Identifying the Role of GluN2A in Cerebral Ischemia

Protection of Gueichih-Fuling-Wan on cerebral ischemia-induced brain injury in rodents is mediated by trans-cinnamaldehyde via inhibition of neuroinflammation and apoptosis

Background

Stroke is the leading cause of mortality and morbidity worldwide, and an effective therapeutic strategy for the prevention of patients with cerebral ischemia induced brain injury is lacking. Traditional Chinese medicine with neuroprotective activities might be beneficial and provide alternative therapeutic opportunities for cerebral ischemia.

Purposes

This study aimed to evaluate the neuroprotection and possible mechanisms of Gueichih-Fuling-Wan (GFW), its' constitutive herbs, and their active compounds on cerebral ischemia/reperfusion (I/R)-induced brain injury in rodents.

Methods

Various doses of extracts (0.25, 0.5, and 1.0 g/kg) of GFW and five constituent herbs (Cinnamomi Cortex, CC; Poria cocos, PC; Paeonia lactifloa, PL; Paeonia suffruticosa, PS and Prunus perisica, PP) were orally administered. Different doses of active compounds (0.5, 1.0, and 2.0 mg/kg) of GFW such as cinnamaldehyde, cinnamic acid (from CC), paeoniflorin (from PL), and paeonol (from PS) were intraperitoneally administered. Their effects on cerebral ischemia/ reperfusion (I/R)induced brain injury in rodents were evaluated.

Results

GFW, its' constituent herbs, and the active compounds reduced the infarct area dose-dependently (***P < 0.001). Cinnamaldehyde showed the most significant reduction (***P < 0.001). Therefore, trans-cinnamaldehyde (TCA) was further used to evaluate the neuroprotective mechanism of the I/R-induced brain injury. TCA (10, 20, 30 mg/ kg, p.o.) showed an inhibitory effect of I/R-induced brain damage in mice in a dose-dependent manner. Besides, GFW and TCA dose-dependently reduced the COX-2 protein expression level, and TCA reduced the TUNEL (+) apoptosis. TCA dose-dependently increased the pro-survival NR2A and Bcl-2 protein expression level and decreased the pro-apoptotic NR2B and cytochrome c, caspase 9, and caspase 3 expression (***P < 0.001).

Conclusion

The above data revealed that GFW, its' constituent herbs, and active compounds protected against I/R-induced brain injury in rodents. TCA from CC might participate in GFW protecting against cerebral ischemia-induced brain injury by inhibiting neuroinflammation and apoptosis.

GluN2A and GluN2B N-Methyl-D-Aspartate Receptor (NMDARs) Subunits: Their Roles and Therapeutic Antagonists in Neurological Diseases

N-methyl-D-aspartate receptors (NMDARs) are ion channels that respond to the neurotransmitter glutamate, playing a crucial role in the permeability of calcium ions and excitatory neurotransmission in the central nervous system (CNS). Composed of various subunits, NMDARs are predominantly formed by two obligatory GluN1 subunits (with eight splice variants) along with regulatory subunits GluN2 (GluN2A-2D) and GluN3 (GluN3A-B). They are widely distributed throughout the CNS and are involved in essential functions such as synaptic transmission, learning, memory, plasticity, and excitotoxicity. The presence of GluN2A and GluN2B subunits is particularly important for cognitive processes and has been strongly implicated in neurodegenerative diseases like Parkinson's disease and Alzheimer's disease. Understanding the roles of GluN2A and GluN2B NMDARs in neuropathologies provides valuable insights into the underlying causes and complexities of major nervous system disorders. This knowledge is vital for the development of selective antagonists targeting GluN2A and GluN2B subunits using pharmacological and molecular methods. Such antagonists represent a promising class of NMDA receptor inhibitors that have the potential to be developed into neuroprotective drugs with optimal therapeutic profiles.

PTPRD and DCC Are Novel BACE1 Substrates Differentially Expressed in Alzheimer's Disease: A Data Mining and Bioinformatics Study

The β-site Amyloid precursor protein Cleaving Enzyme 1 (BACE1) is an extensively studied therapeutic target for Alzheimer's disease (AD), owing to its role in the production of neurotoxic amyloid beta (Aβ) peptides. However, despite numerous BACE1 inhibitors entering clinical trials, none have successfully improved AD pathogenesis, despite effectively lowering Aβ concentrations. This can, in part, be attributed to an incomplete understanding of BACE1, including its physiological functions and substrate specificity. We propose that BACE1 has additional important physiological functions, mediated through substrates still to be identified. Thus, to address this, we computationally analysed a list of 533 BACE1 dependent proteins, identified from the literature, for potential BACE1 substrates, and compared them against proteins differentially expressed in AD. We identified 15 novel BACE1 substrates that were specifically altered in AD. To confirm our analysis, we validated Protein tyrosine phosphatase receptor type D (PTPRD) and Netrin receptor DCC (DCC) using Western blotting. These findings shed light on the BACE1 inhibitor failings and could enable the design of substrate-specific inhibitors to target alternative BACE1 substrates. Furthermore, it gives us a greater understanding of the roles of BACE1 and its dysfunction in AD.

Synaptic GluN2A-Containing NMDA Receptors: From Physiology to Pathological Synaptic Plasticity

N-Methyl-d-Aspartate Receptors (NMDARs) are ionotropic glutamate-gated receptors. NMDARs are tetramers composed by several homologous subunits of GluN1-, GluN2-, or GluN3-type, leading to the existence in the central nervous system of a high variety of receptor subtypes with different pharmacological and signaling properties. NMDAR subunit composition is strictly regulated during development and by activity-dependent synaptic plasticity. Given the differences between GluN2 regulatory subunits of NMDAR in several functions, here we will focus on the synaptic pool of NMDARs containing the GluN2A subunit, addressing its role in both physiology and pathological synaptic plasticity as well as the contribution in these events of different types of GluN2A-interacting proteins.

The differences between GluN2A and GluN2B signaling in the brain

The N-methyl-d-aspartate (NMDA) receptor, a typical ionotropic glutamate receptor, is a crucial protein for maintaining brain function. GluN2A and GluN2B are the main types of NMDA receptor subunit in the adult forebrain. Studies have demonstrated that they play different roles in a number of pathophysiological processes. Although the underlying mechanism for this has not been clarified, the most fundamental reason may be the differences between the signaling pathways associated with GluN2A and GluN2B. With the aim of elucidating the reasons behind the diverse roles of these two subunits, we described the signaling differences between GluN2A and GluN2B from the aspects of C-terminus-associated molecules, effects on typical downstream signaling proteins, and metabotropic signaling. Because there are several factors interfering with the determination of subunit-specific signaling, there is still a long way to go toward clarifying the signaling differences between these two subunits. Developing better pharmacology tools, such as highly selective antagonists for triheteromeric GluN2A- and GluN2B-containing NMDA receptors, and establishing new molecular biological methods, for example, engineering photoswitchable NMDA receptors, may be useful for clarifying the signaling differences between GluN2A and GluN2B.