Peripheral Serotonin and Albinism

Official title

Role of Peripheral Serotonin in Oculocutaneous Albinism

Overview

Serotonin (5-HT or 5-hydroxytryptamine) is a monoamine primarily known for its role as a neurotransmitter in the central nervous system (CNS). However, the functions of serotonin go beyond its role in the central nervous system: different peripheral tissues have the capacity to produce and/or use serotonin locally, forming systems called "micro-serotonergic" systems. Among the peripheral roles of serotonin, previous work by the Iron and Immunity team, INSERM U1016, Institut Cochin (Paris), was able to show that serotonin has a positive role on erythropoiesis and the survival of red blood cells, and the team's ongoing work suggests that serotonin also impacts iron metabolism. In humans and in mouse models, several studies have suggested a role for serotonin in pigmentation. In certain syndromic forms of albinism such as Hermansky Pudlak syndrome, platelet serotonin levels are reduced in connection with a decrease in dense platelet granules (delta granules): this characteristic is even part of the diagnostic criteria. Preliminary data from the Iron and Immunity team found: * Changes in serotonin levels in children with albinism compared to control patients, * Changes in hemoglobin level and mean corpuscular volume (MCV) in children with albinism (towards anemia and microcytosis), * Changes in the iron balance in children with albinism (towards iron deficiency). The hypothesis of this research is that peripheral serotonin plays a role in the clinical and biological manifestations of oculocutaneous albinism.

Detailed description

Serotonin (5-HT or 5-hydroxytryptamine) is a monoamine primarily known for its role as a neurotransmitter in the central nervous system (CNS). However, the functions of serotonin go beyond its role in the central nervous system: different peripheral tissues have the capacity to produce and/or use serotonin locally, forming systems called "micro-serotonergic" systems. Among the peripheral roles of serotonin, previous work by the Iron and Immunity team, INSERM U1016, Institut Cochin (Paris), was able to show that serotonin has a positive role on erythropoiesis and the survival of red blood cells, and the team's ongoing work suggests that serotonin also impacts iron metabolism.

Albinism exhibits significant clinical and genetic heterogeneity with poor genotype-phenotype correlation, and nearly 15% of patients remain without a molecular diagnosis. There is no curative treatment for albinism. Patients with albinism suffer from physical disability throughout their lives, but can also suffer from psychological disability and discrimination. These patients are also more vulnerable to the effects of climate change. The unmet clinical needs are therefore enormous.

In humans and in mouse models, several studies have suggested an unexpected role for serotonin in skin pigmentation at several levels. Transcriptomic studies revealed that the Tph1 gene, responsible for serotonin synthesis outside the CNS, as well as serotonin receptors, were expressed in melanocytic and keratinocytic cell lines. Other studies have indicated that serotonin enhances melanogenesis in three melanocyte cell lines (B16F10, SK-MEL-2, Melan-a). Finally, studies suggest that serotonin is involved in pathologies such as certain congenital dyschromias, Rett syndrome and vitiligo. In certain syndromic forms of albinism such as Hermansky Pudlak syndrome, platelet serotonin levels are reduced in connection with a decrease in dense platelet granules (delta granules): this characteristic is even part of the diagnostic criteria.

Preliminary data from the Iron and Immunity team found:

* Changes in serotonin levels in children with albinism compared to control patients, * Changes in hemoglobin level and mean corpuscular volume (MCV) in children with albinism (towards anemia and microcytosis), * Changes in the iron balance in children with albinism (towards iron deficiency).

The hypothesis of this research is that peripheral serotonin plays a role in the clinical and biological manifestations of oculocutaneous albinism.

The study will assess serotonin and its metabolites in the serum of patients with albinism, and compare the results with controls patients. The level of serotonin and its metabolites will be correlated with the different genotypes, and with the severity of albinism within the same genotypes.

This study also wish to explore the impact of serotonin levels in the development of anemia, microcytosis and/or iron deficiency in patients with albinism. Complete blood counts and iron studies in patients with albinism will be compare to those of control patients too.

Interventions

• Other Dosage of serotonin and metabolites
  The dosages of serotonin and its metabolites will be performed by the INSERM U1016 unit at Cochin Institute.
• Other Blood parameters
  The characterization of blood parameters : complete blood count (CBC), reticulocytes, C-reactive protein (CRP), iron studies (ferritin, serum iron, transferrin and transferrin saturation), hemoglobin electrophoresis, erythropoietin, will be added using standard methods at the Necker hematology laboratory if not carried out as part of the routine care.

Primary outcome measures

• Level of serotonin and its metabolites in serum [Time frame: Day 0]

Secondary outcome measures (4)

• Correlation between serotonin levels and molecular subtype of albinism [Time frame: Day 0]
• Correlation between serotonin levels and severity of albinism [Time frame: Day 0]
• Correlation between serotonin levels and iron studies [Time frame: Day 0]
• Correlation between serotonin levels and hemoglobin [Time frame: Day 0]

Eligibility criteria

Inclusion criteria

Patients:

• Patients with albinism aged 2 to 17 years
• Followed in the MAGEC-Necker reference center (reference center for rare diseases of the skin and mucous membranes of genetic origin), during the inclusion period
• Information of parental authority holders of patients and patients of understanding age, and collection of consent from parental authority holders and patients.

Controls:

• Patients aged 2 to 17 years old
• Having consulted in Necker hospital during the inclusion period in the emergency and surgical services and whose care required a blood test analyzed in the hematology laboratory of the Necker hospital.
• Normal complete blood count (CBC)
• Normal C-reactive protein test (CRP)
• Absence of opposition from parental authority holders within one month of after sending the study information note.

Exclusion criteria

Patients:

\- Inability to have a blood test

Controls:

• Abnormal blood count
• Elevation of CRP above laboratory standard

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Observational model

Case-control

Study locations

France · 1 center

• Hôpital Necker-Enfants Malades — Paris

Publications

• Amireault P, Sibon D, Cote F. Life without peripheral serotonin: insights from tryptophan hydroxylase 1 knockout mice reveal the existence of paracrine/autocrine serotonergic networks. ACS Chem Neurosci. 2013 Jan 16;4(1):64-71. doi: 10.1021/cn300154j. Epub 2012 Nov 7. PMID 23336045
• Yabut JM, Crane JD, Green AE, Keating DJ, Khan WI, Steinberg GR. Emerging Roles for Serotonin in Regulating Metabolism: New Implications for an Ancient Molecule. Endocr Rev. 2019 Aug 1;40(4):1092-1107. doi: 10.1210/er.2018-00283. PMID 30901029
• Fouquet G, Coman T, Hermine O, Cote F. Serotonin, hematopoiesis and stem cells. Pharmacol Res. 2019 Feb;140:67-74. doi: 10.1016/j.phrs.2018.08.005. Epub 2018 Aug 11. PMID 30107202
• English KB, Wang ZZ, Stayner N, Stensaas LJ, Martin H, Tuckett RP. Serotonin-like immunoreactivity in Merkel cells and their afferent neurons in touch domes from the hairy skin of rats. Anat Rec. 1992 Jan;232(1):112-20. doi: 10.1002/ar.1092320112. PMID 1536455
• Johansson O, Liu PY, Bondesson L, Nordlind K, Olsson MJ, Lontz W, Verhofstad A, Liang Y, Gangi S. A serotonin-like immunoreactivity is present in human cutaneous melanocytes. J Invest Dermatol. 1998 Dec;111(6):1010-4. doi: 10.1046/j.1523-1747.1998.00460.x. PMID 9856809
• Lee HJ, Park MK, Kim SY, Park Choo HY, Lee AY, Lee CH. Serotonin induces melanogenesis via serotonin receptor 2A. Br J Dermatol. 2011 Dec;165(6):1344-8. doi: 10.1111/j.1365-2133.2011.10490.x. Epub 2011 Oct 17. PMID 21711335
• Slominski A, Pisarchik A, Semak I, Sweatman T, Wortsman J, Szczesniewski A, Slugocki G, McNulty J, Kauser S, Tobin DJ, Jing C, Johansson O. Serotoninergic and melatoninergic systems are fully expressed in human skin. FASEB J. 2002 Jun;16(8):896-8. doi: 10.1096/fj.01-0952fje. Epub 2002 Apr 23. PMID 12039872
• Slominski A, Pisarchik A, Zbytek B, Tobin DJ, Kauser S, Wortsman J. Functional activity of serotoninergic and melatoninergic systems expressed in the skin. J Cell Physiol. 2003 Jul;196(1):144-53. doi: 10.1002/jcp.10287. PMID 12767050

Identifiers

NCT: NCT06138509 · APHP230808 · 2023-A01431-44

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗