Keratinocyte Cytokines and Growth Factors: Functions in Skin Immunity and Homeostasis

Molecular and cellular pruritus mechanisms in the host skin

Pruritus, also known as itching, is a complex sensation that involves the activation of specific physiological and cellular receptors. The skin is innervated with sensory nerves as well as some receptors for various sensations, and its immune system has prominent neurological connections. Sensory neurons have a considerable impact on the sensation of itching. However, immune cells also play a role in this process, as they release pruritogens. Disruption of the dermal barrier activates an immune response, initiating a series of chemical, physical, and cellular reactions. These reactions involve various cell types, including keratinocytes, as well as immune cells involved in innate and adaptive immunity. Collective activation of these immune responses confers protection against potential pathogens. Thus, understanding the molecular and cellular mechanisms that contribute to pruritus in host skin is crucial for the advancement of effective treatment approaches. This review provides a comprehensive analysis of the present knowledge concerning the molecular and cellular mechanisms underlying itching signaling in the skin. Additionally, this review explored the integration of these mechanisms with the broader context of itch mediators and the expression of their receptors in the skin.

Downregulation of Sonic hedgehog signaling induces G2-arrest in genital warts

BACKGROUND

Human papillomavirus (HPV) infected keratinocyte dysfunction results in the formation of genital warts, and the specific role of Sonic hedgehog (SHh) signaling in genital warts remains elusive. Thus, this study aimed to identify the correlation between wart formation and SHh signaling.

MATERIALS AND METHODS

In this study, nine male patients with genital warts were recruited, and the expression of SHh and its downstream signal molecules Patched-1 and GLI family zinc finger 1 (Ptch1 and Gli1) was detected. Moreover, G2-phase cells in the collected genital warts samples were assessed with normal foreskin samples as a comparison. HPV6/11 were detected via in situ hybridization (ISH), and SHh expression of the corresponding paraffin sections was determined via immunohistochemical staining (IHC). In addition, an in vitro down-regulated SHh model was constructed by siRNA transfection of the HaCaT cell line, and the cell cycle was detected at 36 h by flow cytometry with propidium iodide staining.

RESULTS

SHh, Ptch1, and Gli1 in warts were significantly downregulated in the condyloma acuminatum (CA) group compared to the normal foreskin group. G2-phase cells in the middle section of the spinous layer of CA wart tissues were significantly increased. Moreover, the expression of HPV-DNA was amplified and negatively correlated with SHh activity in CA wart tissues. Lastly, the downregulation of SHh-induced G2 arrest in vitro.

CONCLUSIONS

The downregulation of the SHh signaling promotes HPV replication and the formation of warts by inducing G2/M arrest in the keratinocytes of CA.

Scabies itch: an update on neuroimmune interactions and novel targets

Frequently described as 'the worst itch' one can ever experience scabies itch is the hallmark of Sarcoptes scabiei mite infestation. Notably, the itchiness often persists for weeks despite scabicides therapy. The mechanism of scabies itch is not yet fully understood, and effective treatment modalities are still missing which can severely affect the quality of life. The aim of this review is to provide an overview of the scope of itch in scabies and highlight candidate mechanisms underlying this itch. We herein discuss scabies itch, with a focus on the nature, candidate underlying mechanisms and treatment options. We also synthesize this information with current understanding of the mechanisms contributing to non-histaminergic itch in other conditions. Itch is a major problem in scabies and can lead to grave consequences. We provide the latest insights on host-mite interaction, secondary microbial infection and neural sensitization with special emphasis on keratinocytes and mast cells to better understand the mechanism of itch in scabies. Also, the most relevant current modalities remaining under investigation that possess promising perspectives for scabies itch (i.e. protease-activated receptor-2 (PAR-2) inhibitor, Mas-related G protein-coupled receptor X2 (MRGPRX2) antagonist) are discussed. Greater understanding of these diverse mechanisms may provide a rational basis for the development of improved and targeted approaches to control itch in individuals with scabies.

Cosmeceuticals: The Principles and Practice of Skin Rejuvenation by Nonprescription Topical Therapy

Background

Aesthetic practice relies on a harmonious relationship between medicine and commerce. Bridging the gap is a large number of skincare products that make therapeutic claims while avoiding the regulatory framework of pharmaceuticals. In this gray area, clinicians find themselves poorly disposed to counsel patients wisely as the industry is expanding faster than empirical evidence of efficacy and safety can be acquired. To serve our patients and engage with industry, we must understand the theoretical principles and evaluate the clinical evidence in practice.

Objectives

The purpose of this paper is to classify cosmeceuticals by method of action, explain how they work in principle with reference to skin aging, and evaluate the clinical evidence for them.

Methods

A literature and cosmetic clinic website search was conducted to establish a list of the most commonly advertised cosmeceuticals, and a peer-reviewed literature search was then conducted to establish the clinical evidence for them.

Results

A huge number of cosmeceuticals are marketed for skin rejuvenation but almost invariably they fall into 1 of 4 categories. These include the induction of tissue repair mechanisms, inflammatory modulation, scavenging of reactive oxygen species, or a combination of the 3. With the exception of retinol derivatives and hydroxy acids, the clinical evidence is limited, despite promising preclinical evidence for several cosmeceuticals.

Conclusions

Cosmeceuticals reside within a highly competitive ecosystem and are often brought to market based on preclinical, not clinical evidence. Success and failure will largely be governed by the establishment of clinical evidence in retrospect.

The Skin Microbiota and Itch: Is There a Link?

Itch is an unpleasant sensation that emanates primarily from the skin. The chemical mediators that drive neuronal activity originate from a complex interaction between keratinocytes, inflammatory cells, nerve endings and the skin microbiota, relaying itch signals to the brain. Stress also exacerbates itch via the skin–brain axis. Recently, the microbiota has surfaced as a major player to regulate this axis, notably during stress settings aroused by actual or perceived homeostatic challenge. The routes of communication between the microbiota and brain are slowly being unraveled and involve neurochemicals (i.e., acetylcholine, histamine, catecholamines, corticotropin) that originate from the microbiota itself. By focusing on itch biology and by referring to the more established field of pain research, this review examines the possible means by which the skin microbiota contributes to itch.

R. nukuhivensis acts by reinforcing skin barrier function, boosting skin immunity and by inhibiting IL-22 induced keratinocyte hyperproliferation

Rauvolfia nukuhivensis is a well-known plant used for its wide range of beneficial effects in Marquesas islands. It is made up of diverse indole alkaloids and is used as traditional medicine for skin application. The actual mechanism behind the virtue of this plant is still unknown. Hence, in this study we aimed at deciphering the impact of R. nukuhivensis on skin immune system in context of (1) homeostasis, (2) pathogen infection and (3) inflammation. Here we show that R. nukuhivensis enhances cellular metabolic activity and wound healing without inducing cellular stress or disturbing cellular homeostasis. It reinforces the epithelial barrier by up-regulating hBD-1. Nevertheless, in pathogenic stress, R. nukuhivensis acts by preparing the immune system to be reactive and effective directly. Indeed, it enhances the innate immune response by increasing pathogens sensors such as TLR5. Finally, R. nukuhivensis blocks IL-22 induced hyperproliferation via PTEN and Filaggrin up-regulation as well as BCL-2 downregulation. In conclusion, this study provides evidence on the several cutaneous application potentials of R. nukuhivensis such as boosting the immune response or in restoring the integrity of the epithelial barrier.

The Extract of D. dasycarpus Ameliorates Oxazolone-Induced Skin Damage in Mice by Anti-Inflammatory and Antioxidant Mechanisms

Dictamni dasycarpus is a type of Chinese medicine made from the root bark of D. dasycarpus. It has been reported to show a wide spectrum of biological and pharmacological effects, for example, it has been used widely for the treatment of rheumatism, nettle rash, itching, jaundice, chronic hepatitis and skin diseases. In the current study, D. dasycarpus extract was investigated for its antioxidant and anti-inflammatory effects, as well as its capability to alleviate oxazolone-induced skin damage in mice. The possible anti-inflammatory mechanism of D. dasycarpus extract against oxidative challenge was elucidated by measuring the levels of reactive oxygen species (ROS) production, interleukin-6, Tumor necrosis factor-α, NLRP3 (NACHT, LRR and PYD domains-containing protein 3 (NALP3)) inflammasome and interleukin-1β in HaCaT cells. D. dasycarpus extract did not affect cell viability in basal conditions. The extract significantly reduced oxazolone-induced epidermal swelling compared to untreated animal in the hairless albino mice (ICR mice) model. At the molecular level, Western blot assays indicated that the D. dasycarpus extract attenuated oxazolone-induced activation of apoptosis-associated speck-like protein containing CARD (ASC), procaspase-1, NF-κB and mitogen-activated protein kinase (MAPKs) such as c-Jun N-terminal protein kinase (JNK) and p38. This study demonstrates that D. dasycarpus extract could protect skin cells against oxidative and inflammatory insult by modulating the intracellular levels of ROS, TNF-α, interleukin-1, interleukin-6, NLR family pyrin domain containing 3 (NLRP3) inflammasome generation, antioxidant enzyme activity and cell signaling pathways. D. dasycarpus extract also attenuated the expression of NF-κB in HaCaT keratinocytes and thereby effectively downregulated inflammatory responses in the skin. Furthermore, D. dasycarpus extract alleviated oxazolone-induced damage in mice. Our results suggest the potential application of D. dasycarpus extract in preventing inflammatory processes in dermatitis.

Skin Immune Landscape: Inside and Outside the Organism

The skin is an essential organ to the human body protecting it from external aggressions and pathogens. Over the years, the skin was proven to have a crucial immunological role, not only being a passive protective barrier but a network of effector cells and molecular mediators that constitute a highly sophisticated compound known as the “skin immune system” (SIS). Studies of skin immune sentinels provided essential insights of a complex and dynamic immunity, which was achieved through interaction between the external and internal cutaneous compartments. In fact, the skin surface is cohabited by microorganisms recognized as skin microbiota that live in complete harmony with the immune sentinels and contribute to the epithelial barrier reinforcement. However, under stress, the symbiotic relationship changes into a dysbiotic one resulting in skin disorders. Hence, the skin microbiota may have either positive or negative influence on the immune system. This review aims at providing basic background information on the cutaneous immune system from major cellular and molecular players and the impact of its microbiota on the well-coordinated immune responses in host defense.

Association Between Human Hair Loss and the Expression Levels of Nucleolin, Nucleophosmin, and UBTF Genes

AIMS

Nucleolar organizer regions, also known as argyrophilic nucleolar organizer regions, are associated with ribosomal genes. The main function of the nucleolus is the rapid production of ribosomal subunits, a process that must be highly regulated to provide the appropriate levels for cellular proliferation and cell growth. There are no studies in the literature addressing the expression and function of nucleolar component proteins, including nucleophosmin, nucleolin and the upstream binding transcription factor (UBTF), in human follicular hair cells.

METHODS

Nineteen healthy males who had normal and sufficient hair follicles on the back of the head, but exhibited hair loss on the frontal/vertex portions of the head and 14 healthy males without hair loss were included in the current study. Gene expression levels were measured by relative quantitative real time polymerase chain reaction.

RESULTS

In the individuals suffering from alopecia, the total expression levels of nucleolin, nucleophosmin, and UBTF were lower in normal sites than in hair loss sites. Strong expression level correlations were detected between: nucleophosmin and nucleolin; nucleophosmin and UBTF, and nucleolin and UBTF for both groups.

CONCLUSIONS

There was an association between human hair loss and the expression levels of nucleolin, nucleophosmin, and UBTF genes.

The transcriptional response to distinct growth factors is impaired in Werner syndrome cells

The Werner syndrome protein (WRN) is mutated in Werner syndrome (WS) and plays a role in telomere maintenance, DNA repair and transcription. WS represents a premature aging syndrome with severe growth retardation. Here we show that WRN is critically required to mediate the stimulatory effect of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-b) and epidermal growth factor (EGF) on the activity of RNA polymerase I (Pol I). Recombinant WRN specifically reconstitutes RNA polymerase I transcription in extracts from Werner syndrome fibroblasts in vitro. In addition, we identified a critical role for WRN during promoter clearance of Pol I transcription, but not in elongation. Notably, WRN was isolated in a complex with Pol I and was crosslinked to the unmethylated, active proportion of rDNA genes in quiescent cells suggesting a so far unknown role for WRN in epigenetic regulation. This together with alterations in Pol I transcription provide a novel mechanism possibly underlying at least in part the severe growth retardation and premature aging in Werner syndrome patients.

Role of keratinocyte?fibroblast cross-talk in development of hypertrophic scar

The ability to generate or repair injured tissue is essential to the continuity of human life. As in all other organs, wound healing in the skin is a dynamic process involving tissue response to different types of insults. This process involves a continuous sequence of signals and responses in which platelets, fibroblasts, epithelial, endothelial, and immune cells come together outside their usual domains to orchestrate a very complex event that results in tissue repair. These signals, which are mainly growth factors and cytokines, orchestrate the initiation, continuation, and termination of wound healing. An imbalance in the synthesis and release of these cytokines and growth factors at the wound site, therefore, may result in either retarded wound healing, as is seen in diabetic patients and the elderly population, or overhealing wounds such as fibroproliferative disorders frequently seen following surgical incision, traumatic wounds, and severe electrical and thermal injury. In general, regardless of the site of injury, in any phase of the dynamic healing process, a fine balance between synthesis of extracellular matrix and degradation by a large family of enzymes, known as matrix metalloproteinases, is required for maintaining the structural integrity of healing tissue. The availability of new models such as organotypic co-culture systems have allowed us to gain new insight into the cell-cell interactions at both cellular and molecular levels. Recent evidence indicates that mesenchymal-epithelial interactions play a critical role in regulation of skin homeostasis and this cross-talk is mediated by soluble factors acting as autocrine/paracrine regulators of fibroblast and keratinocyte growth, function, and differentiation. In this review we address the question of how keratinocyte-fibroblast interaction plays a role in controlling the expression of key extracellular matrix molecules such as matrix metalloproteinases, which are critical in the healing process following any types of insults to the skin.

Activation of nuclear factor kappa B by diesel exhaust particles in mouse epidermal cells through phosphatidylinositol 3-kinase/Akt signaling pathway

Diesel exhaust particles (DEP) induce intense inflammatory and allergic immune responses. The epidermal cells receive much exposure to DEP, and are an important source of pro-inflammatory cytokines and other inflammatory mediators. Transcription factors, such as nuclear factor kappa B (NF-kappaB) and activator protein 1 (AP-1), regulate the expression of these mediators. We hypothesize that the transcription factors are target of DEP action. The current study sought to determine whether DEP-activated NF-kappaB and AP-1 in a mouse epidermal cell line, JB6 P(+) cells. Using stable transfectants of JB6 P(+) cells expressing NF-kappaB or AP-1 luciferase reporter constructs, we demonstrated that exposure to DEP at a non-cytotoxic concentration significantly enhanced the transactivation of NF-kappaB, but not AP-1. Furthermore, DEP promoted phosphorylation of Akt, a substrate of phosphatidylinositol 3-kinase (PI3K), on Ser-473 and Thr-308 in a PI3K-dependent manner, and enhanced phosphorylation of down-stream p70/p85 S6 kinases (p70/p85S6K) as well as glycogen synthase kinase-3beta (GSK-3beta). Blockage of PI3K activation eliminated DEP-stimulated NF-kappaB transactivation. Although SAPK/JNK pathway was modestly activated by DEP, it was not involved in NF-kappaB transactivation. DEP had little effect on the phosphorylation of ERKs and p38 MAPK. Thus, DEP-induced transactivation of NF-kappaB is mediated by PI3K/Akt signaling pathway.

Keratinocyte differentiation inversely regulates the expression of involucrin and transforming growth factor beta1

Extensive skin loss from a variety of conditions such as severe thermal injury is associated with significant functional morbidity and mortality. In recent years, the healing quality has been improved for patients who suffer burns due in part to the usage of skin replacement mainly prepared from multi-layered sheets of cultured keratinocytes. Although it is known that keratinocytes are a rich source of wound healing promoting factors such as transforming growth factor-beta1 (TGF-beta1), it is not clear whether differentiated keratinocytes in a multi-layer form release this multi-functional growth factor and has any functional influence on dermal fibroblasts. This study examined the hypothesis that keratinocytes in mono- and multi-layer forms express different levels of TGF-beta1. To address this hypothesis, keratinocytes were grown in serum free medium (KSFM) supplemented with bovine pituitary extract (50 microg/ml) and EGF (5 microg/ml). When cells reached confluency, conditioned medium was removed and replaced with 50% KSFM with no additives and 50% DMEM without serum and cells were allowed to form multi-layers and differentiate. The conditioned medium was then collected every 48 h up to 24 days and the level of TGF-beta1 and the efficacy of a keratinocyte released fibroblast mitogenic factor were evaluated by ELISA and (3)H-thymidine incorporation, respectively. Northern analysis was also employed to evaluate the expression of TGF-beta1, involucrin, TIMP-1, and 18 S ribosomal RNA in keratinocytes at different times of the onset of differentiation. The microscopic morphology of keratinocytes at different times of induction of cell differentiation showed detachments (nodules) of many regions of keratinocyte sheet from culture substratum within 1-2 weeks. The numbers and sizes of these nodules were increased as the process of keratinocyte differentiation proceed. The results of TGF-beta1 evaluation revealed that mono-layers of cultured keratinocytes which were round, attached, and proliferating in KSFM + BPE and EGF containing medium released a significantly higher level of TGF-beta1 (196 +/- 58 pg /ml) relative to those grown in multi-layer forms (28 +/- 7.8 pg/ml). A longitudinal experiment was then conducted and the results showed that cells on the onset of differentiation released even greater level of TGF-beta1 (388 +/- 53 pg/ml) relative to those grown in KSFM + BPE and EGF. This finding was consistent with the expression of TGF-beta1 mRNA evaluated in keratinocytes grown in test medium for various duration. In general, the level of TGF-beta1 protein and mRNA gradually reduced to its lowest level within 12 days of growing cells in our test medium. When aliquots of the collected keratinocyte conditioned medium were added to dermal fibroblasts, the level of (3)H-thymidine incorporation increased only in those cells receiving aliquots of conditioned medium containing high levels of TGF-beta1. When involucrin was used as a differentiation marker for keratinocytes at different time points, the highest level of involucrin mRNA expression was found at the later stage of cell differentiation. In conclusion, high involucrin expressing differentiated keratinocytes seem to be quiescent in releasing both TGF-beta1 and a fibroblast mitogenic factor.

Nickel-induced proteins in human HaCaT keratinocytes: annexin II and phosphoglycerate kinase

It has been established in previous in vitro experiments with human HaCaT keratinocytes that nickel becomes cytotoxic at concentrations higher than 100 microM and that it is accumulated mainly in the cytosolic fraction (Ermolli et al., 2000). The aim of this work was to search possible biomarkers of metal insult, i.e. nickel-binding proteins or proteins differentially expressed in the cytosolic fraction of nickel-exposed cells (up to 1 mM nickel) as compared to controls. Cytosolic proteins were studied by isoelectric focusing (IEF) and two-dimensional gel electrophoresis (2-DE). Separation by IEF revealed nickel-induced changes in the abundance of cytosolic proteins as visualised with nickel-nitrilo-triacetic-alkaline phosphatase (Ni-NTA-AP) in blots. The cytosolic fraction of cells incubated with nickel, at concentrations over 100 microM, showed nickel binding components which were absent or present in significantly lower amounts in control cells. These proteins had isoelectric points (pIs) 6.9, 7.7 and 8.5. After 2-DE silver- and protein staining significantly increased abundance of four proteins was observed. Their pI values corresponded to those of the nickel binding ones seen after IEF. A protein with pI 6.9 had a molecular weight estimated to 38 kDa, two proteins with pI around 7.7 showed molecular weights of 57 and 22 kDa, respectively and another protein with pI of 8.5 had a molecular weight of 33 kDa. The increased abundance of these components, both in IEF experiments and in 2-DE, correlated with the nickel concentration in the culture media. N-terminal amino acid sequencing and database search allowed identification of one a protein as phosphoglycerate kinase and another one as annexin II. The involvement of these proteins in cellular functions and their possible implications in the mechanism of nickel toxicity in keratinocytes are discussed. Some of these proteins may be biomarker candidates for effects of nickel exposure in human keratinocytes.

Self-administered topical 5% imiquimod for the treatment of common warts and molluscum contagiosum

BACKGROUND

Despite numerous therapeutic options the treatment of common warts and molluscum contagiosum remains unsatisfactory for both patients and physicians. Imiquimod, a novel topical immune response modifier, has been successfully used for the treatment of external anogenital warts.

OBJECTIVES

We aimed to evaluate the safety, tolerance and efficacy of imiquimod for the treatment of common cutaneous warts and mollusca that were resistant to previous therapeutic interventions.

METHODS

Imiquimod 5% cream was self-applied by the patients to the warts or mollusca once daily for 5 days per week and left in place overnight. Assessment for response and the occurrence of side-effects was performed every 4 weeks until clinical cure or up to a maximum of 16 weeks.

RESULTS

Twenty-eight of 50 (56%) patients with warts achieved a total clearance (n = 15; 30%) or a > 50% reduction in wart size (n = 13; 26%) after a mean treatment period of 9.2 weeks. Twelve of 15 (80%) patients with mollusca achieved a total clearance (n = 8; 53%) or a > 50% reduction in molluscum size (n = 4; 27%). There was no difference in response with regard to gender, human immunodeficiency virus serostatus or atopic predisposition.

CONCLUSIONS

Patient-applied 5% imiquimod cream holds promise as an effective treatment of common warts and mollusca in a difficult-to-treat patient population.

Induction of bone morphogenetic protein-6 in skin wounds. Delayed reepitheliazation and scar formation in BMP-6 overexpressing transgenic mice

Growth factors of the transforming growth factor-beta superfamily are involved in cutaneous wound healing. In this study we analyze the expression of the bone morphogenetic protein-6 (BMP-6) gene, a transforming growth factor-beta related gene, in skin wounds. In normal mouse skin high levels of BMP-6 mRNA and protein are expressed by postmitotic keratinocytes of stratified epidermis until day 6 after birth. BMP-6 expression is strongly reduced in adult epidermis with diminished mitotic activity. After skin injury we found large induction of BMP-6-specific RNA and protein in keratinocytes at the wound edge and keratinocytes of the newly formed epithelium as well as in fibroblast shaped cells in the wound bed. BMP-6-specific RNA was induced within 24 h after injury, whereas significant upregulation of BMP-6 on the protein level was detected only 2-3 d after injury. Protein was confined to outermost suprabasal epidermal layers, whereas BMP-6-specific RNA was distributed throughout all epidermal layers including basal keratinocytes and the leading edge of the migrating keratinocytes. We also detected high levels of BMP-6-specific RNA and protein in chronic human wounds of different etiology. In contrast to the overall distribution pattern of BMP-6-specific RNA, the protein was not detected in keratinocytes directly bordering the wound. In order to test the influence of BMP-6 abundance on the progress of wound healing, we analyzed the wound response of transgenic mice overexpressing BMP-6 in the epidermis. In these mice, reepitheliazation of skin wounds was significantly delayed, suggesting that strict spatial and temporal regulation of BMP-6 expression is necessary not only for formation but also for reestablishment of a fully differentiated epidermis.

Imiquimod, a patient-applied immune-response modifier for treatment of external genital warts

Genital human papillomavirus infection is one of the most common sexually transmitted diseases. Imiquimod is a new agent, an immune-response modifier, that has been demonstrated to have potent in vivo antiviral and antitumor effects in animal models. The present prospective, multicenter, double-blind, randomized, vehicle-controlled trial evaluated the efficacy and safety of daily patient-applied imiquimod for up to 16 weeks for the treatment of external genital warts. Wart recurrence was investigated during a 12-week treatment-free follow-up period. In the intent-to-treat analysis, baseline warts cleared from 49 of 94 (52%) patients treated with 5% imiquimod cream, 13 of 90 (14%) patients treated with 1% imiquimod cream, and 3 of 95 (4%) vehicle-treated patients; the differences between the groups treated with vehicle and imiquimod were significant (P < 0.0001). For subjects who completed the follow-up period, recurrence rates after a complete response were 19% (9 of 48 patients) in the 5% imiquimod cream group, 17% (2 of 12) in the 1% imiquimod cream group, and 0% (0 of 3) in the vehicle-treated group. There were no systemic reactions, although local skin reactions (generally of mild or moderate severity) were common, particularly in the 5% imiquimod cream group. Local reactions caused two patients to discontinue treatment. The most frequently reported local skin reactions were erythema, excoriation or flaking, and erosion. Patient-applied 5% imiquimod cream is effective for the treatment of external genital warts and has a favorable safety profile.

Treatment of genital warts with an immune-response modifier (imiquimod)

BACKGROUND

Genital warts are a common sexually transmitted disease caused by human papillomavirus. Imiquimod is a novel immune-response modifier capable of inducing a variety of cytokines, including interferon alfa, tumor necrosis factor-alpha, as well as interleukins 1, 6, and 8. In animal models imiquimod has demonstrated antiviral, antitumor, and adjuvant activity. In vitro, imiquimod has no antiviral or antitumor activity.

OBJECTIVE

Our purpose was to determine the safety and efficacy of topical imiquimod for the treatment of external genital warts.

METHODS

This prospective double-blind, placebo-controlled, parallel design clinical trial was performed in three outpatient centers, a public health clinic, a university-based clinic, and a private practice. One hundred eight patients with external genital warts (predominantly white men) were entered into the trial. Fifty-one patients were randomly selected to receive 5% imiquimod cream; 57 patients were randomly chosen to receive placebo cream. Study medication was applied three times weekly for up to 8 weeks. Patients whose warts cleared completely were observed for up to 10 weeks to determine recurrence rates.

RESULTS

In the intent-to-treat analysis, the warts of 37% (19 of 51) of the imiquimod-treated patients and 0% (0 of 57) of the placebo group cleared completely (p < 0.001). In addition, many patients experienced a partial response. A reduction in baseline wart area of 80% or more was observed in 62% of imiquimod-treated patients (28 of 45) and 4% of the placebo group (2 of 50) (p < 0.001); a 50% reduction or more in wart area was noted in 76% of imiquimod-treated patients (34 of 45) and 8% of placebo recipients (4 of 50) (p < 0.001). Of imiquimod-treated patients whose warts cleared completely and who finished the 10-week follow-up period, 19% (3 of 16) experienced recurrences of warts. Imiquimod-treated patients experienced a significantly greater number of local inflammatory reactions than the placebo group. Symptoms and signs associated with the local inflammatory reactions included itching (54.2%), erythema (33.3%), burning (31.3%), irritation (16.7%), tenderness (12.5%), ulceration (10.4%), erosion (10.4%), and pain (8.3%). There were no differences in systemic reactions or laboratory abnormalities between treatment groups.

CONCLUSION

Topical 5% imiquimod cream appears to have a significant therapeutic effect in the treatment of external genital warts.

Characterization and partial purification of a keratinocyte-derived growth factor with wound-healing properties

We have previously described the mitogenic and wound-healing properties of keratinocyte-conditioned medium (KCM). In this study we investigated the effect of KCM on the activation of second messenger systems and the expression of proto-oncogene in cultured human skin fibroblasts. We also present a partial purification of the factor responsible for the mitogenic and wound-healing effects of KCM. KCM was shown to increase the expression of the proto-oncogenes c-fos, c-myc and c-jun. The effect of KCM on three second messenger systems was investigated. The extracellular release of choline metabolites was increased by 40 per cent when cells were stimulated with KCM whereas the formation of cAMP and hydrolysis of phosphatidyl inositol (PI) was unaffected. KCM was purified by ion exchange chromatography and filtration. The biologically active fraction was eluted from an SP column and retained its activity after filtration through a 3-kDa filter. The fraction was inactivated by heat and acid, indicative of a peptide origin. Furthermore, the active fraction was shown to increase the extracellular release of choline metabolites and to stimulate re-epithelialization in wounds in human skin in vitro comparable to KCM. The study indicates that human keratinocytes produce a < 3 kDa peptide which may be partly responsible for the growth stimulatory and wound-healing properties of KCM.

In vivo cytokine and receptor gene expression during the rat hair growth cycle. Analysis by semi-quantitative RT-PCR

A number of cytokines have previously been localised within the developing and adult hair follicle, however, the role they play in producing a mature hair follicle remains unknown. In an attempt to identify dermal papilla specific cytokines and thus those that may have an important controlling role, cytokine gene expression profiles, obtained by reverse transcriptase-polymerase chain reaction (RT-PCR), were compared between whole anagen rat hair follicles, passage 2 dermal papillae (a cell type with hair inductive capacity), and footpad fibroblasts (a non-hair inducing cell type). Based on this qualitative data, we were unable to identify a dermal papilla specific gene. The analysis of the pattern and timing of cytokine gene expression during the hair cycle is likely to be more informative. A semi-quantitative RT-PCR technique was therefore developed for studying trends in the level of in vivo expression of the following cytokines and their receptors from early anagen to early catagen in the rat hair growth cycle: insulin-like growth factor I, transforming growth factor beta 1, tumour necrosis factor, and basic fibroblast growth factor. These genes were found to be differentially expressed and this was correlated with their possible functions in controlling the hair growth cycle, providing valuable insights into the role of cytokines in regulating the hair growth process.

UVB induces IL-12 transcription in human keratinocytes in vivo and in vitro

Human epidermal cells produce a wide range of cytokines, including those characteristic of Th2-like responses such as interleukin (IL)-4 and IL-10. As well, keratinocytes have recently been shown to produce Th1-like cytokines such as IL-12. Exposure to UVB has profound effects on the skin and systemic immune system, which is in part mediated by secretion of tumor necrosis factor (TNF)-alpha by epidermal cells. Because IL-12 induces production of TNF-alpha by certain cells of the immune system, we sought to determine whether UVB is an inducer of IL-12 gene expression in epidermal cells. Human epidermal cells were exposed to UVB radiation in vivo, isolated by suction blister technique and trypsinization and transcription of the IL-12 p35 and p40 chains was examined by RT-PCR. We found the p35 chain of IL-12 to be constitutively expressed and the p40 chain inducible by UVB irradiation. Because epidermis consists of a heterogenous cell population with distinct cytokine repertoires, we sought to determine the cellular source of the IL-12 message after UVB exposure. After depleting UVB-exposed epidermal cells for DR+ cells, no reduction in the IL-12 activity was detected, suggesting that keratinocytes are a source of IL-12 transcripts in UVB-exposed human epidermis. This was supported by the up-regulation of IL-12 p40 transcripts in UV-irradiated cultured keratinocytes that were devoid of DR+ cells. Up-regulation of IL-12 p40 gene expression by UVB as demonstrated here, taken together with the finding that keratinocytes also up-regulate IL-10 transcription, suggests that there is a complex interplay between Th1- and Th2-like epidermis-derived cytokines following exposure to UVB.

Three patterns of cytokine expression potentially involved in epithelial-fibroblast interactions of human ocular surface

Signals transmitted from mesenchyme to epithelia or vice versa constitute the basis of reciprocal epithelial-mesenchymal interactions. As a first step toward understanding epithelial-mesenchymal interactions on the ocular surface where the transit amplifying cell-containing corneal epithelium is anatomically separated from the stem cell-containing limbal epithelium, we sought to characterize the expression patterns of cytokines and their receptors by primary epithelial and early-passaged fibroblast cultures of human cornea and limbus. Northern hybridization with oligonucleotide and cDNA probes to a total of 25 cytokines and 12 of their receptors revealed that the positively expressed cytokines could be divided into the following four patterns. Type I: TGF-alpha, IL-1 beta, and PDGF-B were expressed exclusively by epithelial cells but their respective receptors EGFR and IL-1R were predominantly and PDGFR-beta was exclusively expressed by fibroblasts. Type II: IGF-I, TGF-beta 1, -beta 2, LIF, and bFGF, and their receptors were expressed by both epithelial cells and fibroblasts. FGFR-1 (flg) and FGFR-2 (bek) were expressed more by fibroblasts and bFGF was expressed more by corneal than limbal epithelial cells. Type III: keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) were expressed exclusively by fibroblasts and their respective receptors, KGFR and c-met, were predominantly expressed by epithelial cells. Combined with RT-PCR, the quantity of KGF and KGFR transcripts was highest in limbal fibroblasts and epithelial cells, respectively. In contrast, the quantity of HGF and HGFR (c-met) transcripts was highest in corneal fibroblasts and epithelial cells, respectively. Type IV: M-CSF and IL-8 were expressed by fibroblasts and/or epithelial cells but their receptors were not expressed by epithelial cells nor fibroblasts, but by immune or inflammatory cells. In addition to these potential paracrine actions, autocrine actions mediated by TGF-alpha/EGFR, IL-1 beta/IL1-R, and bFGF/FGFR-1 were more expressed by corneal than limbal epithelial cells. Immunofluorescence staining on human corneoscleral cryosections confirmed that EGFR and bFGF were not expressed by the limbal basal epithelium, but expressed strongly by the corneal epithelium, a pattern consistent with Northern hybridization. These results indicate that ocular surface epithelial cells and fibroblasts can express a myriad of cytokines, among which the first three patterns constitute the network of potential epithelial-mesenchymal cytokine dialogues. The difference of certain cytokine expression between corneal and limbal regions suggests that this network participates in normal epithelial growth and differentiation, and plays an important role in wound healing.

Detection of inflammatory cytokines in psoriatic skin

Recent investigations have revealed the involvement of cytokines in the pathogenesis of psoriasis. This study examined the amount of inflammatory cytokines--interleukin-1 (IL-1), interleukin-6 (IL-6) and granulocyte macrophage colony-stimulating factor (GM-CSF)--released into the supernatants of organ cultures of involved and uninvolved skin from psoriatic patients and normal skin from healthy individuals. Bioassays were employed to detect the activities of IL-1 and IL-6. Enzyme-linked immunosorbent assay (ELISA) methods were used to quantitate immunoreactive IL-1 alpha, IL-1 beta, IL-6 and GM-CSF. The activity of IL-1 in uninvolved psoriatic skin was found to be increased relative to that in involved and normal skin, while immunoreactive IL-1 beta was found only in involved skin. A neutralization experiment showed that bioactive IL-1 was mostly attributable to IL-1 alpha. Uninvolved psoriatic skin also secreted higher amounts of both bioactive and immunoreactive IL-6 compared with involved skin. Immunoreactive GM-CSF was detected in uninvolved skin only. These cytokines detected in uninvolved skin may have been released from epidermal or mesenchymal cells, since uninvolved skin contained fewer inflammatory infiltrates. Our results offer additional evidence that increased amounts of inflammatory cytokines in uninvolved skin may provide a preliminary condition and play important roles in the initial events in the evolution of psoriatic lesions.

Extraction and quantitation of cytokine mRNA from human epidermal blister roofs

The demonstration of cytokine mRNA expression in epidermal cells by the polymerase chain reaction technique preceded by reverse transcription (RT-PCR) requires linear test conditions (i.e. that the product obtained after amplification reflects the relative amounts of starting material) and high reproducibility, specificity, and sensitivity. By combining well-defined techniques for mRNA extraction and concentration measurement with a sensitive and well-calibrated RT-PCR technique, we demonstrated the presence of IL-1 alpha, IL-1 beta, IL-6, and TNF alpha in epidermal cells obtained from suction blister roofs from normal volunteers. Messenger RNA was extracted with superparamagnetic oligo(dT)25 Dynabeads, and the amount of mRNA was measured by spectrophotometry using a Beckman 5-microliters Ultra-Microcell prior to RT-PCR. Linear PCR conditions were obtained by carefully titrating the amounts of mRNA and the number of cycles. Reproducibility was estimated at different steps of the procedure, and the specificity of the enhanced cDNA products was verified by liquid hybridization with end-labelled probes. We suggest that this combination of techniques might prove useful for the simultaneous assessment of the expression of various cytokines from small samples of fresh human epidermal cells.

Cytokine gene expression in intact anagen rat hair follicles

Substantial cellular proliferative activity is necessary to produce a mature hair follicle. Therefore, it is likely that cytokines and their receptors play an important controlling role. To provide an understanding of the mechanisms involved during hair growth, we investigated the expression of cytokines in rat anagen hair follicles. A new technique was developed that allowed the rapid isolation of large numbers of intact, viable, anagen, rat pelage hair follicles. Total RNA was isolated from these follicles using an acid-phenol-chloroform extraction and analyzed for cytokine expression. Using the conventional technique of Northern blotting, it was only possible to detect transcripts for transforming growth factor beta (TGF beta) and insulin-like growth factor I (IGFI). Polymerase chain reaction amplification of reverse-transcribed mRNA detected cDNA fragments for TGF beta, IGF I, IGF II, nerve growth factor beta (NGF beta), and interleukin-1 alpha (IL-1 alpha). The amplified products were confirmed by digestion with restriction endonucleases. The proteins themselves for TGF beta and IGF I have been shown to be present within the anagen hair follicle using immunogold antibody labeling. This study has provided the first reported cytokine expression profile of rat anagen hair follicles. It is likely that the analysis of the pattern and timing of expression of these cytokines in the follicle will provide valuable insights into hair growth regulation.

Coley's toxins, tumor necrosis factor and cancer research: a historical perspective

As far back as the 1700s, it was recorded that certain infectious disease processes could exert a beneficial therapeutic effect upon malignancy. Most prominent among the numerous deliberate efforts made to take advantage of these observations was that of a pioneering New York surgeon, William B. Coley, active career 1891-1936. Using a bacterial vaccine to treat primarily inoperable sarcoma. Coley accomplished a cure rate of better than 10%. This review examines the history of these efforts and presents a discussion of their corresponding relevance to present day immunotherapy.

Cytokine expression by epidermal cell subpopulations

Epidermal cells (EC) are a rich source of cytokines that can regulate the function of cells in skin and in other tissues. To organize the array of data pertaining to cytokine expression by EC subpopulations, we have tabulated such data according to cell source, state of cell activation, and type of assay employed. This information forms a background for our own studies, in which reverse transcriptase-polymerase chain reaction (RT-PCR) was used to show that Langerhans cells (LC) are the principal source of mRNA for interleukin 1 beta and macrophage inflammatory protein-1 alpha (MIP-1 alpha) among unstimulated mouse EC.