Garcinol A Novel Inhibitor of Platelet Activation and Apoptosis

Interaction of Garcinia cambogia (Gaertn.) Desr. and Drugs as a Possible Mechanism of Liver Injury: The Case of Montelukast

Overweight and obesity prevalence has increased worldwide. Apart from conventional approaches, people also resort to botanical supplements for reducing body weight, although several adverse events have been associated with these products. In this context, the present study aimed at evaluating the toxicity of Garcinia cambogia-based products and shedding light on the mechanisms involved. The suspected hepatotoxic reactions related to G. cambogia-containing products collected within the Italian Phytovigilance System (IPS) were examined. Then, an in vitro study was performed to evaluate the possible mechanisms responsible for the liver toxicity, focusing on the modulation of oxidative stress and Nrf2 expression. From March 2002 to March 2022, the IPS collected eight reports of hepatic adverse reactions related to G. cambogia, which exclusively involved women and were mostly severe. The causality assessment was probable in three cases, while it was possible in five. In the in vitro experiments, a low cytotoxicity of G. cambogia was observed. However, its combination with montelukast greatly reduced cell viability, increased the intracellular ROS levels, and affected the cytoplasmic Nrf2 expression, thus suggesting an impairment of the antioxidant and cytoprotective defenses. Overall, our results support the safety concerns about G. cambogia-containing supplements and shed light on the possible mechanisms underpinning its hepatotoxicity.

Garcinol acts as a novel integrin αIIbβ3 inhibitor in human platelets

AIMS

Platelet activation plays a central role in arterial thrombosis. Platelets are activated by adhesive proteins (i.e., collagen) or soluble agonists (i.e., thrombin), the respective receptor-specific signaling cause inside-out signaling, leading to the binding of fibrinogen to integrin α_IIbβ₃. This binding triggers outside-in signaling, resulting in platelet aggregation. Garcinol, a polyisoprenylated benzophenone, is extracted from the fruit rind of Garcinia indica. Although garcinol exhibits considerable bioactivities, few studies have investigated the effect of garcinol on platelet activation.

MAIN METHODS

Aggregometry, immunoblotting, flow cytometer, confocal microscopic analysis, fibrin clot retraction, animal studies such as fluorescein-induced platelet plug formation in mesenteric microvessels, acute pulmonary thromboembolism, and tail bleeding time were performed in this study.

KEY FINDINGS

This study indicates that garcinol inhibited platelet aggregation stimulated by collagen, thrombin, arachidonic acid, and U46619. Garcinol reduced integrin α_IIbβ₃ inside-out signaling, including ATP release; cytosolic Ca²⁺ mobilization; P-selectin expression; and Syk, PLCγ2/PKC, PI3K/Akt/GSK3β, MAPKs, and NF-κB activation stimulated by collagen. Garcinol directly inhibited integrin α_IIbβ₃ activation by interfering with FITC-PAC-1 and FITC-triflavin by collagen. Additionally, garcinol affected integrin α_IIbβ₃-mediated outside-in signaling, such as decreasing platelet adhesion and the single-platelet spreading area; suppressing integrin β₃, Src, FAK, and Syk phosphorylation on immobilized fibrinogen; and inhibiting thrombin-stimulated fibrin clot retraction. Garcinol substantially reduced mortality caused by pulmonary thromboembolism and prolonged the occlusion time of thrombotic platelet plug formation without extending bleeding time in mice.

SIGNIFICANCE

This study identified that garcinol, a novel antithrombotic agent, acts as a naturally occurring integrin α_IIbβ₃ inhibitor.

Imperative and effective reversion of synovial hyperplasia and cartilage destruction in rheumatoid arthritis through multiple synergistic effects of O2 and Ca2

Abnormal synovial hyperplasia and cartilage destruction in a joint cavity are the key causes affecting the pain and disability in rheumatoid arthritis (RA) and, unfortunately, there exists no effective treatment for them. This investigation reports an effective reversion of the above pathological characteristics in RA owing to the use of a prolonged O₂/Ca²⁺-supporting phototherapy hydrogel. The performed in vitro and in vivo experiments exhibit that the prolonged O₂-supporting not only promotes the direct cell-killing effects of singlet oxygen, but also persistently blocks the pathological feedback between the abnormal proliferation of fibroblast-like synoviocyte and the local oxygen depletion. Furthermore, the Ca²⁺, which is the other decomposition product of the O₂ donor, induces mitochondrial Ca²⁺ overload and endoplasmic reticulum Ca²⁺ disorder and triggers Ca²⁺-associated apoptosis and immunogenic cell death. In addition to these multiple synergistic effects on synovial hyperplasia, the prolonged Ca²⁺ support can also induce the regeneration of cartilage in RA affected joints. The present study may thus provide an effective therapeutic strategy for the prevention and reversion of joint lesions and the accompanying arthralgia and deformity in RA.