Curcumin Feeding Research Articles

Regulation of Heme Oxygenase and Its Cross-Talks with Apoptosis and Autophagy under Different Conditions in Drosophila.

Heme oxygenase (HO) is one of the cytoprotective enzymes that can mitigate the effects of oxidative stress. Here, we found that the ho mRNA level oscillates in the brain of Drosophila melanogaster with two minima at the beginning of the day and night. This rhythm was partly masked by light as its pattern changed in constant darkness (DD). It followed a similar trend in the clock mutant per01 under light/dark regime (LD12:12); however, differences between time points were not statistically significant. In older flies (20 days old), the rhythm was vanished; however, 15 days of curcumin feeding restored this rhythm with an elevated ho mRNA level at all time points studied. In addition, flies exposed to paraquat had higher ho expression in the brain, but only at a specific time of the day which can be a protective response of the brain against stress. These findings suggest that the expression of ho in the fly’s brain is regulated by the circadian clock, light, age, exposure to stress, and the presence of exogenous antioxidants. We also found that HO cross-talks with apoptosis and autophagy under different conditions. Induction of neuronal ho was accompanied by increased transcription of apoptosis and autophagy-related genes. However, this trend changed after exposure to curcumin and paraquat. Our results suggest that HO is involved in the control of apoptotic and autophagic key processes protecting the brain against oxidative damage.

Modification of radiation-induced murine thymic lymphoma incidence by curcumin

Introduction: Curcumin is a known antioxidant, preventing radiation damage including carcinogenesis. However, concentration and feeding schedule of curcumin in modification of radiation induced thymic lymphoma incidence in vivo model has not been studied. Materials and Methods: We report here modification of incidence of γ-radiation-induced thymic lymphoma in mice fed with different doses of curcumin (0.05 to 1*) in diet. Results: Female Swiss mice (6-8 weeks) fed with normal diet and exposed to 3 Gy whole body60Co γ-irradiation (WBI) showed 85 * incidence of thymic lymphoma (TL) at 120 days post-irradiation. A concentration of 1 * curcumin was found the most effective in TL incidence prevention than other fed concentrations. The TL incidence was remarkably reduced when curcumin was fed to the mice before than after the radiation exposure. The incidence of TL was reduced to 63* in mice fed with 1* curcumin in diet for 3 weeks after exposure to WBI. On the other hand, when animals were fed with same concentration of curcumin for 2 weeks and 3 weeks before WBI, the TL incidence was reduced to 55* and 35*, respectively. Curcumin feeding resulted in significant prevention in micronucleus formation in the bone marrow, which was corroborated with inhibition in DNA damage quantified by comet assay. Moreover, significant prevention in DNA damage was also observed in the peripheral blood cells in curcumin fed and irradiated mice, which however, was not prominent in thymus. Curcumin was able to prevent apoptotic death in thymus and bone marrow 4 h after irradiation, which however, got attenuated at longer post-irradiation period (24 h). Conclusion: These results suggest modification of TL incidence by curcumin in irradiated mice involving DNA damage and apoptotic death mechanisms.

Rapidly cycling Lgr5+ stem cells are exquisitely sensitive to extrinsic dietary factors that modulate colon cancer risk.

The majority of colon tumors are driven by aberrant Wnt signaling in intestinal stem cells, which mediates an efficient route toward initiating intestinal cancer. Natural lipophilic polyphenols and long-chain polyunsaturated fatty acids (PUFAs) generally suppress Wnt- and NF-κB- (nuclear factor-κ light-chain enhancer of activated B-cell) related pathways. However, the effects of these extrinsic agents on colonic leucine-rich repeat-containing G-protein-coupled receptor 5-positive (Lgr5+) stem cells, the cells of origin of colon cancer, have not been documented to date. Therefore, we examined the effect of n-3 PUFA and polyphenol (curcumin) combination on Lgr5+ stem cells during tumor initiation and progression in the colon compared with an n-6 PUFA-enriched control diet. Lgr5-EGFP-IRES-creERT2 knock-in mice were fed diets containing n-6 PUFA (control), n-3 PUFA, n-6 PUFA+curcumin or n-3 PUFA+curcumin for 3 weeks, followed by 6 azoxymethane (AOM) injections, and terminated 17 weeks after the last injection. To further elucidate the effects of the dietary bioactives at the tumor initiation stage, Lgr5+ stem cells were also assessed at 12 and 24 h post AOM injection. Only n-3 PUFA+curcumin feeding reduced nuclear β-catenin in aberrant crypt foci (by threefold) compared with control at the progression time point. n-3 PUFA+curcumin synergistically increased targeted apoptosis in DNA-damaged Lgr5+ stem cells by 4.5-fold compared with control at 12 h and maximally reduced damaged Lgr5+ stem cells at 24 h, down to the level observed in saline-treated mice. Finally, RNAseq analysis indicated that p53 signaling in Lgr5+ stem cells from mice exposed to AOM was uniquely upregulated only following n-3 PUFA+curcumin cotreatment. These novel findings demonstrate that Lgr5+ stem cells are uniquely responsive to external dietary cues following the induction of DNA damage, providing a therapeutic strategy for eliminating damaged Lgr5+ stem cells to reduce colon cancer initiation.

Independent chemical regulation of health and senescent spans in Drosophila

Curcumin feeding of Drosophila larvae or young adults inhibits TOR and other known longevity genes and induces an extended health span in a normal-lived Ra strain adult. Combining larval curcumin feeding with an adult dietary restriction (DR) diet does not yield an additive effect. The age-specific mortality rate is decreased and is comparable with that of genetically selected long-lived La animals. Feeding Ra adults with the drug their whole life, or only during the senescent span, results in a weak negative effect on median longevity with no increase in maximum lifespan. The La strain shows no response to this DR mimetic. Thus, curcumin acts in a life stage-specific manner to extend the health span. Histone deacetylase inhibitors decrease the longevity of Ra animals if administered over the health span only or over the entire adult lifespan, but these inhibitors increase longevity when administered in the transition or senescent spans. Their major effect is a reduction in the mortality rate of older flies, raising the possibility of reducing frailty in older organisms. Their life stage-specific effects are complementary to that of curcumin. Use of stage-specific drugs may enable targeted increases in health or senescent spans, and thus selectively increase the quality of life.

In vivo study on the effects of curcumin on the expression profiles of anti-tumour genes (VEGF, CyclinD1 and CDK4) in liver of rats injected with DEN

In this study we investigated the effects of curcumin, derived from plant Curcuma longa, on oxidative toxicity, and the possible molecular mechanism of antitumour of curcumin in liver cancer rats. Results showed that blood levels of Gamma-glutamyltransferase, aspartate aminotransferase, alanine aminotransferase, glutathione S-transferase, and liver level of MD were significantly decreased after curcumin feeding. Levels of the liver malondialdehyde MDA, nitric oxide and antioxidant enzymes were significantly increased. Moreover, RT-PCR and Western blot analysis results showed that curcumin treatment significantly decreased liver vascular endothelial growth factor (VEGF), CyclinD1 and CDK4 mRNA expression levels and CyclinD1 and CDK4 proteins levels in liver cancer rats. These findings were confirmed by histopathology. It is concluded that curcumin can protect the liver from the damage caused by N-nitrosodiethylamine. Moreover, curcumin has the potential to be used in a therapy for liver cancer. The present data provide evidence to support the presence of free radicals and VEGF, CyclinD1 and CDK4 mRNA in rat tumour cells. Studies are in progress in order to further characterize the role of VEGF, CyclinD1 and CDK4 mRNA in liver cancer cells and in hepatic therapeutics.

Abstract B77: Curcumin deteriorates trabecular and cortical bone in mice bearing metastatic Lewis lung carcinoma

Abstract Bone is a major target of metastasis for many malignancies; curcumin has been studied for its role in cancer prevention including early phase clinical trials for its efficacy and safe use with cancer patients. The present study investigated the effects of dietary supplementation with curcumin (2% and 4%) on (1) pulmonary metastasis of Lewis lung carcinoma and (2) bone microstructural changes in female C57BL/6 mice. Curcumin significantly increased the size of lung metastases, which was accompanied with significant increases in plasma concentrations of angiogenic factors (e.g. angiogenin, VEGF) and inflammatory cytokines (e.g. IL-1β, MCP-1). Morphometric analysis showed that curcumin at 2% and 4% dietary levels significantly reduced bone volume to total volume ratio (BV/TV), connective density (Conn.D.) and trabecular number (Tb.N.) and significantly increased structure model index (SMI, an indicator of the plate- and rod-like geometry of trabecular structure) and trabecular separation (Tb.Sp.) in vertebral bodies, and at the 4% level curcumin significantly reduced BV/TV and Tb.N. and at either level it significantly reduced trabecular thickness (Tb.Th.) in distal femurs compared with the controls. In the mid-shaft of femur, curcumin at the 4% level significantly reduced cortical bone area to total area ratio (Ct.Ar/Tt.Ar.) and cortical thickness (Ct.Th.) compared with the controls. Furthermore, curcumin feeding resulted in dose-dependent decreases in plasma concentrations of osteocalcin (a marker of bone formation) and increases plasma tartrate-resistant acid phosphate 5b (a marker of bone resorption) compared with the controls, indicating that curcumin may deteriorate trabecular and cortical bone by disrupting the balance of bone remodeling. As skeleton is a favored site of metastasis for many cancers, our results that curcumin (1) enhances metastatic growth and (2) results in osteolytic deterioration of bone suggest the need of assessment of bone structural changes for curcumin cancer prevention studies, particularly for human trials with cancer patients who are the risk of malignant spread, to determine the curcumin effects and its interaction with malignancy on skeleton health. Citation Format: Lin Yan. Curcumin deteriorates trabecular and cortical bone in mice bearing metastatic Lewis lung carcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B77.

Curcumin is an early-acting stage-specific inducer of extended functional longevity in Drosophila

Larval feeding with curcumin induces an extended health span with significantly increased median and maximum longevities in the adult fly. This phenotype is diet insensitive and shows no additive effect on longevity when combined with an adult dietary restriction (DR) diet, suggesting that curcumin and DR operate via the same or overlapping pathways for this trait. This treatment significantly slows the aging rate so that it is comparable with that of genetically selected long lived animals. The larval treatment also enhances the adult animal's geotactic activity in an additive manner with DR, suggesting that curcumin and DR may use different pathways for different traits. Feeding the drug to adults during only the health span also results in a significantly extended health span with increased median and maximum life span. This extended longevity phenotype is induced only during these stage-specific periods. Feeding adults with the drug over their whole life results in a weakly negative effect on median longevity with no increase in maximum life span. There are no negative effects on reproduction, although larval curcumin feeding increases development time, and also apparently accelerates the normal late-life neuromuscular degeneration seen in the legs. Gene expression data from curcumin-fed larvae shows that the TOR pathway is inhibited in the larvae and the young to midlife adults, although several other genes involved in longevity extension are also affected. These data support the hypothesis that curcumin acts as if it is a DR mimetic nutraceutical. These data also suggest that the search for DR mimetics may be enhanced by the use of stage-specific screening of candidate molecules.

Neuroprotective properties of phytochemicals against paraquat-induced oxidative stress and neurotoxicity in Drosophila melanogaster

Environmental toxicants like paraquat (PQ) induce the increase of oxidative stress, which is likely to lead to various neuropathological symptoms. Although the Drosophila system is applicable for anti-oxidative and neuroprotective drug discovery, this system remains to be more exploited in various aspects. In this study, using Drosophila as a model animal, we have examined the anti-oxidative and neuroprotective properties of plant-derived compounds against oxidative damage and neurotoxicity induced by paraquat, which is a widely used herbicide. In this study, paraquat showed LC50 at 24.7mM to adult males of Drosophila melanogaster within 24h. Dietary feeding of curcumin, quercetin, Sanguisorba officinalis, and Zedoariae rhizoma extracts prior to paraquat exposure extended lifespan and enhanced motor activities of flies. These compounds modulated the expression level of several genes associated with anti-oxidative and anti-aging effects such as sod1, sod2, cat, gstD1, and mth genes. Also, same treatments of phytochemicals to flies ameliorated other oxidative stress index factors such as ROS levels and superoxide dismutase. In contrast, no significant effects on catalase activities were observed. Additionally, the dietary feeding of phytochemical substances also reduced acetylcholine esterase activities, which were dramatically increased by paraquat treatment, implying that these phytochemicals also affected neuronal systems. Present study demonstrates that the dietary feeding of phytochemicals prior to paraquat exposure has anti-oxidative and neural protective effects, which leads to the recovery of behaviors and lifespan in fruit flies.

The chemopreventive and clinically used agent curcumin sensitizes HPV- but not HPV+ HNSCC to ionizing radiation, in vitro and in a mouse orthotopic model

Radiation therapy (RT) plays a critical role in the local-regional control of head and neck squamous cell carcinoma (HNSCC). However, the efficacy of RT in treating HNSCC is limited by severe normal tissue toxicity, predominantly mucositis. One pharmacological approach for increasing the clinical response to RT is the use of radiation response modifiers that preferentially sensitize tumor cells. Previously we demonstrated that curcumin, a natural plant polyphenol, increased the radiation sensitivity of HNSCC cells and that the observed sensitization was dependent on curcumin-mediated inhibition of thioredoxin reductase 1 (TxnRd1) a key cytosolic regulator of redox-dependent signaling. Here, we examined curcumin-induced radiation sensitization in HNSCC cell lines with differing HPV status and expressing different levels of TxnRd1, in vitro. The intrinsic radiation resistance of the HPV- cell lines was significantly higher than the HPV+ cell lines used in our study. Notably, all of the HPV- cell lines expressed high levels of TxnRd1 and exhibited higher intrinsic resistance to RT. While curcumin was effective at increasing the radiation response of the resistant HPV- cell lines it had no effect on the HPV+ cells. Based on these findings we employed an orthotopic, HPV- HNSCC tumor model in athymic nude mice to examine the effect of combining curcumin with fractionated RT, in vivo. The combination of curcumin feeding and fractionated RT had a significant effect on tumor doubling time and overall animal survival. We therefore propose that curcumin and RT should be considered as a first line treatment of HPV- HNSCC.

Dietary fish oil and curcumin combine to modulate colonic cytokinetics and gene expression in dextran sodium sulphate-treated mice

Both fish oil (FO) and curcumin have potential as anti-tumour and anti-inflammatory agents. To further explore their combined effects on dextran sodium sulphate (DSS)-induced colitis, C57BL/6 mice were randomised to four diets (2 × 2 design) differing in fatty acid content with or without curcumin supplementation (FO, FO+2 % curcumin, maize oil (control, MO) or MO+2 % curcumin). Mice were exposed to one or two cycles of DSS in the drinking-water to induce either acute or chronic intestinal inflammation, respectively. FO-fed mice exposed to the single-cycle DSS treatment exhibited the highest mortality (40 %, seventeen of forty-three) compared with MO with the lowest mortality (3 %, one of twenty-nine) (P = 0·0008). Addition of curcumin to MO increased (P = 0·003) mortality to 37 % compared with the control. Consistent with animal survival data, following the one- or two-cycle DSS treatment, both dietary FO and curcumin promoted mucosal injury/ulceration compared with MO. In contrast, compared with other diets, combined FO and curcumin feeding enhanced the resolution of chronic inflammation and suppressed (P < 0·05) a key inflammatory mediator, NF-κB, in the colon mucosa. Mucosal microarray analysis revealed that dietary FO, curcumin and FO plus curcumin combination differentially modulated the expression of genes induced by DSS treatment. These results suggest that dietary lipids and curcumin interact to regulate mucosal homeostasis and the resolution of chronic inflammation in the colon.

Interactive Effects of the Feeding of Leucaena Leaves and Curcumin on Macronutrient Digestion and Nitrogen Balance in Beef Cattle

Abstract: Problem statement: The feeding of curcumin to beef cattle has been shown to increase nitrogen retention and decrease the apparent digestibility of acid detergent fiber in beef cattle. It was suggested that there could be interactions between the effects of curcumin and the composition of the ration. Approach: In this study with beef cattle, concentrates without or with curcumin and low or high level of leucaena leaves were fed to assess the possible interactive effects. Apparent macronutrient digestibility and nitrogen balance were measured. Results: When the ration was curcumin free, an increase in the intake of leucaena leaf meal raised the group mean of apparent digestibility of dry matter, organic matter, crude fat, neutral and acid detergent fiber, but the opposite effect was seen for the curcumin-containing rations. Nitrogen retention was raised by extra intake of leucaena leaf meal, but only when the ration did not contain curcumin. The feeding of curcumin intake elevated nitrogen retention, the effect being greater for the ration with low content of leucaena. Conclusion: This study confirms that curcumin feeding has a stimulatory effect on nitrogen retention in beef cattle. The composition of the ration may determine the magnitude of the inhibitory effect of curcumin on the digestibility of acid detergent fiber.

Influence of Dietary Curcumin on Rumen Fermentation, Macronutrient Digestion and Nitrogen Balance in Beef Cattle

: Problem statement: Previous studies have shown that curcumin has antibacterial activity. It was hypothesized that the feeding of curcumin to ruminants may disturb rumen function and affect macronutrient digestibility and nitrogen utilization. Approach: In an experiment with Latin-square design, beef cattle were fed rations consisting of urea-treated rice straw and concentrates without or with 0.1 or 0.2% added curcumin. Indicators of rumen function, apparent macronutrient digestibility and nitrogen balance were determined. Results: Voluntary feed intake was not influenced by the addition of curcumin to the ration. Dietary curcumin raised bacterial counts in the rumen fluid, but lowered the protozoa counts. Ruminal ammonia concentrations were decreased by curcumin. The intake of curcumin did not affect apparent digestibility of dry matter, organic matter, ether extract and neutral detergent fiber, but it reduced the digestibility of acid detergent fiber. Dietary curcumin diminished fecal nitrogen excretion and raised nitrogen absorption and retention. Conclusion: This study shows that the feeding of curcumin changes the ruminal flora and nitrogen metabolism in beef cattle. The curcumin-induced stimulation of nitrogen retention may be considered as a potentially positive effect, but the observed decrease in apparent digestibility of acid detergent fiber could limit the utilization of roughage.

Curcumin improves prostanoid ratio in diabetic mesenteric arteries associated with cyclooxygenase-2 and NF-&amp;kappa;B suppression

BackgroundCurcumin, the active ingredient from turmeric rhizomes, has been shown to have a wide range of pharmacological properties including antioxidant and anti-inflammatory effects. Curcumin has been reviewed for its multiple molecular action on inhibiting tumor angiogenesis via its mechanisms of cyclooxygenase (COX)-2, and vascular endothelial growth factor (VEGF) inhibition. In this present study, we aimed to assess the effects of curcumin on preventing diabetes-induced vascular dysfunction in association with COX-2, nuclear factor-κB (NF-κB) expression, and prostanoid production.MethodsTwelve-week-old male Wistar rats were separated into five groups: 1) diabetes with 0.9% normal saline (DM-NSS; n =10), 2) diabetes treated with curcumin 30 mg/kg (n =10), 3) diabetes treated with curcumin 300 mg/kg (n =10), 4) the control with 0.9% normal saline (n =10), and 5) the control treated with 300 mg/kg (n =10). Daily oral feeding of curcumin was started at 6 weeks after the streptozotocin injection. Levels of 6-keto prostaglandin (PG) F1αand thromboxane (TX) B2 were determined from mesenteric perfusates using enzyme immunoassay kits. Protein kinase C (PKC)-β II and COX-2 with NF-κB levels were analyzed in the mesenteric arteries by immunofluorescent staining and immunohistochemistry, respectively.ResultsThe ratio of 6-keto-PGF1αand TXB2 was significantly decreased in DM-NSS compared with the control (P < 0.05). Double-immunofluorescent staining with specific antibodies for PKC-βII and α-smooth muscle actins showed that the diabetic mesenteric arteries contained increased of PKC-βII within the vascular wall. Also, COX-2 expression and activated NF-κB in the small mesenteric artery of diabetes mellitus rats were markedly increased when compared with the control. Interestingly, curcumin could inhibit the upregulation of all of these biomarkers.ConclusionThese findings show that curcumin can attenuate diabetes-induced vascular dysfunction in association with its potential for COX-2 and NF-κB suppression, PKC inhibition, and improving the ratio of prostanoid products PGI2/TXA2.

Curcumin improves prostanoid ratio in diabetic mesenteric arteries associated with cyclooxygenase-2 and NF-&amp;kappa;B suppression

Curcumin improves prostanoid ratio in diabetic mesenteric arteries associated with cyclooxygenase-2 and NF-&kappa;B suppression Sirada Rungseesantivanon1, Naris Thengchaisri4, Preecha Ruangvejvorachai2, Suthiluk Patumraj31Interdepartment of Physiology, Graduate School, 2Department of Pathology, 3Department of Physiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; 4Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, ThailandBackground: Curcumin, the active ingredient from turmeric rhizomes, has been shown to have a wide range of pharmacological properties including antioxidant and anti-inflammatory effects. Curcumin has been reviewed for its multiple molecular action on inhibiting tumor angiogenesis via its mechanisms of cyclooxygenase (COX)-2, and vascular endothelial growth factor (VEGF) inhibition. In this present study, we aimed to assess the effects of curcumin on preventing diabetes-induced vascular dysfunction in association with COX-2, nuclear factor-&kappa;B (NF-&kappa;B) expression, and prostanoid production.Methods: Twelve-week-old male Wistar rats were separated into five groups: 1) diabetes with 0.9% normal saline (DM-NSS; n = 10), 2) diabetes treated with curcumin 30 mg/kg (n = 10), 3) diabetes treated with curcumin 300 mg/kg (n = 10), 4) the control with 0.9% normal saline (n = 10), and 5) the control treated with 300 mg/kg (n = 10). Daily oral feeding of curcumin was started at 6 weeks after the streptozotocin injection. Levels of 6-keto prostaglandin (PG) F1&alpha; and thromboxane (TX) B2 were determined from mesenteric perfusates using enzyme immunoassay kits. Protein kinase C (PKC)-&szlig;II and COX-2 with NF-&kappa;B levels were analyzed in the mesenteric arteries by immunofluorescent staining and immunohistochemistry, respectively.Results: The ratio of 6-keto-PGF1&alpha; and TXB2 was significantly decreased in DM-NSS compared with the control (P &lt; 0.05). Double-immunofluorescent staining with specific antibodies for PKC-&beta;II and a-smooth muscle actins showed that the diabetic mesenteric arteries contained increased of PKC-&beta;II within the vascular wall. Also, COX-2 expression and activated NF-&kappa;B in the small mesenteric artery of diabetes mellitus rats were markedly increased when compared with the control. Interestingly, curcumin could inhibit the upregulation of all of these biomarkers.Conclusion: These findings show that curcumin can attenuate diabetes-induced vascular dysfunction in association with its potential for COX-2 and NF-&kappa;B suppression, PKC inhibition, and improving the ratio of prostanoid products PGI2/TXA2.Keywords: diabetes, endothelial dysfunction, COX-2, prostanoids

Curcumin improves sclerosing cholangitis in Mdr2−/− mice by inhibition of cholangiocyte inflammatory response and portal myofibroblast proliferation

Background and aimChronic cholangiopathies have limited therapeutic options and represent an important indication for liver transplantation. Curcumin, the yellow pigment of the spice turmeric, has pleiotropic actions and attenuates hepatic...

Effect of curcumin on hyperglycemia-induced vascular endothelial growth factor expression in streptozotocin-induced diabetic rat retina

Diabetic retinopathy is one of the most devastating microvascular complications of long standing type 1 and type 2 diabetes. Neovascularization stimulated by hyperglycemia-mediated induction of vascular endothelial growth factor (VEGF) has been implicated in the pathogenesis. Various small molecules have been investigated for their ability to inhibit angiogenesis. In this study, we evaluated whether curcumin and its dietary source turmeric can inhibit VEGF expression in strepotzotocin (STZ)-induced diabetic rat retina. Diabetes was induced in 3-month-old male WNIN rats by a single intraperitoneal injection of STZ. After induction, one group of diabetic rats were fed only the AIN-93 diet and the rest of the groups were fed with AIN-93 diet containing 0.002% or 0.01% curcumin or 0.5% turmeric for a period of 8 weeks. The control rats received sham injection and fed on the AIN-93 diet. At the end of 8 weeks animals were sacrificed and retina was dissected. The VEGF expression was analyzed by both real time PCR and immunoblotting. There was an increase in VEGF expression in diabetic retina as compared to control retina at both transcript and protein level. Notably, feeding of curcumin and turmeric to diabetic rats inhibited expression of VEGF. This study highlights the importance of biologically active compounds derived from dietary agents that could be explored further for the prevention and/or treatment of diabetic retinopathy.

Elevated expression of αA- and αB-crystallins in streptozotocin-induced diabetic rat

α-Crystallin, a predominant protein of the ocular lens, is composed of two subunits, αA and αB. Of these, αB-crystallin has been shown to present widely in non-lenticular tissues while αA-crystallin is largely lens-specific. Although, expression of αB-crystallin is elevated under various stress and pathological conditions, yet its physiological significance remained unknown. Some studies suggest that the expression of αB-crystallin gene is related to oxidative stress. Persistent hyperglycemia during uncontrolled diabetes is known to cause oxidative stress, which has been implicated in various secondary complications of diabetes. Hence, expression of αA- and αB-crystallins in various tissues of streptozotocin (STZ)-induced diabetic Wistar-NIN rats was investigated by RT-PCR and immunoblotting. While expression of αB-crystallin was noted in the wide range of tissues examined in the study, αA-crystallin expression was detected only in lens and retina. Interestingly, αB-crystallin expression was elevated in lens, heart, muscle, and brain, but decreased in adipose tissue of diabetic rats compared to control rats. αA-Crystallin expression was increased in retina of diabetic rat. Increased oxidative stress appears to be a major stimulus for the enhanced expression of αA- and αB-crystallins in the tissues of diabetic rats and elevated expression of α-crystallin may have a protective role against metabolic stress. Interestingly, feeding of curcumin, a dietary antioxidant, to diabetic rats attenuated the enhanced expression of αB-crystallin. The results indicate that elevated expression of α-crystallins in some tissues may have implications in pathophysiology of diabetic complications.

Dietary supplementation of curcumin enhances antioxidant and phase II metabolizing enzymes in ddY male mice: possible role in protection against chemical carcinogenesis and toxicity.

Dietary antioxidants protect laboratory animals against the induction of tumours by a variety of chemical carcinogens. Among possible mechanism of protection against chemical carcinogenesis could be mediated via-antioxidant-dependent induction of detoxifying enzymes. Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food colouring material and exhibits antiinflammatory antitumour, and antioxidant properties. In this study we therefore investigated the effect of dietary supplementation of curcumin on the activities of antioxidant and phase II-metabolizing enzymes involved in detoxification, and production of reactive oxygen species were quantified in ddY male mice. Dietary supplementation of curcumin (2%, w/v) to male ddY mice for 30 days significantly increased the activities of glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and catalase to 189%, 179%, 189%, and 181% in liver and 143%, 134%, 167% and 115% in kidney respectively as compared with corresponding normal diet fed control (P<0.05-0.001). Parallel to these changes, curcumin feeding to mice also resulted in a considerable enhancement in the activity of phase II-metabolizing enzymes viz. glutathione S-transferase and quinone reductase to 1.7 and 1.8 times in liver and 1.1 and 1.3 times in kidney respectively as compared with corresponding normal diet fed control (P<0.05-0.01). In general, the increase in activities of antioxidant and phase II-metabolizing enzymes was more pronounced in liver as compared to kidney. The induction of such detoxifying enzymes by curcumin suggest the potential value of this compound as protective agent against chemical carcinogenesis and other forms of electrophilic toxicity. The significance of these results can be implicated in relation to cancer chemopreventive effects of curcumin against the induction of tumours in various target organs.

Chemopreventive effect of curcumin on N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats.

Modifying effects of curcumin (derived from the rhizome of Curcuma longa L.) during the initiation or post‐initiation phase of N‐nitrosomethylbenzylamine (NMBA)‐induced esophageal carcinogenesis were investigated in male F344 rats. Five‐week‐old rats were divided into 5 groups, and groups 1, 2 and 3 were given intraperitoneal injections of NMBA (0.5 mg/kg body weight/injection 15 times) for 5 weeks from 7 weeks old to induce esophageal neoplasms. Groups 2 and 3 were fed the diet containing 500 ppm curcumin during the initiation and post‐initiation phases, respectively. Group 4 was given the diet containing curcumin throughout the experiment, and group 5 was kept on the basal diet alone and served as an untreated control. Incidence and multiplicity of esophageal neoplasms of group 1 (NMBA alone) were 66.7% and 0.83 ±0.70, respectively. Those of groups 2 and 3 were significantly less than those of group 1 (39.3%, 0.46±0.64, P < 0.05; 33.3%, 0.36±0.56, P < 0.05, respectively). Furthermore, the incidence and multiplicity of esophageal preneoplastic lesions (moderate or severe epithelial dysplasia) of group 2 (57.1%, 0.61±0.57; 40%, 0.29±0.46) or 3 (56.7%, 0.67±0.66; 23.3%, 0.23±0.43) were less than those of group 1 (100%, 1.67±0.70; 70.8%, 0.92±0.72) (P < 0.05). In this experiment, feeding of curcumin significantly decreased the expression of cell proliferation biomarkers (5‐bromo‐2′‐deoxyuridine labeling index) in the non‐lesional esophageal epithelium (P < 0.01). These findings indicate that curcumin inhibits NMBA‐induced esophageal carcinogenesis when given during the post initiation as well as initiation phase. This inhibition may be related to suppression of the increased cell proliferation induced by NMBA in the esophageal epithelium.

Mechanism of inhibition of benzo[a]pyrene-induced forestomach cancer in mice by dietary curcumin.

Curcumin (diferuloylmethane), the major yellow pigment in turmeric, has been shown to inhibit benzo[a]pyrene (BaP)-induced forestomach cancer in mice through mechanism(s) not fully understood. It is well known that while cytochrome P4501A1 (CYP1A1) and epoxide hydrolase (EH) are important in the conversion of BaP to its activated form, (+)-anti-7,8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BaPDE], the detoxification of (+)-anti-BaPDE is accomplished by glutathione (GSH) S-transferases (GST). Therefore, it seems reasonable to postulate that curcumin may exert anti-carcinogenic activity either by inhibiting activation of BaP or (and) by enhancing the detoxification of (+)-anti-BaPDE. Administration p.o. of 2% curcumin in the diet to female A/J mice for 14 days, which has been shown to cause a significant inhibition in BaP-induced forestomach tumorigenesis, resulted in a modest but statistically significant reduction in hepatic ethoxyresorufin O-deethylase (EROD) activity, a reaction preferentially catalyzed by CYP1A1. While EROD activity could not be detected in the forestomach of either control or treated mice, curcumin feeding caused a statistically significant increase (approximately 2.3-fold) in hepatic EH and GST activities. Hepatic and forestomach GSH levels, and forestomach EH and GST activities were not affected by curcumin treatment. Even though the levels of various hepatic GST isoenzymes were significantly increased upon curcumin feeding, maximum induction was noticed for the pi class isoenzyme (mGSTP1-1), which among murine hepatic GSTs is highly efficient in the detoxification of (+)-anti-BaPDE. In conclusion, the results of the present study suggest that curcumin may inhibit BaP-induced forestomach cancer in mice by affecting both activation as well as inactivation pathways of BaP metabolism in the liver.