Suppressive effects of aloin on polyphosphate-mediated vascular inflammatory responses

New opportunities and perspectives on biosynthesis and bioactivities of secondary metabolites from Aloe vera

Historically, the genus Aloe has been an indispensable part of both traditional and modern medicine. Decades of intensive research have unveiled the major bioactive secondary metabolites of this plant. Recent pandemic outbreaks have revitalized curiosity in aloe metabolites, as they have proven pharmacokinetic profiles and repurposable chemical space. However, the structural complexity of these metabolites has hindered scientific advances in the chemical synthesis of these compounds. Multi-omics research interventions have transformed aloe research by providing insights into the biosynthesis of many of these compounds, for example, aloesone, aloenin, noreugenin, aloin, saponins, and carotenoids. Here, we summarize the biological activities of major aloe secondary metabolites with a focus on their mechanism of action. We also highlight the recent advances in decoding the aloe metabolite biosynthetic pathways and enzymatic machinery linked with these pathways. Proof-of-concept studies on in vitro, whole-cell, and microbial synthesis of aloe compounds have also been briefed. Research initiatives on the structural modification of various aloe metabolites to expand their chemical space and activity are detailed. Further, the technological limitations, patent status, and prospects of aloe secondary metabolites in biomedicine have been discussed.

Polyphosphate as an antithrombotic target and hemostatic agent

Polyphosphate (PolyP) is a polymer comprised of linear phosphate units connected by phosphate anhydride bonds. PolyP exists in a diverse range of eukaryotes and prokaryotes with varied chain lengths ranging from six to thousands of phosphate units. Upon activation, human platelets and neutrophils release short-chain PolyP, along with other components, to initiate the coagulation pathway. Long-chain PolyP derived from cellular or bacterial organelles exhibits higher proinflammatory and procoagulant effects compared to short-chain PolyP. Notably, PolyP has been identified as a low-hemorrhagic antithrombotic target since neutralizing plasma PolyP suppresses the thrombotic process without impairing the hemostatic functions. As an inorganic polymer without uniform steric configuration, PolyP is typically targeted by cationic polymers or recombinant polyphosphatases rather than conventional antibodies, small-molecule compounds, or peptides. Additionally, because of its procoagulant property, PolyP has been incorporated in wound-dressing materials to facilitate blood hemostasis. This review summarizes current studies on PolyP as a low-hemorrhagic antithrombotic target and the development of hemostatic materials based on PolyP.

The potential health benefits of aloin from genus Aloe

The Aloe species is known for its medicinal and cosmetic properties. Aloin is an active ingredient found in the leaves of medicinal plants of the genus Aloe. Aloin has attracted considerable interest for its antiinflammatory, anticancer, antibacterial, and antioxidant activities. However, since its clinical application is restricted by its unclear mechanism of action, a deeper understanding of its pharmacological activity is required. This review provides an overview of current pharmacological and toxicological studies published in English from February 2000 to August 2021. Herein, we summarized the sources and potential health benefits of aloin from a clinical application perspective to guide for further studies on the sources of aloin, aimed at efficiently increasing aloin production. Importantly, the function and mechanism of action of aloin remain unclarified. In future research, it is necessary to develop new approaches for studying the pharmacological molecular mechanisms underlying the activity of this compound against various diseases.

[Aloin inhibits lactate-induced proliferation and migration of gastric cancer cells by downregulating HMGB1 expression]

OBJECTIVE

To assess the inhibitory effects of aloin on lactate-induced gastric proliferation and migration of cancer cells and explore the underlying molecular mechanism.

METHODS

Gastric cancer BGC-823 cells were treated with aloin, lactate or the combination of lactate and different doses of aloin. EdU assay was used to detect the proliferation of BGC-823 cells, and colony formation ability of the cells was evaluated with colony forming assay; wound healing and Transwell assays were used to detect the changes in migration ability of the treated cells. The expression levels of cyclin D1, cyclin E1, PCNA, N-cadherin, E-cadherin, MMP-2, MMP-9 and HMGB1 were determined using Western blotting, and ELISA was performed to detect HMGB1 release. HMGB1 expression was knocked down in BGC-823 cells using RNA interference technique, and the effects of HMGB1 knockdown on proliferation and migration of the cells stimulated with lactate for 24 h were examined using EdU and wound healing assays.

RESULTS

Aloin treatment significantly inhibited lactate-induced proliferation of gastric cancer cells, lowered the colony forming ability of lactate-treated cells, and suppressed lactate-induced migration of the cells. Treatment with lactate obviously up-regulated the expressions of cyclin D1, cyclin E1, PCNA, N-cadherin, MMP-2, MMP-9 and HMGB1, which were significantly inhibited by aloin; aloin significantly reversed inhibition of E-cadherin and blocked the release of HMGB1 in lactate-treated cells. BGC-823 cells with HMGB1 knockdown, as compared with the cells transfected with the negative control plasmid, showed significantly lowered proliferation and migration abilities following lactate treatment.

CONCLUSION

Aloin inhibits lactate-induced proliferation and migration of gastric cancer cells by down-regulating the expression and release of HMGB1 and the expressions of proliferation- and migration-related proteins.

Molecular mechanisms and associated cell signalling pathways underlying the anticancer properties of phytochemical compounds from Aloe species (Review)

Naturally occurring components from various species of Aloe have been used as traditional folk medicine since the ancient times. Over the last few decades, the therapeutic effects of extracts and phytochemical compounds obtained from Aloe vera have been proven in preclinical and clinical studies. Recently, compounds from other Aloe species apart from Aloe vera have been investigated for the treatment of different diseases, with a particular focus on cancer. In the present review, the effects of phytochemical compounds obtained from different Aloe species are discussed, with a specific focus on the effects on cell signalling in cancer and normal cells, and their selectivity and efficacy. This information will be useful for the application of Aloe-derived compounds as therapeutic agents, either alone or in combination with other standard drugs for cancer treatment.