Biology subjects

Nozaki, C.

Publications and source records attributed to Nozaki, C..

3 recordsLinked to original sources

bioRxiv2024

Mitochondrial Dysfunction and ER Stress in CB1 Receptor Antagonist-Induced Apoptosis in Human Neuroblastoma SH-SY5Y Cells

Cannabinoid receptor type 1 (CB1R) is the key modulator of neuronal viability. In particular, CB1R antagonists provide neuroprotective effects on neurotoxicity caused by e.g. neuronal injury. However, the underlying mechanisms and potential limitations of CB1R antagonism remain unclear. Here we investigated the impact of environmental conditions on CB1R antagonist effects. Unexpectedly, we have found that cell-permeable CB1R antagonists, rimonabant and AM251, induced significant cell death in human neuroblastoma SH-SY5Y cells under serum-free conditions. Mitochondrial morphological analysis revealed mitochondrial swelling characterized by their network fragmentation and cristae reduction. Additionally, phosphoproteomics analysis showed an upregulation of phosphorylated EIF2AK3 (also known as PERK), leading to the activation of the eIF2/ATF4/CHOP pathway, indicative of endoplasmic reticulum (ER) stress. Rimonabant and AM251 treatment also triggered caspase-dependent apoptosis, evidenced by the detection of cleaved caspase 3 and cleaved PARP. These results suggest that cell-permeable CB1R antagonists promote apoptosis via mitochondrial dysfunction and ER stress under serum-free conditions in SH-SY5Y cells. Our findings indicate that while CB1R antagonists may be neuroprotective in certain conditions, they may also pose a neurotoxic risk in environments characterized by cellular stress or nutrient deprivation.

pharmacology and toxicology↗

bioRxiv2024

Cannabinoid CB2 receptors enhance high-fat diet evoked peripheral neuroinflammation

It is known that cannabinoid type 2 (CB2) receptor has anti-inflammatory role, therefore animals without CB2 receptors show enhanced inflammation and pain in the model of chronic pain e.g. neuropathic pain. We previously proposed the upregulated leptin signaling at the peripheral nerve as one of the underlying molecular mechanisms of pain exacerbation in nerve-injured CB2 knockouts, as they displayed robust upregulation of leptin receptors and leptin signaling in peripheral nerve. Due to these past results we hypothesized that CB2 receptor deficiency might also modify the peripheral neuroinflammation lead by chronic exposure to high fat diet (HFD). Interestingly, CB2 knockout animals showed the significant resistance to the HFD-induced neuroinflammation. Namely, 5-week feeding of HFD induced substantial hypersensitivity in WT animals, while tactile sensitivity of HFD-fed CB2 knockouts remained intact. HFD-fed WT animals also displayed the robust upregulation of chemokine CXCR4 expression with increased macrophage infiltration, which was never observed in HFD-fed CB2 knockout mice. Moreover, 5-week HFD-exposure lead significant increase of CD11b+Ly6G-Ly6Chigh cells and decrease of CD11b+Ly6G+Ly6Clow cells in the spleen of WT animals, which was also not found in either HFD-fed CB2 knockouts or standard diet-fed WT and CB2 animals. Together with past report, these results suggest that CB2 receptors might have the double-sided regulatory role in context of the inflammation development, or more widely, immune system regulation. We propose that CB2 signaling is not always anti-inflammatory and could take pro-inflammatory role depending on the cause of the inflammation.

pathology↗

bioRxiv2024

Cellulose Rich Food Leads Anxiety through Gut-Brain Axis-mediated Amygdalar Dopamine Upregulation.

It is widely said that healthy intestinal environment takes essential role for better mental condition. One of the known dietary nutrients which maintains intestinal environment is the dietary fiber. Recent study showed that maintaining intestinal environment by dietary fiber succeeded to alleviate the psychiatric disorder symptoms in animals. However, such effects have only been reported with soluble fiber, which is highly fermentable and promotes short-chain fatty acid (SCFA) production, and not with insoluble fiber. Therefore, we aimed to verify whether insoluble fiber, such as cellulose, can alter emotion via changes in the gut. We divided mice into two groups and fed either standard diet (SD, contains both insoluble and soluble dietary fibers) or cellulose rich diet (CRD, contains cellulose alone as the dietary fibers). The CRD-fed mice displayed 1) the increased the anxiety-like behavior accompanied with 2) the modified amygdalar dopamine signaling. We further found the decreased intestinal SCFA levels along with intestinal permeability, dysmotility and hypersensitivity in CRD-fed mice. These behavioral and physiological effect of CRD has been completely abolished in vagotomized mice, indicating the direct link between intestinal environment exacerbation to the emotion through gut-brain axis. Additionally, the opioid antagonist abolished the CRD-induced anxiety, suggesting the involvement of opioidergic system to the anxiety which may evoked by increased amygdalar dopamine levels. Altogether, our findings suggest that consumption of cellulose alone as the dietary fiber may evoke intestinal abnormalities which fires the vagus nerve then opiodergic system and amygdalar dopamine upregulation, resulting in the enhancement of anxiety. Graphical Abstract: Possible mechanism of CRD-induced anxiety unveiled by current studyOur study clarified that long-consumption of cellulose-rich food (CRD) will lead decrease of SCFAs which may cause the intestinal disability, including decreased motility and increased intestinal permeability as well as upregulation of TRPA1 and SGLT1. These physiological modifications resulted as the intestinal hypersensitivity, which possibly overstimulate the vagal transmission which may activate endogenous opioidergic systems such as enkephalin (Enk) at the nucleus tractus solitarii (NTS). The activation of opioidergic system may suppress the GABAergic neuron in ventral tegmental area (VTA), resulting in the excess release of dopamine and further receptor modification in amygdala (Amyg), which might in the end cause the characteristic anxiety. The figure was created with BioRender.com. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/593082v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1a0c4aborg.highwire.dtl.DTLVardef@1cfefceorg.highwire.dtl.DTLVardef@88cfc0org.highwire.dtl.DTLVardef@1ff5b0a_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗