Evidence for alpha-MSH binding sites on human scalp hair follicles: preliminary results

Progress in our understanding of plant responses to the stress of heavy metal cadmium

Heavy metal pollution is a major environmental stress affecting plant growth and development. The heavy metal cadmium inhibits various physiological processes in plants, including seed germination and seedling growth, photosynthesis, and antioxidation. Extensive research has been conducted on the toxic effects of Cd²⁺ on plants and the mechanisms of Cd²⁺ tolerance. Here, we review recent advancements in our understanding of the absorption, transport, and accumulation of Cd²⁺ in plants and the mechanisms of Cd²⁺ tolerance.

Hair melanocytes as neuro-endocrine sensors--pigments for our imagination

We are currently experiencing a spectacular surge in our knowledge of skin function both at the organ and organismal levels, much of this due to a flurry of cutaneous neuroendocrinologic data, that positions the skin as a major sensor of the periphery. As our body's largest organ, the skin incorporates all major support systems including blood, muscle and innervation as well as its role in immuno-competence, psycho-emotion, ultraviolet radiation sensing, endocrine function, etc. It is integral for maintenance of mammalian homeostasis and utilizes locally-produced melanocortins to neutralize noxious stimuli. In particular, the cutaneous pigmentary system is an important stress response element of the skin's sensing apparatus; where stimuli involving corticotrophin-releasing hormone (CRH) and proopiomelanocortin (POMC) peptides help regulate pigmentation in the hair follicle and the epidermis. These pigmentary units are organized into symmetrical functional pigmentary units composed of corticotropin-releasing hormone, and the melanocortin POMC peptides melanocyte stimulating hormone, adrenocorticotropic hormone and also the opiate beta-endorphin. These new findings have led to the concept of "self-similarity" of melanocortin systems based on their expression both at the local (skin) and systemic (CNS) levels, where the only major apparent difference appears to be one of scale. This review explores this concept and describes how the components of the CRH/POMC systems may help regulate the human hair follicle pigmentary unit.

A fully functional proopiomelanocortin/melanocortin-1 receptor system regulates the differentiation of human scalp hair follicle melanocytes

The proopiomelanocortin (POMC)-derived peptides, ACTH and alpha-MSH, are the principal mediators of human skin pigmentation via their action at the melanocortin-1 receptor (MC-1R). Recent data have demonstrated the existence of a functionally active beta-endorphin/mu-opiate receptor system in both epidermal and hair follicle melanocytes, whereby beta-endorphin can regulate melanogenesis, dendricity, and proliferation in these cells. However, a role for ACTH and alpha-MSH in the regulation of the human follicular pigmentary unit has not been determined. This study was designed to examine the involvement of ACTH and the alpha-MSH/MC-1R system in human follicular melanocyte biology. To address this question we employed RT-PCR and immunohisto/cytochemistry, and a functional role for these POMC peptides was assessed in follicular melanocyte cultures. Human scalp hair follicle melanocytes synthesized and processed POMC. ACTH and alpha-MSH in association with their processing enzymes and MC-1R are expressed in human follicular melanocytes at the message level in vitro and at the protein level both in situ and in vitro. The expression of the POMC/MC-1R receptor system was confined only to subpopulations of poorly and moderately differentiated melanocytes. In addition, functional studies revealed that ACTH and alpha-MSH are able to promote follicular melanocyte differentiation by up-regulating melanogenesis, dendricity, and proliferation in less differentiated melanocyte subpopulations. Thus, these findings suggest a role for these POMC peptides in regulating human hair follicle melanocyte differentiation.

Characterization of a polyclonal antibody raised against the human melanocortin-1 receptor

We have generated a polyclonal antibody raised against a synthetic peptide corresponding to the amino acids 2-18 of the extracellular, N-terminal domain of the human melanocortin-1 receptor (MC-1R). Specificity of the affinity-purified anti-MC-1R antibody was confirmed by dot blot analysis with the antigenic peptide. The antibody detected MC-1R antigenicity on the surface of normal human melanocytes and WM35 melanoma cells, as shown by FACS and immunofluorescence analysis. The antibody was suitable for immunoperoxidase staining of deparaffinized skin sections, revealing prominent MC-1R staining of a cutaneous melanoma as opposed to undiseased skin in which normal melanocytes were only occasionally immunoreactive. Distinct adnexal structures in normal skin also displayed MC-1R immunostaining. Specificity of the MC-1R immunoreactivity in each technique was confirmed by preabsorption with the immunogenic peptide, omission, or substitution of the primary antibody with preimmune serum. Our results provide a baseline for future studies on MC-1R expression in diseased human skin.

Molecules of the cycling hair follicle--a tabulated review

In this review we tabulated molecules which have been experimentally identified to be associated with, or play a role in, hair follicle growth. While compiling these data we were impressed by the fact that this field is only now beginning to be developed in terms of molecular analysis. Ironically, hair was used in some of the earliest molecular approaches to biologic structure (e.g. Astbury and Street, 1931), but the field did not develop from there. From our review we have come to the following conclusions. (1) As indicated by the growing number of reports dealing with follicle-associated molecules in the past 3 years, the field of hair biology has entered a new molecular era. (2) In many reported hair biology studies not enough emphasis has been placed on the fact that the follicle is a dynamic structure. All too often a study is limited to follicles of one particular phase of the cycle or one phase of development. Students in the field have to be more sensitive to the remarkable changes that this deceptively simple structure can undergo during its cycle. (3) Although we have not been able to find any molecules unique to the follicle, some of the structural molecules come close to an ideal tool. It is our impression that even more specific molecule tags will be found. Whether this requires a subtraction library approach or gene mapping of specific mutants is not yet clear. It would appear that the large, diverse family of intermediate filament-associated proteins will prove to be an excellent source of unique follicle-labeling molecules. (4) There is an acute need for molecules which distinguish the phases of the cycle, e.g. telogen from early anagen. Telogen is by far the most difficult phase to identify morphologically since the earliest phase of anagen and the latest phase of catagen may appear structurally like telogen. That these phases are functionally distinguishable must imply a molecular difference. As the number of recognized hair follicle-associated molecules and their interactions increase, it will be essential to assemble libraries of highly specific RNA and antibody probes for localization and mapping studies. We recognize that this review, as written, is imperfect. It is particularly deficient in making any effort towards identifying unifying principles of structure and function. We look forward to returning to this subject within 3 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Gamma-melanocyte stimulating hormone (gamma-MSH)-like immunoreactivity is present in certain normal human keratinocytes

Using the indirect immunohistochemical approach, the occurrence of gamma-melanocyte stimulating hormone (gamma-MSH)-like immunoreactivity in human normal keratinocytes is described. The positive cells were observed in each layer of the epidermis (except stratum corneum) and often, at the level of the stratum spinosum, also around the orifices of cutaneous accessory organs, such as sweat glands and sebaceous glands/hair follicles. Combining these data with our previous investigations, the results support the possibility that locally produced gamma-MSH could be involved in cutaneous immune response, pigmentation and epithelial proliferation, as well as neuromodulation.

Hair melanins and hair color: ultrastructural and biochemical aspects

The color variants of mammalian hair, including spotting and albinism, are the result of melanocyte activity and have been shown to be determined by the action of multiple genes, some of which operate through the milieu in which the pigment cell resides; others appear to act intracellularly to control the type of melanogenesis. Although there has been much descriptive work on the mode of action of these genes, it has only been with the recent advances in the chemistry and molecular biology of melanin pigmentation that some progress is being made in understanding the nature and origin of hair color. It is the purpose of this article to provide an integrated overview of the major advances so made and to draw attention to certain peculiarities of the melanization processes of hair with respect to those underlying skin pigmentation. Key words: melanins, melanocytes, melanogenesis, hair.

On the potential role of proopiomelanocortin in skin physiology and pathology

Pro-opiomelanocortin (POMC) is the precursor of ACTH, alpha-MSH and beta-endorphin, neuropeptides with multiple regulatory functions. Both the pituitary gland and peripheral tissues such as mammalian skin are capable of generating POMC-derived neuropeptides. Mammalian skin is also a target for POMC products; their possible roles in skin physiology and pathology are discussed in this communication.