Morphine is one of the most prescribed and effective drugs used for the treatment of acute and chronic pain conditions. In addition to its central effects, morphine can also produce peripheral analgesia. However, the mechanisms underlying this peripheral action of morphine have not yet been fully elucidated. Here, we show that the peripheral antinociceptive effect of morphine is lost in neuronal nitric-oxide synthase null mice and that morphine induces the production of nitric oxide in primary nociceptive neurons. The activation of the nitric-oxide pathway by morphine was dependent on an initial stimulation of PI3Kγ/AKT protein kinase B (AKT) and culminated in increased activation of K ATP channels. In the latter, this intracellular signaling pathway might cause a hyperpolarization of nociceptive neurons, and it is fundamental for the direct blockade of inflammatory pain by morphine. This understanding offers new targets for analgesic drug development.M orphine is one of the most prescribed and effective drugs used for treatment of postoperatory and acute severe pain. Nevertheless, its use is frequently limited by undesirable side effects including respiratory depression, tolerance, and addiction. The discovery that morphine can also produce peripheral analgesia in the setting of inflammatory pain opened the possibility of developing peripheral restricted opioids devoid of central side effects (1).Morphine peripheral analgesia was discovered by its direct effect on already established inflammatory hypernociception induced by prostaglandin E 2 (PGE 2 ) injected in rat hind paws (1). Therefore, in contrast to aspirin-like drugs whose analgesic mechanism depends on prevention of nociceptor sensitization by inhibiting synthesis of prostaglandins, opioids are able to directly block ongoing nociceptor sensitization. However, the molecular mechanisms triggered by morphine to promote this action have not been fully elucidated. The present study reports on a series of experiments using behavioral, biochemical, and electrophysiological approaches to address this issue. The following major findings are reported herein: (i) the activation of peripheral opioid receptors in primary nociceptive neurons by morphine triggers a cascade of intracellular signaling events initiated by PI3Kγ/Protein kinase B (AKT); (ii) this is accompanied by activation of neuronal nitric oxide synthase (nNOS) and nitric oxide (NO) production, which (iii) induces an increase in K ATP channel currents; and (iv) it causes a hyperpolarization of nociceptive neurons. Results and DiscussionBased on the evidence that cAMP was the key intracellular second messenger involved in PGE 2 -induced nociceptor sensitization (2) and that opioid-receptor activation in vitro was coupled to adenylyl-cyclase inhibition (3), it was initially suggested that these drugs counteracted inflammatory hypernociception directly through inhibition of PGE 2 -induced adenylyl-cyclase activation (1, 4). Subsequent in vitro studies, which confirmed the ability of opioids to inhibit ad...

This is the first study to demonstrate that necrostatins inhibit myocardial cell death and reduce infarct size, possibly via a mechanism independent of the MPTP.

Amyloid ␤ peptides generate oxidative stress in hippocampal astrocytes through a mechanism sensitive to inhibitors of the NADPH oxidase [diphenylene iodonium (DPI) and apocynin]. Seeking evidence for the expression and function of the enzyme in primary hippocampal astrocytes, we confirmed the expression of the subunits of the phagocyte NADPH oxidase by Western blot analysis and by immunofluorescence and coexpression with the astrocyte-specific marker glial fibrillary acidic protein both in cultures and in vivo. Functional assays using lucigenin luminescence, dihydroethidine, or dicarboxyfluorescein fluorescence to measure the production of reactive oxygen species (ROS) demonstrated DPI and apocynin-sensitive ROS generation in response to the phorbol ester PMA and to raised [Ca 2ϩ ] c after application of ionomycin or P 2u receptor activation. Stimulation by PMA but not Ca 2ϩ was inhibited by the protein kinase C (PKC) inhibitors staurosporine and hispidin. Responses were absent in transgenic mice lacking gp91phox. Expression of gp91phox and p67phox was increased in reactive astrocytes, which showed increased rates of both resting and stimulated ROS generation. NADPH oxidase activity was modulated by intracellular pH, suppressed by intracellular alkalinization, and enhanced by acidification. The protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone suppressed basal ROS generation but markedly increased PMA-stimulated ROS generation. This was independent of mitochondrial ROS production, because it was unaffected by mitochondrial depolarization with rotenone and oligomycin. Thus, the NADPH oxidase is expressed in astrocytes and is functional, activated by PKC and intracellular calcium, modulated by pHi, and upregulated by astrocyte activation. The astrocytic NADPH oxidase is likely to play important roles in CNS physiology and pathology.

Photodynamic therapy (PDT) is an established anticancer treatment employing a phototoxin (photosensitizer), visible light and oxygen. The latter is photochemically converted into reactive oxygen species, which are highly toxic to the cells. Hypericin, a natural pigment of hypericum plants, is prominent among photosensitizers. The unique perylenequinone structure of hypericin is responsible for its intriguing multifaceted photochemical cytotoxicity. The diverse photodynamic action of hypericin targets a range of subcellular organelles most importantly the mitochondria and the endoplasmic reticulum (ER)-Golgi complex. Hypericin exerts its phototoxicity through intricate mechanisms, implicating key proteins, vital enzymes, organelle membranes and changes in cellular homeostasis. This, depending on drug and light administration conditions, leads to cell death, which occurs mainly by the induction of apoptosis and/or necrosis. Cell photosensitization with hypericin is also associated with the stimulation of macroautophagy, which may promote cell demise when the apoptotic machinery is defective. Herein, we aim to integrate the most important findings with regard to hypericin photocytotoxicity, into a unified scenario, detailing its potential in cancer photomedicine.