Heat Shock Preconditioning and Eicosanoid Pathways Modulate Caspase 3-Like Activity in Superficially Injured Isolated Guinea Pig Gastric Mucosa

Essential role for zinc-triggered p75NTR activation in preconditioning neuroprotection

Ischemic preconditioning (PC) of the brain is a phenomenon by which mild ischemic insults render neurons resistant to subsequent strong insults. Key steps in ischemic PC of the brain include caspase-3 activation and poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, but upstream events have not been clearly elucidated. We have tested whether endogenous zinc is required for ischemic PC of the brain in rats. Mild, transient zinc accumulation was observed in certain neurons after ischemic PC. Moreover, intraventricular administration of CaEDTA during ischemic PC abrogated both zinc accumulation and the protective effect against subsequent full ischemia. To elucidate the mechanism of the zinc-triggered PC (Zn PC) effect, cortical cultures were exposed to sublethal levels of zinc, and 18 h later to lethal levels of zinc or NMDA. Zn PC exhibited the characteristic features of ischemic PC, including caspase-3 activation, PARP-1 cleavage, and HSP70 induction, all of which are crucial for subsequent neuroprotection against NMDA or zinc toxicity. HSP70 induction was necessary for protection, as it halted caspase-3 activation before apoptosis. Interestingly, in both Zn PC in vitro and ischemic PC in vivo, p75(NTR) was necessary for neuroprotection. These results suggest that caspase-3 activation during ischemic PC, a necessary event for subsequent neuroprotection, may result from mild zinc accumulation and the consequent p75(NTR) activation in neurons.

Heat shock preconditioning induces protein carbonylation and alters antioxidant protection in superficially injured guinea pig gastric mucosa in vitro

According to our previous studies, heat shock preconditioning of gastric mucosa requires modulation of protein synthesis and eicosanoid pathways to induce protection against superficial injury. This may be caused by heat shock-induced oxidative stress. We studied the effect of heat shock preconditioning with normothermic recovery on redox status in superficially injured (1.25 mmol NaCl for 5 min) Ussing chamber perfused guinea pig gastric mucosa allowed to recover for 3 hr after injury. Protein oxidation, lipid peroxidation, level of superoxide dismutase, level of heat shock protein 72 (HSP72), and level of oxygen radical absorbance capacity were measured. Superficial injury increased lipid peroxidation. Heat shock preconditioning decreased oxygen radical absorbance capacity and increased protein carbonyl and HSP72 levels, but inhibited electrophysiologic recovery. Exposure to indomethacin and arachidonic acid (AA) partially abolished this pro-oxidative and inhibitory effect on recovery, but maintained HSP72 levels and decreased protein carbonyls, lipid peroxidation, and oxygen radical absorbance capacity. In conclusion, superficial injury increased lipid peroxidation. Heat shock preconditioning alone induced oxidative stress via indomethacin- and AA-sensitive mechanisms. The development of optimal cytoprotective strategy may therefore require control of oxidative stress and modulation of the eicosanoid pathways.

Heat Shock Protein 60 or 70 Activates Nitric-oxide Synthase (NOS) I- and Inhibits NOS II-associated Signaling and Depresses the Mitochondrial Apoptotic Cascade during Brain Stem Death

The cellular and molecular basis of brain stem death remains an enigma. As the origin of a "life-and-death" signal that reflects the progression toward brain stem death, the rostral ventrolateral medulla (RVLM) is a suitable neural substrate for mechanistic delineation of this phenomenon. Here, we evaluated the hypothesis that heat shock proteins (HSPs) play a neuroprotective role in the RVLM during brain stem death and delineated the underlying mechanisms, using a clinically relevant animal model that employed the organophosphate pesticide mevinphos (Mev) as the experimental insult. In Sprague-Dawley rats, proteomic, Western blot, and real-time PCR analyses demonstrated that Mev induced de novo synthesis of HSP60 or HSP70 in the RVLM without affecting HSP90 level. Loss-of-function manipulations of HSP60 or HSP70 in the RVLM using anti-serum or antisense oligonucleotide potentiated Mev-elicited cardiovascular depression alongside reduced nitric-oxide synthase (NOS) I/protein kinase G signaling, enhanced NOS II/peroxynitrite cascade, intensified nucleosomal DNA fragmentation, elevated cytoplasmic histone-associated DNA fragments or activated caspase-3, and augmented the cytochrome c/caspase-3 cascade of apoptotic signaling in the RVLM. Co-immunoprecipitation experiments further revealed a progressive increase in the complex formed between HSP60 and mitochondrial or cytosolic Bax or mitochondrial Bcl-2 during Mev intoxication, alongside a dissociation of the cytosolic HSP60-Bcl-2 complex. We conclude that HSP60 and HSP70 confer neuroprotection against Mev intoxication by ameliorating cardiovascular depression via an anti-apoptotic action in the RVLM. The possible underlying intracellular processes include enhancing NOS I/protein kinase G signaling and inhibiting the NOS II/peroxynitrite cascade. In addition, HSP60 exerts its effects against apoptosis by blunting Mev-induced activation of the Bax/cytochrome c/caspase-3 cascade.

Montelukast in allergic rhinitis: a systematic review and meta-analysis

Allergic rhinitis is common. This systematic review outlines the evidence regarding montelukast in allergic rhinitis and provides a meta-analysis of its efficacy. The evidence suggests that montelukast does reduce nasal symptom score by 3.4% (95% CI: 2.5% to 4.2%) when compared with placebo. Montelukast is not as effective as topical nasal steroids or antihistamines and should therefore be regarded as second line therapy. When used, montelukast should be used in combination with an antihistamine.

Heat shock protein 60 in rostral ventrolateral medulla reduces cardiovascular fatality during endotoxaemia in the rat

The rostral ventrolateral medulla (RVLM) is the origin of a 'life-and-death' signal that reflects central cardiovascular regulatory failure during brain stem death. Using an experimental endotoxaemia model, we evaluated the hypothesis that the 60 kDa heat shock protein 60 (HSP60) reduces cardiovascular fatality during brain stem death via an anti-apoptotic action in the RVLM. In Sprague-Dawley rats maintained under propofol anaesthesia, proteomic or Western blot analysis revealed a progressive augmentation of HSP60 expression in the RVLM after intravenous administration of Escherichia coli lipopolysaccharide (30 mg kg(-1)). Pretreatment with a microinjection of actinomycin D or cycloheximide into bilateral RVLM significantly blunted this HSP60 increase, whereas real-time PCR showed progressive augmentation of hsp60 mRNA. Intriguingly, superimposed on the augmented expression was a progressive decline in mitochondrial, or elevation in cytosolic, HSP60 in ventrolateral medulla. Loss-of-function manipulations in the RVLM using anti-HSP60 antiserum or antisense hsp60 oligonucleotide exacerbated mortality by potentiating the cardiovascular depression during experimental endotoxaemia, alongside intensified nucleosomal DNA fragmentation, elevated cytoplasmic histone-associated DNA fragments or augmented cytochromec-caspase-3 cascade of apoptotic signalling in the RVLM. Immunoprecipitation coupled with immunoblot analysis further revealed a progressive increase in the complex formed between HSP60 and mitochondrial or cytosolic Bax or mitochondrial Bcl-2 during endotoxaemia, alongside a dissociation of the cytosolic HSP60-Bcl-2 complex. We conclude that HSP60 redistributed from mitochondrion to cytosol in the RVLM confers neuroprotection against fatal cardiovascular depression during endotoxaemia via reduced activation of the cytochrome c-caspase-3 cascade of apoptotic signalling through enhanced interactions with mitochondrial or cytosolic Bax or Bcl-2.