Melanin - Causes and Functions

Introduction

Melanin is the pigment present in the epidermis, and the cells responsible for the production of melanin are the melanocytes. Melanocytes are derived from the neural crest cells. Melanin is the pigment responsible for various functions such as biological function, skin pigmentation, hair pigmentation, and the photoprotection of the skin and eye. Melanin is divided into three types, and melanin disorders are due to the abnormal production of melanin pigment. It is found that the color of the skin and hair is due to the different proportions of melanin. The altered mechanism in the formation and transportation of melanin pigment leads to melanin disorders.

What Is Melanin?

Melanin is the natural pigment of the skin, hair, and eye produced by the specialized group of cells called melanocytes. Melanocytes are the cells responsible for the production of melanin. Melanocytes are present in the basal layer of the epidermis called the stratum basale. Melanosomes are round membrane-bound organelles containing melanin. Increased melanin pigment causes the color of the skin and hair to become darker, and the decreased melanin pigment results in a lighter shade of the skin, hair, and eye. The amount of melanin pigment in an individual is also based on their genes. In addition, melanin protects the skin from harmful ultraviolet or UV rays.

What Are the Types of Melanin?

Melanin is classified into three types, eumelanin, pheomelanin, and neuromelanin. Eumelanin is subdivided into brown and black forms of melanin. Eumelanin and pheomelanin are produced in the stratum basale layer, called the superficial layer of the epidermis. The melanocytes produce eumelanin and pheomelanin. The dark color of the hair, skin, and eyes is due to the eumelanin, and the different mixes of black and brown forms of eumelanin cause the black hair, whereas the blonde hair is due to the brown eumelanin. Pheomelanin is responsible for the parts of the body that are pink in color, such as lips and nipples. An equal amount of pheomelanin and eumelanin causes red hair. Neuromelanin is found in the brain.

The three types of melanin are given below.

1. Eumelanin is subdivided into brown melanin and black melanin.

2. Pheomelanin.

3. Neuromelanin.

• Eumelanin causes differences in skin and hair color.

• Pheomelanin causes pinkish-colored parts of the body, including the lips, vagina, nipples, and penis.

• Neuromelanin does not add color to the skin and hair. Neuromelanin is found in the brain.

What Are the Functions of Melanin?

Melanin protects the skin from photodamage. It also protects the eyes, and melanin is distributed in the iris and choroid. Gray, blue and green eye colors are due to the various distributions of melanin, and the various types of melanin also determine hair color. The functions of melanin are described in the following points.

• Skin protection from harmful ultraviolet rays or UV rays.

• Eye protection from photodamage.

• Melanins are responsible for the color of the eyes, including brown, blue, and red.

• Red hair occurs due to the equal proportion of pheomelanin and eumelanin.

• Black hair is due to the eumelanin, and brown hair results from the brown eumelanin.

• Strawberry blonde hair color is due to the brown eumelanin and pheomelanin.

• The absence of black eumelanin and the presence of brown eumelanin causes blonde hair.

• Aids in hearing.

What Are the Disorders Associated With Melanin Pigment?

Melanin disorders are due to the abnormal transportation and formation of melanin. Dysfunction of melanoblasts, melanocytes, melanosome, tyrosinase, and dopaminergic neurons has much clinical significance, causing disorders. Some of the disorders due to melanin deficiency are given below.

• The skin color is lost in vitiligo, and white patches are observed.

• Albinism is a rare disorder; the clinical features include pale skin, white hair, and an increased risk of vision loss.

• Melasma, brown or blue-gray watches on faces,

• Hearing loss, melanin pigment is seen in the stria vascularis in the inner ear.

• In Parkinson's disease, neuromelanin decreases in the brain, causing Parkinson's disease. The hallmark finding of the Parkinson's is the depigmentation of the substantia nigra pars compacta.

• Waardenburg syndrome, autosomal recessive disease. The clinical features include skin hypopigmentation and premature graying.

• Chediak-Higashi syndrome is an autosomal recessive disorder.

• The clinical features of phenylketonuria include low intellectual ability or IQ, epilepsy, fair, blue eyes, hair is blonde and eye-related problems.

• Vogt-Koyanagi- Harada syndrome is characterized by alopecia, depigmentation that resembles vitiligo, and recurrent uveitis.

What Are Congenital Melanin Disorders?

Abnormal production of melanin causes the disorders. Increased melanin pigmentation is called hyperpigmentation, and decreased melanin pigments are called hypopigmentation.

Some of the congenital melanin disorders are listed below.

• Nevus cell nevus.

• Spitz nevus.

• Nevus spilus.

• Blue nevus.

• Dermal melanosis.

• Nevus Ito.

• Mongolian spot. Ephelides.

• Spitzen pigment.

• Acropigmentation.

• Lentiginosis.

• LEOPARD syndrome is characterized by multiple lentigines, cardiac abnormalities, hypertelorism in the eye, and growth retardation.

• Menkes disease.

• Wilson disease.

• Nevus depigmentosus.

• Charcot -Marie- tooth disease.

• Xeroderma pigmentosum or XP.

• Incontinentia pigment.

What Are the Acquired Melanin Disorders?

Sometimes certain factors will affect the production and transportation of melanin. Such acquired melanin disorders cause both hypopigmentation and hyperpigmentation.

Some of the acquired melanin disorders are given below.

• Senile lentigines.

• Lentigo melasma.

• Chloasma.

• Riehl's melanosis.

• Penile or vulvovaginal melanosis.

• UV or ultraviolet rays induced pigmentation.

• Drug-induced pigmentation, the causative drugs include cyclophosphamide, phenytoin, tetracycline, methotrexate, and chloroquine.

• Pigmentary demarcation lines.

• Foreign materials, including silver, gold, bismuth, mercury, and tattoos, induce depigmentation.

• Amyloidosis.

• Cushing's syndrome.

• Addison's disease.

• Hyperthyroidism.

• Nutritional disorders include pellagra, vitamin B12 deficiency, and prurigo pigmentosa.

• Infections cause pigmentation. The infections include measles and syphilis.

• Watson syndrome.

• Bloom syndrome.

• Sutton nevus.

• Melanoma.

• Mycosis fungoides.

• Tuberous sclerosis.

• Ataxia telangiectasia.

• Vogt-Koyanagi-Harada disease.

What Are the Foods That Help in Melanin Production?

Foods containing antioxidants help in melanin production. Likewise, the consumption of foods containing nutrients helps in melanin production.

Some of the nutritional foods that help increase melanin production are below.

• Dark green leafy vegetables.

• Dark berries.

• Dar chocolates.

• Carrots.

• Spinach.

• Squash.

• Sweet potatoes.

• Fish and meat.

• Green tea and turmeric.

• Whole grains.

• Nuts.

• Seeds.

Conclusion

Melanin is the natural pigment present in the skin produced by melanocytes. Melanin plays a vital role in skin protection from the sun and ultraviolet or UV rays. Melanin types include eumelanin, pheomelanin, and neuromelanin, which are responsible for skin color, hair, and other body regions. Abnormalities in the production and transportation of melanin lead to melanin disorders. Melanin disorders can be either congenital or acquired. Consumption of some foods may help to avoid melanin deficiency. Nutritional foods are consumed to avoid the risk of melanin disorders and to improve the quality of life.