A secretory phospholipase A2-mediated neuroprotection and anti-apoptosis.

BACKGROUND: Phospholipase A2 liberates free fatty acids and lysophospholipids upon hydrolysis of phospholipids and these products are often associated with detrimental effects such as inflammation and cerebral ischemia. The neuroprotective effect of neutral phospholipase from snake venom has been investigated. RESULTS: A neutral anticoagulant secretory phospholipase A2 (nPLA) from the venom of Naja sputatrix (Malayan spitting cobra) has been found to reduce infarct volume in rats subjected to focal transient cerebral ischemia and to alleviate the neuronal damage in organotypic hippocampal slices subjected to oxygen-glucose deprivation (OGD). Real-time PCR based gene expression analysis showed that anti-apoptotic and pro-survival genes have been up-regulated in both in vivo and in vitro models. Staurosporine or OGD mediated apoptotic cell death in astrocytoma cells has also been found to be reduced by nPLA with a corresponding reduction in caspase 3 activity. CONCLUSION: We have found that a secretory phospholipase (nPLA) purified from snake venom could reduce infarct volume in rodent stroke model. nPLA, has also been found to reduce neuronal cell death, apoptosis and promote cell survival in vitro ischemic conditions. In all conditions, the protective effects could be seen at sub-lethal concentrations of the protein.

Chloro-oxime derivatives as novel small molecule chaperone amplifiers.

Chloro-oxime derivatives were investigated as novel small molecule chaperone amplifiers. Lead optimization led to the discovery of compounds that displayed potent HSF1 activation activity, significant cytoprotection in MG-132 stress, ER stress and PolyQ stress cell models (EC(50)<10 microM).

Identification of chaulmoogric acid as a small molecule activator of protein phosphatase 5.

Protein phosphatase 5 (PP5) is an important protein phosphatase that is abundantly expressed in the central nervous system. Recent studies showed that PP5 activity in the neocortex from patients with Alzheimer's disease (AD) is decreased significantly, suggesting that small molecule PP5 activator may have therapeutic potential for AD. We performed a biochemical screening for PP5 activators with the microsource compound library. Chaulmoogric acid was identified to be an effective activator with EC(50) value of 134.5 microM. Importantly, results from circular dichroism (CD) and limited proteolysis study showed that chaulmoogric acid binds to a region of tetratricopeptide repeat (TPR) domain of PP5 resulting in complete loss of helical contents. These results demonstrate a different mechanism of action from that of arachidonic acid, a known activator for PP5 dephosphorylation activity. Synergistic activation of PP5 enzymatic activity was also observed with combined application of both compounds at relatively low concentrations. Therefore, further structure activity relationship study of chaulmoogric acid may facilitate the discovery of small molecules that can synergize with endogenous arachidonic acid for PP5 activation.

Pulmonary inflammation and edema induced by phospholipase A2: global gene analysis and effects on aquaporins and Na+/K+-ATPase.

Victims of snakebite quickly succumb to severe respiratory failure, which can be fatal if left untreated. One of the most toxic components of snake venom is phospholipase A2 (PLA2; EC 3.1.1.4). PLA2 isolated from the elapid, Naja sputatrix, induced pulmonary inflammation and edema when administered intravenously and intratracheally to rats. Analysis of pulmonary gene expression profiles using oligonucleotide microarrays revealed 60 genes whose expression was altered by at least 3-fold in response to intratracheal instillation of PLA2 for 3 h as compared with controls. In addition to genes encoding cytokines and chemokines responsible for inflammatory processes, the Na+/K+-ATPase gene has been found to be involved in edema formation. Real-time PCR, Western blot, and immunohistochemical analyses confirmed that the expression of AQP1 and AQP5 mRNAs and proteins was decreased. Besides providing an experimental model for studies on the pathophysiology of the lung, this investigation yields a clue to the mechanisms by which endogenous PLA2s could mediate inflammation in conditions such as allergy and rheumatoid arthritis.