Furoxans (Oxadiazole-4 N-oxides) with Attenuated Reactivity are Neuroprotective, Cross the Blood Brain Barrier, and Improve Passive Avoidance Memory.

Nitric oxide (NO) mimetics and other agents capable of enhancing NO/cGMP signaling have demonstrated efficacy as potential therapies for Alzheimer's disease. A group of thiol-dependent NO mimetics known as furoxans may be designed to exhibit attenuated reactivity to provide slow onset NO effects. The present study describes the design, synthesis, and evaluation of a furoxan library resulting in the identification of a prototype furoxan, 5a, which was profiled for use in the central nervous system. Furoxan 5a demonstrated negligible reactivity toward generic cellular thiols under physiological conditions. Nonetheless, cGMP-dependent neuroprotection was observed, and 5a (20 mg/kg) reversed cholinergic memory deficits in a mouse model of passive avoidance fear memory. Importantly, 5a can be prepared as a pharmaceutically acceptable salt and is observed in the brain 12 h after oral administration, suggesting potential for daily dosing and excellent metabolic stability. Continued investigation into furoxans as attenuated NO mimetics for the CNS is warranted.

Withania somnifera Improves Ischemic Stroke Outcomes by Attenuating PARP1-AIF-Mediated Caspase-Independent Apoptosis.

Withania somnifera (WS), popularly known as "Ashwagandha" has been used for centuries as a nerve tonic. Its protective effect has been elucidated in many neurodegenerative pathologies, although there is a paucity of data regarding its effects in ischemic stroke. We examined the neuroprotective properties of an aqueous extract of WS in both pre- and poststroke treatment regimens in a mouse model of permanent distal middle cerebral artery occlusion (pMCAO). WS (200 mg/kg) improved functional recovery and significantly reduced the infarct volume in mice, when compared to those treated with vehicle, in both paradigms. We investigated the protective mechanism/s induced by WS using brain cortices by testing its ability to modulate the expression of key proteins in the ischemic-apoptotic cascade. The Western blots and immunofluorescence analyses of mice cortices revealed that WS upregulated the expression of hemeoxygenase 1 (HO1) and attenuated the expression of the proapoptotic protein poly (ADP-ribose) polymerase-1 (PARP1) via the PARP1-AIF pathway, thus preventing the nuclear translocation of apoptosis-inducing factor (AIF), and subsequent apoptosis. Semaphorin-3A (Sema3A) expression was reduced in WS-treated group, whereas Wnt, pGSK3ß, and pCRMP2 expression levels were virtually unaltered. These results indicate the interplay of antioxidant-antiapoptic pathways and the possible involvement of angiogenesis in the protective mechanism of WS while emphasizing the noninvolvement of one of the prime pathways of neurogenesis. Our results suggest that WS could be a potential prophylactic as well as a therapeutic agent aiding stroke repair, and that part of its mechanism could be attributed to its antiapoptotic and antioxidant properties.

Flavonoids isolated from Rumex aquaticus exhibit neuroprotective and neurorestorative properties by enhancing neurite outgrowth and synaptophysin.

There is heightened interest in the field of stroke recovery as there is need for agents that would prevent the debilitating effects of the disorder, thereby tremendously reducing the societal and economic costs associated with it. In this study, the isolation of two flavonoids--quercetin-3-O-galactoside (1) and quercetin-3-O-arabinoside (2)--from Rumex aquaticus (western dock) and their neuroprotective effects were reported in the oxygen-glucose deprivation (OGD) model of in vitro ischemia using rat pheochromocytoma (PC12) cell line. Bioassay-guided fractionation of the ethyl-acetate extract of Rumex aquaticus L. afforded the isolation of compounds 1 and 2. The structures of compounds were established on the basis of spectroscopic analyses (UV, mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). Both compounds were isolated for the first time from this species. In the course of the pharmacological experiments it was detected that these flavonoids at 10 µM concentration significantly improved cell survival in the oxygen-glucose deprivation model of ischemia. Moreover, they also increased neurite outgrowth in differentiated PC12 cells subjected to ischemic insult. Investigations on the cellular mechanism for the observed effect revealed that compound 1 (10 µM) enhances the expression of synaptophysin - a marker of synapses, and an indicator of synaptic plasticity. Rapid restoration of neurological function following injury is paramount to the prevention of debilitating consequences of ischemic stroke. This combination of neuroprotection and neuritogenic potential could be particularly useful in the recovery phase of stroke.

A derivative of the CRMP2 binding compound lanthionine ketimine provides neuroprotection in a mouse model of cerebral ischemia.

Lanthionines are novel neurotrophic and neuroprotective small molecules that show promise for the treatment of neurodegenerative diseases. In particular, a recently developed, cell permeable lanthionine derivative known as LKE (lanthionine ketimine 5-ethyl ester) promotes neurite growth at low nanomolar concentrations. LKE also has neuroprotective, anti-apoptotic, and anti-inflammatory properties. Its therapeutic potential in cerebral ischemia and its mechanisms of neurotrophic action remain to be fully elucidated. Here, we hypothesize that the neuroprotective actions of LKE could result from induction or modulation of CRMP2. We found that treating primary cultured mouse neurons with LKE provided significant protection against t-butyl hydroperoxide-induced neuronal death possibly through CRMP2 upregulation. Similarly, in vivo studies showed that LKE pre and/or post-treatment protects mice against permanent distal middle cerebral artery occlusion (p-MCAO) as evidenced by lower stroke lesions and improved functional outcomes in terms of rotarod, grip strength and neurologic deficit scores in treated groups. Protein expression levels of CRMP2 were higher in brain cortices of LKE pretreated mice, suggesting that LKE's neuroprotective activity may be CRMP2 dependent. Lower activity of cleaved PARP-1 and higher activity of SIRT-1 was also observed in LKE treated group suggesting its anti-apoptotic properties. Our results suggest that LKE has potential as a therapeutic intervention in cerebral ischemia and that part of its protective mechanism may be attributed to CRMP2 mediated action and PARP-1/SIRT-1 modulation.

Sirtuins in neurodegenerative diseases: a biological-chemical perspective.

Sirtuins, commonly known as NAD(+)-dependent class III histone deacetylase enzymes, have been extensively studied to evaluate their potential role in different disease states. Based on the published literature, sirtuins have been implicated in providing a myriad of intrinsic and extrinsic biological effects, which in turn may play an important role in the treatment of various disorders such as type II diabetes, obesity, cancer, aging and different neurodegenerative diseases. In particular, a number of studies have unequivocally supported the idea of sirtuins having therapeutic potential in neurodegenerative diseases such as stroke, ischemic brain injury, Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. To exploit the therapeutic potential of sirtuins, their manipulation in terms of development of small-molecule modulators, inhibitors and analogs has increased dramatically since their inception, in both scientific and industrial worlds. Studies on the structure and catalytic core of sirtuins along with chemical mechanisms and substrate specificity have provided important input into the design and synthesis of sirtuin modulators. To study the role of sirtuins in the biological system, it has become extremely important to understand the molecular and chemical structure of sirtuins. In this review, we have discussed the biological role of sirtuins in various neurodegenerative diseases, and also provided an insight into their chemical structure.