Mice Lacking Functional Fas Death Receptors Are Protected from Kainic Acid-Induced Apoptosis in the Hippocampus

Abstract

The Fas receptor (FasR)/Fas ligand (FasL) system plays a significant role in the process of neuronal loss in neurological disorders. Thus, in the present study, we used a real-time PCR array focused apoptosis (Mouse Apoptosis RT 2 PCR Array) to study the role of the Fas pathway in the apoptotic process that occurs in a kainic acid (KA) mice experimental model. In fact, significant changes in the transcriptional activity of a total of 23 genes were found in the hippocampus of wild-type C57BL/6 mice after 12 h of KA treatment compared to untreated mice. Among the upregulated genes, we found key factors involved in the extrinsic apoptotic pathway, such as tnf, fas and fasL, and also in caspase genes (caspase-4, caspase-8 and caspase-3). To discern the importance of the FasR/FasL pathway, mice lacking the functional Fas death receptor (lpr) were also treated with KA. After 24 h of neurotoxin treatment, lpr mice exhibited a reduced number of apoptotic positive cells, determined by the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) method in different regions of the hippocampus, when compared to wild-type mice. In addition, treatment of lpr mice with KA did not produce significant changes in the transcriptional activity of genes related to apoptosis in the hippocampus, either in the fas and fas ligand genes or in caspase-4 and caspase-8 and the executioner caspase-3 genes, as occurred in wild-type C57BL/6 mice. Thus, these data provide direct evidence that Fas signalling plays a key role in the induction of apoptosis in the hippocampus following KA treatment, making the inhibition of the death receptor pathway a potentially suitable target for excitotoxicity neuroprotection in neurological conditions such as epilepsy.

Regulation of hippocampal Fas receptor and death-inducing signaling complex after kainic acid treatment in mice

“…Interestingly, N-glycosylation of Fas receptor was shown to reduce pro-caspase-8 activation (Shatnyeva et al, 2011), which is in line with p18 fragment downregulation reported in the present study. A recent investigation has also revealed the important role played by Fas receptor (mRNA) in KA-induced hippocampal neuronal death in mice (Ettcheto et al, 2014), but this study did not quantify the status of Fas receptor protein forms.…”

“…Neuronal caspase-8 deletion attenuated cell death induced by systemic KA-injection in the mouse hippocampal CA3 region (Krajewska et al, 2011). Recently, KA-induced hippocampal (CA1/3) neuronal death was markedly attenuated in mice lacking Fas receptor mRNA (Ettcheto et al, 2014; the absence of Fas protein was not tested), further indicating the participation of the extrinsic death pathway.…”

Bi-directional genetic modulation of GSK-3β exacerbates hippocampal neuropathology in experimental status epilepticus

“…GSK-3 has been shown to promote the intrinsic apoptotic pathway but also to inhibit the extrinsic apoptotic pathway 64 . Both are activated by seizures and have been previously linked to seizure-induced cell death 65 , 66 , 75 , 76 .…”

Recommendations from the INHAND Apoptosis/Necrosis Working Group

“…However in adult animals, most pathologists have been taught that the classic “dead red” neuron, which is the most common morphologic manifestation of neuronal death, is a necrotic cell (Figure 19A) (Morgan et al 2004). During the past 10 – 15 years a substantial amount of research has been done to characterize the mechanism of cell death resulting from various toxicants (e.g., domoic or kainic acid, TMT, lead) and pathologic conditions (e.g., seizures, cortical trauma), and it is becoming increasingly apparent that both necrosis and apoptosis can occur in response to the same type of insult, and with similar morphological features with H&E staining (Figure 19B) (Ettcheto et al 2015; Giordano et al 2008; Glassford et al 2002; Krajewska et al 2011; Martin et al 1998; Wang et al 2005; Zhang and Zhu 2011). Morphologically, one may have a sense for which process predominates based on cellular features (Figure 19C), the extent of neuronal loss/death, the amount of tissue damage, and the glial/inflammatory response, but it may be difficult to discern with certainty in most cases without special stains.…”