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.

Dendritic cells and their receptors in antitumor immune response.

DCs are recognized as the pivotal group of lymphocytes, which induce a variety of antitumor immune responses. Enduring professional antigen presenting cells, DCs eminence to induce adaptive antitumor immune response was exploited, which showed promising results in DCs-based phased clinical studies. Nevertheless, DCs also influence other immune cells to induce multiple arms of immune system to cure cancer.

Immunomodulatory effects of curcumin: in-vivo.

Curcumin specifically exhibits cytostatic and cytotoxic effects against tumors of multiple origin. Previously we have demonstrated apoptotic activity of curcumin against tumor cells with no effect on normal cells in-vitro. Many anti-cancer drugs exhibit deleterious effects on immune cells, which restrict their wide use in-vivo.

The ischemia-responsive protein 94 (Irp94) activates dendritic cells through NK cell receptor protein-2/NK group 2 member D (NKR-P2/NKG2D) leading to their maturation.

Tumor recognition and killing, the uptake of released immunogenic substrate, and the generation of immunity are crucial aspects of dendritic cell (DC)-mediated antitumor immune response. In the context of direct tumoricidal activity, we have recently shown NK cell receptor protein-2 (NKR-P2)/NK group 2 member D (NKG2D) as a potent activation receptor on rat DCs. The activation of DCs with agonistic anti-NKR-P2 mAb, the binding of soluble NKR-P2 to the AK-5 tumor, and DC maturation with fixed AK-5 cells led us to identify a putative NKR-P2 ligand on the AK-5 cell surface.

Cross-linking a mAb to NKR-P2/NKG2D on dendritic cells induces their activation and maturation leading to enhanced anti-tumor immune response.

NKR-P2/NKG2D is the chief tumor recognition receptor of NK cells and some T cells, which recognizes stress inducible ligands on tumors and mediates cell activation. We have recently reported the involvement of NKR-P2 in rat dendritic cell (DC) activation. We demonstrate the potential of agonistic anti-NKR-P2 mAb (1A6), which mimics the NKR-P2 ligand and induces activation and maturation of DCs.

Heat stress induced apoptosis in BC-8 cells derived from AK-5 tumor involves downregulation of Bcl-2 and generation of reactive oxygen species.

BC-8, a rat histiocytoma undergoes apoptosis after heat shock, which is due to lack of an effective heat shock response. Heat shock induced generation of free radicals, which in turn are involved in the induction of apoptotic death in BC-8 cells. Treatment of BC-8 cells with N-acetylcysteine partially inhibited the heat induced apoptosis.

Biological effects of curcumin and its role in cancer chemoprevention and therapy.

Curcumin, a natural component of the rhizome of curcuma longa has emerged as one of the most powerful chemopreventive and anticancer agents. Its biological effects range from antioxidant, anti-inflammatory to inhibition of angiogenesis and is also shown to possess specific antitumoral activity. The molecular mechanism of its varied cellular effects has been studied in some details and it has been shown to have multiple targets and interacting macromolecules within the cell.

A transmembrane-anchored rat RAE-1-like transcript as a ligand for NKR-P2, the rat ortholog of human and mouse NKG2D.

NKG2D is a potent activating immunoreceptor that has been extensively characterized in NK cells and shown to lend costimulatory functions in CD8(+) T cells under certain conditions. The list is growing of ligands for NKG2D, which are distantly related to MHC class I molecule and are often up-regulated during cellular distress. Here, we describe the cloning of a novel (and incidentally the first) ligand for NKR-P2, the rat ortholog of human and mouse NKG2D, termed as rat RAE-1-like transcript (RRLT).

Role of STAT3 and NFkappaB signaling in the serum factor-induced apoptosis in AK-5 cells.

AK-5, a rat histiocytoma, is rejected in about 70% of the syngeneic animals when injected subcutaneously. The sera from the tumor rejecting animals possess a potent factor, referred to as serum factor (SF) that induces apoptosis in AK-5 tumor cells. In the present study, we show that treatment with SF or JAK/STAT inhibitors AG490 and Piceatannol induces apoptosis to a similar extent in BC-8 (a single cell clone of AK-5) cells.

Differential cytotoxic effects of Annona squamosa seed extracts on human tumour cell lines: role of reactive oxygen species and glutathione.

Annonaceous acetogenins are a new class of compounds that have been reported to have potent pesticidal, parasiticidal, anti-microbial, cell growth inhibitory activities. In this study, organic and aqueous extracts from the defatted seeds of Annona squamosa (custard apple) were tested on different human tumour cell lines for antitumoural activity. While organic and aqueous extracts induced apoptosis in MCF-7 and K-562 cells, they failed to do so in COLO-205 cells.

Differential apoptotic and redox regulatory activities of curcumin and its derivatives.

We have synthesized different bioconjugates of curcumin, which were tested for their pro- and antioxidant properties. In the present study five representative derivatives of curcumin, i.e.

Effect of curcumin on normal and tumor cells: role of glutathione and bcl-2.

Curcumin, a well-known dietary pigment derived from Curcuma longa, inhibited growth of several types of malignant cells both in vivo and in vitro. However, its mechanism of action still remains unclear. In this study, we have focused primarily on the cytotoxic effects of curcumin on three human tumor cell lines and rat primary hepatocytes.

Migration of antigen presenting cells from periphery to the peritoneum during an inflammatory response: role of chemokines and cytokines.

We demonstrate the migration of antigen presenting cells (APCs), macrophages, and dendritic cells from the subcutaneous site to the peritoneum after they have picked up the antigen, using cell tracking dye. The migration of the APCs is more universal as it was also observed after injection of MethA tumor, DH-5alpha cells, and leishmania parasites, in addition to AK-5 tumor cells. Cellular migration is mediated by several chemokines and cytokines that also induce heavy influx of immune cells into the peritoneum.

Antitumour activity of Annona squamosa seed extracts is through the generation of free radicals and induction of apoptosis.

The plant, Annona squamosa traditionally known as custard apple possesses potent bioactive principles in all its parts. The effect of aqueous and organic extracts from defatted seeds of A. squamosa was studied on a rat histiocytic tumour cell line, AK-5.

Involvement of NKR-P2/NKG2D in DC-mediated killing of tumor targets: indicative of a common, innate, target-recognition paradigm?

DC are the most efficient antigen-presenting cells that regulate the immune response. Here, we demonstrate the expression of NK cell receptor protein-2 (NKR-P2) on rat and mouse DC, and we show that NKR-P2 gets reorganized upon antigen contact. DC activated with anti-NKR-P2 mAb exhibit enhanced apoptotic killing of tumor targets, whereas blocking the interaction between NKR-P2 and its ligand with rNKR-P2 abrogated apoptotic killing, suggesting NKR-P2 to function as an activating molecule on DC.

Suppression of macrophage function in AK-5 tumor transplanted animals: role of TGF-beta1.

Transforming growth factor-beta 1 (TGF-beta1), a multifunctional cytokine secreted by various cell types has been implicated in diverse physiologic and pathophysiologic functions, including immunological, inflammatory, and neoplastic processes. AK-5 tumor cells when injected intraperitoneally grow as ascites, causing 100% mortality. Peritoneal macrophages cocultured with AK-5 cells, in vitro showed specific suppression of tumoricidal function.

Antitumour immune responses.

The role of the immune system in combating tumour progression has been studied extensively. The two branches of the immune response - humoral and cell-mediated - act both independently and in concert to combat tumour progression, the success of which depends on the immunogenicity of the tumour cells. The immune system discriminates between transformed cells and normal cells by virtue of the presence of unique antigens on tumour cells.

Interleukin-12 secreted by mature dendritic cells mediates activation of NK cell function.

Dendritic cells (DCs) are known to modulate immune response by activating effector cells of both the innate and the adaptive immune system. In the present study, we demonstrate that co-culture of DCs with paraformaldehyde-fixed tumor cells augments the secretion of interleukin (IL)-12 by DCs and these activated DCs upon co-culture with naive NK cells enhance the cytolytic activity of NK cells against NK-sensitive target YAC-1. Similarly, DCs isolated from tumor-bearing animals also activated NK cells in vitro.

Phycocyanin-mediated apoptosis in AK-5 tumor cells involves down-regulation of Bcl-2 and generation of ROS.

C-phycocyanin, which is a major biliprotein of the blue-green algae, has been shown to possess cyclooxygenase-2 inhibitory activity. We have studied the effect of phycocyanin on a rat histiocytic tumor line. AK-5 cells are induced into apoptotic death program when treated with phycocyanin, which involves the activation of caspase-3.

Protection conferred by Bcl-2 expression involves reduced oxidative stress and increased glutathione production during hypothermia-induced apoptosis in AK-5 tumor cells.

Hypothermia is known to retard mammalian cell growth, however, BC-8 cells, which have originated from AK-5 tumor after single cell cloning, were triggered into apoptotic pathway when grown at 30 degrees C. Cell death process showed typical apoptotic features like DNA fragmentation, cytochrome c release, etc. Introduction of Bcl-2 gene in BC-8 cells inhibited hypothermia-induced apoptotic process, which is ascribed to reduced ROS generation and higher glutathione production.

Activating and inhibitory receptors and their role in natural killer cell function.

Last decade has seen a significant advancement in our understanding of the Natural Killer (NK) cell biology and function. Several receptors present on NK cells have been identified, which are involved in either their activation or inhibition. Similarly, a large number of interacting ligands have been identified on the target cells that upon interaction transmit either activating or inhibitory signals.

Baculoviral p35 inhibits oxidant-induced activation of mitochondrial apoptotic pathway.

In this study we report that the baculovirus p35 anti-apoptotic protein prevents cell death by quenching free radicals at a very upstream step in the apoptotic pathway. Mitochondria of activated rat peritoneal macrophages as well as Spodoptera frugiperda (Sf9) insect cells, following treatment with oxidants, H(2)O(2)/UVB irradiation, release cytochrome c followed by activation of caspase-3. Transfection of macrophages/Sf9 cells with a construct carrying the p35 gene under the CMV/HSP promoters resulted in p35 expression and consequent arrest of oxidative stress-induced apoptosis.

Dendritic cells as natural adjuvants and modulators of immune response in cancer immunotherapy.

Dendritic cells (DCs) are potent antigen presenting cells. Mature DCs activate antigen specific naïve T cells, B cells and NK cells. Under certain conditions, DCs even silence T cell immune responses in vivo, thus, modulating the immune response.

Role of reactive nitrogen intermediates and protein nitration during immune response against a rat histiocytoma.

The ability of macrophages to produce reactive nitrogen species, particularly nitric oxide (NO) is correlated with an enhanced microbicidal or tumoricidal activity during pathogenic or tumoral invasion, respectively. NO reacts in water with oxygen and its reactive intermediates to yield, among others, nitrite and nitrate, which are relatively, stable anions. In this study, we show the varying concentrations of nitrite and nitrate present in different body fluids during AK-5 tumor growth and regression in Wistar rats.

Subcellular localization and physiological consequences of introducing a mitochondrial matrix targeting signal sequence in bax and its mutants.

Bax, a proapoptotic member of the Bcl-2 family of proteins, resides in the cytosol and translocates to the mitochondrial membrane upon induction of apoptosis. It has been proposed that Bax does not translocate to mitochondria under normal physiological conditions, due to interaction between amino (ART) and carboxy (TM) terminal domains. Here, we report the physiological consequences of introducing a matrix targeting mitochondrial signal sequence (Su9) at the amino terminus of Bax and its mutants lacking ART, TM, or both segments.