhibitory ascidian metabolites.

The aim of this study was to design and synthesize COX-1/COX-2 balanced inhibitors incorporating the structural motifs of anti-inflammatory ascidian metabolites. We designed a series of substituted indole analogs that incorporate the key structures of the ascidian metabolites, herdmanines C and D. The synthesized analogs were tested for their inhibitory activity against COX-1 and COX-2, and compound 5m, which displayed balanced inhibition, was further evaluated for in vitro anti-inflammatory activity. Compound 5m suppressed the expression of pro-inflammatory factors, including iNOS, COX-2, TNF-α, and IL-6 in LPS-stimulated murine RAW264.7 macrophages. The reduction of PGE2, NO, and ROS was also observed, together with the suppression of NF-κB, IKK, and IκBα phosphorylation. Our results characterized 5m as a COX-1/COX-2 balanced inhibitor that subsequently caused ROS inhibition and NF-κB suppression, and culminated in the suppression of iNOS, COX-2, TNF-α, and IL-6 expression.

An Algal Metabolite-Based PPAR-γ Agonist Displayed Anti-Inflammatory Effect via Inhibition of the NF-κB Pathway.

In our previous study, a synthetic compound, (+)-(R,E)-6a1, that incorporated the key structures of anti-inflammatory algal metabolites and the endogenous peroxisome proliferator-activated receptor γ (PPAR-γ) ligand 15-deoxy-∆12,14-prostaglandin J2 (15d-PGJ2), exerted significant PPAR-γ transcriptional activity. Because PPAR-γ expressed in macrophages has been postulated as a negative regulator of inflammation, this study was designed to investigate the anti-inflammatory effect of the PPAR-γ agonist, (+)-(R,E)-6a1. Compound (+)-(R,E)-6a1 displayed in vitro anti-inflammatory activity in lipopolysaccharides (LPS)-stimulated murine RAW264.7 macrophages. Compound (+)-(R,E)-6a1 suppressed the expression of proinflammatory factors, such as nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), possibly by the inhibition of the nuclear factor-κB (NF-κB) pathway. In macrophages, (+)-(R,E)-6a1 suppressed LPS-induced phosphorylation of NF-κB, inhibitor of NF-κB α (IκBα), and IκB kinase (IKK). These results indicated that PPAR-γ agonist, (+)-(R,E)-6a1, exerts anti-inflammatory activity via inhibition of the NF-κB pathway.

Novel SIRT1 inhibitor 15-deoxy-Δ12,14-prostaglandin J2 and its derivatives exhibit anticancer activity through apoptotic or autophagic cell death pathways in SKOV3 cells.

Clinically relevant sirtuin (SIRT) inhibitors may possess antitumor activities. A previous study indicated that 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) exhibited potent anticancer activity by SIRT1 inhibition. Therefore, the aim of the present study was to investigate whether its derivatives (J11-C1 and J19) exhibited anticancer activity against ovarian cancer SKOV3 cells. Cell viability was determined using an MTT assay. Cell cycle arrest, apoptosis and autophagy were determined using flow cytometry or western blot analysis. J11-Cl and J19 were less cytotoxic to SKOV3 cells compared with 15d-PGJ2. Molecular docking studies supported the interactions of 15d-PGJ2, J11-Cl and J19 with various amino acids in SIRT1 proteins. Similar to 15d-PGJ2, J11-C1 and J19 inhibited SIRT1 enzymatic activity and decreased SIRT1 expression levels in a concentration-dependent manner. J11-C1 induced apoptotic cell death more effectively compared with J19, which was associated with markedly decreased expression of the anti-apoptotic molecule B-cell lymphoma 2 (Bcl-2). Furthermore, the levels of light chain 3-Ⅱ (LC3-II) and beclin-1 were clearly induced in SKOV3 cells treated with J11-Cl. Thus, 15d-PGJ2 and its derivatives exhibited anticancer activity possibly by inducing apoptotic or autophagic cell death pathways. Collectively, the results of the present study suggest that 15d-PGJ2 and its derivatives exerted antitumor activity by selectively modulating the expression of genes associated with cell cycle arrest, apoptosis and autophagy. Notably, J11-C1 is a novel candidate SIRT1 inhibitor with anticancer activity.

Design of PPAR-γ agonist based on algal metabolites and the endogenous ligand 15-deoxy-Δ12, 14-prostaglandin J2.

In a previous study, we synthesized endocyclic enone jasmonate derivatives that function as anti-inflammatory and PPAR-γ-activating entities by using key functional moieties of anti-inflammatory algal metabolites. Herein, we designed additional derivatives containing an exocyclic enone moiety that resembles the key structure of the natural PPAR-γ ligand, 15-deoxy-Δ12, 14-prostaglandin J2 (15 d-PGJ2). The exocyclic enone moiety of 15 d-PGJ2 is essential for covalent bonding with the Cys285 residue in the PPAR-γ ligand-binding domain (LBD). In silico analysis of the designed compounds indicated that they may form hydrogen bonds with key amino acid residues in the PPAR-γ LBD, and thus, secure a position in the bioactive cavity in a similar fashion as does rosiglitazone and 15 d-PGJ2. By a luciferase reporter assay on rat liver Ac2F cells, the synthesized compounds were evaluated for PPAR-γ transcriptional activity. The differential PPAR-γ transcriptional activities of the geometric and enantiomeric isomers of the selected analog were also evaluated; based on our results, the enantiopure compound (+)-(R,E)-6a1 was suggested as a potential PPAR-γ ligand.

A bile acid derivative with PPARγ-mediated anti-inflammatory activity.

During our search for bioactive secondary metabolites in the jellyfish-derived fungus Penicillium chrysogenum J08NF-4, several bile acid derivatives (2-6) were isolated along with a new steroidal artifact (1). An in vitro anti-inflammatory assay showed that pretreatment with 1 suppressed NO production and the gene expressions of the pro-inflammatory mediators iNOS and TNF-α in LPS-induced RAW 264.7 macrophages. Docking analysis of 1 revealed that it might bind to the ligand binding domain (LBD) of PPARγ in a manner similar to that of the synthetic steroid mifepristone (7), which is used clinically to treat hypercortisolism and was recently reported to be a PPARγ agonist. Compound 1 activated PPARγ in murine Ac2F liver cells and suppressed the LPS-induced phosphorylation of the NF-κB p65 subunit leading to downregulation of pro-inflammatory mediators. Our findings suggest that 1 acts as a steroidal PPARγ activator that downregulates the expressions of pro-inflammatory mediators by suppressing the NF-κB signaling pathway.

Suppressive Effect of 4-Hydroxy-2-(4-Hydroxyphenethyl) Isoindoline-1,3-Dione on Ovalbumin-Induced Allergic Asthma.

4-Hydroxy-2-(4-hydroxyphenethyl)isoindoline-1,3-dione (PD1) is a synthetic phthalimide derivative of a marine compound. PD1 has peroxisome proliferator-activated receptor (PPAR) γ agonistic and anti-inflammatory effects. This study aimed to investigate the effect of PD1 on allergic asthma using rat basophilic leukemia (RBL)-2H3 mast cells and an ovalbumin (OVA)-induced asthma mouse model. In vitro, PD1 suppressed ß-hexosaminidase activity in RBL-2H3 cells. In the OVA-induced allergic asthma mouse model, increased inflammatory cells and elevated Th2 and Th1 cytokine levels were observed in bronchoalveolar lavage fluid (BALF) and lung tissue. PD1 administration decreased the numbers of inflammatory cells, especially eosinophils, and reduced the mRNA and protein levels of the Th2 cytokines including interleukin (IL)-4 and IL-13, in BALF and lung tissue. The severity of inflammation and mucin secretion in the lungs of PD1-treated mice was also less. These findings indicate that PD1 could be a potential compound for anti-allergic therapy.

An Anti-Inflammatory PPAR-γ Agonist from the Jellyfish-Derived Fungus Penicillium chrysogenum J08NF-4.

An investigation of the jellyfish-derived fungus Penicillium chrysogenum J08NF-4 led to the isolation of two new meroterpene derivatives, chrysogenester (1) and 5-farnesyl-2-methyl-1-O-methylhydroquinone (2), and four known farnesyl meroterpenes. Docking analysis of 1 showed that it binds to PPAR-γ in the same manner as the natural PPAR-γ agonist amorfrutin B (7). Compound 1 activated PPAR-γ in murine Ac2F liver cells and increased nuclear PPAR-γ protein levels in murine RAW 264.7 macrophages. Because one of the main biological functions of PPAR-γ agonists is to suppress inflammatory response, an in vitro study was performed to explore the anti-inflammatory potency of 1 and the mechanism involved. In RAW 264.7 macrophages, 1 inhibited phosphorylation of the NF-κB p65 subunit and suppressed the expression of the pro-inflammatory mediators iNOS, NO, COX-2, TNF-α, IL-1ß, and IL-6. We propose 1 suppresses inflammatory responses by activating PPAR-γ and subsequently downregulating the NF-κB signaling pathway, thus reducing the expressions of pro-inflammatory mediators.

Antibacterial activities of viriditoxin congeners and synthetic analogues against fish pathogens.

Viriditoxin is a fungal secondary metabolite of the fungus Paecilomyces variotii derived from the inner tissues of the giant jellyfish Nemopilema nomurai. Viriditoxin exhibits antibacterial activity against Streptococcus iniae and Streptococcus parauberis, which are major pathogens of aqua cultured fish. Viriditoxin induced abnormal cell morphologies in the fish pathogens S. iniae and S. parauberis, presumably by inhibiting FtsZ polymerization as was previously observed in Escherichia coli. Synthetic analogues of viriditoxin, designed based on docking simulation results to FtsZ of Staphylococcus aureus, were prepared and compared with viriditoxin for antibacterial activity. Reconstitution of free hydroxyl or carboxyl groups of the methoxyl or methyl ester groups of viriditoxin led to significant reduction of antibacterial activity, implying that the natural molecule is optimized for antibacterial activity to deter bacteria potentially harmful to Paecilomyces.

Marine-Derived Penicillium Species as Producers of Cytotoxic Metabolites.

Since the discovery of penicillin, Penicillium has become one of the most attractive fungal genera for the production of bioactive molecules. Marine-derived Penicillium has provided numerous excellent pharmaceutical leads over the past decades. In this review, we focused on the cytotoxic metabolites * (* Cytotoxic potency was referred to five different levels in this review, extraordinary (IC50/LD50: <1 µM or 0.5 µg/mL); significant (IC50/LD50: 1~10 µM or 0.5~5 µg/mL); moderate (IC50/LD50: 10~30 µM or 5~15 µg/mL); mild (IC50/LD50: 30~50 µM or 15~25 µg/mL); weak (IC50/LD50: 50~100 µM or 25~50 µg/mL). The comparative potencies of positive controls were referred when they were available). produced by marine-derived Penicillium species, and on their cytotoxicity mechanisms, biosyntheses, and chemical syntheses.

Evaluation of the inhibitory effects of eckol and dieckol isolated from edible brown alga Eisenia bicyclis on human monoamine oxidases A and B.

Eckol and dieckol are important phlorotannins found in edible brown algae including Eisenia bicyclis, Ecklonia stolonifera, and others. Inhibition of monoamine oxidase (MAO) play an important role in the early management of Parkinson's disease (PD). The aim of this study was to determine the effectiveness of eckol and dieckol isolated from the methanolic extract of E. bicyclis against PD by the inhibition of human MAO-A and MAO-B (hMAO-A and hMAO-B). A sensitive enzyme-based chemiluminescent assay and kinetics methods were used to investigate enzyme inhibition and mode of inhibition. A molecular docking simulation was performed to clarify the binding characteristics of eckol and dieckol to hMAO-A and hMAO-B. The results suggested that methanolic extract of E. bicyclis and its isolated phlorotannins, eckol and dieckol, have potent inhibitory activity against hMAO-A and hMAO-B. The enzyme-based kinetics results demonstrated eckol mixed and non-competitive inhibition of hMAO-A and hMAO-B, respectively, while dieckol non-competitively inhibited both hMAOs. Molecular docking simulation predicted that eckol and dieckol exhibit higher binding affinity towards hMAO-A and hMAO-B through hydrogen bonding and hydrophobic interactions. These findings implicate eckol and dieckol as inhibitors of hMAOs that might be of potential value in the management of PD.

New metabolites from the sponge-derived fungus Aspergillus sydowii J05B-7F-4.

Two new metabolites, diorcinolic acid (1) and ß-d-glucopyranosyl aspergillusene A (8), together with six diphenylethers (2-7), a diketopiperazine (9), a chromone (10) and a xanthone (11) were isolated from the fungus Aspergillus sydowii derived from the marine sponge Stelletta sp. The planar structures and their relative configurations were elucidated by analysing 1D, 2D NMR and HRESIMS data. Compound 8 is the first glycoside of phenolic bisabolane sesquiterpenes. Compounds 1 and 8 exhibited mild cytotoxicity against KB (human nasopharyngeal carcinoma cells), HepG2 (human liver cancer cells) and HCT 116 (human colon cancer cells). All compounds were evaluated for antibacterial activity and their abilities to suppress LPS-induced nitric oxide (NO) production. Compounds 2 and 4-7 showed mild antibacterial activity against human pathogen Staphylococcus aureus and fish pathogens Streptococcus iniae and Vibrio ichthyoenteri, and compounds 4 and 7 weakly suppressed NO production.

The In Vitro and In Vivo Anti-Inflammatory Effects of a Phthalimide PPAR-γ Agonist.

Previously, the authors found that 4-hydroxy-2-(4-hydroxyphenethyl) isoindoline-1,3-dione (PD1) (a phthalimide analogue) bound to and activated peroxisome proliferator-activated receptor-γ (PPAR-γ). Since PPAR-γ suppresses inflammatory responses, the present study was undertaken to investigate the anti-inflammatory effects of PD1. In lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages, PD1 suppressed the inductions of pro-inflammatory factors, including inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase 2 (COX-2), tumor necrosis factor α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6). Concomitantly, PD1 enhanced the expressions of anti-inflammatory factors, such as arginase-1 and interleukin-10 (IL-10), and suppressed LPS-evoked nuclear factor kappa B (NF-κB) p65 subunit phosphorylation in macrophages. In addition, PPAR-γ activated by PD1 was intensively translocated to the nucleus. These observations suggest that the anti-inflammatory mechanism of PD1 involves inhibition of the NF-κB pathway. In a subsequent in vivo animal experiment conducted using a carrageenan-induced acute inflammatory rat paw edema model, intraperitoneal injection of PD1 significantly reduced paw swelling. Histological analysis of rat paw tissue sections revealed less infiltration of immune cells in PD1-pretreated animals. These findings suggest that PD1 be viewed as a lead compound for the development of novel anti-inflammatory therapeutics.