scholarly journals D-Cell Hypothesis (Trace Amine Hypothesis) of Schizophrenia, and importance of Trace Amine-Associated Receptor, Type 1 (TAAR1)

Author(s):  
Keiko Ikemoto

Mesolimbic dopamine (DA) hyperactivity is a well-known pathophysiological hypothesis of schizophrenia. The author shows a hypothesis to clarify the molecular basis of mesolimbic DA hyperactivity of schizophrenia. An immunohistochemical method was used to show D-neuron (trace amine (TA) neuron) decrease in the nucleus accumbens (Acc) of postmortem brains with schizophrenia. The striatal D-neuron decrease in schizophrenia and consequent (TAAR1) stimulation decrease onto terminals of midbrain ventral tegmental area (VTA) DA neurons induces mesolimbic DA hyperactivity of schizophrenia. Dysfunction of subventricular neural stem cells (NSC), located partially overlapping Acc is the cause of D-neuron decrease in Acc. DA hyperactivity, which inhibits NSC proliferation, causes disease progression of schizophrenia. The highlight is the rational that the “D-cell hypothesis (TA hypothesis) of schizophrenia” is a pivotal theory to link NSC dysfunction hypothesis to DA hypothesis. From a therapeutic direction, (1) TAAR1 agonists, (2) DA D2 antagonists, and (3) neurotrophic substances have potential to normalize mesolimbic DA hyperactivity. To develop novel therapeutic strategies, metabolisms of TAAR1 ligands, and NSC- and D-neuron-pathophysiology of neuropsychiatric illnesses should further be explored.

2021 ◽  
Vol 1 (1) ◽  
pp. 031-038
Author(s):  
Keiko Ikemoto

The latest psychopharmacological study showed effectiveness of a novel non-D2-receptor-binding drug, SEP-363856, for the treatment of schizophrenia. The compound is trace amine-associated receptor 1 (TAAR1) full agonist and also 5-hydroxytryptamin 1A (5-HT 1A) receptor partial agonist. I found the TAAR1 ligand neuron, D-neuron, in the striatum and nucleus accumbens (Acc), a neuroleptic acting site, of human brains, though failed to find in the homologous area of monkey brains. To study human D-neuron functions, total of 154 post-mortem brains, and a modified immunohistochemical method using high qualified antibodies against monoamine-related substances, was applied. The number of D-neuron in the caudate nucleus, putamen, and Acc was reduced in post-mortem brains with schizophrenia. The reduction was significant (p<0.05) in Acc. I proposed “D-cell hypothesis of schizophrenia”, that NSC dysfunction-based D-neuron reduction is cellular and molecular basis of mesolimbic dopamine (DA) hyperactivity, progressive pathophysiology and prospectiveness of TAAR1 medicinal chemistry, emphasizing importance of D-neuron.


2018 ◽  
Vol 19 (2) ◽  
pp. 165-176 ◽  
Author(s):  
Yan Wang ◽  
Zhao-Peng Liu

Statins are currently the major therapeutic strategies to lower low-density lipoprotein cholesterol (LDL-C) levels. However, a number of hypercholesterolemia patients still have a residual cardiovascular disease (CVD) risk despite taking the maximum-tolerated dose of statins. Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low-density lipoprotein receptor (LDLR), inducing its degradation in the lysosome and inhibiting LDLR recirculating to the cell membranes. The gain-offunction mutations in PCSK9 elevate the LDL-C levels in plasma. Therefore, PCSK9 inhibitors become novel therapeutic approaches in the treatment of hypercholesterolemia. Several PCSK9 inhibitors have been under investigation, and much progress has been made in clinical trials, especially for monoclonal antibodies (MoAbs). Two MoAbs, evolocumab and alirocumab, are now in clinical use. In this review, we summarize the development of PCSK9 inhibitors, including antisense oligonucleotides (ASOs), small interfering RNA (siRNA), small molecule inhibitor, MoAbs, mimetic peptides and adnectins, and the related safety issues.


Biology ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 485
Author(s):  
Lorenzo Cuollo ◽  
Fabrizio Antonangeli ◽  
Angela Santoni ◽  
Alessandra Soriani

Cellular senescence represents a robust tumor-protecting mechanism that halts the proliferation of stressed or premalignant cells. However, this state of stable proliferative arrest is accompanied by the Senescence-Associated Secretory Phenotype (SASP), which entails the copious secretion of proinflammatory signals in the tissue microenvironment and contributes to age-related conditions, including, paradoxically, cancer. Novel therapeutic strategies aim at eliminating senescent cells with the use of senolytics or abolishing the SASP without killing the senescent cell with the use of the so-called “senomorphics”. In addition, recent works demonstrate the possibility of modifying the composition of the secretome by genetic or pharmacological intervention. The purpose is not to renounce the potent immunostimulatory nature of SASP, but rather learning to modulate it for combating cancer and other age-related diseases. This review describes the main molecular mechanisms regulating the SASP and reports the evidence of the feasibility of abrogating or modulating the SASP, discussing the possible implications of both strategies.


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