A novel apoptosis-like pathway, independent of mitochondria and caspases, induced by curcumin in human lymphoblastoid T (Jurkat) cells

Apoptotic bodies: bioactive treasure left behind by the dying cells with robust diagnostic and therapeutic application potentials

Apoptosis, a form of programmed cell death, is essential for growth and tissue homeostasis. Apoptotic bodies (ApoBDs) are a form of extracellular vesicles (EVs) released by dying cells in the last stage of apoptosis and were previously regarded as debris of dead cells. Recent studies unraveled that ApoBDs are not cell debris but the bioactive treasure left behind by the dying cells with an important role in intercellular communications related to human health and various diseases. Defective clearance of ApoBDs and infected-cells-derived ApoBDs are possible etiology of some diseases. Therefore, it is necessary to explore the function and mechanism of the action of ApoBDs in different physiological and pathological conditions. Recent advances in ApoBDs have elucidated the immunomodulatory, virus removal, vascular protection, tissue regenerative, and disease diagnostic potential of ApoBDs. Moreover, ApoBDs can be used as drug carriers enhancing drug stability, cellular uptake, and targeted therapy efficacy. These reports from the literature indicate that ApoBDs hold promising potential for diagnosis, prognosis, and treatment of various diseases, including cancer, systemic inflammatory diseases, cardiovascular diseases, and tissue regeneration. This review summarizes the recent advances in ApoBDs-related research and discusses the role of ApoBDs in health and diseases as well as the challenges and prospects of ApoBDs-based diagnostic and therapeutic applications.

Curcumin loaded Ag-TiO2-halloysite nanotubes platform for combined chemo-photodynamic therapy treatment of cancer cells

The use of naturally occurring anticancer materials in combination with doped metal oxide has emerged as one of the most promising ways for improving anticancer treatment efficacy. In this study, the anticancer potential of curcumin-loaded Ag-TiO2-halloysite nanotubes (curcumin-loaded Ag-TiO2-HNTs) was examined. Ag-TiO2-HNTs with different wt% of Ag-TiO2 were synthesized and characterized using XRD, TGA, FT-IR, UV-Vis spectroscopy, and SEM-EDX. The XRD results revealed the presence of crystalline TiO2. However, the presence of Ag was detected through the SEM-EDX analysis. Cyclic voltammetry measurements suggested the enhancement of the release of ROS from TiO2 upon deposition with Ag. FT-IR and TGA analysis confirmed the successful loading of curcumin inside the nanotubes of the halloysite. In vitro drug released studies revealed the release of approximately 80-99% curcumin within 48 hours. Kinetic model studies revealed that the release of curcumin from HNT and Ag-TiO2-HNT followed the first-order and Higuchi models, respectively. The light irradiated curcumin-loaded Ag-TiO2-HNTs samples exhibited considerable anticancer potential as compared to the free curcumin, irradiated Ag-TiO2 NPs samples, and unirradiated curcumin loaded Ag-TiO2-HNTs samples. The obtained results revealed that combined chemo- and photodynamic therapy using curcumin-loaded Ag-TiO2-HNTs nanomaterial has the potential as an effective anticancer treatment method.

Pomegranate juice anthocyanidins induce cell death in human cancer cells by mobilizing intracellular copper ions and producing reactive oxygen species

Anthocyanidins are the most abundant polyphenols in pomegranate juice. This class of molecules includes Delphinidin (Del), Cyanidin (Cya), and Pelargonidin (Pel). Using prostate, breast and pancreatic cancer cell lines PC3, MDA-MB-231, BxPC-3 and MiaPaCa-2, we show that anthocyanidins inhibit cell proliferation (measured by MTT assay) and induce apoptosis like cell death (measured by DNA/Histone ELISA). Copper chelator neocuproine and reactive oxygen species scavengers (thiourea for hydroxyl radical and superoxide dismutase for superoxide anion) significantly inhibit this reaction thus demonstrating that intracellular copper reacts with anthocyanidins in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitizes normal breast epithelial cells (MCF-10A) to Del-mediated growth inhibition as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters Ctr1 and ATP7A in MCF-10A cells, which is attenuated by the addition of Del in the medium. We propose that the copper mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of anthocyanidins.

Immunomodulatory Effects of Herbal Compounds Quercetin and Curcumin on Cellular and Molecular Functions of Bovine-Milk-Isolated Neutrophils toward Streptococcus agalactiae Infection

Herbal phytochemicals featuring active ingredients including quercetin and curcumin have shown potential in treating human and animal diseases. The current study investigated their potential function in vitro for host immunomodulation associated with Streptococcus agalactiae subclinical bovine mastitis via milk-isolated neutrophils. Our results showed a positive influence on cellular migration, reactive oxygen species (ROS) generation, phagocytosis, and bacterial killing as well as neutrophil extracellular traps (NETs) release. This study also highlighted several important molecular aspects of quercetin and curcumin in milk-isolated neutrophils. Gene expression analyses by RT-PCR revealed significant changes in the expression of proinflammatory cytokines (IL1B, IL6, and TNF), ROS (CYBA), phagocytosis (LAMP1), and migration (RAC). The expression levels of apoptotic genes or proteins in either pro-apoptosis (CASP3 and FAS) or anti-apoptosis (BCL2, BCL2L1, and CFLAR) were significantly manipulated by the effects of either quercetin or curcumin. A principal component analysis (PCA) identified the superior benefit of quercetin supplementation for increasing both cellular and molecular functions in combating bacterial mastitis. Altogether, this study showed the existing and potential benefits of these test compounds; however, they should be explored further via in vivo studies.

Phenolic Compounds from Morus nigra Regulate Viability and Apoptosis of Pancreatic β-Cells Possibly via SERCA Activity

The ability of phenolic compounds from Morus nigra to modulate sarco-endoplasmic Ca²⁺-ATPase (SERCA1) activity was analyzed. Enzyme activity decrease correlated with the binding energy of agents to SERCA1. Results from theoretical and experimental approaches were coherent in identifying binding sites to SERCA1. Albanol A inhibited SERCA1 by immersion in the luminal gate at the site of Ca²⁺ release. Kuwanon U exerted an inhibitory effect by preventing ATP binding in the cytosolic region of SERCA1, and this was associated with conformational alterations. On the basis of similarities of SERCA isoforms, the viability of beta-cells containing SERCA2b was analyzed. Both correlation of viability and negative correlation of SERCA2b expression with SERCA1 activity were found for agents with the highest binding energy to SERCA1. The compounds studied may regulate viability and apoptosis of pancreatic beta-cells via modulation of SERCA activity. Novel pharmacological interventions in diabetes may be realized via compounds restoring ER calcium levels.

A randomized, phase 1, placebo-controlled trial of APG-157 in oral cancer demonstrates systemic absorption and an inhibitory effect on cytokines and tumor-associated microbes

BACKGROUND

Although curcumin's effect on head and neck cancer has been studied in vitro and in vivo, to the authors' knowledge its efficacy is limited by poor systemic absorption from oral administration. APG-157 is a botanical drug containing multiple polyphenols, including curcumin, developed under the US Food and Drug Administration's Botanical Drug Development, that delivers the active components to oromucosal tissues near the tumor target.

METHODS

A double-blind, randomized, placebo-controlled, phase 1 clinical trial was conducted with APG-157 in 13 normal subjects and 12 patients with oral cancer. Two doses, 100 mg or 200 mg, were delivered transorally every hour for 3 hours. Blood and saliva were collected before and 1 hour, 2 hours, 3 hours, and 24 hours after treatment. Electrocardiograms and blood tests did not demonstrate any toxicity.

RESULTS

Treatment with APG-157 resulted in circulating concentrations of curcumin and analogs peaking at 3 hours with reduced IL-1β, IL-6, and IL-8 concentrations in the salivary supernatant fluid of patients with cancer. Salivary microbial flora analysis showed a reduction in Bacteroidetes species in cancer subjects. RNA and immunofluorescence analyses of tumor tissues of a subject demonstrated increased expression of genes associated with differentiation and T-cell recruitment to the tumor microenvironment.

CONCLUSIONS

The results of the current study suggested that APG-157 could serve as a therapeutic drug in combination with immunotherapy.

LAY SUMMARY

Curcumin has been shown to suppress tumor cells because of its antioxidant and anti-inflammatory properties. However, its effectiveness has been limited by poor absorption when delivered orally. Subjects with oral cancer were given oral APG-157, a botanical drug containing multiple polyphenols, including curcumin. Curcumin was found in the blood and in tumor tissues. Inflammatory markers and Bacteroides species were found to be decreased in the saliva, and immune T cells were increased in the tumor tissue. APG-157 is absorbed well, reduces inflammation, and attracts T cells to the tumor, suggesting its potential use in combination with immunotherapy drugs.

Dietary Polyphenols and Mitochondrial Function: Role in Health and Disease

Mitochondria are cytoplasmic double-membraned organelles that are involved in a myriad of key cellular regulatory processes. The loss of mitochondrial function is related to the pathogenesis of several human diseases. Over the last decades, an increasing number of studies have shown that dietary polyphenols can regulate mitochondrial redox status, and in some cases, prevent or delay disease progression. This paper aims to review the role of four dietary polyphenols - resveratrol, curcumin, epigallocatechin-3-gallate nd quercetin - in molecular pathways regulated by mitochondria and their potential impact on human health. Cumulative evidence showed that the aforementioned polyphenols improve mitochondrial functions in different in vitro and in vivo experiments. The mechanisms underlying the polyphenols' beneficial effects include, among others, the attenuation of oxidative stress, the regulation of mitochondrial metabolism and biogenesis and the modulation of cell-death signaling cascades, among other mitochondrial-independent effects. The understanding of the chemicalbiological interactions of dietary polyphenols, namely with mitochondria, may have a huge impact on the treatment of mitochondrial dysfunction-related disorders.

The Role of Curcumin in the Modulation of Ageing

It is believed that postponing ageing is more effective and less expensive than the treatment of particular age-related diseases. Compounds which could delay symptoms of ageing, especially natural products present in a daily diet, are intensively studied. One of them is curcumin. It causes the elongation of the lifespan of model organisms, alleviates ageing symptoms and postpones the progression of age-related diseases in which cellular senescence is directly involved. It has been demonstrated that the elimination of senescent cells significantly improves the quality of life of mice. There is a continuous search for compounds, named senolytic drugs, that selectively eliminate senescent cells from organisms. In this paper, we endeavor to review the current knowledge about the anti-ageing role of curcumin and discuss its senolytic potential.

Microfluidic Assisted Nanoprecipitation of PLGA Nanoparticles for Curcumin Delivery to Leukemia Jurkat Cells

The ability to control particle size and size distribution of nanoparticles for drug delivery is essential because it impacts on the biodistribution and cellular uptake of nanoparticles. We present a novel microfluidic assisted nanoprecipitation strategy that enables synthesis of surfactant-free curcumin encapsulated poly(lactide- co-glycolide) nanoparticles (Cur-PLGA NP) with adjustable particle diameters (30-70 nm) and narrow particle size distribution (polydispersity index less than 0.2). Our Cur-PLGA NP exhibit excellent colloidal stability and inhibit degradation of curcumin. We further demonstrate the potential of our Cur-PLGA NP as a nanotoxic delivery system for curcumin. Cellular viability assay validates a dose-dependent cytotoxicity of Cur-PLGA NP in leukemia Jurkat cells. In contrast, Cur-PLGA NP does not alter the viability of fibroblast NIH3T3 cells, which suggests that the cytotoxicity of Cur-PLGA NP is specific to cell types. Furthermore, there is no detectable effect by PLGA NP to both leukemia Jurkat cells and fibroblast NIH3T3 cells, highlighting the nontoxic nature of our delivery system. Confocal cell uptake studies indicate that PLGA NP do not alter the cell uptake of curcumin. Our microfluidic assisted approach offers a controlled and effective nanobiomaterials synthesis of drug delivery system for curcumin, which can be extended to different capsule materials for a variety of biomedical applications.

Cucurmin, anticancer, & antitumor perspectives: A comprehensive review

Cucurmin, a naturally yellow component isolated from turmeric, ability to prevent various life-style related disorders. The current review article mainly emphasizes on different anticancer perspectives of cucurmin, i.e., colon, cervical, uterine, ovarian, prostate head and neck, breast, pulmonary, stomach and gastric, pancreatic, bladder oral, oesophageal, and bone cancer. It holds a mixture of strong bioactive molecule known as cucurminoids that has ability to reduce cancer/tumor at initial, promotion and progression stages of tumor development. In particular, these compounds block several enzymes required for the growth of tumors and may therefore involve in tumor treatments. Moreover, it modulates an array of cellular progressions, i.e., nitric oxide synthetase activity, protein kinase C activity, epidermal growth factor (EGF) receptor intrinsic kinase activity, nuclear factor kappa (NF-kB) activity, inhibiting lipid peroxidation and production of reactive oxygen species. However, current manuscript summarizes most of the recent investigations of cucurmin but still further research should be conducted to explore the role of curcumin to mitigate various cancers.

Pycnogenol Cytotoxicity in Pancreatic INS-1E β cells Induced by Calcium Dysregulation

Natural standardized flavonoid extract from the bark of Pinus pinaster, Pycnogenol (Pyc), was recently found to decrease intensively the activity of sarcoplasmic reticulum Ca²⁺ -ATPase of rabbit skeletal muscle (SERCA1). On the basis of this inhibitory effect in a cell-free system and similarities of SERCA1 to its other isoforms, proapoptotic properties of Pyc may be expected in cellular systems. Pycnogenol (40-100 μg/mL) induced a concentration-dependent decrease of the viability of pancreatic INS-1E β cells associated with induction of apoptosis. In addition, intracellular Ca²⁺ level increase was found along with reduction of protein expression level of SERCA2b and impairment of insulin secretion by β cells. These facts indicate that Pyc may induce apoptosis by impairment of calcium homeostasis. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis and biological assessment of novel N-(hydroxy/methoxy)alkyl β-enaminone curcuminoids

Curcumin, a natural compound extracted from the rhizomes of Curcuma Longa, is known to display pronounced anticancer activity but lacks good pharmacokinetic properties. In that respect, augmenting the water solubility by structural modification of the curcumin scaffold may result in improved bioavailability and pharmacokinetics. A possible scaffold modification, especially important for this study, concerns the imination of the labile β-diketone moiety in curcumin. Previous work revealed that novel N-alkyl β-enaminones showed a similar water solubility as compared to curcumin, accompanied by a stronger anti-proliferative activity. To extend this β-enaminone compound library, new analogues were prepared in this work using more polar amines (hydroxyalkylamines and methoxyalkylamines instead of alkylamines) with the main purpose to improve the water solubility without compromising the biological activity of the resulting curcuminoids. Compared to their respective parent compounds, i.e. curcumin and bisdemethoxycurcumin, the bisdemethoxycurcumin N-(hydroxy/methoxy)alkyl enaminone analogues showed better water solubility, antioxidant and anti-proliferative activities. In addition, the curcumin enaminones displayed activities comparable to or better than curcumin, and the water solubility was improved significantly. The constructed new analogues may thus be of interest for further exploration concerning their impact on oxidative stress related diseases such as cancer.

Mobilization of Intracellular Copper by Gossypol and Apogossypolone Leads to Reactive Oxygen Species-Mediated Cell Death: Putative Anticancer Mechanism

There is compelling evidence that serum, tissue and intracellular levels of copper are elevated in all types of cancer. Copper has been suggested as an important co-factor for angiogenesis. It is also a major metal ion present inside the nucleus, bound to DNA bases, particularly guanine. We have earlier proposed that the interaction of phenolic-antioxidants with intracellular copper leads to the generation of reactive oxygen species (ROS) that ultimately serve as DNA cleaving agents. To further validate our hypothesis we show here that the antioxidant gossypol and its semi-synthetic derivative apogossypolone induce copper-mediated apoptosis in breast MDA-MB-231, prostate PC3 and pancreatic BxPC-3 cancer cells, through the generation of ROS. MCF10A breast epithelial cells refractory to the cytotoxic property of these compounds become sensitized to treatment against gossypol, as well as apogossypolone, when pre-incubated with copper. Our present results confirm our earlier findings and strengthen our hypothesis that plant-derived antioxidants mobilize intracellular copper instigating ROS-mediated cellular DNA breakage. As cancer cells exist under significant oxidative stress, this increase in ROS-stress to cytotoxic levels could be a successful anticancer approach.

Albumin–polymer conjugate nanoparticles and their interactions with prostate cancer cells in 2D and 3D culture: comparison between PMMA and PCL

Using proteins as the hydrophilic moiety can dramatically improve the biodegradability and biocompatibility of self-assembled amphiphilic nanoparticles in the field of nanomedicine.

Redox cycling of endogenous copper by ferulic acid leads to cellular DNA breakage and consequent cell death: A putative cancer chemotherapy mechanism

Ferulic acid (FA) is a plant polyphenol showing diverse therapeutic effects against cancer, diabetes, cardiovascular and neurodegenerative diseases. FA is a known antioxidant at lower concentrations, however at higher concentrations or in the presence of metal ions such as copper, it may act as a pro-oxidant. It has been reported that copper levels are significantly raised in different malignancies. Cancer cells are under increased oxidative stress as compared to normal cells. Certain therapeutic substances like polyphenols can further increase this oxidative stress and kill cancer cells without affecting the proliferation of normal cells. Through various in vitro experiments we have shown that the pro-oxidant properties of FA are enhanced in the presence of copper. Comet assay demonstrated the ability of FA to cause oxidative DNA breakage in human peripheral lymphocytes which was ameliorated by specific copper-chelating agent such as neocuproine and scavengers of ROS. This suggested the mobilization of endogenous copper in ROS generation and consequent DNA damage. These results were further validated through cytotoxicity experiments involving different cell lines. Thus, we conclude that such a pro-oxidant mechanism involving endogenous copper better explains the anticancer activities of FA. This would be an alternate non-enzymatic, and copper-mediated pathway for the cytotoxic activities of FA where it can selectively target cancer cells with elevated levels of copper and ROS.

Plant polyphenol induced cell death in human cancer cells involves mobilization of intracellular copper ions and reactive oxygen species generation: a mechanism for cancer chemopreventive action

SCOPE

Anticancer polyphenolic nutraceuticals from fruits, vegetables, and spices are generally recognized as antioxidants, but can be prooxidants in the presence of copper ions. We earlier proposed a mechanism for such activity of polyphenols and now we provide data in multiple cancer cell lines in support of our hypothesis.

METHODS AND RESULTS

Through multiple assays, we show that polyphenols luteolin, apigenin, epigallocatechin-3-gallate, and resveratrol are able to inhibit cell proliferation and induce apoptosis in different cancer cell lines. Such cell death is prevented to a significant extent by cuprous chelator neocuproine and reactive oxygen species scavengers. We also show that normal breast epithelial cells, cultured in a medium supplemented with copper, become sensitized to polyphenol-induced growth inhibition.

CONCLUSION

Since the concentration of copper is significantly elevated in cancer cells, our results strengthen the idea that an important anticancer mechanism of plant polyphenols is mediated through intracellular copper mobilization and reactive oxygen species generation leading to cancer cell death. Moreover, this prooxidant chemopreventive mechanism appears to be a mechanism common to several polyphenols with diverse chemical structures and explains the preferential cytotoxicity of these compounds toward cancer cells.

Curcuminoid binding to embryonal carcinoma cells: reductive metabolism, induction of apoptosis, senescence, and inhibition of cell proliferation

Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4–6 days to either preparation in cell culture media reduced cell division (1–5 µM), induced senescence (6–7 µM) or comprehensive cell death (8–10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5–4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6–10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways.

Curcumin-induced autophagy contributes to the decreased survival of oral cancer cells

Curcumin, a major active component of turmeric Curcuma longa, has been shown to have inhibitory effects on cancers. In vitro studies suggest that curcumin inhibits cancer cell growth by activating apoptosis, but the mechanism underlying the anticancer effects of curcumin is unclear. Recently, it has been suggested that autophagy may play an important role in cancer therapy. However, little data are available regarding the role of autophagy in oral cancers. In this study, we have shown that curcumin has anticancer activity against oral squamous cell carcinoma (OSCC). Induction of autophagy, marked by autophagic vacuoles formation, was detected by acridine orange staining and monodansylcadaverine (MDC) dye after exposure to curcumin. Conversion of LC3-I to LC3-II, a marker of active autophagosome formation, was also detectable by Western blot following curcumin treatment. We have also observed that curcumin induced reactive oxygen species (ROS) production and autophagic vacuoles formation by curcumin was almost completely blocked in the presence of N-acetylcystein (NAC), an antioxidant. Rescue experiments using an autophagy inhibitor suppressed curcumin-induced cell death in OSCC, confirming that autophagy acts as a pro-death signal. Furthermore, curcumin shows anticancer activity against OSCC via both autophagy and apoptosis. These findings suggest that curcumin may potentially contribute to oral cancer treatment and provide useful information for the development of a new therapeutic agent.

Curcumin affects cell survival and cell volume regulation in human renal and intestinal cells

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1E,6E-heptadiene-3,5-dione or diferuloyl methane) is a polyphenol derived from the Curcuma longa plant, commonly known as turmeric. This substance has been used extensively in Ayurvedic medicine for centuries for its anti-oxidant, analgesic, anti-inflammatory and antiseptic activity. More recently curcumin has been found to possess anti-cancer properties linked to its pro-apoptotic and anti-proliferative actions. The underlying mechanisms of these diverse effects are complex, not fully elucidated and subject of intense scientific debate. Despite increasing evidence indicating that different cation channels can be a molecular target for curcumin, very little is known about the effect of curcumin on chloride channels. Since, (i) the molecular structure of curcumin indicates that the substance could potentially interact with chloride channels, (ii) chloride channels play a role during the apoptotic process and regulation of the cell volume, and (iii) apoptosis is a well known effect of curcumin, we set out to investigate whether or not curcumin could (i) exert a modulatory effect (direct or indirect) on the swelling activated chloride current ICl(swell) in a human cell system, therefore (ii) affect cell volume regulation and (iii) ultimately modulate cell survival. The ICl(swell) channels, which are essential for regulating the cell volume after swelling, are also known to be activated under isotonic conditions as an early event in the apoptotic process. Here we show that long-term exposure of a human kidney cell line to extracellular 0.1-10 μM curcumin modulates ICl(swell) in a dose-dependent manner (0.1 μM curcumin is ineffective, 0.5-5.0 μM curcumin increase, while 10 μM curcumin decrease the current), and short-term exposure to micromolar concentrations of curcumin does not affect ICl(swell) neither if applied from the extracellular nor from the intracellular side - therefore, a direct effect of curcumin on ICl(swell) can be ruled out. Furthermore, we show that curcumin exposure induces apoptosis in human kidney cells, and at a concentration of 5.0-10 μM induces the appearance of a sub-population of cells with a dramatically increased volume. In these cells the regulation of the cell volume seems to be impaired, most likely as a consequence of the ICl(swell) blockade. Similarly, 50 μM curcumin induced apoptosis, caused cell cycle arrest in G1-phase and increased the volume of human colorectal adenocarcinoma HT-29 cells. The cell cycle arrest in G1 phase may be the mechanism underlying the volume increase observed in this cell line after exposure to curcumin.

Curcumin suppresses T cell activation by blocking Ca2+ mobilization and nuclear factor of activated T cells (NFAT) activation

Curcumin is the active ingredient of the spice turmeric and has been shown to have a number of pharmacologic and therapeutic activities including antioxidant, anti-microbial, anti-inflammatory, and anti-carcinogenic properties. The anti-inflammatory effects of curcumin have primarily been attributed to its inhibitory effect on NF-κB activity due to redox regulation. In this study, we show that curcumin is an immunosuppressive phytochemical that blocks T cell-activation-induced Ca(2+) mobilization with IC(50) = ∼12.5 μM and thereby prevents NFAT activation and NFAT-regulated cytokine expression. This finding provides a new mechanism for curcumin-mediated anti-inflammatory and immunosuppressive function. We also show that curcumin can synergize with CsA to enhance immunosuppressive activity because of different inhibitory mechanisms. Furthermore, because Ca(2+) is also the secondary messenger crucial for the TCR-induced NF-κB signaling pathway, our finding also provides another mechanism by which curcumin suppresses NF-κB activation.

Inhibition of Ca2+-release-activated Ca2+ channel (CRAC) and K+ channels by curcumin in Jurkat-T cells

The increase in cytoplasmic Ca(2+) concentration (Δ[Ca(2+)](c)) mediated by the Ca(2+)-release-activated Ca(2+) channel (CRAC) is a critical signal for the activation of lymphocytes. Also, the voltage-gated K(+) channel (K(v)) and intermediate-conductance Ca(2+)-activated K(+) channel (IKCa1/SK4) have drawn attention as pharmacological targets for regulating immune responses. Since polyphenolic agents have various immunomodulatory effects, here we compared the effects of curcumin, rosmarinic acid, resveratrol, and epigallocatechin gallate on the ionic currents through CRAC (I(CRAC)), K(v) (I(Kv)), SK4 (I(SK4)) and on the Δ[Ca(2+)](c) of Jurkat-T cells using the patch clamp technique and fura-2 spectrofluorimetry. Curcumin (10 µM) inhibited store-operated Ca(2+) entry (SOCE). Consistently, dose-dependent inhibition of I(CRAC) by curcumin was confirmed in Jurkat-T (IC(50), 5.9 µM) and the HEK293 cells overexpressing Orai1 and STIM1 (IC(50), 0.6 µM). Also, curcumin inhibited both I(Kv) (IC(50), 11.9 µM) and I(SK4) (IC(50), 4.2 µM). The other polyphenols (rosmarinic acid, resveratrol, and epigallocatechin gallate at 10 - 30 µM) had no effect on SOCE and showed only a partial inhibition of the K(+) currents. In summary, among the tested polyphenolic agents, curcumin showed prominent inhibition of major ion channels in lymphocytes, which might contribute to the anti-inflammatory effects of curcumin. [Supplementary Figures: available only at http://dx.doi.org/10.1254/jphs.10209FP].

Physiological and therapeutical roles of ginger and turmeric on endocrine functions

The natural product ginger (Zingiber officinale) has active constituents gingerol, Shogaol and Zerumbone, while turmeric (Curcuma longa) contains three active major curcuminoids, namely, curcumin, demethoxycurcumin, and bisdemethoxycurcumin. They have the same scientific classification and are reported to have anti-inflammatory and many therapeutic effects. This article reviews the physiological and therapeutic effects of ginger and turmeric on some endocrine gland functions, and signal pathways involved to mediate their actions. With some systems and adipose tissue, ginger and turmeric exert their actions through some/all of the following signals or molecular mechanisms: (1) through reduction of high levels of some hormones (as: T4, leptin) or interaction with hormone receptors; (2) by inhibition of cytokines/adipokine expression; (3) acting as a potent inhibitor of reactive oxygen species (ROS)-generating enzymes, which play an essential role between inflammation and progression of diseases; (4) mediation of their effects through the inhibition of signaling transcription factors; and/or (5) decrease the proliferative potent by down-regulation of antiapoptotic genes, which may suppress tumor promotion by blocking signal transduction pathways in the target cells. These multiple mechanisms of protection against inflammation and oxidative damage make ginger and curcumin particularly promising natural agents in fighting the ravages of aging and degenerative diseases, and need to be paid more attention by studies.

Immunomodulatory and therapeutic activity of curcumin

Inflammation is a disease of vigorous uncontrolled activated immune responses. Overwhelming reports have suggested that the modulation of immune responses by curcumin plays a dominant role in the treatment of inflammation and metabolic diseases. Observations from both in-vitro and in-vivo studies have provided strong evidence towards the therapeutic potential of curcumin. These studies have also identified a plethora of biological targets and intricate mechanisms of action that characterize curcumin as a potent 'drug' for numerous ailments. During inflammation the functional influence of lymphocytes and the related cross-talk can be modulated by curcumin to achieve the desired immune status against diseases. This review describes the regulation of immune responses by curcumin and effectiveness of curcumin in treatment of diseases of diverse nature.

Caspase-dependent inhibition of store-operated Ca(2+) entry into apoptosis-committed Jurkat cells

Activation of T-cells triggers store-operated Ca(2+) entry, which begins a signaling cascade leading to induction of appropriate gene expression and eventually lymphocyte proliferation and differentiation. The simultaneous enhancement of Fas ligand gene expression in activated cells allows the immune response to be limited by committing the activated cells to apoptosis. In apoptotic cells the store-operated calcium entry is significantly inhibited. It has been documented that moderate activation of Fas receptor may cause reversible inhibition of store-operated channels by ceramide released from hydrolyzed sphingomyelin. Here we show that activation of Fas receptor in T-cells results in caspase-dependent decrease of cellular STIM1 and Orai1 protein content. This effect may be responsible for the substantial inhibition of Ca(2+) entry into Jurkat cells undergoing apoptosis. In turn, this inhibition might prevent overloading of cells with calcium and protect them against necrosis.

Curcumin disrupts meiotic and mitotic divisions via spindle impairment and inhibition of CDK1 activity

OBJECTIVES

Curcumin, a natural compound, is a potent anti-cancer agent, which inhibits cell division and/or induces cell death. It is believed that normal cells are less sensitive to curcumin than malignant cells; however, the mechanism(s) responsible for curcumin's effect on normal cells are poorly understood. The aim of this study was to verify the hypothesis that curcumin affects normal cell division by influencing microtubule stability, using mouse oocyte and early embryo model systems.

MATERIALS AND METHODS

Maturating mouse oocytes and two-cell embryos were treated with different concentrations of curcumin (10-50 microm), and meiotic resumption and mitotic cleavage were analysed. Spindle and chromatin structure were visualized using confocal microscopy. In addition, acetylation and in vitro polymerization of tubulin, in the presence of curcumin, were investigated and the damage to double-stranded DNA was studied using gammaH2A.X. CDK1 activity was measured.

RESULTS AND CONCLUSIONS

We have shown for the first time, that curcumin, in a dose-dependent manner, delays and partially inhibits meiotic resumption of oocytes and inhibits meiotic and mitotic divisions by causing disruption of spindle structure and does not induce DNA damage. Our analysis indicated that curcumin affects CDK1 kinase activity but does not directly affect microtubule polymerization and tubulin acetylation. As our study showed that curcumin impairs generative and somatic cell division, its future clinical use or of its derivatives with improved bioavailability after oral administration, should take into consideration the possibility of extensive side-effects on normal cells.

Himalayan Bioresource Rhodiola imbricata as a promising radioprotector for nuclear and radiological emergencies

In recent years, a lot of interest has been generated world over in the area of radioprotection for first responders going to work in the hot zones at the incident site. A large number of molecular drugs have been screened for radioprotective efficacy, but with little success. The requirement of differential radioprotection necessitates a holistic approach, which can be realized using herbs in view of their multifaceted mode of action. Our earlier studies showed the radioprotective potential of Rhodiola imbricata, a Himalayan high-altitude plant. In this study, our focus has been to compare the pro-oxidant/antioxidant activities of three fractionated extracts of R. imbricata. The aqueous fraction exhibited significant (P < 0.05) pro-oxidant activity (up to 100 μg/ml) under metal ion-induced stress ± flux [transition metal (Fe/Cu) ± 0.25 kGy]. A decrease in the dielectric constant of the solvent system utilized for extraction, exhibited a significant (P < 0.05) negative correlation (-0.955) with mean protection potential of lipid against radiation flux. Such an effect was visualized as a significant shift from pro-oxidant to antioxidant activity in methanolic fraction (dielectric constant = 33), as compared to aqueous fraction (dielectric constant = 80). Aqueous fraction is predominantly pro-oxidant at maximal concentrations, indicating its anticancer potential. The presence of transition metals modulates such a biphasic activity differentially in various fractions, i.e., the conversion of Fe(III) or Cu(II) to Fe(II) or Cu(I), respectively, due to the presence of certain bioactive constituents (electron donation at lower concentrations), favors pro-oxidant activity. On the other hand, certain other active constituents involved in metal ion chelation contributed to the overall antioxidant activity. The methanolic fraction exhibited significant antioxidant activity up to 250 μg/ml, which contributed to its radioprotective efficacy. The aquo-methanolic fraction exhibited (disparate properties), i.e., concentration-dependant cytotoxicity (up to 250 μg/ml) and cytoprotection at 1000 μg/ml. R. imbricata, in general, exhibited a significant solvent-dependant variation in radioprotective efficacy. In conclusion, solvent extraction and dose are crucial in bioactivity modulation and R. imbricata could be developed as a potential prophylactic radiation countermeasure for use in nuclear and radiological emergencies.

NKX3.1 potentiates TNF-alpha/CHX-induced apoptosis of prostate cancer cells through increasing caspase-3 expression and its activity

NKX3.1, a prostate-specific homeobox gene, plays an important role in prostate cancer and usually functions as tumor suppressor gene. Previously we have demonstrated that forced expression of NKX3.1 reduced cell growth and invasion in prostate cancer cell line PC-3. Presently, we investigated the effect of NKX3.1 on the sensitivity of the prostate cancer cells to apoptosis inducer tumor necrosis factor-alpha (TNF-alpha) and cycloheximide (CHX). PC-3 cells were transfected with NKX3.1 expression plasmid (pcDNA3.1-NKX3.1) and LNCaP cells were transfected with siRNA expression plasmid (pRNAT-RNAi1) targeting NKX3.1. The cell morphology and apoptotic rate were analyzed by Hoechst 33342 staining and Flow Cytometry in absence or presence of TNF-alpha and CHX. The activity of caspase-3 was determined using DEVD-pNA as substrate. Simultaneously, the effect of NKX3.1 on caspase-3 expression was detected using RT-PCR and Western blot. The results showed that ectopic expression of NKX3.1 promoted TNF-alpha/CHX-induced apoptosis in PC-3 cells, whereas knockdown of NKX3.1 protected LNCaP cells from apoptosis induced by TNF-alpha/CHX. The pro-apoptosis activity of NKX3.1 might partially contribute to its elevation of caspase-3 expression and activity. Manipulating NKX3.1 expression should be a promising therapeutic strategy for treating both androgen-dependent and androgen-independent prostate cancer.

Uncoupling of oxidative phosphorylation by curcumin: implication of its cellular mechanism of action

Curcumin is a phytochemical isolated from the rhizome of turmeric. Recent reports have shown curcumin to have antioxidant, anti-inflammatory and anti-tumor properties as well as affecting the 5'-AMP activated protein kinase (AMPK), mTOR and STAT-3 signaling pathways. We provide evidence that curcumin acts as an uncoupler. Well-established biochemical techniques were performed on isolated rat liver mitochondria in measuring oxygen consumption, F(0)F(1)-ATPase activity and ATP biosynthesis. Curcumin displays all the characteristics typical of classical uncouplers like fccP and 2,4-dinitrophenol. In addition, at concentrations higher than 50 microM, curcumin was found to inhibit mitochondrial respiration which is a characteristic feature of inhibitory uncouplers. As a protonophoric uncoupler and as an activator of F(0)F(1)-ATPase, curcumin causes a decrease in ATP biosynthesis in rat liver mitochondria. The resulting change in ATP:AMP could disrupt the phosphorylation status of the cell; this provides a possible mechanism for its activation of AMPK and its downstream mTOR and STAT-3 signaling.

Involvement of VDAC, Bax and ceramides in the efflux of AIF from mitochondria during curcumin-induced apoptosis

Background

We previously identified curcumin as a potent inducer of fibroblast apoptosis, which could be used to treat hypertrophic scar formation. Here we investigated the underlying mechanism of this process.

Principal Findings

Curcumin-induced apoptosis could not be blocked by caspase-inhibitors and we could not detect any caspase-3/7 activity. Curcumin predominantly induced mitochondria-mediated ROS formation and stimulated the expression of the redox-sensitive pro-apoptotic factor p53. Inhibition of the pro-apoptotic signaling enzyme glycogen synthase kinase-3β (GSK-3β) blocked curcumin-induced apoptosis. Apoptosis was associated with high molecular weight DNA damage, a possible indicator of apoptosis-inducing factor (AIF) activity. Indeed, curcumin caused nuclear translocation of AIF, which could be blocked by the antioxidant N-acetyl cysteine. We next investigated how AIF is effluxed from mitochondria in more detail. The permeability transition pore complex (PTPC), of which the voltage-dependent anion channel (VDAC) is a component, could be involved since the VDAC-inhibitor DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid) efficiently blocked AIF translocation. However, PTPC is not involved in AIF release since cyclosporine A, a specific inhibitor of the complex did not block apoptosis. Alternatively, the pro-apoptotic protein Bax could have formed mitochondrial channels and interacted with VDAC. Curcumin caused mitochondrial translocation of Bax, which was blocked by DIDS, suggesting a Bax-VDAC interaction. Interestingly, ceramide channels can also release apoptogenic factors from mitochondria and we found that addition of ceramide induced caspase-independent apoptosis. Surprisingly, this process could also be blocked by DIDS, suggesting the concerted action of Bax, VDAC and ceramide in the efflux of AIF from the mitochondrion.

Conclusions

Curcumin-induced fibroblast apoptosis is totally caspase-independent and relies on the mitochondrial formation of ROS and the subsequent nuclear translocation of AIF, which is released from a mitochondrial pore that involves VDAC, Bax and possibly ceramides. The composition of the AIF-releasing channel seems to be much more complex than previously thought.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.

Curcumin suppresses PPARδ expression and related genes in HT-29 cells

AIM: To investigate the effects of curcumin on the expression of peroxisome proliferator-activated receptorδ (PPARδ) and related genes in HT-29 cells.

METHODS: HT-29 cells were treated with curcumin (0-80 &mgr;mol/L) for 24 h. The effects of curcumin on the morphology of HT-29 cells were studied by Hoechst 33342 staining. The activity of caspase-3 was determined using DEVD-pNA as substrate. The levels of peroxisome PPARδ, 14-3-3epsilon and vascular endothelial growth factor (VEGF) in HT-29 cells were determined by Western blotting analysis and their mRNA expression was determined by real-time quantitative RT-PCR.

RESULTS: Treatment with 10-80 &mgr;mol/L curcumin induced typical features of apoptosis and activated the caspase-3 in HT-29 cells. The expression of PPARδ, 14-3-3epsilon and VEGF was reduced and the activity of β-catenin/Tcf-4 signaling was inhibited by curcumin treatment.

CONCLUSION: Curcumin can induce apoptosis of HT-29 cells and down-regulate the expression of PPARδ, 14-3-3epsilon and VEGF in HT-29.

Curcumin induces apoptosis through the mitochondria-mediated apoptotic pathway in HT-29 cells

OBJECTIVE

To investigate the effects of curcumin on release of cytochrome c and expressions of Bcl-2, Bax, Bad, Bcl-xL, caspase-3, poly ADP-ribose polymerase (PARP), and survivin of HT-29 cells.

METHODS

HT-29 cells were treated with curcumin (0 approximately 80 micromol/L) for 24 h. The release of cytochrome c from the mitochondria and the apoptosis-related proteins Bax, Bcl-2, Bcl-xL, Bad, caspase-3, PARP, and survivin were determined by Western blot analysis and their mRNA expressions by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Curcumin significantly induced the growth inhibition and apoptosis of HT-29 cells. A decrease in expressions of Bcl-2, Bcl-xL and survivin was observed after exposure to 10 approximately 80 micromol/L curcumin, while the levels of Bax and Bad increased in the curcumin-treated cells. Curcumin also induced the release of cytochrome c, the activation of caspase-3, and the cleavage of PARP in a dose-dependent manner.

CONCLUSION

These data suggest that curcumin induced the HT-29 cell apoptosis possibly via the mitochondria-mediated pathway.

Modulation of steroid activity in chronic inflammation: a novel anti-inflammatory role for curcumin

The expression of NF-kappaB (NF-kappaB)-dependent pro-inflammatory genes in response to oxidative stress is regulated by the acetylation-deacetylation status of histones bound to the DNA. It has been suggested that in severe asthma and in chronic obstructive pulmonary disease (COPD) patients, oxidative stress not only activates the NF-kappaB pathway but also alters the histone acetylation and deacetylation balance via post-translational modification of histone deacetylases (HDACs). Corticosteroids have been one of the major modes of therapy against various chronic respiratory diseases such as asthma and COPD. Failure of corticosteroids to ameliorate such disease conditions has been attributed to their inability to either recruit HDAC2 or to the presence of an oxidatively modified HDAC2 in asthmatics and COPD subjects. Naturally occurring polyphenols such as curcumin and resveratrol have been increasingly considered as safer nutraceuticals. Curcumin is a polyphenol present in the spice turmeric, which can directly scavenge free radicals such as superoxide anion and nitric oxide and modulate important signaling pathways mediated via NF-kappaB and mitogen-activated protein kinase pathways. Polyphenols also down-regulate expression of pro-inflammatory mediators, matrix metalloproteinases, adhesion molecules, and growth factor receptor genes and they up-regulate HDAC2 in the lung. Thus, curcumin may be a potential antioxidant and anti-inflammatory therapeutic agent against chronic inflammatory lung diseases.

Tunicamycin desensitizes store-operated Ca2+ entry to ATP and mitochondrial potential

Tunicamycin effect on thapsigargin-induced store-operated calcium entry was investigated. Ca2+ influx was stimulated by 50% upon exposure of Jurkat cells to tunicamycin. Moreover, tunicamycin efficiently prevented the inhibition of store-operated calcium entry caused by dissipation of mitochondrial membrane potential. Protective action of tunicamycin on store-operated Ca2+ entry was also partially preserved in Jurkat cells depleted of ATP, while Ca2+ entry into ATP-deprived cells grown in tunicamycin-free medium was almost completely inhibited. Tunicamycin-evoked changes in cellular Ca2+ fluxes coincided with decreased glycosylation of STIM1 protein. Although the latter observation is correlative and needs additional confirmation it may suggest that deglycosylation of STIM1 protein deprives store-operated calcium entry system of an important regulatory mechanism. This study suggests a novel mechanism of modulation of the activity of store-operated calcium channels in lymphoidal cells.

Pharmacokinetics of curcumin conjugate metabolites in healthy human subjects

BACKGROUND

Curcumin is a polyphenol, found in the spice turmeric, that has promising anticancer properties, but previous studies suggest that absorption of curcumin may be limited.

METHODS

This study examined the pharmacokinetics of a curcumin preparation in healthy human volunteers 0.25 to 72 h after a single oral dose. Curcumin was administered at doses of 10 g (n = 6) and 12 g (n = 6). Subjects were randomly allocated to dose level for a total of six subjects at each dose level. Serum samples were assayed for free curcumin, for its glucuronide, and for its sulfate conjugate. The data were fit to a one-compartment absorption and elimination model.

RESULTS

Using a high-performance liquid chromatography assay with a limit of detection of 50 ng/mL, only one subject had detectable free curcumin at any of the 14 time points assayed, but curcumin glucuronides and sulfates were detected in all subjects. Based on the pharmacokinetic model, the area under the curve for the 10 and 12 g doses was estimated (mean +/- SE) to be 35.33 +/- 3.78 and 26.57 +/- 2.97 mug/mL x h, respectively, whereas C(max) was 2.30 +/- 0.26 and 1.73 +/- 0.19 mug/mL. The T(max) and t(1/2) were estimated to be 3.29 +/- 0.43 and 6.77 +/- 0.83 h. The ratio of glucuronide to sulfate was 1.92:1. The curcumin conjugates were present as either glucuronide or sulfate, not mixed conjugates.

CONCLUSION

Curcumin is absorbed after oral dosing in humans and can be detected as glucuronide and sulfate conjugates in plasma.

Curcumin as a DNA Topoisomerase II Poison

Curcumin, the major active component of the spice turmeric, is recognised as a safe compound with great potential for cancer chemoprevention and cancer therapy. It induces apoptosis, but its initiation mechanism remains poorly understood. Curcumin has been assessed on the human cancer cell lines, TK-10, MCF-7 and UACC-62, and their IC50 values were 12.16, 3.63, 4.28 microM respectively. The possibility of this compound being a topoisomerase II poison has also been studied and it was found that 50 microM of curcumin is active in a similar fashion to the antineoplastic agent etoposide. These results point to DNA damage induced by topoisomerase II poisoning as a possible mechanism by which curcumin initiates apoptosis, and increase the evidence suggesting its possible use in cancer therapy.

Modulation of anti-apoptotic and survival pathways by curcumin as a strategy to induce apoptosis in cancer cells

Apoptosis is a highly regulated mechanism by which cells undergo cell death in an active way. As one of the most challenging tasks concerning cancer is to induce apoptosis in malignant cells, researchers increasingly focus on natural products to modulate apoptotic signaling pathways. Curcumin, a natural compound isolated from the plant Curcuma longa, has chemopreventive properties, which are mainly due to its ability to arrest cell cycle and to induce apoptosis. This article reviews the main effects of curcumin on the different apoptotic signaling pathways involved in curcumin-induced apoptosis of cancer cells, including the intrinsic and extrinsic apoptosis pathways, the NF-kappaB-mediated pathway as well as the PI3K/Akt signaling pathway. This review also focuses on the sensitization of cells to TRAIL-induced apoptosis after curcumin treatment and shows that curcumin enhances the capacity to induce cell death of different chemotherapeutical drugs.

The ADP and ATP transport in mitochondria and its carrier

Different from some more specialised short reviews, here a general although not encyclopaedic survey of the function, metabolic role, structure and mechanism of the ADP/ATP transport in mitochondria is presented. The obvious need for an "old fashioned" review comes from the gateway role in metabolism of the ATP transfer to the cytosol from mitochondria. Amidst the labours, 40 or more years ago, of unravelling the role of mitochondrial compartments and of the two membranes, the sequence of steps of how ATP arrives in the cytosol became a major issue. When the dust settled, a picture emerged where ATP is exported across the inner membrane in a 1:1 exchange against ADP and where the selection of ATP versus ADP is controlled by the high membrane potential at the inner membrane, thus uplifting the free energy of ATP in the cytosol over the mitochondrial matrix. Thus the disparate energy and redox states of the two major compartments are bridged by two membrane potential responsive carriers to enable their symbiosis in the eukaryotic cell. The advance to the molecular level by studying the binding of nucleotides and inhibitors was facilitated by the high level of carrier (AAC) binding sites in the mitochondrial membrane. A striking flexibility of nucleotide binding uncovered the reorientation of carrier sites between outer and inner face, assisted by the side specific high affinity inhibitors. The evidence of a single carrier site versus separate sites for substrate and inhibitors was expounded. In an ideal setting principles of transport catalysis were elucidated. The isolation of intact AAC as a first for any transporter enabled the reconstitution of transport for unravelling, independently of mitochondrial complications, the factors controlling the ADP/ATP exchange. Electrical currents measured with the reconstituted AAC demonstrated electrogenic translocation and charge shift of reorienting carrier sites. Aberrant or vital para-functions of AAC in basal uncoupling and in the mitochondrial pore transition were demonstrated in mitochondria and by patch clamp with reconstituted AAC. The first amino acid sequence of AAC and of any eukaryotic carrier furnished a 6-transmembrane helix folding model, and was the basis for mapping the structure by access studies with various probes, and for demonstrating the strong conformation changes demanded by the reorientation mechanism. Mutations served to elucidate the function of residues, including the particular sensitivity of ATP versus ADP transport to deletion of critical positive charge in AAC. After resisting for decades, at last the atomic crystal structure of the stabilised CAT-AAC complex emerged supporting the predicted principle fold of the AAC but showing unexpected features relevant to mechanism. Being a snapshot of an extreme abortive "c-state" the actual mechanism still remains a conjecture.