Khushwant S. Bhullar

Polyphenols: Multipotent Therapeutic Agents in Neurodegenerative Diseases

Aging leads to numerous transitions in brain physiology including synaptic dysfunction and disturbances in cognition and memory. With a few clinically relevant drugs, a substantial portion of aging population at risk for age-related neurodegenerative disorders require nutritional intervention. Dietary intake of polyphenols is known to attenuate oxidative stress and reduce the risk for related neurodegenerative diseases such as Alzheimers disease (AD), stroke, multiple sclerosis (MS), Parkinsons disease (PD), and Huntingtons disease (HD). Polyphenols exhibit strong potential to address the etiology of neurological disorders as they attenuate their complex physiology by modulating several therapeutic targets at once. Firstly, we review the advances in the therapeutic role of polyphenols in cell and animal models of AD, PD, MS, and HD and activation of drug targets for controlling pathological manifestations. Secondly, we present principle pathways in which polyphenol intake translates into therapeutic outcomes. In particular, signaling pathways like PPAR, Nrf2, STAT, HIF, and MAPK along with modulation of immune response by polyphenols are discussed. Although current polyphenol researches have limited impact on clinical practice, they have strong evidence and testable hypothesis to contribute clinical advances and drug discovery towards age-related neurological disorders.

Lifespan and healthspan extension by resveratrol

A number of small molecules with the ability to extend the lifespan of multiple organisms have recently been discovered. Resveratrol, amongst the most prominent of these, has gained widespread attention due to its ability to extend the lifespan of yeast, worms, and flies, and its ability to protect against age-related diseases such as cancer, Alzheimers, and diabetes in mammals. In this review, we discuss the origins and molecular targets of resveratrol and provide an overview of its effects on the lifespan of simple model organisms and mammals. We also examine the unique ability of resveratrol to extend the healthy years, or healthspan, of mammals and its potential to counteract the symptoms of age-related disease. Finally, we explore the many scientific, medical, and economic challenges faced when translating these findings to the clinic, and examine potential approaches for realizing the possibility of human lifespan extension. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

Curcumin and its carbocyclic analogs: structure-activity in relation to antioxidant and selected biological properties.

Curcumin is the major phenolic compound present in turmeric (Curcuma longa L.). Curcumin and 15 novel analogs were investigated for their antioxidant and selected biological activities. Strong relationships between the structure and evaluated activity revealed that the compounds with specific functional groups and carbon skeleton had specific biological profiles. Among the compounds tested, the derivatives (E)-2-(3,4-dimethoxybenzylidene)-5-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclopentanone (3e), and (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)-cyclopentanone (3d) and the parent compound curcumin exhibited the strongest free radical scavenging and antioxidant capacity. Concerning the other biological activities studied the compound (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxy-phenyl)-acryloyl)cyclopentanone (3d) was the most potent angiotensin converting enzyme (ACE) inhibitor, while the derivatives (E)-2-(4-hydroxybenzylidene)-6-((E)-3-(4-hydroxyphenyl)acryloyl)cyclohexanone (2b), (E)-2-(3,4-dimethoxybenzylidene)-6-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclohexanone (2e) and (E)-2-(3,4-dimethoxybenzylidene)-5-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclopentanone (3e) exhibited strong tyrosinase inhibition. Moreover, (E)-2-(3,4-dimethoxybenzylidene)-6-((E)-3-(3,4-dimethoxyphenyl)-acryloyl)cyclohexanone (2e) was also found to be the strongest human HIV-1 protease inhibitor in vitro among the tested compounds. Cytotoxicity studies using normal human lung cells revealed that the novel curcumin as well as its carbocyclic analogs are not toxic.

Biocatalytic synthesis, structural elucidation, antioxidant capacity and tyrosinase inhibition activity of long chain fatty acid acylated derivatives of phloridzin and isoquercitrin

Our present investigation describes the regioselective enzymatic acylation of two series of acylated derivatives of phloridzin and isoquercitrin with six different long chain saturated, mono- and poly-unsaturated fatty acids. The biocatalytic synthesis was optimized to achieve 81-98% yields, using immobilized lipase B, from Candida antarctica (Novozym 435), in acetone at 45°C. The synthesized esters have been analyzed by (1)H NMR, (13)C NMR spectroscopy and evaluated for their antioxidant capacity and tyrosinase inhibition, using in vitro assays. Among all the phloridzin and isoquercitrin derivatives, the greatest potential for inhibition of tyrosinase activity (p ≤ 0.05) was exhibited by the α-linolenic acid ester of isoquercitrin.

Antioxidant and cytoprotective properties of partridgeberry polyphenols.

Partridgeberry (Vaccinium vitis-idaea) is a polyphenol-rich berry of the Ericaceous family, grown in Newfoundland and Labrador province of Canada. The aims of this study were to identify extraction solvents for the maximum recovery of polyphenols, to establish fractionation technique for isolation of major sub-classes of polyphenols, and to evaluate antioxidant and cytoprotective properties of the partridgeberry polyphenol preparations. The acidified 70% acetone was identified as the ideal solvent for the maximum recovery of polyphenols from partridgeberry. Further, aqueous two-phase extraction, column chromatography and UPLC-MS/MS were employed to produce three partridgeberry polyphenol fractions, rich in either, anthocyanins, flavan-3-ols or flavonols. All the three PPF were potent antioxidants and displayed cytoprotective activity through the activation of nuclear factor erythroid 2-related factor 2 pathway, scavenging of reactive oxygen species, and inhibition of cellular death. The current study suggests that partridgeberry has numerous potential health implications in both prevention and amelioration of various diseases involving oxidative stress.

Antihypertensive effect of caffeic acid and its analogs through dual renin-angiotensin-aldosterone system inhibition.

Hypertension is a crucial risk factor for cardiovascular diseases and contributes to one third of global mortality. In addition to conventional antihypertensive drugs such as captopril, naturally occurring phytochemicals and their analogs are used for reducing the risk and occurrence of hypertension. Herein, we demonstrate the possible use of caffeic acid and its derivatives in the treatment of hypertension through multi-target modulation of renin-angiotensin-aldosterone system (RAAS). Caffeic acid along with its nineteen novel derivatives, chlorogenic acid, quercetin and captopril were all investigated for the inhibition of renin and angiotensin converting enzyme (ACE) activities and production of aldosterone. Compound 22 with CH2CH(Ph)2 moiety exhibited the strongest renin inhibition (IC50=229µM) among all compounds tested (P≤0.05). Caffeic acid was the weakest renin inhibitor (IC50=5704µM) among all the compounds assayed. Similar to renin inhibition, compound 22 (IC50=9.1µM) also exhibited about 47 times stronger ACE inhibition compared to the parent compound. Analysis of aldosterone revealed that compound 8 with n-Pr moiety was the strongest modulator of aldosterone production among all the derivatives (P≤0.05). Toxicity analysis using human fibroblasts (WI-38 cells) confirmed the non-toxic manifestations of caffeic acid and its derivatives in comparison to clinically used drug captopril.

Novel carbocyclic curcumin analog CUR3d modulates genes involved in multiple apoptosis pathways in human hepatocellular carcinoma cells.

Anticancer activity of a novel curcumin analog (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)cyclopentanone (CUR3d) was studied using a human hepatocellular carcinoma cell line (HepG2). The results showed that CUR3d completely inhibits the tumor cell proliferation in a dose- and time-dependent manner. CUR3d at 100 μmol/L activated the pro-apoptotic caspase-3 along with downregulation of anti-apoptotic BIRC5 and Bcl2. CUR3d treatment controlled the cancer cell growth by downregulating the expression of PI3K/Akt (Akt1, Akt2) pathway along with NF-κB. CUR3d down-regulated the members of epidermal growth receptor family (EGFR, ERBB3, ERBB2) and insulin like growth receptors (IGF1, IGF-1R, IGF2). This correlated with the downregulation of G-protein (RHOA, RHOB) and RAS (ATF2, HRAS, KRAS, NRAS) pathway signaling. CUR3d also arrested cell cycle via inhibition of CDK2, CDK4, CDK5, CDK9, MDM2, MDM4 and TERT genes. Cell cycle essential aurora kinases (AURKα, AURKβ) and polo-like kinases (PLK1, PLK2, PLK3) were also modulated by CUR3d. Topoisomerases (TOP2α, TOP2β), important factors in cancer cell immortality, as well as HIF-1α were downregulated following CUR3d treatment. The expression of protein kinase-C family (PRKC-A, PRKC-D, PRKC-E) was also attenuated by CUR3d. The downregulation of histone deacetylases (Class I, II, IV) and PARP I further strengthened the anticancer efficacy of CUR3d. Downregulation of carcinogenic cathepsins (CTSB, CTSD) and heat shock proteins exhibited CUR3ds potency as a potential immunological adjuvant. Finally, the non-toxic manifestation of CUR3d in healthy liver and lung cells along with downregulation of drug resistant gene ABCC1 further warrant need for advance investigations.

All trans 1-(3-arylacryloyl)-3,5-bis(pyridin-4-ylmethylene)piperidin-4-ones as curcumin-inspired antineoplastics

A series of eleven N-acryloyl/N-cinnamoyl 3,5-bis(pyridin-4-yl)methylene-4-piperidones were synthesized as curcumin-based candidate antineoplastic agents. The cytostatic potency of these compounds was evaluated against three representative cell lines and all compounds were found to exhibit significant anti-cancer cell activity in vitro. QSAR studies using several physicochemical parameters and 50% inhibitory concentration (IC50) values resulted in certain important correlations which will aid design of more potent analogs. Representative test compounds were investigated in the NCI 60-cell line panel where they were found to display a profound cytotoxicity. These compounds were also potent anti-oxidants and inhibitors of human topoisomerase IIα. Representative compounds were well-tolerated by human fibroblasts and by mice during the survival/toxicity studies.

Partridgeberry polyphenols protect primary cortical and hippocampal neurons against β-amyloid toxicity

β-Amyloid (Aβ) deposition elicits a toxic effect on neurons and plays a crucial role in the etiology and/or progression of Alzheimers disease (AD). Polyphenols found in fruits are endorsed for nutritional intervention in AD, since they are known to have extensive therapeutic properties apropos of brain health owing to their anti-oxidative effects against Aβ and neural reactive oxygen species (ROS). The present study was aimed to investigate the neuroprotective potential of polyphenols of partridgeberry (Vaccinium vitis-idaea L.) and elucidate the mechanism by which they confer protection against Aβ toxicity in rat primary neurons in vitro. The pre-treatment of rat primary cortical and hippocampal neurons with partridgeberry polyphenols (10-200μgmL-1) significantly attenuated Aβ-induced cell death and membrane damage. The flavan-3-ol- and flavonol-rich fractions of the partridgeberry exhibited the strongest ability to maintain cell viability (EC50 5.9μgmL-1) and prevent lactose dehydrogenase release (IC50 0.01μgmL-1) (P≤0.05). Similar to the maintenance of cellular viability, the flavan-3-ol- and flavonol-rich fractions also amplified the greatest activity of SOD and catalase among all polyphenol preparations exposed to neurons (P≤0.05). All four partridgeberry polyphenol preparations reduced the intracellular Aβ levels by 7-15 folds, and initiated Aβ clearance from neurons as compared to untreated cells (P≤0.05). Partridgeberry derived polyphenol preparations; especially the flavonol-rich fraction (IC50 97.1μgmL-1) significantly modulated the apoptotic targets and in vitro acetylcholinesterase activity (P≤0.05), indicating potential pharmacotherapy application in AD. Furthermore, the restoration of hyperactive caspases and Bcl2 family of apoptotic architects added to the neuroprotective candidacy of PPFs. These findings suggest that partridgeberry polyphenols, especially flavan-3-ol- and flavonol-rich fractions, could be of importance in prevention and/or treatment of AD.

Kinase-targeted cancer therapies: progress, challenges and future directions

The human genome encodes 538 protein kinases that transfer a γ-phosphate group from ATP to serine, threonine, or tyrosine residues. Many of these kinases are associated with human cancer initiation and progression. The recent development of small-molecule kinase inhibitors for the treatment of diverse types of cancer has proven successful in clinical therapy. Significantly, protein kinases are the second most targeted group of drug targets, after the G-protein-coupled receptors. Since the development of the first protein kinase inhibitor, in the early 1980s, 37 kinase inhibitors have received FDA approval for treatment of malignancies such as breast and lung cancer. Furthermore, about 150 kinase-targeted drugs are in clinical phase trials, and many kinase-specific inhibitors are in the preclinical stage of drug development. Nevertheless, many factors confound the clinical efficacy of these molecules. Specific tumor genetics, tumor microenvironment, drug resistance, and pharmacogenomics determine how useful a compound will be in the treatment of a given cancer. This review provides an overview of kinase-targeted drug discovery and development in relation to oncology and highlights the challenges and future potential for kinase-targeted cancer therapies.