Translocation of telomerase reverse transcriptase coincided with ATP release in postnatal cochlear supporting cells

The spontaneous bursts of electrical activity in the developing auditory system are derived from the periodic release of adenosine triphosphate(ATP)by supporting cells in the Kölliker’s organ.However,the mechanisms responsible for initiating spontaneous ATP release have not been determined.Our previous study revealed that telomerase reverse transcriptase(TERT)is expressed in the basilar membrane during the first postnatal week.Its role in cochlear development remains unclear.In this study,we investigated the expression and role of TERT in postnatal cochlea supporting cells.Our results revealed that in postnatal cochlear Kölliker’s organ supporting cells,TERT shifts from the nucleus into the cytoplasm over time.We found that the TERT translocation tendency in postnatal cochlear supporting cells in vitro coincided with that observed in vivo.Further analysis showed that TERT in the cytoplasm was mainly located in mitochondria in the absence of oxidative stress or apoptosis,suggesting that TERT in mitochondria plays roles other than antioxidant or anti-apoptotic functions.We observed increased ATP synthesis,release and activation of purine signaling systems in supporting cells during the first 10 postnatal days.The phenomenon that TERT translocation coincided with changes in ATP synthesis,release and activation of the purine signaling system in postnatal cochlear supporting cells suggested that TERT may be involved in regulating ATP release and activation of the purine signaling system.Our study provides a new research direction for exploring the spontaneous electrical activity of the cochlea during the early postnatal period.

Maxi-anion channel as a candidate pathway for osmosensitive ATP release from mouse astrocytes in primary culture

In the present study, we aimed to evaluate the pathways contributing to ATP release from mouse astrocytes during hypoosmotic stress. We first examined the expression of mRNAs for proteins constituting possible ATP- releasing pathways that have been suggested over the past several years. In RT-PCR analysis using both control and osmotically swollen astrocytes, amplification of cDNA fragments of expected size was seen for connexins （Cx32, Cx37, Cx43）, pannexin 1 （Pxl）, the P2X7 receptor, MRP1 and MDR1, but not CFTR. Inhibitors of exocytotic vesicular release, gap junction hemi-channels, CFTR, MRP1, MDR1, the P2X7 receptor, and volume-sensitive outwardly rectifying chloride channels had no significant effects on the massive ATP release from astrocytes. In contrast, the hypotonicity-induced ATP release from astrocytes was most effectively inhibited by gadolinium （50 μM）, an inhibitor of the maxi-anion channel, which has recently been shown to serve as a pathway for ATP release from several other cell types. Thus, we propose that the maxi-anion channel constitutes a major pathway for swelling-induced ATP release from cultured mouse astrocytes as well.

Effect of SJAMP on ATP Release of Platelet

The aggregation and ATP release of placelet of normal subjects were measured by platelet lumi aggregometer. It was found that the aggregation curve induced by SJAMP at the concentration of 100 mg/L was a typical second phase aggregation. There existed a certain lag between platelet aggregation and secretion. The secretion actually began slightly after the second phase of aggregation, suggesting that the second phase aggregation induced by SJAMP is not dependent upon the release of contents of dense granule alone. If platelets were incubated with cyclo oxygenase inhibitor, the second phase aggregation was inhibited and no ATP was released. The results indicated that the aggregation and release reaction induced by SJAMP were dependent upon the generation of prostaglandin endoperoxides and TXA 2 in normal subjects. The amount of ATP release was 0.69±0.22 nmol/10 8 platelets as stimulated with SJAMP (100 mg/L). But the amount of ATP release were 1.60±0.25 and 1.37±0.15 nmol/10 8 platelets when platelets were stimulated with ADP (5 μmol/L) and collagen (5 mg/L). The amount of ATP release induced by SJAMP was significantly lower than that of ADP and collagen. These findings indicated that SJAMP was a weaker agonist than ADP in terms of platelets release reaction.

The neuroprotection of electro-acupuncture via the PGC-1α/TFAM pathway in transient focal cerebral ischemia rats

ATP depletion is one of the pathological bases in cerebral ischemia.Electro-acupuncture(EA)is widely used in clinical practice for ischemia.However,the mechanism of EA remains unclear.The purpose of this study was to investigate whether EA could activate the AMPK/PGC-1α/TFAM signaling pathway and,consequently,increase the preservation of ATP in rats with ischemia.In this study,48 rats were randomly divided into four groups as a sham-operation control group(sham group),a middle cerebral artery occlusion group(MCAO group),an EA group,and an EA group blocked by the AMPK inhibitor compound C(EA+CC group)(N=12/group).The rats of the EA group and EA+CC group received the EA treatment for 7 days.The rats that belonged in the two remaining groups were only grasped in the same condition.Then,their brain tissues were collected for further detection.When compared with other groups,EA significantly reduced neurological deficits score and increased motor function.The cerebral infarction volume was significantly reduced in the EA group according to TTC staining.With western blot,we found that EA improved the ratio of p-AMPKα/AMPKα(P<0.05),however,there is no difference between the MCAO group and sham group(P>0.05).In addition,EA also increased the expression of PGC-1αand TFAM(all P<0.05).By Elisa,we observed that EA increased the preservation of ATP(P<0.05)and mitochondrial respiratory enzymes,including Complex I(P<0.05),Complex IV(P<0.05),but not Complex III(P>0.05).In summary,we conclude that EA may protect against ischemic damage in MCAO rats,improve the preservation of ATP and mitochondrial respiratory enzymes.This effect may be positively regulated by the activation of the PGC-1α/TFAM signaling pathway.