The Cyanobacterial "Nutraceutical" Phycocyanobilin Inhibits Cysteine Protease Legumain.

The blue biliprotein phycocyanin, produced by photo-autotrophic cyanobacteria including spirulina (Arthrospira) and marketed as a natural food supplement or "nutraceutical," is reported to have anti-inflammatory, antioxidant, immunomodulatory, and anticancer activity. These diverse biological activities have been specifically attributed to the phycocyanin chromophore, phycocyanobilin (PCB). However, the mechanism of action of PCB and the molecular targets responsible for the beneficial properties of PCB are not well understood. We have developed a procedure to rapidly cleave the PCB pigment from phycocyanin by ethanolysis and then characterized it as an electrophilic natural product that interacts covalently with thiol nucleophiles but lacks any appreciable cytotoxicity or antibacterial activity against common pathogens and gut microbes. We then designed alkyne-bearing PCB probes for use in chemical proteomics target deconvolution studies. Target identification and validation revealed the cysteine protease legumain (also known as asparaginyl endopeptidase, AEP) to be a target of PCB. Inhibition of this target may account for PCB's diverse reported biological activities.

Nutraceutical and therapeutic potential of Phycocyanobilin for treating Alzheimer's disease.

Alzheimer's disease (AD) is a devastating neurodegenerative condition provoking the loss of cognitive and memory performances. Despite huge efforts to develop effective AD therapies, there is still no cure for this neurological condition. Here, we review the main biological properties of Phycocyanobilin (PCB), accounting for its potential uses against AD. PCB, given individually or released in vivo from C-Phycocyanin (C-PC), acts as a bioactive-molecule-mediating antioxidant, is anti-inflammatory and has immunomodulatory activities. PCB/C-PC are able to scavenge reactive oxygen and nitrogen species, to counteract lipid peroxidation and to inhibit enzymes such as NADPH oxidase and COX-2. In animal models of multiple sclerosis and ischemic stroke, these compounds induce remyelination as demonstrated by electron microscopy and the expression of genes such as Mal up-regulation of and Lingo-1 down-regulation. These treatments also reduce pro-inflammatory cytokines levels and induce immune suppressive genes. PCB/C-PC protects isolated rat brain mitochondria and inactivate microglia, astrocytes and neuronal apoptosis mediators. Such processes are all involved in the pathogenic cascade of AD, and thus PCB may effectively mitigate the injury in this condition. Furthermore, PCB can be administered safely by oral or parenteral routes and therefore, could be commercially offered as a nutraceutical supplement or as a pharmaceutical drug.

Co-administration of Phycocyanobilin and/or Phase 2-Inducer Nutraceuticals for Prevention of Opiate Tolerance.

Chronic use of opiates for control of chronic pain is complicated by the development of tolerance and hyperalgesia, and hence usually entails dose escalation and diminished efficacy. Our evolving understanding of the mechanisms mediating induction of morphine tolerance may enable discovery of adjunct measures which can prevent this tolerance; this essay proposes that certain nutraceuticals may have utility in this regard. Considerable evidence now points to an obligate role for production of peroxynitrite and other oxidants in the dorsal horn in development of morphine tolerance. Various isoforms of NADPH oxidase are the chief source of the superoxide which gives rise to these oxidants. Since heme oxygenase, via its products bilirubin and carbon monoxide, functions as a physiological inhibitor of various isoforms of NADPH oxidase, phase 2-inducing nutraceuticals with blood brain-barrier permeability such as lipoic acid, an effective inducer of heme oxygenase-1, may have potential for prevention of morphine tolerance; indeed, this has been demonstrated in a mouse study. The phycocyanobilin (PhyCB) chromophore of spirulina, a structural analog of biliverdin, shares bilirubin's ability to inhibit NAPDH oxidase complexes; hence, administration of spirulina or of PhyCB-enriched spirulina extracts merits evaluation in rodent models of morphine tolerance. Uric acid quenches peroxynitrite-derived radicals, and its plasma level can be boosting via supplementation with inosine; indeed, administration of inosine has been shown to counteract development of hyperalgesia in rodents. If practical doses of these agents can be shown to prevent morphine tolerance and hyperalgesia in rodents, their use as adjuvants to clinical opiate therapy should be assessed.

Oxygen radical absorbance capacity of phycocyanin and phycocyanobilin from the food supplement Aphanizomenon flos-aquae.

The oxygen radical absorbance capacity (ORAC) assay has been widely used to quantify peroxyl radical scavenging capacity of pure antioxidant compounds and antioxidant plant/food extracts. However, it has never been applied to natural compounds derived from microalgae-based dietary supplements, namely, phycocyanin (PC) and phycocyanobilin (PCB), for which a strong radical scavenger activity has been documented. In this article, we applied the ORAC method to investigate the capacity of PC and PCB purified from the edible microalga Aphanizomenon flos-aquae to directly quench peroxyl radicals in comparison to well-known antioxidants molecules such as Trolox, ascorbic acid, and reduced glutathione. As a result, PCB was found to have the highest ORAC value (22.18 micromol of Trolox/micromol of compound), comparable to that of PC (20.33 micromol of Trolox/micromol of compound), hence confirming that PCB is mostly responsible for the scavenger activity of PC and making the protein a possible source of the antioxidant in vivo. Our data further corroborate the use of these natural compounds from A. flos-aquae as dietary antioxidant supplements in the treatment of clinical conditions related to oxidative stress.