Histological studies of neuroprotective effects of Curcuma longa Linn. on neuronal loss induced by dexamethasone treatment in the rat hippocampus.

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Histological studies of neuroprotective effects of Curcuma longa Linn. on neuronal loss induced by dexamethasone treatment in the rat hippocampus Acharaporn Issuriya a , Ekkasit Kumarnsit a,b , Chatchai Wattanapiromsakul c , Uraporn Vongvatcharanon d,∗ a

Department of Physiology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand Natural Product Research Center of Excellence, Faculty of Science, Prince of Songkla University, Songkhla, Thailand c Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Science, Prince of Songkla University, Songkhla, Thailand d Department of Anatomy, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla, Thailand b

a r t i c l e

i n f o

Article history: Received 22 July 2014 Received in revised form 22 September 2014 Accepted 23 September 2014 Available online xxx Keywords: Curcuma longa Dexamethasone Chronic stress Cresyl violet Glial fibrillary acidic protein Hippocampus Rats

a b s t r a c t Long term exposure to dexamethasone (Dx) is associated with brain damage especially in the hippocampus via the oxidative stress pathway. Previously, an ethanolic extract from Curcuma longa Linn. (CL) containing the curcumin constituent has been reported to produce antioxidant effects. However, its neuroprotective property on brain histology has remained unexplored. This study has examined the effects of a CL extract on the densities of cresyl violet positive neurons and glial fibrillary acidic protein immunoreactive (GFAP-ir) astrocytes in the hippocampus of Dx treated male rats. It showed that 21days of Dx treatment (0.5 mg/kg, i.p. once daily) significantly reduced the densities of cresyl violet positive neurons in the sub-areas CA1, CA3 and the dentate gyrus, but not in the CA2 area. However, CL pretreatment (100 mg/kg, p.o.) was found to significantly restore neuronal densities in the CA1 and dentate gyrus. In addition, Dx treatment also significantly decreased the densities of the GFAP-ir astrocytes in the subareas CA1, CA3 and the dentate gyrus. However, CL pretreatment (100 mg/kg, p.o.) failed to protect the loss of astrocytes in these sub-areas. These findings confirm the neuroprotective effects of the CL extract and indicate that the cause of astrocyte loss might be partially reduced by a non-oxidative mechanism. Moreover, the detection of neuronal and glial densities was suitable method to study brain damage and the effects of treatment. © 2014 Elsevier GmbH. All rights reserved.

Introduction Neurodegenerative diseases are irreparable conditions that result in a progressive degeneration and destruction of nerve cells. They cause impairments especially malfunctions of movement and mentality. In general, neurodegeneration affects memory processing, thinking abilities, personality and behavior. The number of patients diagnosed with neurodegenerative disorders is

Abbreviations: ACTH, adrenocorticotropic hormone; CL, Curcuma longa Linn.; CRH, corticotropin releasing hormone; DG, dentate gyrus; Dx, dexamethasone; GCs, glucocorticoids; GFAP-ir, glial fibrillary acidic protein immunoreactive; HPA, hypothalamic pituitary adrenal; NaCl, sodium chloride; PBS, phosphate buffered saline; veh, vehicle. ∗ Corresponding author. E-mail address: [email protected] (U. Vongvatcharanon).

progressively increasing owing to a growing proportion of an aging population. Etiology of the diseases is complicated with interactions among individuals, genetics and diverse factors such as aging, sex hormones, disorders and stressful life incidents (Esch et al., 2002; Hoenicka, 2006; Winner et al., 2011). One of the strong candidate factors for neurodegenerative diseases is stress, present in daily life, or from clinical situations. Stress induces the secretion of the corticotropin releasing hormone (CRH) that activates the hypothalamic pituitary adrenal axis (HPA axis) and sympathetic nervous system (O’Connor et al., 2000). Basically, CRH stimulates the release of the adrenocorticotropic hormone (ACTH) from the pituitary gland, which in turn leads to the secretion of glucocorticoids (GCs) from the adrenal cortex as an end point of activation of the HPA axis (Hauger et al., 1987). GCs serve to maintain the homeostatic energy supply for urgent responses during stress. However, long term activation of the HPA axis leads to various aversive consequences. Chronic psychosocial

http://dx.doi.org/10.1016/j.acthis.2014.09.009 0065-1281/© 2014 Elsevier GmbH. All rights reserved.

Please cite this article in press as: Issuriya A, et al. Histological studies of neuroprotective effects of Curcuma longa Linn. on neuronal loss induced by dexamethasone treatment in the rat hippocampus. Acta Histochemica (2014), http://dx.doi.org/10.1016/j.acthis.2014.09.009

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Fig. 1. Micrographs of representative coronal sections of the rat hippocampus showing CA (1), CA2 (2), CA3 (3) and the dentate gyrus (DG) (4) of the four different treatment groups: Control, Curcuma longa extract (CL), Dexamethasone (Dx), and Curcuma longa extract + Dexamethasone + (Dx + CL) groups. Scale bar = 40 ␮m.

stress was found to trigger an excessive increase of GC levels (Quax et al., 2013; Srinivasan et al., 2013). The augmented GC levels in blood have been positively correlated with aging in humans and animals (Landfield et al., 1978). A link between the consequences of stress and neurodegeneration has been hypothesized, in particular when hypersecretion of GCs was revealed in neurologic disorders such as Alzheimer’s, Parkinson’s and Huntington’s·diseases (Hartmann et al., 1997; Notarianni, 2013; Vyas and Maatouk, 2013). In extreme cases such as in Cushing’s syndrome, high plasma levels of cortisol were associated with a diminished hippocampal volume and with severely impaired cognitive functions (Starkman et al., 1992). The brain is a major target for action of GCs with a high lipophilicity for passing the blood brain barrier (BBB) to bind their receptors on neurons and glia (Reul and de Kloet, 1985). In an animal study, hypercortisolemia was demonstrated to cause cognitive impairments associated with a decrease of hippocampal volume (O’Brien et al., 2004). Chronic exposure to GCs that accompanied psychosocial stress also resulted in elevation of apoptosis in the hippocampal regions (Arbel et al., 1994). The hippocampus is a major region of the brain for memory processing. It has a high density of GR receptors that have been hypothesized to underlie memory impairment following long term exposure to stress (Elliott et al., 1993). In an acute study, dexamethasone (synthetic steroid glucocorticoids) induced the death of neuronal cells through the

apoptotic process (Mitchell et al., 1998). It increased glutamate accumulation in the synapses that led to increased cytosolic calcium levels and enhanced oxygen radical activities that would finally promote cell death pathways (Tongjaroenbuangam et al., 2011). Curcuma longa Linn. (CL) or turmeric belongs to the Zingiberaceae family. CL plants are predominantly found in tropical Asia and Africa (Ammon and Wahl, 1991). The yellow rhizome is widely used as a relish, colorant and spice additive in food. CL bioactive ingredients in food and their effects on health have been extensively studied. The suppressive effects on reactive oxygen species by CL extracts have generated enormous interest. CL is a dietary food ingredient and is also used as a medicinal herb with antioxidant properties (Maheshwari et al., 2006). Curcumin, the major active component of a CL ethanolic extract, was also known to be an antioxidant with the potential to replace vitamins for neuroprotection of neurological disorders (Kelloff et al., 1996; Garcia-Alloza et al., 2007). In terms of mechanisms, a CL ethanolic extract appeared to reduce oxidative damage and exhibited antioxidative action via potent scavengers of hydroxyl radicals that promoted neurodegenerative processes (Sreejayan and Rao, 1994; Cohly et al., 1998; Barclay et al., 2000; Lim et al., 2001). It is of particular interest when studies in animal models justified that curcumin was safe to use even at very high doses (Wahlstrom and Blennow, 1978).




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Fig. 2. Representative micrographs of the CA1 area magnified from the framed area No.1 (1) in Fig. 1 showing the cresyl violet positive neurons (arrows) in brain section of the 4 different treatment groups. Scale bar = 400 ␮m. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

The initial phase of research on neuronal death had a major focus on microglial involvement. Microglial activation has been associated with many neurodegenerative mechanisms (Jebelli et al., 2014; Wada et al., 2001). However, in recent decades, additional evidence has also been obtained from astroglial studies. Neuronastrocyte mal-interaction was found to underlie pathology of Parkinson’s disease (Kordower et al., 1999) or Alzheimer’s disease (Colombo et al., 2002; Heneka and O’Banion, 2007). A link between astrocytes and neurodegenerative diseases has gained considerable interest. Basically, the astrocytes are known to play supportive roles for neurons. Many studies have set the aim of astrocyte application for therapeutic purposes. However, both neuroprotective and detrimental roles were reported in terms of critical roles for neuronal survival (Rappold and Tieu, 2010). This suggests that the functional role of the astrocytes remains largely inconclusive. In the present experiments, long term pretreatment with a C. longa Linn. ethanolic extract was hypothesized to attenuate dexamethasone-induced neuronal and astrocytic damage in the hippocampus of rats. The numbers of neurons and astrocytes in CA1, CA2, CA3 and DG of the hippocampus were counted in histological studies using Nissl staining and glial fibrillary acidic protein immunoreactivity (GFAP-ir), respectively.

Materials and methods Animals Adult male Wistar rats (weighing 300–350 g) were obtained from the Southern Laboratory Animal Facility, Prince of Songkla University, Thailand and maintained at 22 ◦ C with a 12/12 dark/light cycle (light on at 07:00 a.m.). Standard commercial food pellets and filtered tap water were available ad libitum. The experimental protocols described in this study were approved and guided by the Animal Ethics Committee of the Prince of Songkla University. Neurodegeneration was induced by a once a day intraperitoneal injection of dexamethasone (0.5 mg/kg) for 21 consecutive days. Control animals received normal saline as a vehicle (veh). However, animals began to receive once a day intragastric treatment with either vehicle (distilled water) or CL 5 days before the start of the dexamethasone injection. During a period of 21 days, animals received both treatment and dexamethasone. Altogether, rats were randomly divided into four groups (for intragastric and intraperitoneal administration, respectively) which included control (veh + veh), dexamethasone (veh + Dx), CL (CL + veh) and CL + dexamethasone (CL + Dx) groups.




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Fig. 3. Representative micrographs of the CA2 magnified area from the framed area No.2 (2) in Fig. 1 showing the cresyl violet positive neurons (arrows) in brain sections of the 4 different treatment groups. Scale bar = 400 ␮m. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Dexamethasone preparation

Tissue preparation

Dexon® (General Drugs House co., Ltd.) was diluted with normal saline (0.9% NaCl) to a final concentration (0.5 mg/ml). Dexamethasone was intraperitoneally injected at a volume of 1 ml/kg. The parallel control animals received the vehicle only.

At the end of the experiment, the rats were deeply anaesthetized with Thiopental sodium (100 mg/kg, i.p.), and perfused transcardially with 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.4). The brains were removed and post-fixed with the same fixative solution overnight at 4 ◦ C. Following cryoprotection in 30% sucrose in 0.1 M PBS, coronal serial sections (20 ␮m thick) were cut using a cryostat and mounted on Tespa coated slides for staining with 0.1% cresyl violet.

Curcuma longa Linn. extract preparation C. longa Linn. (CL) was processed at the Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Thailand. The herb (20 kg) was obtained from fresh rhizome of the plant. The ground herbal material was dried at 45–50 ◦ C, powdered and extracted with ethanol three times. After extraction, the mixture was concentrated with a rotary vacuum evaporator. The evaporation yielded 11.23% of a dry yellow crude extract. The crude extract was diluted with 5% Tween 20 in distilled-water (vehicle) to a concentration of 100 mg/ml. For intragastric administration, a solution of CL extract was given to animals at a volume of 1 ml/kg using a ball-tipped gavage needle.

Cresyl violet staining and quantification of the neurons in the hippocampus The sections were de-fatted with alcohol/chloroform, followed by a rehydration process through alcohol and distilled water. Then, the sections were soaked in 0.1% cresyl violet solution (Merck, Darmstadt, Germany) and coverslipped using a gelatin mounting medium. Each sub-area of the hippocampus (CA1, CA2, CA3 and dentate gyrus) was identified using a rat brain atlas (Paxinos and Watson, 2007). The sections were selected by systematic random sampling and coded for subsequent blind analyses. About eight sections from each animal of each staining (n = 8) were used in this




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Fig. 4. Representative micrographs of the CA3 magnified area from the framed area No.3 (3) in Fig. 1 showing the cresyl violet positive neurons (arrows) in brain section of the 4 different treatment groups. Scale bar = 400 ␮m. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

study. The sub areas of the micrograph from selected sections were captured by a digital camera (DP50, Olympus, Japan). The numbers of cresyl violet positive neurons in each micrograph were counted and so were sub-areas of each section examined using image analysis software (Olympus, Japan). The results were expressed as the number of cresyl violet positive neurons per mm2 . Immunohistochemistry The imunohistochemical method has been described previously (Vongvatcharanon et al., 2010). Briefly, free-floating sections were incubated in the following solution and between each of the steps the sections were rinsed with 0.1 M PBS: (1) 2% normal horse serum (Vctor Labs, Burlingame, CA, USA) in PBS with 0.3% Triton X-100 (J.T. Baker Inc., Phillipsburg, NJ, USA) for 1 h; (2) anti-mouse glial fibrillary acidic protein (GFAP) monoclonal antibody (1:200 dilution, Chemicon, USA) overnight at 4 ◦ C; (3) Texas Red anti-mouse IgG (1:200 dilution, Vector Labs, Burlingame, CA, USA) for 1 h at room temperature. Following all the histochemical procedures, the sections were processed through a final rinse with 0.1 M PBS, mounted with Vectashield (Vector Labs, Burlingame, CA) coverslipped and sealed with nail polish. Control sections were processed using a parallel method but omitting the primary antibody to ensure that any observed staining was only due to the binding of antibody to

the GFAP antigen. These controls showed no labeling. The morphology of the GFAP-ir astrocytes was studied with an Olympus BX 50 fluorescence microscope (Olympus Corp., Tokyo, Japan). Data analysis and statistical analysis The numbers of neurons in the hippocampus were reported as positive neurons/mm2 whereas the numbers of GFAP-ir astrocytes were reported in GFAP-ir/mm2 . All data were expressed as a mean value ± S.E.M. Differences between the treatments were analyzed using one-way ANOVA, followed by the Student–Newman–Keuls method. Differences with a p < 0.05 was considered to be statistically significant. Results The density of neurons in the hippocampus Neurons were identified in four sub-areas of the hippocampus; CA1, CA2, CA3 and DG of the 4 different groups of animals (Fig. 1). The distribution of neurons in these sub-areas is collectively shown for comparison among the different treatments (Figs. 2–5). Changes of neuronal density in each sub-area were separately determined (Fig. 6). One-way ANOVA revealed significant differences in the




Fig. 5. Representative micrographs magnified from the framed area of the dentate gyrus (DG) (4) in Fig. 1 showing the cresyl violet positive neurons in each of the treatment groups. Scale bar = 400 ␮m.

sub-areas CA1 [F(3, 31) = 30.26, p < 0.001], CA3 [F(3, 31) = 5.55, p = 0.004], and the dentate gyrus [F(3, 31) = 10.02, p < 0.001], but not CA2. Multiple comparisons also indicated the specific effect of CL treatment in the sub-area CA1. Significant changes were induced by

dexamethasone in sub-areas CA1, CA3 and the dentate gyrus when compared to that of the control levels. Among the changes induced by dexamethasone, treatment with CL extract was found to significantly retain the densities of neurons in the CA1 and the dentate gyrus.

Quantitative data of the GFAP-ir astrocytes in the hippocampus

Fig. 6. Histogram of the neuronal numbers in sub-areas CA1, CA2, CA3 and DG of the rat hippocampus in the 4 different treatment groups (* significantly different from the control group, p < 0.05; # significantly different from the dexamethasone treated group, p < 0.05).

GFAP-ir astrocytes were identified in all four sub-areas of the hippocampus; CA1, CA2, CA3 and DG (Figs. 7–10). One way ANOVA revealed significant changes in the density of the GFAP-ir astrocytes in CA1 [F(3, 31) = 1.43, p = 0.049], CA3 [F(3, 31) = 1.45, p = 0.031], and DG [F(3, 31) = 8.38, p < 0.001] but not CA2 (Fig. 11). Multiple comparisons confirmed that the only significant effect was by dexamethasone treatment on the densities of GFAP-ir astrocyte in sub-areas CA1, CA3 and the DG of the hippocampus. Also no significant effect was observed for the CL extract nor for the CL treatment with dexamethasone whereas dexamethasone alone induced a reduction of the GFAP-ir astrocytes. Altogether, the density of the GFAP-ir astrocytes in most of the hippocampal sub-areas was decreased by dexamethasone treatment. In addition, the CL extract did not alter the density from the baseline levels or prevent the density decreased by the dexamethasone treatment.




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Fig. 7. Micrographs of GFAP-ir astrocytes (arrows) in sub-area CA1 of the rat hippocampus in the four different treatment groups. Scale bar = 400 ␮m.

Discussion The present findings strongly confirmed that this histological study was beneficial for the identification of neurodegeneration

and the efficacy of CL treatment. Dexamethasone treatment for 21 days reduced both the cresyl violet positive neurons and the GFAP-ir astrocytes in the hippocampal regions. These data were consistent with previous reports (Sapolsky et al., 1985; Woolley

Fig. 8. Micrographs of GFAP-ir astrocytes (arrows) in sub-area CA2 of the rat hippocampus in the four different treatment groups. Scale bar = 400 ␮m.




Fig. 9. Micrographs of the GFAP-ir astrocytes (arrows) in sub-area CA3 of the rat hippocampus in the four different treatment groups. Scale bar = 400 ␮m.

et al., 1990; Reagan and McEwen, 1997; Hibberd et al., 2000; Haynes et al., 2001; Conrad et al., 2007). Chronic administration of dexamethasone has been associated with learning and memory impairments (Sekita-Krzak et al., 2003; Danilczuk et al., 2006; Tongjaroenbuangam et al., 2011) that are accompanied by severe

histological damage and neuronal apoptosis in the hippocampus (Li et al., 2010). Dexamethasone-induced neuronal apoptosis is mediated via a type II glucocorticoid receptor-dependent mechanism (Haynes et al., 2001). It has been hypothesized that glucocorticoids (GCs)

Fig. 10. Micrographs of the GFAP-ir astrocytes (arrows) in sub-area DG of the rat hippocampus in the four different treatment groups. Scale bar = 400 ␮m.




Fig. 11. Histogram of the numbers of GFAP-ir astrocytes sub-areas CA1, CA2, CA3 and DG of the rat hippocampus in the four different treatment groups (* significantly different from the control group, p < 0.05).

could impair energy metabolism by inhibiting glucose transport (Virgin, Jr. et al., 1991) and an upregulation of a glutamate neurotransmitter (Moghaddam et al., 1994). Thus, overstimulation of the glutamate receptors could result in an excessive calcium influx and disturbance of the postsynaptic calcium homeostasis leading to the production of free radicals via Ca2+ -dependent enzymes. These factors are known to cause degradation of intracellular components and mitochondrial damage leading to a degeneration of cytoskeletal proteins and finally neuronal damage (Szatkowski and Attwell, 1994; Sapolsky, 1996; Abraham et al., 2001). On the other hand, GCs could also enhance neuronal damage by diminishing the antioxidant enzyme capacity in the brain (McIntosh and Sapolsky, 1996). In addition, the effects of GCs on astrocytes are particularly more direct. Exposure to GCs was found to reduce the numbers of astrocytes through the inhibition of astrocyte proliferation in vivo (Unemura et al., 2012). Consistently, reductions of GFAP expression both in terms of the RNA or protein levels, as well as the number of GFAP positive cells, were induced by exposure to GCs (Nichols et al., 1990; Czeh et al., 2006; Claessens et al., 2012). In terms of mechanism, GCs cause the astrocytes to exit from the cell cycle that contribute to a functional remodeling and imbalance of astrocytes (Yu et al., 2008). At some levels, GCs exposure might share some common mechanisms with chronic stress by interfering with glial cell metabolism through glutamatergic mechanisms (Banasr et al., 2010). GCs are important mediators of the classic stress responses. Increases in the levels of GCs during chronic psychosocial stressors have been hypothesized to affect the structure and function of the central nervous system (CNS), especially the hippocampus. Previously, elevated levels of GCs were associated with neurotoxicity (Hibberd et al., 2000; Conrad et al., 2007). The neurotoxic action of GCs were positively correlated to some forms of dementia, such as posttraumatic dementia, cognitive impairments in patients with depression even Cushing’s syndrome, with difficulties in memory and concentration in patients treated with exogenous corticosteroids (Sekita-Krzak et al., 2003). The expression of receptors for GCs was especially demonstrated on both neurons (McEwen et al., 1968) and astrocytes (Vielkind et al., 1990). These results might explain why exposure to GCs causes cognitive impairment and loss of brain cells. The hippocampus has been extensively studied in terms of the consequences of stress. Dysfunctions of the hippocampus could result in endocrine abnormalities, as well as cognitive and memory deficits. Hippocampal neurons are reported to be damaged by

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exposure to stressor activation of the hypothalamic–pituitary– adrenal (HPA) axis and elevation of GCs (Jacobson and Sapolsky, 1991; Yu et al., 2004). High levels of GCs are associated with synaptic loss in the hippocampus, hippocampal atrophy, and cognitive decline during aging in some individuals (Nichols et al., 2001). GFAP is an intermediate filament protein expressed by numerous cell types of the CNS including astrocytes (Szymas et al., 1986). GFAP preserves astrocyte mechanical strength (Cullen et al., 2007) and is involved in many important CNS processes including cell communication and the functioning of the blood brain barrier (Liedtke et al., 1996). Clinically, astrocytic loss and dysfunction have been implicated in the pathogenesis of psychiatric disorders such as major depression (Yu et al., 2011). The histological data of this study also demonstrated the neuroprotective effects of a C. longa Linn. (CL) ethanolic extract. Curcumin, the major compound in a CL ethanolic extract, is capable of scavenging oxygen free radicals such as superoxide anions and hydroxyl radicals (Reddy and Lokesh, 1992). The phenolic and the methoxy group on the phenyl ring appear to be important structural features for these actions (Araujo and Leon, 2001). Moreover, another possible anti-oxidative mechanism of curcumin is to increase the activity of antioxidant enzymes such as GSH, superoxide dismutase and catalase (Shukla et al., 2003). Previously, pretreatment with curcumin was shown to significantly attenuate kainic acid induced neuronal cell death via the oxidative stress pathway in CA1 and CA3 sub-regions of the rat hippocampus (Sumanont et al., 2006). Apart from its protective effects, curcumin administration also increased hippocampal neurogenesis in chronically stress-induced behavioral abnormalities and hippocampal neuronal damage in rats (Xu et al., 2007). In aged rats, prolonged treatment of curcumin was found to enhance hippocampal neurogenesis (Dong et al., 2012). On the other hand, there was no protective effect of the CL extract on the density of GFAP-ir astrocytes observed. In general, astrocytes have a lower level of ROS under resting conditions and generate lower ROS levels when exposed to GCs. Thus, astrocytes are less likely to suffer from any distruption induced by ROS such as in the permeability of the mitochondrial membrane, a major trigger of apoptosis (Garrido et al., 2006). Therefore, this reason might explain why a compound with antioxidant activity like the CL extract did not protect astrocytes from oxidative damage and cell loss. However, over a longer time period, the dysfunction of glial cells might exert adverse consequences on several brain functions. This is because most of the normal brain mechanisms are maintained by functional astrocytes. In particular, astrocytes play a major role in the maintenance of the blood brain barrier (Abbott, 2002). In addition, astrocytes have been found to support normal brain function through their housekeeping activities (Maragakis and Rothstein, 2006). In conclusion, long term exposure to dexamethasone decreased the densities of both neurons and astrocytes in the hippocampus. The CL ethanolic extract exhibited a protective effect against the dexamethasone-induced loss of neurons but not the astrocytes. These findings indicate that histological methods can effectively provide scientific evidence of neurodegenerative processes and treatment mechanisms.

Acknowledgements This work was financially supported by grants from the Graduate School, Prince of Songkla University and Departments of Physiology, Faculty of Science, Prince of Songkla University. Thanks to Dr Brian Hodgson for assistance with the English.




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In vitro larvicidal effects of ethanolic extract of Curcuma longa Linn. on Haemonchus larval stage.

Toxicity studies on Alpinia galanga and Curcuma longa.

Pharmacology of Curcuma longa.

Neuroprotective effects of Psoralea corylifolia Linn seed extracts on mitochondrial dysfunction induced by 3-nitropropionic acid.

Q-TOF-MS: An Application in Turmeric Cultivation.

Effects of cycloheximide on delayed neuronal death in rat hippocampus.

Adriamycin-induced oxidative stress is prevented by mixed hydro-alcoholic extract of Nigella sativa and Curcuma longa in rat kidney.

Anti-fatty liver effects of oils from Zingiber officinale and Curcuma longa on ethanol-induced fatty liver in rats.

Synergistic effects of Rhizoma Paridis and Rhizoma Curcuma longa on different animal tumor models.

Fuel smoke condensate induced DNA damage in human lymphocytes and protection by turmeric (Curcuma longa).

Melatonin ameliorates dexamethasone-induced inhibitory effects on the proliferation of cultured progenitor cells obtained from adult rat hippocampus.

Prevention by the NMDA receptor antagonist, MK801 of neuronal loss produced by tetanus toxin in the rat hippocampus.

Protective effect of vinconate on ischemia-induced neuronal damage in the rat hippocampus.

Dose-dependent effect of Curcuma longa for the treatment of Parkinson's disease.

A histological study of toxic effects of aluminium sulfate on rat hippocampus.

Dexamethasone enhances necrosis-like neuronal death in ischemic rat hippocampus involving μ-calpain activation.

Neuronal supersensitivity to acetylcholine induced by kindling in the rat hippocampus.

Effects of alcoholization on the rat hippocampus.

Isolation and characterization of bacterial endophytes of Curcuma longa L.

Neuroprotective effects of Rhizoma Dioscoreae polysaccharides against neuronal apoptosis induced by in vitro hypoxia.

Characterization of polysaccharides having activity on the reticuloendothelial system from the rhizome of Curcuma longa.

Correction by dexamethasone treatment of the altered lipolytic cascade induced by adrenalectomy in rat adipocytes.

Neuroprotective effect of quercetin against oxidative damage and neuronal apoptosis caused by cadmium in hippocampus.

Transcriptome profiling of Curcuma longa L. cv. Suvarna.