Mitochondrial Division Inhibitor 1 (mdivi-1) Protects Neurons against Excitotoxicity through the Modulation of Mitochondrial Function and Intracellular Ca2+ Signaling

Abstract

Excessive dynamin related protein 1 (Drp1)-triggered mitochondrial fission contributes to apoptosis under pathological conditions and therefore it has emerged as a promising therapeutic target. Mitochondrial division inhibitor 1 (mdivi-1) inhibits Drp1-dependent mitochondrial fission and is neuroprotective in several models of brain ischemia and neurodegeneration. However, mdivi-1 also modulates mitochondrial function and oxidative stress independently of Drp1, and consequently the mechanisms through which it protects against neuronal injury are more complex than previously foreseen. In this study, we have analyzed the effects of mdivi-1 on mitochondrial dynamics, Ca2+ signaling, mitochondrial bioenergetics and cell viability during neuronal excitotoxicity in vitro. Time-lapse fluorescence microscopy revealed that mdivi-1 blocked NMDA-induced mitochondrial fission but not that triggered by sustained AMPA receptor activation, showing that mdivi-1 inhibits excitotoxic mitochondrial fragmentation in a source specific manner. Similarly, mdivi-1 strongly reduced NMDA-triggered necrotic-like neuronal death and, to a lesser extent, AMPA-induced toxicity. Interestingly, neuroprotection provided by mdivi-1 against NMDA, but not AMPA, correlated with a reduction in cytosolic Ca2+ ([Ca2+]cyt) overload and calpain activation indicating additional cytoprotective mechanisms. Indeed, mdivi-1 depolarized mitochondrial membrane and depleted ER Ca2+ content, leading to attenuation of mitochondrial [Ca2+] increase and enhancement of the integrated stress response (ISR) during NMDA receptor activation. Finally, lentiviral knockdown of Drp1 did not rescue NMDA-induced mitochondrial fission and toxicity, indicating that neuroprotective activity of mdivi-1 is Drp1-independent. Together, these results suggest that mdivi-1 induces a Drp1-independent protective phenotype that prevents predominantly NMDA receptor-mediated excitotoxicity through the modulation of mitochondrial function and intracellular Ca2+ signaling.

Lipopolysaccharide‐induced alteration of mitochondrial morphology induces a metabolic shift in microglia modulating the inflammatory response in vitro and in vivo

“…DRP1 and mitochondrial fission 1 protein (FIS1) are the main mitochondrial fission mediators (Frezza et al, ). We used the mitochondrial fission inhibitor Mdivi‐1 (Ruiz, Alberdi, & Matute, ) as the high (100 ng/mL) dose of LPS induced an increase in fragmented mitochondria (Figure b). We examined the effect of pharmacologically blocking mitochondrial fission in LPS‐exposed microglia cells cultured from Cox8/EGFP mice by pretreatment with 25 μM Mdivi‐1 for 1 hr followed by incubation with LPS (100 ng/mL) for 24 hr.…”

Identification of novel dynamin‐related protein 1 (Drp1) GTPase inhibitors: Therapeutic potential of Drpitor1 and Drpitor1a in cancer and cardiac ischemia‐reperfusion injury

“…Mdivi-1 reduces ischemia-reperfusion (IR) injury in the kidney 6 and heart by inhibiting pathologic fission, thereby decreasing the production of reactive oxygen species (ROS). 13,14 Therefore, we wanted to discover additional more potent and specific Drp1 GTPase inhibitors that are orally bioavailable and nontoxic for use in the treatment of cardiovascular diseases and cancer. 10,11 Coordinated mitochondrial fission that accompanies cell division (mitosis) is called mitotic fission and inhibition of mitotic fission causes cell cycle arrest.…”

Sephin1 Protects Neurons against Excitotoxicity Independently of the Integrated Stress Response

“…In addition, there is some evidence linking excitotoxic conditions to ISR. Neurons exposed to kainate [ 23 ] and NMDA [ 24 , 25 ] showed a phosphorylation of eIF2α and in both cases excitotoxicity was attenuated by salubrinal, which enhances both constitutive (GADD34-independent) and stress-induced (GADD34-mediated) ISR. Importantly, Milhaud et al [ 26 ] reported that guanabenz and other imidazolines inhibit NMDARs in a non-competitive manner and exert neuroprotection against excitotoxicity.…”