[Lotus]

Apologies TWN for the late response. The research I look at these days has dramatically increased in complexity, I mean sheesh...I used to read about 20-30 science literature at a time, lol...now it's maybe half of that. Maybe because I narrow the field faster?, or maybe I'm just old, idk. So, now you know why Lotus takes so long to respond. 


So there's a few OTC PDE4 inhibitors and pharma meds I've found and one pro-aromatase unaffected by the PDE4 enzyme:

PDE4 Inhibitors 
Taurine 
Artichoke extract 
Bitter Orange (stay away from this one)
D1 agonists, (e.g. mucuna pruriens)
Pharma
β2-adrenergic receptor (β2AR) agonists 
Rolipram
others are available, just google PDE4 inhibitors agonists 

other methods:
Resveratrol-RSVL is an agonist for the cAMP/kinase-A, but is unaffected by PDE.
(This is a new find...very interested in this one).

Forskolin stimulates adenylyl cyclase activity, (loosely translated, forskolin stimulates aromatase). But it also stimulates PDE4 in the brain. I know what you're gonna say...but Lotus how could it (forskolin) stimulate aromatase if it's not inhibiting PDE4 in the brain?, and my answer would be to stack artichoke extract (which is a PDE4 inhibitor) with forskolin. But so far, stimulating PDE4 via forskolin only occurs in the brain...remember, we want to inhibit PDE4, NOT stimulate it.


NOTES

There's four types of PDE4 enzymes (PDE4A, PDE4B, PDE4C and PDE4D), 
and of those there's a long and short form, the long form PDE4 inhibition is more selective for PKA (Protein Kinase A) phosphorylation. And for our purposes of NBE this phosphorylation process  stimulates aromatase.

PDE4D1 and PDE4D2 mRNA levels rise in response to increased cAMP and this transcription is driven by a cAMP responsive promoter (Swinnen et al., 1991;

Increased intracellular cAMP levels have been demonstrated to increase cellular PDE4 activity (see Houslay, 2001; Houslay et al., 1998 for reviews). This is believed to perform an adaptive role in desensitising cellular processes to increased levels of cAMP. The long-term elevation of intracellular cAMP levels has been shown to cause an increase in the levels of mRNA and protein expression for various PDE4 isoforms, in particular the PDE4D1 and PDE4D2 short forms (Erdogan & Houslay, 1997; Kovala et al., 1994; Sette et al., 1994b; Seybold et al., 1998; Swinnen et al., 1989; Verghese et al., 1995; Vicini & Conti, 1997) where a cAMP-controlled promoter has been identified (Vicini & Conti, 1997). However, a second cAMP-driven controlling mechanism that has been identified is the rapid activation of the PDE4D3 isoform that is achieved through direct PKA-mediated phosphorylation (Alvarez et al., 1995; Hoffmann et al., 1998; Sette & Conti, 1996; Sette et al., 1994a, 1994b).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1573369/

The long form stimulates more growth (mRNA synthesis) and protein expression, aka the potentiation of breast growth.

Inhibition of PDE4 protects neurons against oxygen-glucose deprivation-induced endoplasmic reticulum stress through activation of the Nrf-2/HO-1 pathway

Phosphodiesterase 4 (PDE4) is an enzyme that specifically hydrolyzes cyclic adenosine monophosphate (cAMP) and, thus, regulates the concentration of intracellular cAMP.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6807264/

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