MicroRNA-138-5p Targets Pro-Apoptotic Factors and Favors Neural Cell Survival: Analysis in the Injured Spinal Cord

Abstract

The central nervous system microRNA miR-138-5p has attracted much attention in cancer research because it inhibits pro-apoptotic genes including CASP3. We hypothesize that miR-138-5p downregulation after SCI leads to overexpression of pro-apoptotic genes, sensitizing neural cells to noxious stimuli. This study aimed to identify miR-138-5p targets among pro-apoptotic genes overexpressed following SCI and to confirm that miR-138-5p modulates cell death in neural cells. Gene expression and histological analyses revealed that the drop in miR-138-5p expression after SCI is due to the massive loss of neurons and oligodendrocytes and its downregulation in neurons. Computational analyses identified 176 potential targets of miR-138-5p becoming dysregulated after SCI, including apoptotic proteins CASP-3 and CASP-7, and BAK. Reporter, RT-qPCR, and immunoblot assays in neural cell cultures confirmed that miR-138-5p targets their 3′UTRs, reduces their expression and the enzymatic activity of CASP-3 and CASP-7, and protects cells from apoptotic stimuli. Subsequent RT-qPCR and histological analyses in a rat model of SCI revealed that miR-138-5p downregulation correlates with the overexpression of its pro-apoptotic targets. Our results suggest that the downregulation of miR-138-5p after SCI may have deleterious effects on neural cells, particularly on spinal neurons.

MiR-138-5p upregulation during neuronal maturation parallels with an increase in neuronal survival

“…Similarly, miR-138-5p which is involved in migration, axonal growth or in determining the size of dendritic spines [Kisliouk and Meiri, 2013; Liu et al ., 2013; Bicker et al ., 2014], has been shown to regulate both the expression and activity of pro-apoptotic factors (i.e. Casp3, Casp7 and Bak1) following traumatic spinal cord injury [Maza et al ., 2022]. This microRNA is upregulated during CNS maturation as observed previously in cortical development [Liu et al ., 2013].…”

“…1101 Post-transcriptional regulation by microRNAs has been described among many modulators of apoptotic effectors (such as caspases) during the maturation of neuronal cells. Several microRNAs target the Casp3 gene (coding for caspase-3 or CASP-3 protein) and control its expression, such as miR-138-5p [Park et al, 2018;Maza et al, 2022]. This microRNA is one of the most enriched in the CNS [Obernosterer et al, 2006;Ludwig et al, 2016], mainly expressed in both brain and spinal cord neurons and varying depending on neuronal subtype [Maza et al, 2022].…”

“…Several microRNAs target the Casp3 gene (coding for caspase-3 or CASP-3 protein) and control its expression, such as miR-138-5p [Park et al ., 2018;Maza et al ., 2022]. This microRNA is one of the most enriched in the CNS [Obernosterer et al ., 2006; Ludwig et al ., 2016], mainly expressed in both brain and spinal cord neurons and varying depending on neuronal subtype [Maza et al ., 2022]. It has heterogeneous expression and distribution throughout the neural tissue, which changes during CNS development[Obernosterer et al ., 2006; Tatro et al ., 2013; Daswani et al ., 2022].…”

“…Moreover, it has also been shown that its expression levels change over the days of neuronal culture in vitro [Weiss et al ., 2019]. On the other hand, miR-138-5p is known to regulate apoptotic cell death by regulating the expression of pro-apoptotic genes, among which Casp3 [Maza et al ., 2022]. In the present work, we hypothesize that changes in miR-138-5p expression during neuronal maturation could control pro-apoptotic Caspase 3 expression and activity, thereby aiding the survival of neurons exposed to noxious stimuli.…”

Identification Of A New Role Of miR-199a-5p As Factor Implied In Neuronal Damage: Decreasing The Expression Of Its Target X-Linked Anti-Apoptotic Protein (XIAP) After SCI.

“…The miRNAs are short (19-25 nt) non-coding RNA sequences, involved in the regulation of cell physiological and pathophysiological mechanisms, including cell proliferation or death [26][27][28][29][30][31][32]. Studies from our group and other laboratories have shown the dysregulation of miRNA expression following traumatic SCI including those that regulate programmed cell death proteins [33][34][35]. The incremented miR-711 expression after SCI is associated with downregulation of the pro-survival protein Akt [36], whereas decreases in miR-27a may facilitate programmed cell death by allowing expression of pro-apoptotic Bcl-2 family proteins such as Noxa, Puma, and Bax [37].…”