mRNA levels of Ca2+-independent forms of protein kinase C in postischemic gerbil brain by Northern blot analysis

Abstract

To investigate the role of Ca(2+)-independent forms of protein kinase C (PKC) in ischemic neuronal injury, mRNA expression of PKC was studied by Northern blot analysis. Ischemia was produced in gerbils by 10-min bilateral carotid artery occlusion and was followed by recirculation for 15 min, 6 h, and 24 h. Brains of postischemic and sham-operated animals were removed, forebrains fresh frozen, and processed for Northern blot analysis. Three synthetic oligonucleotide probes based on published cDNA sequences of rat brain PKC for the isozymes delta, epsilon, and zeta were utilized for hybridization. Northern blot analysis showed increased hybridization signal for all three PKC isozymes examined in the 6- and 24-h postischemic groups. Of these, the twofold increases in the expression of PKC delta and zeta were statistically significant in comparison to the control. These results suggest that the mRNA levels of Ca(2+)-independent forms of PKC, in particular, delta and zeta, are temporally stimulated by ischemic injury in the brain and may imply an important role of the enzyme in postischemic neuronal damage. However, since the protein itself was not examined in this study, the significance of the increased expression cannot be ascertained. However, it may reflect a compensatory response to the loss of PKC reported to occur in the reperfusion phase.

Alterations in protein kinase C isoforms in experimentally-induced colitis in the rat

“…In the present study RT-PCR revealed that the mRNA for PKCa decreased while PKCz mRNA increased correspondingly with their respective protein levels. Changes in PKC mRNA in response to tissue injury has been demonstrated in response to an ischemic insult [39,40]. The corresponding changes in mRNA and protein expression for PKCa and PKCz suggest that these isoforms are transcriptionally-regulated.…”

The Role of Protein Kinase C in Cerebral Ischemic and Reperfusion Injury

“…26,48 Some reports demonstrate sustained activation of ⑀PKC after OGD 35,49 and, in response to kainic acid, a glutamate analog. 50 Other reports suggest that ⑀PKC is not activated in response to ischemia 51,52 in an in vivo model of spreading depression by cortical KCl application or by ischemic preconditioning. 31,53 ⑀PKC mRNA increases slightly at 1 hour after reperfusion; however, more significant upregulations were observed in the transcription of other PKC isozymes.…”

“…89,90 Studies demonstrate that ␦PKC is specifically upregulated and rapidly activated in response to reperfusioninduced intracellular signaling; in transient focal and global ischemia models, ␦PKC mRNA is upregulated within 24 hours after ischemia, as seen in perifocal cortex and in CA1 neurons, respectively. 51,91,92 Concomittantly, ␦PKC protein levels are increased in the perifocal region during reperfusion, 92 suggesting a role for this enzyme in mediating delayed-injury processes. Studies in an in vivo transient ischemia model show ␦PKC is rapidly activated at the onset of reperfusion, although this activity is not sustained at 24 hours after ischemia.…”

Suppression of δPKC Activation after Focal Cerebral Ischemia Contributes to the Protective Effect of Hypothermia

“…The CF-dPKC is a constitutively active enzyme, because it is freed from the autoinhibitory constraints imposed by theDelta protein kinase C has been implicated in mediating ischemic and reperfusion brain injuries. Delta protein kinase C mRNA increases after ischemia in CA1 neurons in gerbil and rat models of global ischemia (Savithiry and Kumar, 1994;Koponen et al, 2000). Delta protein kinase C mRNA and protein levels increase near an ischemic lesion after focal cerebral ischemia in rat (Miettinen et al, 1996).…”