Ram Raghubir

Molecular Mechanisms of Apoptosis in Cerebral Ischemia: Multiple Neuroprotective Opportunities

Cerebral ischemia/reperfusion (I/R) injury triggers multiple and distinct but overlapping cell signaling pathways, which may lead to cell survival or cell damage. There is overwhelming evidence to suggest that besides necrosis, apoptosis do contributes significantly to the cell death subsequent to I/R injury. Both extrinsic and intrinsic apoptotic pathways play a vital role, and upon initiation, these pathways recruit downstream apoptotic molecules to execute cell death. Caspases and Bcl-2 family members appear to be crucial in regulating multiple apoptotic cell death pathways initiated during I/R. Similarly, inhibitor of apoptosis family of proteins (IAPs), mitogen-activated protein kinases, and newly identified apoptogenic molecules, like second mitochondrial-activated factor/direct IAP-binding protein with low pI (Smac/Diablo), omi/high-temperature requirement serine protease A2 (Omi/HtrA2), X-linked mammalian inhibitor of apoptosis protein-associated factor 1, and apoptosis-inducing factor, have emerged as potent regulators of cellular apoptotic/antiapoptotic machinery. All instances of cell survival/death mechanisms triggered during I/R are multifaceted and interlinked, which ultimately decide the fate of brain cells. Moreover, apoptotic cross-talk between major subcellular organelles suggests that therapeutic strategies should be optimally directed at multiple targets/mechanisms for better therapeutic outcome. Based on the current knowledge, this review briefly focuses I/R injury-induced multiple mechanisms of apoptosis, involving key apoptotic regulators and their emerging roles in orchestrating cell death programme. In addition, we have also highlighted the role of autophagy in modulating cell survival/death during cerebral ischemia. Furthermore, an attempt has been made to provide an encouraging outlook on emerging therapeutic approaches for cerebral ischemia.

Anticancer, Anti-inflammatory and Analgesic Activity Evaluation of Heterocyclic Compounds Synthesized by the Reaction of 4-Isothiocyanato-4-methylpentan-2-one with Substituted o-Phenylenediamines, o-Diaminopyridine and (Un)Substituted o

4,5-Dimethyl-1,2-phenylenediamine and 4-chloro-1,2-phenylenediamine react with 4-isothiocyanato-4-methylpentan-2-one (15) to give compounds (3a) and (3b), respectively. 3,4-Diaminobenzoic acid reacts similarly with (15) to give a mixture of compounds, possibly (2a) and (2b), which could be cyclized at pH ~5 to compound (3c). 3,4-Diaminopyridine reacted with (15) in DMF to give compounds (5) and (6), whereas condensation of 5,6-diaminopyrimidine and 4,5,6-triaminopyrimidine sulfate under similar conditions gave compounds (8a) and (8b), respectively. Compounds (8a) and (8b) at pH ~4 gave a mixture of compounds (9a), (10a) and (9b), (10b), respectively. Condensation of 4,5-diamino-6-hydroxy-2-mercaptopyrimidine, 4,5-diamino-2,6-dimercapto-pyrimidine and 5,6-diamino-1,3-dimethyluracil hydrate with (15) gave corresponding mercaptopyrimidines (12a), (12b) and (14), respectively. The evaluation of (3a–c), (8a,b), (12a,b) and (14) aganist a small panel of six cancer cell lines, consisting of prostate (DU145), colon (HT29), melanoma (LOX), breast (MCF, MCF7/ADR), ovarian (OVCAR3) and CNS (U251) is reported. The most active was compound (8b), against colon (HT29) (44.2 M). Anti-inflammatory and analgesic activity is also reported.

Healing potential of Calotropis procera on dermal wounds in Guinea pigs

Calotropis procera (Asclepiadaceae) is a well known plant in the Ayurvedic system of medicine. Based on its traditional use this plant was selected for evaluation of its wound healing potential. For this purpose four full thickness excisional wounds of 8.0 mm diameter were inflicted on the back of guinea pigs. Topical application of 20 microl of 1.0% sterile solution of the latex of C. procera twice daily was followed for 7 days. The latex significantly augmented the healing process by markedly increasing collagen, DNA and protein synthesis and epithelisation leading to reduction in wound area. Thus the present study provides a scientific rationale for the traditional use of this plant in the management of wound healing.

Pharmacological evaluation of glutamate transporter 1 (GLT-1) mediated neuroprotection following cerebral ischemia/reperfusion injury ☆

Recently glutamate transporters have emerged as a potential therapeutic target in a wide range of acute and chronic neurological disorders, owing to their novel mode of action. The modulation of GLT-1, a major glutamate transporter has been shown to exert neuroprotection in various models of ischemic injury and motoneuron degeneration. Therefore, an attempt was made to explore its neuroprotective potential in cerebral ischemia/reperfusion injury using ceftriaxone, a GLT-1 modulator. Pre-treatment with ceftriaxone (100mg/kg. i.v) for five days resulted in a significant reduction (P<0.01) in neurological deficit as well as cerebral infarct volume after 1h of ischemia followed by 24h of reperfusion injury. It also caused a significant (P<0.05) upregulation of GLT-1 mRNA, protein and glutamine synthetase (GS) activity. Furthermore, inhibition of ceftriaxone-mediated increased glutamine synthetase activity by dihydrokainate (DHK), a GLT-1 specific inhibitor, confirms the specific effect of ceftriaxone on GLT-1 activity. In addition, ceftriaxone also induced a significant (P<0.01) increase in [(3)H]-glutamate uptake, mediated by GLT-1 in glial enriched preparation, as evidenced by use of DHK and DL-threo-beta-benzyloxyaspartate (DL-TBOA). Thus, the present study provides overwhelming evidence that modulation of GLT-1 protein expression and activity confers neuroprotection in cerebral ischemia/reperfusion injury.

Candesartan improves memory decline in mice: involvement of AT1 receptors in memory deficit induced by intracerebral streptozotocin.

The Renin-angiotensin system, besides blood pressure regulation, affects learning and memory as evidenced by improvement of cognition in hypertensive patients being treated with AT1 receptor blockers like candesartan. The present study examined the influence of candesartan on memory impairment induced by intracerebral streptozotocin (IC STZ 0.5 mg/kg) in mice. Candesartan (0.05 mg/kg and 0.1 mg/kg, i.p.) was given for 14 days following IC STZ administration. The dose of 0.1 mg/kg significantly improved latency period in passive avoidance test. Further, treatment with 0.1 mg/kg candesartan for 14 days significantly improved spatial memory in mice in water maze test also. In another group, after memory impairment in mice following IC STZ administration, memory improving effect of a 7 days treatment with 0.1 mg/kg candesartan lasted only for 3 subsequent days in water maze task. IC STZ increased oxidative stress but pretreatment with 0.1 mg/kg candesartan decreased oxidative stress as indicated by a decrease in MDA and increase in GSH. Further, candesartan decreased free radicals as evidenced by flow cytometry. IC STZ affected cholinergic system also by increasing acetylcholine esterase activity that was restored by pretreatment with 0.1 mg/kg candesartan. Locomotor activity and serum glucose level remained unaffected by candesartan treatment. These results suggest that AT1 receptors play a facilitatory role in STZ induced memory deficit and corroborate number of human studies that AT1 receptor blockers can be used therapeutically against cognitive decline in hypertensive patients.

Antioxidant status during cutaneous wound healing in immunocompromised rats

The present investigation was undertaken to investigate the endogenous status of free radical scavengers during cutaneous wound healing in immunocompromised rats. Antioxidant contents and lipid peroxidation product in terms of malondialdehyde (MDA) have been monitored in the wound tissues of immunosuppressed rats at different time intervals (2, 7 and 14 days) following cutaneous injury. A significant increase in MDA content and decrease in glutathione and vitamin C content was observed in the skin of immunocompromised rats as compared to control subjects. Further, a significant decrease in vitamin C, vitamin E content, catalase and glutathione peroxidase activity was observed at 2 days postwounding in immunocompromised rats. A significant and time-dependent decrease in glutathione content was also observed at 7 and 14 days postwounding. However, the healing tissue on 2 and 7 days postwounding exhibited significantly elevated superoxide dismutase activity. The MDA content was augmented only at 2 days postwounding in immunosuppressed rats. Thus significant alterations in the antioxidant profile accompanied by elevated levels of MDA, a marker of free radical damage may be contributory to impaired wound healing in immunocompromised rats.

Hypoxia Inducible Factor-1: Its Potential Role In Cerebral Ischemia

A divergence in the supply and consumption of oxygen in brain tissue initiates complex cycle of biochemical and molecular events resulting in neuronal death. To overcome such adverse situation, the tissue has to adopt some cellular mechanisms such as induction of various transcription factors, such as hypoxia inducible factor (HIF). It is a transcriptional regulator of oxygen homeostasis and key factor to generate the adaptive responses through upregulation of various target genes involved in the erythropoiesis, angiogenesis as well as glucose metabolism and transport. On the other hand, some studies do suggest that HIF also plays a detrimental role in ischemic reperfusion injury by inducing the pro apoptotic molecules, cytokines such as Nix, BNip3, and IL-20 which cause mitochondrial dysfunction leading to cell death. Hence, modulation of HIF-1 activity seems to provide an innovative therapeutic target to reduce the cellular damage, which arises from ischemic injury. Apart from traditional oxygen dependent HIF regulation, the focus has now shifted toward oxygen independent regulation in cell specific manner through reactive oxygen species involving hypoxia-associated factor, and heat shock protein 90, etc. Therefore, future development of such small molecule regulators for HIF-1 stability and signaling may prove useful to therapeutically target for enhancing recovery and repair in I/R injury.

Rare dipeptide and urea derivatives from roots of Moringa oleifera as potential anti-inflammatory and antinociceptive agents.

In the course of our studies on the isolation of bioactive compounds from the roots of Moringa oleifera, a traditional herb in southeast Asia, rare aurantiamide acetate 4 and 1,3-dibenzyl urea 5 have been isolated and characterized. And also, this is the first report of isolation from this genus. Isolated compound inhibited the production of TNF-alpha and IL-2; further compound 5 showed significant analgesic activities in a dose dependant manner. These findings may help in understanding the mechanism of action of this traditional plant leading to control of activated mast cells on inflammatory conditions like arthritis, for which the crude extract has been used.

Cassane Diterpenes from Caesalpinia bonduc.

Three cassane diterpene hemiketals, caesalpinolide-C, caesalpinolide-D, caesalpinolide-E and one cassane furanoditerpene were isolated from Caesalpinia bonduc. The molecular structures were elucidated using NMR spectroscopy in combination with IR, UV and mass spectral data and relative stereochemistries were determined through ROESY correlation. The isolated compounds were tested for their antiproliferative activity against MCF-7 (breast adenocarcinoma), DU145 (prostate carcinoma), C33A (Cervical carcinoma) and Vero (African green monkey kidney fibroblast) cells.

Synthesis and Anticancer, Antiinflammatory,and Analgesic Activity Evaluation of Some Sulfa Drug and Acridine Derivatives

Summary. Various sulfa drugs were condensed with 4-isothiocyanato-4-methyl-2-pentanone at pH∼3–5 by refluxing in methanol to give various substituted mercaptopyrimidines. On condensation with 9-chloro-2-substituted or -unsubstituted acridines, sulfathiazole gave the corresponding condensed products. N-Ethylaminoadenosine reacted with 9-chloroacridine to the coupled product. Condensation of sulfathiazole with 9-isothiocyanato-2,4-substituted or -unsubstituted acridines afforded the corresponding condensed compounds. The structures of all synthesized compounds were confirmed by spectroscopic methods. Anticancer, antiinflammatory, and analgesic activities of all compounds were investigated.