Does 5-HTP supplementation improve Crohn's symptoms?

Hydroxytryptophan from Wikipedia

5-HTP from The University of Maryland Medical Center


"The serotonin precursor 5-hydroxytryptophan reinforces intestinal barrier function" from Top Institute Food and Nutrition, Wageningen [no date]
"Tight junctions between intestinal epithelial cells form a selective barrier that contributes to gut homeostasis. Alterations in intestinal barrier function are considered to be early factors in the pathogenesis of irritable bowel syndrome (IBS). ... Oral administration of 5-HTP reinforces small intestinal barrier function by lowering intestinal sugar permeability, inducing the expression of the tight junction protein ZO-1 and rearranging tight junction proteins. These changes are associated with 5-HTP-induced alterations in mucosal serotonin metabolism. These data point to a role for serotonergic metabolism in reinforcing intestinal barrier function."

"Production and Peripheral Roles of 5-HTP, a Precursor of Serotonin" in Int J Tryptophan Res (2009) [full text]
"Physiological roles of 5-HTP in the brain have not been reported. On the other hand, 5-HTP has a specific function in the gut. As a unique BH4 [ 6R-L-erythro-5,6,7,8-tetrahydrobiopterin] transport mechanism, BH4 that transiently enters cells can be rapidly oxidized to BH2 and is exported back to the extracellular space. Meanwhile, the intestinal epithelial cells take up BH4 as its reduced form. Therefore, the intestine shares a unique BH4 transporter mechanism and a specific function of 5-HTP. Further studies would clarify the intestine-specific machinery linking the specific mechanism of BH4-dependent 5-HTP production to the specific function of 5-HTP. A 5-HT precursor 5-HTP is sometimes administered to patients with metabolic disorder.27 The finding on the function of 5-HTP in the intestine might create an opportunity to explore the effects of exogenously-applied 5-HTP on the intestine in man."

"Gut hormones: emerging role in immune activation and inflammation" in Clinical and Experimental Immunology (2010) [full article]
"The studies discussed in this review provide evidence in favour of a key role of gut hormones in intestinal inflammation. In addition to the contribution in GI physiology, such as motility and secretion, gut hormones can also play an important role in immune activation and in the generation of inflammation in gut. The precise mechanisms by which gut hormones regulate the inflammation remain to be determined. The data generated from the studies on 5-HT in gut inflammation suggest strongly that increased 5-HT released by luminal inflammatory stimuli can activate immune cells such as macrophages, dendritic cells, lymphocytes and enteric nerves via specific 5-HT receptors, which can enhance the production of proinflammatory mediators via triggering activation of the NF-κB pathway and/or other possible proinflammatory signalling systems, and which subsequently can up-regulate the inflammatory response (Fig. 1). It will be interesting to see roles of specific 5-HT receptor subtype(s) in immune activation and generation of intestinal inflammation.
...
These studies provide novel information on the role of gut hormones in immune signalling and regulation of gut inflammation. Despite being a challenging and complicated area to explore, recent studies on immunoendocrine interaction has generated new interest to elucidate the role of gut hormones in the inflammatory process and immune function. In addition to enhancing our understanding on the pathogenesis of inflammatory changes, these studies give new information on 5-HT and Cgs [chromogranins] in the context of immunoendocrine interactions in gut and intestinal homeostasis. This is very important, due not only to the alteration in enteric endocrine cells functions observed in various GI inflammatory conditions but also in non-GI inflammatory disorders and functional GI disorders such as IBS. These data may have implications in understanding the role of gut hormone in the pathogenesis of both GI and non-GI inflammation, which may lead ultimately to improved therapeutic strategies in inflammatory disorders."

If 5-HTP improves intestinal barrier function, but serotonin stimulates Crohn' symptomology, how can this be reconciled? Is 5-HTP supplementation helpful or ultimately harmful?

See my post entitled Does serotonin production worsen Crohn's symptoms?"