Mast cells in UV-B-induced immunosuppression

Molecular Mechanisms of Scombroid Food Poisoning

Scombroid food poisoning (SFP) is a foodborne disease that develops after consumption of fresh fish and, rarely, seafood that has fine organoleptic characteristics but contains a large amount of exogenous histamine. SFP, like other food pseudo-allergic reactions (FPA), is a disorder that is clinically identical to allergic reactions type I, but there are many differences in their pathogenesis. To date, SFP has been widespread throughout the world and is an urgent problem, although exact epidemiological data on incidence varies greatly. The need to distinguish SFP from true IgE-associated allergy to fish and seafood is one of the most difficult examples of the differential diagnosis of allergic conditions. The most important difference is the absence of an IgE response in SFP. The pathogenesis of SFP includes a complex system of interactions between the body and chemical triggers such as exogenous histamine, other biogenic amines, cis-urocanic acid, salicylates, and other histamine liberators. Because of the wide range of molecular pathways involved in this process, it is critical to understand their differences. This may help predict and prevent poor outcomes in patients and contribute to the development of adequate hygienic rules and regulations for seafood product safety. Despite the vast and lengthy history of research on SFP mechanisms, there are still many blank spots in our understanding of this condition. The goals of this review are to differentiate various molecular mechanisms of SFP and describe methods of hygienic regulation of some biogenic amines that influence the concentration of histamine in the human body and play an important role in the mechanism of SFP.

Autophagy plays an essential role in ultraviolet radiation-driven skin photoaging

Photoaging is characterized by a chronic inflammatory response to UV light. One of the most prominent features of cutaneous photoaging is wrinkling, which is due primarily to a loss of collagen fibers and deposits of abnormal degenerative elastotic material within the dermis (actinic elastosis). These changes are thought to be mediated by inflammation, with subsequent upregulation of extracellular matrix-degrading proteases and down-regulation of collagen synthesis. Autophagy is a vital homeostatic cellular process of either clearing surplus or damaged cell components notably lipids and proteins or recycling the content of the cells’ cytoplasm to promote cell survival and adaptive responses during starvation and other oxidative and/or genotoxic stress conditions. Autophagy may also become a means of supplying nutrients to maintain a high cellular proliferation rate when needed. It has been suggested that loss of autophagy leads to both photodamage and the initiation of photoaging in UV exposed skin. Moreover, UV radiation of sunlight is capable of regulating a number of autophagy-linked genes. This review will focus on the protective effect of autophagy in the skin cells damaged by UV radiation. We hope to draw attention to the significance of autophagy regulation in the prevention and treatment of skin photoaging.

Molecular Background, Clinical Features and Management of Pediatric Mastocytosis: Status 2021

Pediatric mastocytosis is a heterogeneous disease characterized by accumulation of mast cells in the skin and less frequently in other organs. Somatic or germline mutations in the KIT proto-oncogene are detected in most patients. Cutaneous mastocytosis is the most common form of the disease in children. In the majority of cases, skin lesions regress spontaneously around puberty. However, in few patients, mastocytosis is not a self-limiting disease, but persists into adulthood and can show signs of systemic involvement, especially when skin lesions are small-sized and monomorphic. Children with mastocytosis often suffer from mast cell mediator-related symptoms. Severe hypersensitivity reactions can also occur, mostly in patients with extensive skin lesions and blistering. In a substantial number of these cases, the triggering factor of anaphylaxis remains unidentified. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers, treatment with H1 and H2 histamine receptor blockers, and equipment of patients and their families with epinephrine auto-injectors for use in severe anaphylactic reactions. Advanced systemic mastocytosis occurs occasionally. All children with mastocytosis require follow-up examinations. A bone marrow investigation is performed when advanced systemic mastocytosis is suspected and has an impact on therapy or when cutaneous disease persists into adulthood.

Narrow-band UVB phototherapy and psoralen-ultraviolet A photochemotherapy in the treatment of cutaneous mastocytosis: a study in 20 patients

BACKGROUND

In mastocytosis, the skin is almost invariably involved, and cutaneous symptoms deeply affect patients' quality of life.

METHODS

A retrospective observational analysis of patients affected by cutaneous mastocytosis (CM) and indolent systemic mastocytosis (ISM) treated with phototherapy/photochemotherapy (PUVA or NB-UVB) has been conducted. For each patient, total numbers of PUVA or NB-UVB exposures, the cumulative UV dose (J/cm² ), serum tryptase profile, and pruritus, before and after treatment, according to the visual analogue scale (VAS) were considered. Skin lesions of each patient were assessed, before and after treatment, according to a cutaneous scale score.

RESULTS

Twenty patients affected by CM and ISM were studied; in particular, 10 patients received NB-UVB therapy, and other 10 patients received PUVA. A statistically significant mean reduction of pruritus in both groups (P < 0.01) was observed. The number of treatments necessary to obtain symptom relief was significantly lower in the PUVA group, but the mean exposure dose was significantly higher, if compared to the NB-UVB group. Serum tryptase levels showed a downward trend. The cutaneous score improved in both groups.

LIMITATIONS

This study was a retrospective study with a small sample size and without a control group.

CONCLUSION

This work provides evidence that both NB-UVB and PUVA represent a safe and useful second-line therapy of the cutaneous symptoms in mastocytosis.

Serotonin signalling is crucial in the induction of PUVA-induced systemic suppression of delayed-type hypersensitivity but not local apoptosis or inflammation of the skin

Psoralen and UVA (PUVA) has immunosuppressive and proapoptotic effects, which are thought to be responsible alone or in combination for its therapeutic efficacy. However, the molecular mechanism by which PUVA mediates its effects is not well understood. Activation of the serotonin (5-hydroxytryptamine, 5-HT) pathway has been suggested to be involved in the modulation of T-cell responses and found to mediate UVB-induced immune suppression. In particular, the activation of the 5-HT2A receptor has been proposed as one mechanism responsible for UV-induced immune suppression. We therefore hypothesized that 5-HT may play a role in PUVA-induced effects. The model of systemic suppression of delayed-type hypersensitivity (DTH) to Candida albicans was used to study immune function after exposure of C3H and KIT(W) (-Sh/W-Sh) mice to a minimal inflammatory dose of topical PUVA. The intra-peritoneal injection of the 5-HT2 receptor antagonist ketanserin or cyproheptadine or an anti-5-HT antibody immediately before PUVA exposure entirely abrogated suppression of DTH but had no significant effect on inflammation, as measured by swelling and cellular infiltration of the skin, and apoptosis as determined by the number of sunburn cells in C3H mice. Importantly, the systemic injection of 5-HT recapitulated PUVA immune suppression of DTH but did not induce inflammation or apoptosis in the skin. KIT(W) (-Sh/W-Sh) mice (exhibiting myelopoietic abnormalities, including lack of 5-HT-containing mast cells) were resistant to PUVA-induced suppression of DTH but not local skin swelling. Thus, this points towards a crucial role of 5-HT signalling in PUVA-induced immune suppression but not inflammation or apoptosis in situ in the skin.

Internal pigment cells respond to external UV radiation in frogs

Fish and amphibians have pigment cells that generate colorful skins important for signaling, camouflage, thermoregulation, and protection against ultraviolet radiation (UVR). However, many animals have also pigment cells inside their bodies, on their internal organs and membranes. In contrast to external pigmentation, internal pigmentation is remarkably little studied and its function is not well known. Here, we tested genotoxic effects of UVR and its effects on internal pigmentation in a Neotropical frog, Physalaemus nattereri. We found an increased body darkness and internal melanin pigmentation in testes and heart surfaces, in the mesenterium and lumbar region after just a few hours of UVR exposure. The melanin dispersion in melanomacrophages in the liver and melanocytes in testes increased after UV exposure. In addition, the amount of melanin inside melanomacrophages cells increased too. While mast cells were quickly activated by UVR, only longer UVR exposures resulted in genotoxic effects inside frogs, by increasing the frequency of micronuclei in red blood cells. This is the first study to describe systemic responses of external UVR on internal melanin pigmentation, melanomacrophages, and melanocytes in frogs and thus provide a functional explanation to the presence of internal pigmentation.

Indolent systemic mastocytosis treated with narrow-band UVB phototherapy: study of five cases

BACKGROUND

Mastocytoses represent a heterogeneous group of stem cell disorders marked by an abnormal hyperplasia and accumulation of mast cells in one or more tissues, including bone marrow, gastrointestinal tract, liver, spleen, lymph nodes and skin. Indolent systemic mastocytosis (ISM) is characterized by red-brownish and pruriginous maculopapular lesions, a bone marrow infiltration without functional impairment and an indolent clinical course with a good prognosis. In particular, the most common cutaneous symptoms are urticarial rash and mild-to-high pruritus.

OBJECTIVES

This study analyses the clinical outcome of patients affected by ISM with prevalent pruriginous cutaneous symptoms and a scarce response to anti-histamines treated using narrowband ultraviolet B (NB-UVB) phototherapy.

METHODS

Narrowband ultraviolet B phototherapy was administered in a UV-irradiation cabin equipped with fluorescent UVB lamps with a peak emission at 311-313 nm. The perception of pruritus severity was assessed using the Visual Analogue Scale (VAS) before starting the treatment and at each control.

RESULTS

A complete remission of the cutaneous lesions and pruritus was documented in all patients after a median of 40.3 UV treatments and a median cumulative dose of 51.4 J/cm(2), with a lasting remission over a 6-month follow-up. The median VAS score at the beginning of the treatment was 86.6 (SD=6.64), whereas it decreased to 6.66 (SD=3.75) after 3 months of therapy.

CONCLUSIONS

Our work provides evidence that NB-UVB phototherapy is useful for the treatment of the cutaneous symptoms and pruritus in ISM.

Mast cells in health and disease

Although MCs (mast cells) were discovered over 100 years ago, for the majority of this time their function was linked almost exclusively to allergy and allergic disease with few other roles in health and disease. The engineering of MC-deficient mice and engraftment of these mice with MCs deficient in receptors or mediators has advanced our knowledge of the role of MCs in vivo. It is now known that MCs have very broad and varied roles in both physiology and disease which will be reviewed here with a focus on some of the most recent discoveries over the last year. MCs can aid in maintaining a healthy physiology by secreting mediators that promote wound healing and homoeostasis as well as interacting with neurons. Major developments have been made in understanding MC function in defence against pathogens, in recognition of pathogens as well as direct effector functions. Probably the most quickly developing area of understanding is the involvement and contribution MCs make in the progression of a variety of diseases from some of the most common diseases to the more obscure.

Mast cells: multifaceted immune cells with diverse roles in health and disease

Mast cells were discovered more than 100 years ago and until recently, have been considered renegades of the host with the sole purpose of perpetuating allergy. The discovery of mast cell-deficient mice that could be reconstituted with mast cells (the so called "mast cell knock-in" mice) has allowed the study of the in vivo functions of mast cells and revealed several new facets of these cells. It is now evident that mast cells have a much broader impact on many physiological and pathologic processes. Mast cells, particularly through their dynamic interaction with the nervous system, have been implicated in wound healing, tissue remodeling, and homeostasis. Perhaps the most progress has been made in our understanding of the role of mast cells in immunity outside the realm of allergy, and host defense. Mast cells play critical roles in both innate and adaptive immunity, including immune tolerance. Greater insight into mast cell biology has prompted studies probing the additional consequences of mast cell dysfunction, which reveal a central role for mast cells in the pathogenesis of autoimmune disorders, cardiovascular disorders, and cancer. Here, we review recent developments in the study of mast cells, which present a complex picture of mast cell functions.

Acute exposure of human skin to ultraviolet or infrared radiation or heat stimuli increases mast cell numbers and tryptase expression in human skin in vivo

BACKGROUND

Mast cells are key effector cells in diverse immunological and pathological processes. It is still unclear why there are more mast cells at peripheral and sun-exposed skin sites than at sun-protected sites.

OBJECTIVES

To investigate changes in mast cell numbers associated with natural ageing and photoageing, and to observe the effects of ultraviolet (UV) and infrared (IR) radiation and heat on the prevalence of mast cells and tryptase expression in human skin in vivo.

METHODS

Sun-exposed and sun-protected skin samples were taken from individuals in four different age groups. UV, IR or heat-treated buttock skin of young volunteers was also obtained. Mast cells were quantified by immunohistochemical staining of mast cell-specific tryptase and chymase. The expression of tryptase was determined by Western blotting.

RESULTS

Both sun-exposed and sun-protected skin showed a gradual decrease in total mast cells (MC(Total)) number with ageing. The number of mast cells in sun-exposed skin was significantly higher than that in sun-protected skin. After UV irradiation (2 minimal erythema doses), MC(Total) and mast cells expressing tryptase and chymase were significantly increased at 24 and 48 h postirradiation. After IR irradiation (3 minimal heating doses) and heat treatment (43 degrees C for 90 min), MC(Total) reached peak induction at 8 and 48 h after stimulation, respectively. Tryptase expression was also clearly upregulated by UV, IR and heat.

CONCLUSIONS

Our data demonstrate that mast cell numbers decreased with ageing in human skin. Also, mast cells may be activated and recruited by UV, IR and heat. These findings should further our understanding of the reason for the high prevalence of mast cells at peripheral sun-exposed skin sites.

Intradermal vaccine delivery: will new delivery systems transform vaccine administration? Vaccine. 2008;26:3197-3208. [PMID: 18486285 DOI: 10.1016/j.vaccine.2008.03.095]

There has been a recent resurgence of interest in intradermal vaccine delivery. The physiological advantages of intradermal vaccine delivery have been known for some time, but the difficulties associated with performing an intradermal injection have historically limited its use. New delivery systems currently in development facilitate convenient intradermal vaccination, unlocking the potential advantages of this delivery route, and potentially transforming vaccine delivery.

Epidermal cis-urocanic acid levels correlate with lower specific cellular immune responses after hepatitis B vaccination of ultraviolet B-exposed humans

Urocanic acid (UCA) is a major UV-absorbing chromophore in the epidermis and has been suggested to act as one of the initiators of UV-induced immunosuppression. cis-UCA, the isomer from UCA that is formed upon UV exposure, has been shown to impair some cellular immune responses. cis-UCA levels were determined in a study in which the influence of ultraviolet B (UVB) exposure on immune responses after hepatitis B vaccination in human volunteers was established. A significant increase in cis-UCA levels was found in the skin of UVB-exposed volunteers compared with controls. cis-UCA levels, calculated as the percentage of the total UCA amount, in UVB-exposed volunteers correlated significantly with the cumulative UVB dose received in 5 consecutive days, i.e. the higher the UVB dose (J/m2), the higher the cis-UCA levels (until a cis-UCA plateau was reached in the so-called photostationary state). Correlations between skin cis-UCA levels and immune responses were determined, and they revealed no statistically significant correlations among lymphocyte proliferation responses after either mitogenic stimulation or stimulation with recall antigens. No correlation was found between cis-UCA levels and hepatitis B-specific antibody titers. However, we found a statistically significant negative correlation between cis-UCA levels and hepatitis B-specific lymphocyte proliferation responses when volunteers were irradiated with UVB before hepatitis B vaccination. In other words, volunteers with high cis-UCA levels caused by UVB exposure showed lower cellular immune responses against hepatitis B antigen after hepatitis B vaccination.

Can smoking and/or occupational UV exposure have any role in the development of the morpheaform basal cell carcinoma? A critical role for peritumoral mast cells

BACKGROUND

The stroma of basal cell carcinoma (BCC) is rich in mast cells. Morpheaform BCC has been reported to contain many more mast cells than the other types of BCC. However, pathogenesis and clinical relevance of this observation are currently unclear. Smoking and ultraviolet (UV) exposure have recently been suggested to be related to the development of morpheaform BCC.

METHODS

With a retrospective study, we aimed to investigate the possible roles of smoking and occupational UV exposure in the development of morpheaform BCC through the quantification of peritumoral mast cells. Our case population consisted of 34 patients with morpheaform BCC and 50 patients with solid BCC. After identification of mast cells with toluidine blue stain, a mast cell index was determined in each case.

RESULTS

Mean mast cell index of morpheaform BCCs was significantly higher than that of solid BCCs (P < 0.02). Increased mast cell indices were associated with smoking (P = 0.003), but not with UV exposure (P > 0.05), irrespective of the tumor type. Morpheaform BCC was significantly more frequent in smokers compared to solid BCC (P < 0.05). In the cases with morpheaform BCC, mean mast cell index of smokers was significantly higher than that of nonsmokers (P = 0.02). Mean mast cell index of smokers with morpheaform BCC was also significantly higher than that of the smokers with solid BCC (P = 0.04). Ultraviolet exposure alone had no significant influence on mast cell indices, nor on the frequency of morpheaform BCC.

CONCLUSION

We suggest that smoking can play a key role in the differentiation of BCC toward its sclerosing form, through the increased peritumoral mast cell numbers.