scholarly journals DOPA Homeostasis by Dopamine: A Control-Theoretic View

2021 ◽  
Vol 22 (23) ◽  
pp. 12862
Author(s):  
Rune Kleppe ◽  
Qaiser Waheed ◽  
Peter Ruoff

Dopamine (DA) is an important signal mediator in the brain as well as in the periphery. The term “dopamine homeostasis” occasionally found in the literature refers to the fact that abnormal DA levels can be associated with a variety of neuropsychiatric disorders. An analysis of the negative feedback inhibition of tyrosine hydroxylase (TH) by DA indicates, with support from the experimental data, that the TH-DA negative feedback loop has developed to exhibit 3,4-dihydroxyphenylalanine (DOPA) homeostasis by using DA as a derepression regulator. DA levels generally decline when DOPA is removed, for example, by increased oxidative stress. Robust DOPA regulation by DA further implies that maximum vesicular DA levels are established, which appear necessary for a reliable translation of neural activity into a corresponding chemical transmitter signal. An uncontrolled continuous rise (windup) in DA occurs when Levodopa treatment exceeds a critical dose. Increased oxidative stress leads to the successive breakdown of DOPA homeostasis and to a corresponding reduction in DA levels. To keep DOPA regulation robust, the vesicular DA loading requires close to zero-order kinetics combined with a sufficiently high compensatory flux provided by TH. The protection of DOPA and DA due to a channeling complex is discussed.

2008 ◽  
Vol 4 ◽  
pp. T735-T736
Author(s):  
Sivan Vadakkadath Meethal ◽  
Hsien Chan ◽  
Erika Ginsburg ◽  
Andrea C. Wilson ◽  
Richard L. Bowen ◽  
...  

2021 ◽  
Vol 22 (16) ◽  
pp. 8472
Author(s):  
Senem Aykul ◽  
Jordan Maust ◽  
Vijayalakshmi Thamilselvan ◽  
Monique Floer ◽  
Erik Martinez-Hackert

Adipose tissues (AT) expand in response to energy surplus through adipocyte hypertrophy and hyperplasia. The latter, also known as adipogenesis, is a process by which multipotent precursors differentiate to form mature adipocytes. This process is directed by developmental cues that include members of the TGF-β family. Our goal here was to elucidate, using the 3T3-L1 adipogenesis model, how TGF-β family growth factors and inhibitors regulate adipocyte development. We show that ligands of the Activin and TGF-β families, several ligand traps, and the SMAD1/5/8 signaling inhibitor LDN-193189 profoundly suppressed 3T3-L1 adipogenesis. Strikingly, anti-adipogenic traps and ligands engaged the same mechanism of action involving the simultaneous activation of SMAD2/3 and inhibition of SMAD1/5/8 signaling. This effect was rescued by the SMAD2/3 signaling inhibitor SB-431542. By contrast, although LDN-193189 also suppressed SMAD1/5/8 signaling and adipogenesis, its effect could not be rescued by SB-431542. Collectively, these findings reveal the fundamental role of SMAD1/5/8 for 3T3-L1 adipogenesis, and potentially identify a negative feedback loop that links SMAD2/3 activation with SMAD1/5/8 inhibition in adipogenic precursors.


2016 ◽  
Vol 24 (3) ◽  
pp. 421-432 ◽  
Author(s):  
Yanbo Wang ◽  
Hongwei Liang ◽  
Geyu Zhou ◽  
Xiuting Hu ◽  
Zhengya Liu ◽  
...  

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