Opioids and the skin - where do we stand?

Delta opioid receptor expression correlates to skin ageing and melanin expression in Asian women

While the evidence for the implication of opioid receptors (OPr) in ageing is growing, there is, to our knowledge, no study focusing directly on changes in vivo cutaneous OPr expression with increasing age. We thus investigated OPr expression in 30 healthy female Asian volunteers in Southern China whose ages range from the early 20s to the early 60s. Excisional biopsies were taken from the sun-exposed extensor area of the lower arm and the photo-protected area of the upper inner arm. The thickness of the epidermal layers, melanin content, as well as expression of mu-opioid receptors (MOPr) and delta-opioid receptors (DOPr) were compared between different age ranges and photo-exposure status. Significant increased epidermal hypertrophy on the extensor surface was observed. There was significant reduction of DOPr in the epidermis with increasing age, independent of photo-ageing. The increase of melanin was significantly correlated with epidermal DOPr expression, not with MOPr expression. DOPr expression could thus serve as a marker for real biological ageing unaffected by chronic photo-exposure. Additionally, DOPr expression was inversely correlated with the deposition of melanin. Based on these results, we hypothesise that regulation of DOPr expression could be used to improve aged skin, including hyperpigmentation.

The Opioid Receptor Influences Circadian Rhythms in Human Keratinocytes through the β-Arrestin Pathway

The recent emphasis on circadian rhythmicity in critical skin cell functions related to homeostasis, regeneration and aging has shed light on the importance of the PER2 circadian clock gene as a vital antitumor gene. Furthermore, delta-opioid receptors (DOPrs) have been identified as playing a crucial role in skin differentiation, proliferation and migration, which are not only essential for wound healing but also contribute to cancer development. In this study, we propose a significant association between cutaneous opioid receptor (OPr) activity and circadian rhythmicity. To investigate this link, we conducted a 48 h circadian rhythm experiment, during which RNA samples were collected every 5 h. We discovered that the activation of DOPr by its endogenous agonist Met-Enkephalin in N/TERT-1 keratinocytes, synchronized by dexamethasone, resulted in a statistically significant 5.6 h delay in the expression of the core clock gene PER2. Confocal microscopy further confirmed the simultaneous nuclear localization of the DOPr-β-arrestin-1 complex. Additionally, DOPr activation not only enhanced but also induced a phase shift in the rhythmic binding of β-arrestin-1 to the PER2 promoter. Furthermore, we observed that β-arrestin-1 regulates the transcription of its target genes, including PER2, by facilitating histone-4 acetylation. Through the ChIP assay, we determined that Met-Enkephalin enhances β-arrestin-1 binding to acetylated H4 in the PER2 promoter. In summary, our findings suggest that DOPr activation leads to a phase shift in PER2 expression via β-arrestin-1-facilitated chromatin remodeling. Consequently, these results indicate that DOPr, much like its role in wound healing, may also play a part in cancer development by influencing PER2.

Pathomechanism of Pruritus in Psoriasis and Atopic Dermatitis: Novel Approaches, Similarities and Differences

Pruritus is defined as an unpleasant sensation that elicits a desire to scratch. Nearly a third of the world's population may suffer from pruritus during their lifetime. This symptom is widely observed in numerous inflammatory skin diseases-e.g., approximately 70-90% of patients with psoriasis and almost every patient with atopic dermatitis suffer from pruritus. Although the pathogenesis of atopic dermatitis and psoriasis is different, the complex intricacies between several biochemical mediators, enzymes, and pathways seem to play a crucial role in both conditions. Despite the high prevalence of pruritus in the general population, the pathogenesis of this symptom in various conditions remains elusive. This review aims to summarize current knowledge about the pathogenesis of pruritus in psoriasis and atopic dermatitis. Each molecule involved in the pruritic pathway would merit a separate chapter or even an entire book, however, in the current review we have concentrated on some reports which we found crucial in the understanding of pruritus. However, the pathomechanism of pruritus is an extremely complex and intricate process. Moreover, many of these signaling pathways are currently undergoing detailed analysis or are still unexplained. As a result, it is currently difficult to take an objective view of how far we have come in elucidating the pathogenesis of pruritus in the described diseases. Nevertheless, considerable progress has been made in recent years.

Hydrogen peroxide production by epidermal dual oxidase 1 regulates nociceptive sensory signals

Keratinocytes of the mammalian skin provide not only mechanical protection for the tissues, but also transmit mechanical, chemical, and thermal stimuli from the external environment to the sensory nerve terminals. Sensory nerve fibers penetrate the epidermal basement membrane and function in the tight intercellular space among keratinocytes. Here we show that epidermal keratinocytes produce hydrogen peroxide upon the activation of the NADPH oxidase dual oxidase 1 (DUOX1). This enzyme can be activated by increasing cytosolic calcium levels. Using DUOX1 knockout animals as a model system we found an increased sensitivity towards certain noxious stimuli in DUOX1-deficient animals, which is not due to structural changes in the skin as evidenced by detailed immunohistochemical and electron-microscopic analysis of epidermal tissue. We show that DUOX1 is expressed in keratinocytes but not in the neural sensory pathway. The release of hydrogen peroxide by activated DUOX1 alters both the activity of neuronal TRPA1 and redox-sensitive potassium channels expressed in dorsal root ganglia primary sensory neurons. We describe hydrogen peroxide, produced by DUOX1 as a paracrine mediator of nociceptive signal transmission. Our results indicate that a novel, hitherto unknown redox mechanism modulates noxious sensory signals.

Uremic pruritus: pathophysiology, clinical presentation, and treatments

Uremic pruritus is one of the most common and bothersome symptoms in patients with end-stage renal disease. Most patients with uremic pruritus experience a prolonged and relapsing course and significant impairments of quality of life. The pathophysiology of uremic pruritus is not completely understood. A complex interplay among cutaneous biology and the nervous and immune systems has been implicated, with the involvement of various inflammatory mediators, neurotransmitters, and opioids. Uremic pruritus treatment outcomes are often unsatisfactory. Clinical trials have mostly been small in scale and have reported inconsistent results. Recent evidence shows that gabapentinoids, nalfurafine, and difelikefalin are effective for relieving uremic pruritus in hemodialysis patients. This review provides an overview of the epidemiology and proposed mechanisms of uremic pruritus, then highlights the manifestations of and clinical approach to uremic pruritus. Current evidence regarding treatment options, including topical treatments, treatment of underlying disease, phototherapy, and systemic treatments, is also outlined. With a better understanding of uremic pruritus, more therapeutic options can be expected in the near future.

Etiopathogenesis of chronic kidney disease-associated pruritus: putting the pieces of the puzzle together

Defined as the unpleasant sensation that causes the desire to scratch, pruritus is the most common skin symptom associated with uremia and appears in almost half of patients with advanced chronic kidney disease (CKD). Beyond its direct impact on quality of life, CKD-associated pruritus (CKD-aP) is an independent predictor of mortality that also has a synergistic effect with other quality of life-related symptoms, such as insomnia, depression, and anxiety. Although different mechanisms have been proposed to explain the origin of Pa-ERC, its etiopathogenesis is still not fully understood. Since new therapeutic targets have been identified and several clinical trials have recently shown promising results, our current understanding of the interrelationships has expanded significantly and the pathophysiological mechanisms underlying CKD-aP are now considered to be multifactorial. The potential triggers of pruritus in patients with CKD are discussed in this review, including hypotheses about skin xerosis, accumulation of uremic toxins, dysregulation of the immune system and systemic inflammation, uremic neuropathy, and imbalances in the endogenous opioid system. Other non-uremic causes of pruritus are also discussed, with the aim of guiding the physicians to apply an adequate aetiopathogenic approach to CKD-aP in their day-to-day clinical practice.

Nouvelles thérapies dans la prise en charge du patient avec maladie rénale chronique souffrant de prurit : une revue de la littérature New therapies in the management of chronic kidney disease associated pruritus

Chronic Kidney Disease associated Pruritus (CKD-aP) is a well-established and frequent complication observed in patient with CKD, especially in dialysis patients. However, the management of CKD-aP remains a challenge as the pathophysiology and research studies are too small. Finally, there are a few proposed treatment options with significant clinical benefits. This general review will summarize all the available treatments for the CKD-aP and will highlight the clinical efficacy and limits of the current drugs. Notably, we will focus on the implication of the opioid receptor in the pathophysiology of the CKD-aP and the recently Kappa opioid receptor agonist. © 2022 Published by Elsevier Masson SAS on behalf of Société francophone de néphrologie, dialyse et transplantation.

Neuroendocrine signaling in the skin with a special focus on the epidermal neuropeptides

The skin, which is comprised of the epidermis, dermis, and subcutaneous tissue, is the largest organ in the human body and it plays a crucial role in the regulation of the body's homeostasis. These functions are regulated by local neuroendocrine and immune systems with a plethora of signaling molecules produced by resident and immune cells. In addition, neurotransmitters, endocrine factors, neuropeptides, and cytokines released from nerve endings play a central role in the skin's responses to stress. These molecules act on the corresponding receptors in an intra-, juxta-, para-, or autocrine fashion. The epidermis as the outer most component of skin forms a barrier directly protecting against environmental stressors. This protection is assured by an intrinsic keratinocyte differentiation program, pigmentary system, and local nervous, immune, endocrine, and microbiome elements. These constituents communicate cross-functionally among themselves and with corresponding systems in the dermis and hypodermis to secure the basic epidermal functions to maintain local (skin) and global (systemic) homeostasis. The neurohormonal mediators and cytokines used in these communications regulate physiological skin functions separately or in concert. Disturbances in the functions in these systems lead to cutaneous pathology that includes inflammatory (i.e., psoriasis, allergic, or atopic dermatitis, etc.) and keratinocytic hyperproliferative disorders (i.e., seborrheic and solar keratoses), dysfunction of adnexal structure (i.e., hair follicles, eccrine, and sebaceous glands), hypersensitivity reactions, pigmentary disorders (vitiligo, melasma, and hypo- or hyperpigmentary responses), premature aging, and malignancies (melanoma and nonmelanoma skin cancers). These cellular, molecular, and neural components preserve skin integrity and protect against skin pathologies and can act as "messengers of the skin" to the central organs, all to preserve organismal survival.

Treatment Options for Troublesome Itch

Itch (or pruritus) is an unpleasant sensation, inducing the desire to scratch. It is also a major and distressing symptom of many skin and systemic diseases. The involvement of histamine, which is a major itch mediator, has been extensively examined. Recent studies suggest that histamine-independent pathways may play roles in chronic itch. Therefore, antihistamines are not always effective in the treatment of patients with chronic itch. The development of biologics and κ-opioid receptor (KOR) agonists has contributed to advances in the treatment of itch; however, since biologics are expensive for patients to purchase, some patients may limit or discontinue their use of these agents. Furthermore, KOR agonists need to be prescribed with caution due to risks of side effects in the central nervous system. Janus kinase (JAK) inhibitors are sometimes associated with side effects, such as infection. In this review, we summarize antidepressants, antineuralgics, cyclosporine A, antibiotics, crotamiton, phosphodiesterase 4 inhibitor, botulinum toxin type A, herbal medicines, phototherapy, and acupuncture therapy as itch treatment options other than antihistamines, biologics, opioids, and JAK inhibitors; we also explain their underlying mechanisms of action.

Efficacy and Safety of Topical Morphine: A Narrative Review

Background. Opioids are the cornerstone of the therapy used in both acute and chronic pain syndromes to treat pain of moderate to severe intensity. The knowledge that opioid receptors also occur in other tissues outside the central nervous system has created a possibility for the topical use of opioids. Thus, local analgesia may be obtained without systemic adverse effects. Methods. A narrative review of scientific papers discussing the topical use of morphine was conducted. For this purpose, the PubMed, Google Scholar, Cochrane Library, and Mendeley databases were searched. Results. The current knowledge on topical morphine does not allow for its recommended use in everyday medical practice, but suggests it may be effective, particularly in the treatment of ulcers and erosions of inflammatory etiology and painful skin lesions including persistent post-mastectomy pain due to breast cancer. Conclusions. Topical morphine has its place beside other analgesics. An important issue is the practical possibility to meet the demand for topical formulations, which is limited by technical difficulties.

Opioidergic Signaling-A Neglected, Yet Potentially Important Player in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases, the prevalence of which is especially high among children. Although our understanding about its pathogenesis has substantially grown in recent years, and hence, several novel therapeutic targets have been successfully exploited in the management of the disease, we still lack curative treatments for it. Thus, there is an unmet societal demand to identify further details of its pathogenesis to thereby pave the way for novel therapeutic approaches with favorable side effect profiles. It is commonly accepted that dysfunction of the complex cutaneous barrier plays a central role in the development of AD; therefore, the signaling pathways involved in the regulation of this quite complex process are likely to be involved in the pathogenesis of the disease and can provide novel, promising, yet unexplored therapeutic targets. Thus, in the current review, we aim to summarize the available potentially AD-relevant data regarding one such signaling pathway, namely cutaneous opioidergic signaling.

The Local Neuropeptide System of Keratinocytes

Neuropeptides have been known for over 50 years as chemical signals in the brain. However, it is now well established that the synthesis of this class of peptides is not restricted to neurons. For example, human skin not only expresses several functional receptors for neuropeptides but, also, can serve as a local source of neuroactive molecules such as corticotropin-releasing hormone, melanocortins, and β-endorphin. In contrast, an equivalent of the hypothalamic-pituitary axis in the oral mucosa has not been well characterized to date. In view of the differences in the morphology and function of oral mucosal and skin cells, in this review I surveyed the existing evidence for a local synthesis of hypothalamic-pituitary, opiate, neurohypophyseal, and neuroendocrine neuropeptides in both epidermal and oral keratinocytes.

The Expression Pattern of Genes Related to Melanogenesis and Endogenous Opioids in Psoriasis

The melanocortin system is a major regulator of stress responses in the skin and is responsible for the induction of melanin synthesis through activation of melanogenesis enzymes. The expression of both melanocortin system genes and melanogenesis enzyme genes is altered in psoriasis, and the focus here was on twelve genes related to the signal transduction between them. Additionally, five endogenous opioid system genes that are involved in cutaneous inflammation were examined. Quantitative real-time-PCR was utilized to measure mRNA expression in punch biopsies from lesional and non-lesional skin of psoriasis patients and from the skin of healthy control subjects. Most of the genes related to melanogenesis were down-regulated in patients (CREB1, MITF, LEF1, USF1, MAPK14, ICAM1, PIK3CB, RPS6KB1, KIT, and ATRN). Conversely, an up-regulation occurred in the case of opioids (PENK, PDYN, and PNOC). The suppression of genes related to melanogenesis is in agreement with the reported reduction in pigmentation signaling in psoriatic skin and potentially results from the pro-inflammatory environment. The increase in endogenous opioids can be associated with their involvement in inflammatory dysregulation in psoriasis.

Topical opioid use in dermatologic disease: A systematic review

Topical opioid formulations offer a potential solution to manage pain and decrease the use of systemic opioids. Synthesis of use and efficacy of topical opioids in dermatological conditions has not been well characterized. We conducted a systematic search of the PubMed, Embase, and Cochrane databases from 1980 to February 2021. This study analyzed data from 14 articles and 263 patients on the use of topical opioids for pain related to chronic ulcers, burns, oral lichen planus, photodynamic therapy, and split-thickness skin grafts. Topical opioids included in this review were topical morphine and diamorphine. Common formulations consisted of 0.2-10 mg of opioid compounded with hydrogel or IntraSite gel. Topical opioids were variably effective in the use for pain control related to chronic ulcers and other dermatologic conditions. For example, the use of topical opioids appears to be effective in the reduction of pain related to pressure ulcers. Topical opioids were generally well tolerated. Insufficient data exist to adequately evaluate the efficacy and safety of topical opioid use in the context of nonpressure ulcers, burns, oral lichen planus, photodynamic therapy, and split-thickness skin grafts.

[Pruritus associated chronic kidney disease]

Pruritus associated with chronic kidney disease is a frequent and disabling symptom in patients with severe chronic kidney disease treated by dialysis. It is associated with a poor quality of life, an increased risk of comorbidities and even mortality. Nevertheless, its prevalence is underestimated by nephrologists. The pathophysiology of pruritus associated with chronic kidney disease is not well understood, but several mechanisms seem to contribute to its occurrence: accumulation and skin deposition of uremic toxins, peripheral neuropathy causing an activation of the pruritogenic cowhage pathway, chronic microinflammation, opioid imbalance, and kidney disease-related skin xerosis. Optimization of the treatment of chronic kidney disease treatment, of dialysis parameters, and general skin care measures should always be performed prior to the introduction of systemic therapy targeting one or more of these mechanisms. The available therapeutic trials remain mostly at high risk of bias, with small patient numbers. Gabapentinoids are the molecules recommended as first-line therapy. Peripheral opioid agonists could find a place of choice in the treatment of pruritus associated with chronic kidney disease and will soon be available in France. The low level of evidence for the other molecules does not currently allow us to specify a second-line treatment for this condition.

Neurocosmetics in Skincare—The Fascinating World of Skin–Brain Connection: A Review to Explore Ingredients, Commercial Products for Skin Aging, and Cosmetic Regulation

The “modern” cosmetology industry is focusing on research devoted to discovering novel neurocosmetic functional ingredients that could improve the interactions between the skin and the nervous system. Many cosmetic companies have started to formulate neurocosmetic products that exhibit their activity on the cutaneous nervous system by affecting the skin’s neuromediators through different mechanisms of action. This review aims to clarify the definition of neurocosmetics, and to describe the features of some functional ingredients and products available on the market, with a look at the regulatory aspect. The attention is devoted to neurocosmetic ingredients for combating skin stress, explaining the stress pathways, which are also correlated with skin aging. “Neuro-relaxing” anti-aging ingredients derived from plant extracts and neurocosmetic strategies to combat inflammatory responses related to skin stress are presented. Afterwards, the molecular basis of sensitive skin and the suitable neurocosmetic ingredients to improve this problem are discussed. With the aim of presenting the major application of Botox-like ingredients as the first neurocosmetics on the market, skin aging is also introduced, and its theory is presented. To confirm the efficacy of the cosmetic products on the market, the concept of cosmetic claims is discussed.

Neuroendocrine Factors in Melanoma Pathogenesis

Simple Summary

Melanoma is a very aggressive and fatal malignant tumor. While curable if diagnosed in its early stages, advanced melanoma, despite the complex therapeutic approaches, is associated with one of the highest mortality rates. Hence, more and more studies have focused on mechanisms that may contribute to melanoma development and progression. Various studies suggest a role played by neuroendocrine factors which can act directly on tumor cells, modulating their proliferation and metastasis capability, or indirectly through immune or inflammatory processes that impact disease progression. However, there are still multiple areas to explore and numerous unknown features to uncover. A detailed exploration of the mechanisms by which neuroendocrine factors can influence the clinical course of the disease could open up new areas of biomedical research and may lead to the development of new therapeutic approaches in melanoma.

Abstract

Melanoma is one of the most aggressive skin cancers with a sharp rise in incidence in the last decades, especially in young people. Recognized as a significant public health issue, melanoma is studied with increasing interest as new discoveries in molecular signaling and receptor modulation unlock innovative treatment options. Stress exposure is recognized as an important component in the immune-inflammatory interplay that can alter the progression of melanoma by regulating the release of neuroendocrine factors. Various neurotransmitters, such as catecholamines, glutamate, serotonin, or cannabinoids have also been assessed in experimental studies for their involvement in the biology of melanoma. Alpha-MSH and other neurohormones, as well as neuropeptides including substance P, CGRP, enkephalin, beta-endorphin, and even cellular and molecular agents (mast cells and nitric oxide, respectively), have all been implicated as potential factors in the development, growth, invasion, and dissemination of melanoma in a variety of in vitro and in vivo studies. In this review, we provide an overview of current evidence regarding the intricate effects of neuroendocrine factors in melanoma, including data reported in recent clinical trials, exploring the mechanisms involved, signaling pathways, and the recorded range of effects.

Spinal endomorphins attenuate burn-injury pain in male mice by inhibiting p38 MAPK signaling pathway through the mu-opioid receptor

Burn injury is one of the main causes of mortality worldwide and frequently associated with severe and long-lasting pain that compromises the quality of patient life. Several studies have shown that the mu-opioid system plays an important role in burn pain relief. In this study, we investigated the spinal antinociception induced by the endogenous mu-opioid receptor (MOR) agonists endomorphins and explored their mechanisms of actions in burn injury-induced pain model. Our results showed that intrathecal injection of endomorphin-1 and -2 dose-dependently attenuated mechanical allodynia and thermal hyperalgesia via the mu-opioid receptor in mice on day 3 after burn injury, which was consistent with the data obtained from the mu-opioid receptor knockout mice. Western blot showed that the phosphorylation levels of extracellular signal-regulated kinase1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) in ipsilateral spinal cord tissues were significantly up-regulated after burn injury. Intrathecal injection of endomorphins selectively inhibited the activation of p38 MAPK on day 3 after burn injury via the mu-opioid receptor. Further studies found that repeated application of the specific p38 MAPK inhibitor SB203580 dose-dependently inhibited burn-injury pain, as well as the activation of spinal p38 MAPK. Taken together, our present study demonstrates that intrathecal injection of endomorphins attenuates burn-injury pain in male mice by affecting the spinal activation of p38 MAPK via the mu-opioid receptor.

Intractable Itch in Atopic Dermatitis: Causes and Treatments

Itch or pruritus is the hallmark of atopic dermatitis and is defined as an unpleasant sensation that evokes the desire to scratch. It is also believed that itch is a signal of danger from various environmental factors or physiological abnormalities. Because histamine is a well-known substance inducing itch, H₁-antihistamines are the most frequently used drugs to treat pruritus. However, H₁-antihistamines are not fully effective against intractable itch in patients with atopic dermatitis. Given that intractable itch is a clinical problem that markedly decreases quality of life, its treatment in atopic dermatitis is of high importance. Histamine-independent itch may be elicited by various pruritogens, including proteases, cytokines, neuropeptides, lipids, and opioids, and their cognate receptors, such as protease-activated receptors, cytokine receptors, Mas-related G protein-coupled receptors, opioid receptors, and transient receptor potential channels. In addition, cutaneous hyperinnervation is partly involved in itch sensitization in the periphery. It is believed that dry skin is a key feature of intractable itch in atopic dermatitis. Treatment of the underlying conditions that cause itch is necessary to improve the quality of life of patients with atopic dermatitis. This review describes current insights into the pathophysiology of itch and its treatment in atopic dermatitis.

Nanomaterials Versus The Microbial Compounds With Wound Healing Property

Age and diabetes related slow-healing or chronic wounds may result in morbidity and mortality through persistent biofilms infections and prolonged inflammatory phase. Nano-materials [metal/metal oxide NPs (39%), lipid vehicles (21%), polymer NPs (19%), ceramic nanoparticles (NPs) (14%), and carbon nanomaterials (NMs) (7%)] can be introduced as a possible next-generation therapy because of either their intrinsic wound healing activity or via carrying bioactive compounds including, antibiotics, antioxidants, growth factor or stem cell. The nanomaterials have been shown to implicate in all four stages of wound healing including hemostasis (polymer NPs, ceramic NPs, nanoceria-6.1%), inflammation (liposome/vesicles/solid lipid NPs/polymer NPs/ceramic NPs/silver NPs/gold NPs/nanoceria/fullerenes/carbon-based NPs-32.7%), proliferation (vesicles/liposome/solid lipid NPs/gold NPs/silver NPs/iron oxide NPs/ceramic NPs/copper NPs/self-assembling elastin-like NPs/nanoceria/micelle/dendrimers/polymer NPs-57.1%), remodeling (iron oxide NPs/nanoceria-4.1%). Natural compounds from alkaloids, flavonoids, retinoids, volatile oil, terpenes, carotenoids, or polyphenolic compounds with proven antioxidant, anti-inflammatory, immunomodulatory, or antimicrobial characteristics are also well known for their potential to accelerate the wound healing process. In the current paper, we survey the potential and properties of nanomaterials and microbial compounds in improving the process of wound and scar healing. Finally, we review the potential biocompounds for incorporation to nano-material in perspective to designate more effective or multivalent wound healing natural or nano-based drugs.

Molecular Aspects of Pruritus Pathogenesis in Psoriasis

Psoriasis is a chronic, systemic inflammatory disease with a genetic background that involves almost 3% of the general population worldwide. Approximately, 70–90% of patients with psoriasis suffer from pruritus, an unpleasant sensation that provokes a desire to scratch. Despite the enormous progress in understanding the mechanisms that cause psoriasis, the pathogenesis of psoriasis-related pruritus still remains unclear. In order to improve patients’ quality of life, development of more effective and safer antipruritic therapies is necessary. In turn to make it possible, better understanding of complexed and multifactorial pathogenesis of this symptom is needed. In this article we have systematized the current knowledge about pruritus origin in psoriasis.

Recent advances in the opioid mu receptor based pharmacotherapy for rheumatoid arthritis

INTRODUCTION

Opioids are used for severe forms of acute and cancer pain. Over the last years, their potential use in patients with noncancer pain such as those with rheumatoid arthritis (RA) has been postulated. A recent population-based comparative study showed that chronic opioid use was 12% vs. 4% among RA and non-RA patients, respectively. Another study showed an increase from 7.4% to 16.9% (2002 to 2015). In general, there has been an increasing tendency to use opioids in recent years.

AREAS COVERED

The authors have performed an extensive literature search using PubMed for articles including noncancer pain and the use of the mu opioid receptor (MOR) agonists in patients with RA.

EXPERT OPINION

Data is not sufficient to support opioid use for the treatment of chronic pain in patients with RA. Data is scarce and inconclusive. Rheumatologists should think and ponder the question: Why is this patient in pain? Differential diagnosis should include a disease flare, degenerative changes of the musculoskeletal system, and fibromyalgia. And while there are new strategies for opioid administration currently being researched, unfortunately, they are far from being applied to human subjects in the everyday clinical setting, and are still being evaluated at an experimental level. CNS: Central nervous system; DORs: delta opioid receptor agonists; GI: Gastrointestinal; GPCRs: G protein-coupled receptors; IL: Interleukin; JAK: Janus kinase; KORs: kappa opioid receptor agonists; MCPs: Metacarpophalangeal joints; MORs: Mu opioid receptor agonists; MTPs: Metatarsophalangeal joints; NSAIDs: Non-steroidal anti-inflammatory drugsOA: Osteoarthritis; ORs: Opioid receptors; PD: Pharmacodynamic; PIPs: Proximal interphalangeal joints; PK: Pharmacokinetic; PNS: Peripheral nervous system; RA: Rheumatoid arthritis; RGS: Regulator of G protein signaling; SSRIs: Selective serotonin reuptake inhibitors; TNF: Tumor necrosis factor.

β-Neoendorphin Enhances Wound Healing by Promoting Cell Migration in Keratinocyte

The skin is the largest and a remarkably plastic organ that serves as a protective barrier against environmental stimuli and injuries throughout life. Skin injuries are serious health problems, and wound healing is a critical process to replace devitalized cellular and tissue structures. Although some endogenous opioids are known to be involved in the modulation of wound healing, it remains to be determined whether the β-neoendorphin (β-NEP), an endogenous opioid, has beneficial effects on wound repair in human keratinocyte. In this study, we found that β-NEP accelerated wound repair through activation of mitogen-activated protein kinase (MAPK)/Erk1/2 signaling pathways in human keratinocytes. Moreover, the wound healing effect of β-NEP is mainly through the acceleration of keratinocyte migration without affecting cell proliferation. Therefore, our studies reveal that β-NEP plays an important role in the regulation of wound repair and suggest a therapeutic strategy to promote wound healing using β-NEP.

Topical Application of Loperamide/Oxymorphindole, Mu and Delta Opioid Receptor Agonists, Reduces Sensitization of C-fiber Nociceptors that Possess NaV1.8

It was recently shown that local injection, systemic administration or topical application of the peripherally-restricted mu-opioid receptor (MOR) agonist loperamide (Lo) and the delta-opioid receptor (DOR) agonist oxymorphindole (OMI) synergized to produce highly potent anti-hyperalgesia that was dependent on both MOR and DOR located in the periphery. We assessed peripheral mechanisms by which this Lo/OMI combination produces analgesia in mice expressing the light-sensitive protein channelrhodopsin2 (ChR2) in neurons that express Na_V1.8 voltage-gated sodium channels. These mice (Na_V1.8-ChR2⁺) enabled us to selectively target and record electrophysiological activity from these neurons (the majority of which are nociceptive) using blue light stimulation of the hind paw. We assessed the effect of Lo/OMI on nociceptor activity in both naïve mice and mice treated with complete Freund's adjuvant (CFA) to induce chronic inflammation of the hind paw. Teased fiber recording of tibial nerve fibers innervating the plantar hind paw revealed that the Lo/OMI combination reduced responses to light stimulation in naïve mice and attenuated spontaneous activity (SA) as well as responses to light and mechanical stimuli in CFA-treated mice. These results show that Lo/OMI reduces activity of C-fiber nociceptors that express Na_V1.8 and corroborate recent behavioral studies demonstrating the potent analgesic effects of this drug combination. Because of its peripheral site of action, Lo/OMI might produce effective analgesia without the side effects associated with activation of opioid receptors in the central nervous system.

Non-neuronal kappa-opioid receptor activation enhances epidermal keratinocyte proliferation, and modulates mast cell functions in human skin ex vivo

Kappa-opioid receptor (KOR) activation reportedly elicits anti-inflammatory responses and can downregulate neuropeptide release from sensory nerve fibers. While this renders KOR agonists (KORAs) potentially interesting therapeutics in skin diseases associated with neurogenic inflammation, it remains poorly understood how KOR agonists impact on human skin and dermal mast cells (MCs) ex vivo, in the absence of functional innervation. The KORA 5a was administrated to the culture medium (200 nmol/L and 1 µmol/L) in human skin organ culture, thus mimicking a "systemic" mode of application. We show that KORA significantly increased epidermal thickness and upregulated the number and proliferation of epidermal keratinocytes. Unexpectedly, it also stimulated epidermal keratinocyte apoptosis in situ, compared with vehicle. Moreover, KORA significantly decreased the number of c-Kit-positive MCs, but did not significantly alter the number or degranulation of mature (tryptase- or toluidine blue-positive) MCs. These pilot observations render the tested KORA (5a) an interesting candidate for the management of inflammatory dermatoses in which MC-dependent neurogenic skin inflammation plays an important role (e.g. atopic dermatitis, psoriasis).

CKD-Associated Pruritus: New Insights Into Diagnosis, Pathogenesis, and Management

Chronic kidney disease–associated pruritus (CKD-aP) is a common, troubling and in some cases debilitating problem for patients with CKD and end-stage renal disease. Despite a prevalence rate of approximately 20% in CKD and 40% in end-stage renal disease, and a clear association with poorer psychosocial and medical outcomes, this condition is often underreported by patients and overlooked by health care providers. This is likely due, in part, to uncertainty regarding its pathogenesis and treatment. Most commonly, CKD-aP is attributed to toxin build-up, peripheral neuropathy, immune system dysregulation, or opioid dysregulation. Prior treatment studies of CKD-aP have targeted these potential etiologies but have been limited by noncontrolled design, small sample size, and non-uniform definitions of CKD-aP. Recently, several large, randomized controlled trials targeting opioid dysregulation have yielded promising results. These trials have spurred new hope for understanding and treating this condition.

Effects of Stress on Itch

PURPOSE

Psychological stress and ensuing modulation of the immune and nervous systems can have a significant impact on itch. Stress can exacerbate itch and vice versa, resulting in a vicious cycle that can greatly impair a patient's quality of life. This review summarizes the association between stress and itch, elucidates the mechanism by which these two phenomena influence one another, and explores treatment modalities that aim to reduce stress-induced itch.

METHODS

A complete search of the PubMed and Google Scholar databases was completed and literature pertinent to this review was compiled.

FINDINGS

Both acute and chronic stress can significantly affect itch in healthy individuals and in those diagnosed with itchy skin diseases as well as systemic diseases, thus resulting in a vicious cycle in which stress exacerbates itch and vice versa. The mechanisms by which stress induces or aggravates itch include both central and peripheral activation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system. Activation of these systems, in turn, affects the mast cells, keratinocytes, and nerves that secrete neuropeptides, such as substance P, nerve growth factor, acetylcholine, histamine, and itchy cytokines. A dysfunctional parasympathetic response is thought to be involved in the chronic stress/itch response. Brain structures associated with emotion, such as the limbic system and periaqueductal gray, which work on the descending facilitation of itch, play a significant role in stress-induced itch.

IMPLICATIONS

As specific brain structures are associated with stress, drug treatments targeting these areas (ie, γ-aminobutyric acid-ergic drugs, serotonin and norepinephrine reuptake inhibitors) may help to modulate itch. Stress can also be combatted using nonpharmacologic treatments such as cognitive-behavioral therapies and stress-relieving holistic approaches (eg, yoga, acupuncture).

The analgesic hybrid of dermorphin/substance P and analog of enkephalin improve wound healing in streptozotocin-induced diabetic rats

The purpose of this study was to investigate the effect of the peptide analgesic hybrid compounds: AWL3106 analog of dermorphin and substance P (7-11), and biphalin enkephalin analog on wound healing in streptozotocin-induced diabetic rats. The diabetes was induced in 6-7 week-old male Wistar rats by intraperitoneal injection of streptozotocin. After 70 days, the wounds were created on the back of the rats and then, once a day for 21 days, the dressing containing lanolin ointment, 10% of keratin scaffolds, and 1 mM of AWL3106 or biphalin was applied. The wounds histology were analyzed by hematoxylin and eosin staining. The orientation and organization of collagen was analyzed by Masson's trichome staining. The number of macrophages, blood vessels, and fibroblasts were visualized by CD68, CD34, and vimentin immunoreactivity, respectively. Our results demonstrated that the wound area of AWL3106- and biphalin-treated groups was greatly reduced (up to 47% on the 7 day) in comparison with untreated diabetic groups. The immunohistochemical staining of macrophages demonstrated that AWL3106 and biphalin accelerated inflammatory progression and subsequently decreased persistent inflammation. The histological analysis showed that the structure of tissue in the groups under the study was very similar to the one of wound tissue in N-DM group. The H&E and Masson's trichome staining demonstrated that the orientation and organization of collagen as well as the number and shape of blood vessels were better in 3106- and BIF-treated group than in DM group. In conclusion, the obtained data suggested that our hybrid peptides enhanced wound healing, particularly by accelerating the inflammatory phase and promoted the wound closure.

The prevalence of ADH1B and OPRM1 alleles predisposing for alcohol consumption are increased in the Hungarian psoriasis population

Alcohol intake affects in great the symptoms and life of  psoriasis patients, although the association of SNPs related to increased alcohol consumption with psoriasis has not been elucidated. Therefore, to investigate the association of psoriasis with established alcohol consumption and dependence-related gene variants we conducted a population-based case-control study including 3743 subjects (776 psoriasis cases and 2967 controls from the general Hungarian population). Genotyping of 23 SNPs at ADH1B, ADH1C, ALDH1A1, ALDH2, SLC6A3, DDC, GABRA2, GABRG1, HTR1B, MAOA, TPH2, CHRM2, GRIN2A, POMC, OPRM1, OPRK1 and BDNF were determined and differences in genotype and allele distributions were investigated. Multiple logistic regression analyses were implemented. Analysis revealed association between C allele of the rs1229984 polymorphism (ADH1B gene) and psoriasis risk (OR_additive = 1.58, 95% CI 1.23-2.03, p < 0.001, OR_recessive = 1.58, 95% CI 1.22-2.04, p = 0.001). Furthermore, the G allele of rs1799971 polymorphism (OPRM1 gene) increased the risk of familial aggregation (OR_additive = 1.99, 95% CI 1.36-2.91, p < 0.001 OR_dominant = 2.01, 95% CI 1.35-3.01, p < 0.001). In subgroups of psoriatic patients with history of early onset and familial aggregation effect allele 'C' of rs1229984 showed association in the additive and recessive models (OR_additive = 2.41, 95% CI 1.26-4.61, p < 0.01, OR_recessive = 2.42, 95% CI 1.26-4.68, p < 0.01). While effect allele 'G' of rs1799971 (OPRM1) also associated with increased risk of early onset and familial aggregation of psoriasis in the additive and dominant models (OR_additive = 1.75, 95% CI 1.27-2.43, p = 0.001, OR_dominant = 1.82, 95% CI 1.26-2.63, p = 0.001). Our results suggest that genetically defined high-risk individuals for alcohol consumption are more common in the psoriasis population.

Aspects of Nanomaterials in Wound Healing

Wound infections impose a remarkable clinical challenge that has a considerable influence on morbidity and mortality of patients, influencing the cost of treatment. The unprecedented advancements in molecular biology have come up with new molecular and cellular targets that can be successfully applied to develop smarter therapeutics against diversified categories of wounds such as acute and chronic wounds. However, nanotechnology-based diagnostics and treatments have achieved a new horizon in the arena of wound care due to its ability to deliver a plethora of therapeutics into the target site, and to target the complexity of the normal wound-healing process, cell type specificity, and plethora of regulating molecules as well as pathophysiology of chronic wounds. The emerging concepts of nanobiomaterials such as nanoparticles, nanoemulsion, nanofibrous scaffolds, graphene-based nanocomposites, etc., and nano-sized biomaterials like peptides/proteins, DNA/RNA, oligosaccharides have a vast application in the arena of wound care. Multi-functional, unique nano-wound care formulations have acquired major attention by facilitating the wound healing process. In this review, emphasis has been given to different types of nanomaterials used in external wound healing (chronic cutaneous wound healing); the concepts of basic mechanisms of wound healing process and the promising strategies that can help in the field of wound management.

Improved Morphine-Loaded Hydrogels for Wound-Related Pain Relief

The use of morphine applied topically to painful wounds has potential advantages, such as dose reduction, fewer side effects and compound formulations, have been proposed for this purpose. Given the potential high impact of drug product quality on a patient’s health, the aim of the present study was to develop two stable sterile hydrogels containing morphine hydrochloride, intended for topical application on painful wounds. Two carboxymethylcellulose sodium-based hydrogels were prepared containing 0.125% w/w (F1-MH semi-solid formulation) and 1.0% w/w (F2-MH fluid formulation) morphine hydrochloride (MH), respectively. Studies included a risk assessment approach for definition of the quality target product profile (QTPP) and assessment of critical quality attributes (CQA) of the hydrogels to support product quality and safety. Safe, odourless, yellowish, translucent and homogeneous gels were obtained, with suitable microbiological and pharmaceutical characteristics. The active substance concentration was adapted according to the characteristics of the dose-metering device. Release profiles were investigated using Franz diffusion cells, and characterised by different kinetic models. Increasing gel viscosity prolonged drug release, with rates of 17.9 ± 2.2 μg·cm⁻²·h⁻¹ (F1-MH) and 258.0 ± 30.4 μg·cm⁻²·h⁻¹ (F2-MH), allowing for the reduction of the number of applications and improving patient compliance. The gels proved to be stable for up to 60 days at room temperature. The semi-solid and fluid MH-containing hydrogel formulations are safe, stable and suitable for use in hospital settings, which is rather important for wound-related pain management in cancer palliative care or burn patients.

Evidence for the involvement of opioid and cannabinoid systems in the peripheral antinociception mediated by resveratrol

Despite all the development of modern medicine, around 100 compounds derived from natural products were undergoing clinical trials only at the end of 2013. Among these natural substances in clinical trials, we found the resveratrol (RES), a pharmacological multi-target drug. RES analgesic properties have been demonstrated, although the bases of these mechanisms have not been fully elucidated. The aim of this study was to evaluate the involvement of opioid and cannabinoid systems in RES-induced peripheral antinociception. Paw withdrawal method was used and hyperalgesia was induced by carrageenan (200 μg/paw). All drugs were given by intraplantar injection in male Swiss mice (n = 5). RES (100 μg/paw) administered in the right hind paw induced local antinociception that was antagonized by naloxone, non-selective opioid receptor antagonist, and clocinnamox, μOR selective antagonist. Naltrindole and nor-binaltorfimine, selective antagonists for δOR and kOR, respectively, did not reverse RES-induced peripheral antinociception. CB₁R antagonist AM251, but not CB₂R antagonist AM630, antagonized RES-induced peripheral antinociception. Peripheral antinociception of RES intermediate-dose (50 μg/paw) was increased by: (i) bestatin, inhibitor of endogenous opioid degradation involved-enzymes; (ii) MAFP, inhibitor of anandamide amidase; (iii) JZL184, inhibitor of 2-arachidonoylglycerol degradation involved-enzyme; (iv) VDM11, endocannabinoid reuptake inhibitor. Acute and peripheral administration of RES failed to affect the amount of μOR, CB₁R and CB₂R. Experimental data suggest that RES induces peripheral antinociception through μOR and CB₁R activation by endogenous opioid and endocannabinoid releasing.

Preoperative Chronic Opioid Therapy: A Risk Factor for Complications, Readmission, Continued Opioid Use and Increased Costs After One- and Two-Level Posterior Lumbar Fusion

STUDY DESIGN

Retrospective, economic analysis.

OBJECTIVE

To study patient profile associated with preoperative chronic opioid therapy (COT), and study COT as a risk factor for 90-day complications, emergency department (ED) visits, and readmission after primary one- to two-level posterior lumbar fusion (PLF) for degenerative spine disease. We also evaluated associated costs, risk factors, and adverse events related to long-term postoperative opioid use.

SUMMARY OF BACKGROUND DATA

Chronic opioid use is associated with poor outcomes and dependence after spine surgery. Risk factors, complications, readmissions, adverse events, and costs associated with COT in patients undergoing lumbar fusion are not entirely known. As providers look to reduce healthcare costs and improve outcomes, identification of modifiable risk factors is important.

METHODS

Commercial insurance data from 2007 to Q3-2015 was used to study preoperative opioid use in patients undergoing primary one- to two-level PLF. Ninety-day complications, ED visits, readmissions, 1-year adverse events, and associated costs have been described. Multiple-variable regression analyses were done to study preoperative COT patient profile and opioid use as a risk factor for complications and adverse events.

RESULTS

A total of 24,610 patients with a mean age of 65.6 ± 11.5 years were included. Five thousand five hundred (22.3%) patients had documented opioid use for more than 6 months before surgery, and 87.4% of these had continued long-term use postoperatively. On adjusted analysis, preoperative COT was found to be a risk factor for 90-day wound complications, pain diagnoses, ED visits, readmission, and continued use postoperatively. Postspinal fusion long-term opioid users had an increased utilization of epidural/facet joint injections, risk for revision fusion, and increased incidence of new onset constipation within 1 year postsurgery. The cost associated with increase resource use in these patients has been reported.

CONCLUSION

Preoperative COT is a modifiable risk factor for complications, readmission, adverse events, and increased costs after one- or two-level PLF.

LEVEL OF EVIDENCE

3.

Topical drug therapeutics for neuropathic pain

INTRODUCTION

Neuropathic pain (NP) is a particularly severe and intractable chronic condition that is not well treated by commonly recommended systemic pharmacological therapies, partly due to dose-limiting side effects or adverse events. The use of topical therapeutics for NP is growing and benefits from the reduced potential for adverse effects, as well as the ability to directly target peripheral pathological processes.

AREAS COVERED

The current review defines and describes the limitations of various commonly prescribed systemic pharmacological therapies for NP. It also provides a justification for increased research aimed at developing topical therapeutics for NP, particularly localized and peripheral NP. The review discusses the various classes of topical treatments used for NP, including agents that: block sensory inputs; activate inhibitory systems; provide mechanism-based therapeutics; are used in mucosal tissues; and include combinations that produce multimodal therapeutic effects.

EXPERT OPINION

There are arguments that the current topical therapeutics for NP rely too heavily on the use of local anesthetics and capsaicinoids, and more research is certainly needed on topical therapies that are multimodal and/or are targeted at the peripheral sources of pathology. The potential for novel topical therapeutics may be enhanced by further research on topical co-drugs, drug-drug salts, co-crystals and hydrates, and ionic liquids.

The Roles of Opioid Receptors in Cutaneous Wound Healing

The process of recovery from skin wounding can be protracted and painful, and scarring may lead to weakness of the tissue, unpleasant sensations such as pain or itch, and unfavorable cosmetic outcomes. Moreover, some wounds simply fail to heal and become a chronic burden for the sufferer. Understanding the mechanisms underlying wound healing and the concomitant sensory disorders and how they might be manipulated for therapeutic benefit has attracted much interest in recent years, and here we discuss the latest developments in the field, focusing on the emergent roles of the peripheral opioid receptor (OPr) system.

Investigating endogenous µ-opioid receptors in human keratinocytes as pharmacological targets using novel fluorescent ligand

Opioids in skin function during stress response, regeneration, ageing and, particularly in regulating sensation. In chronic pruritus, topical treatment with Naltrexone changes μ-opioid receptor (μ-OR) localization to relieve itch. The molecular mechanisms behind the effects of Naltrexone on μ-OR function in reduction of itching behavior has not been studied. There is an immediate need to understand the endogenous complexity of μ-OR dynamics in normal and pathological skin conditions. Here we evaluate real-time behavior of μ-OR-Endomorphine complexes in the presence of agonist and antagonists. The μ-OR ligand Endomorphine-1 (EM) was conjugated to the fluorescent dye Tetramethylrhodamine (TAMRA) to investigate the effects of agonist and antagonists in N/TERT-1 keratinocytes. The cellular localization of the EM-TAMRA was followed through time resolved confocal microscopy and population analysis was performed by flow cytometry. The in vitro analyses demonstrate fast internalization and trafficking of the endogenous EM-TAMRA-μ-OR interactions in a qualitative manner. Competition with Endomorphine-1, Naltrexone and CTOP show both canonical and non-canonical effects in basal and differentiated keratinocytes. Acute and chronic treatment with Naltrexone and Endomorphine-1 increases EM-TAMRA binding to skin cells. Although Naltrexone is clinically effective in relieving itch, the mechanisms behind re-distribution of μ-ORs during clinical treatments are not known. Our study has given insight into cellular mechanisms of μ-OR ligand-receptor interactions after opioid agonist and antagonist treatments in vitro. These findings potentially offer opportunities in using novel treatment strategies for skin and peripheral sensory disorders.

Peripheral Antinociception Induced by Aripiprazole Is Mediated by the Opioid System

Background

Aripiprazole is an antipsychotic drug used to treat schizophrenia and related disorders. Our previous study showed that this compound also induces antinociceptive effects. The present study aimed to assess the participation of the opioid system in this effect.

Methods

Male Swiss mice were submitted to paw pressure test and hyperalgesia was induced by intraplantar injection of prostaglandin E₂ (PGE₂, 2 μg). Aripiprazole was injected 10 min before the measurement. Naloxone, clocinnamox, naltrindole, nor-binaltorphimine, and bestatin were given 30 min before aripiprazole. Nociceptive thresholds were measured in the 3rd hour after PGE₂ injection.

Results

Aripiprazole (100 μg/paw) injected locally into the right hind paw induced an antinociceptive effect that was blocked by naloxone (50 μg/paw), a nonselective opioid receptor antagonist. The role of μ-, δ-, and κ-opioid receptors was investigated using the selective antagonists, clocinnamox (40 μg/paw), naltrindole (15, 30, and 60 μg/paw), and nor-binaltorphimine (200 μg/paw), respectively. The data indicated that only the δ-opioid receptor antagonist inhibited the peripheral antinociception induced by aripiprazole. Bestatin (400 μg), an aminopeptidase-N inhibitor, significantly enhanced low-dose (25 μg/paw) aripiprazole-induced peripheral antinociception.

Conclusion

The results suggest the participation of the opioid system via δ-opioid receptor in the peripheral antinociceptive effect induced by aripiprazole.

Opioids and opioid receptors orchestrate wound repair

We have previously shown that topical opioids including morphine and its congeners promote healing of full thickness ischemic wounds in rats. We examined the contribution of mu opioid receptor (MOPr)-mediated healing of full thickness ischemic wounds using MOPr and delta or kappa opioid receptor knockout (KO) mice. Wound closure in the early (day 5) as well as later phases was delayed in topical morphine or PBS-treated MOPr-KO mice compared with reciprocal treatments of wounds in wild-type (WT) mice. MOPr expression was significantly upregulated at 30 min in the wound margins and colocalized with wound margins and vasculature in the epidermal and dermal layers of the skin. We next examined whether neuropeptide expression was involved in the mechanism of MOPr-mediated wound closure. Substance P (SP) and calcitonin gene-related peptide immunoreactivity (ir) was significantly increased in the skin of MOPr-KO mice as compared with WT mice. Neuropeptide-ir was increased significantly in PBS-treated wounds of MOPr and WT mice, but morphine treatment reduced neuropeptide immunoreactivity in both as compared with PBS. Wounding of keratinocytes led to the release of opioid peptide beta-endorphin (β-END) in conditioned medium, which stimulated the proliferation of endothelial cells. MOPr-selective (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2, CTOP) and nonselective OPr antagonist naloxone-inhibited endothelial proliferation induced by wounded keratinocyte-conditioned medium. In addition, accelerated wound area closure in vitro by morphine was suppressed by methylnaltrexone, a nonselective OPr antagonist with high affinity for MOPr. Morphine and its congeners stimulated the proliferation of endothelial cells from WT mice but not those from MOPr-KO mice. Furthermore, morphine-induced mitogen-activated protein kinase/extracellular signal-regulated kinase phosphorylation in endothelial cells was significantly decreased in MOPr-KO mice as compared with WT mice. Collectively, these data suggest that MOPr plays a critical role in the proliferation phase with the formation of granulation tissue during wound healing.

Molecular Pharmacology of δ-Opioid Receptors

Opioids are among the most effective analgesics available and are the first choice in the treatment of acute severe pain. However, partial efficacy, a tendency to produce tolerance, and a host of ill-tolerated side effects make clinically available opioids less effective in the management of chronic pain syndromes. Given that most therapeutic opioids produce their actions via µ-opioid receptors (MOPrs), other targets are constantly being explored, among which δ-opioid receptors (DOPrs) are being increasingly considered as promising alternatives. This review addresses DOPrs from the perspective of cellular and molecular determinants of their pharmacological diversity. Thus, DOPr ligands are examined in terms of structural and functional variety, DOPrs' capacity to engage a multiplicity of canonical and noncanonical G protein-dependent responses is surveyed, and evidence supporting ligand-specific signaling and regulation is analyzed. Pharmacological DOPr subtypes are examined in light of the ability of DOPr to organize into multimeric arrays and to adopt multiple active conformations as well as differences in ligand kinetics. Current knowledge on DOPr targeting to the membrane is examined as a means of understanding how these receptors are especially active in chronic pain management. Insight into cellular and molecular mechanisms of pharmacological diversity should guide the rational design of more effective, longer-lasting, and better-tolerated opioid analgesics for chronic pain management.

Giant Basal Cell Carcinomas Express Neuroactive Mediators and Show a High Growth Rate: A Case-Control Study and Meta-Analysis of Etiopathogenic and Prognostic Factors

BACKGROUND

Giant basal cell carcinomas (GBCCs), (BCC ≥ 5 cm), are often painless, destructive tumors resulting from poorly understood patient neglect.

OBJECTIVES

To elucidate etiopathogenic factors distinguishing GBCC from basal cell carcinoma (BCC) and identify predictors for disease-specific death (DSD).

METHODS

Case-control study examining clinicopathologic and neuroactive factors (β-endorphin, met-enkephalin, serotonin, adrenocorticotropic hormone, and neurofilament expression) in GBCC and BCC. Systematic literature review to determine DSD predictors.

RESULTS

Thirteen GBCCs (11 patients) were compared with 26 BCCs (25 patients). GBCC significantly differed in size, disease duration, and outcomes; patients were significantly more likely to live alone, lack concern, and have alcoholism. GBCC significantly exhibited infiltrative/morpheic phenotypes, perineural invasion, ulceration, and faster growth. All neuromediators were similarly expressed. Adenoid phenotype was significantly more common in GBCC. Adenoid tumors expressed significantly more β-endorphin (60% vs. 18%, P = 0.01) and serotonin (30% vs. 4%, P = 0.02). In meta-analysis (n ≤ 311: median age 68 years, disease duration 90 months, tumor diameter 8 cm, 18.4% disease-specific mortality), independent DSD predictors included tumor diameter (cm) (hazard ratio (HR): 1.12, P = 0.003), bone invasion (HR: 4.19, P = 0.015), brain invasion (HR: 8.23, P = 0.001), and distant metastases (HR: 14.48, P = 0.000).

CONCLUSIONS

GBCC etiopathogenesis is multifactorial (ie, tumor biology, psychosocial factors). BCC production of paracrine neuromediators deserves further study.

Relationship between opioid treatment and rate of healing in chronic wounds

Opioids are routinely used analgesics in patients with chronic wounds; however the impact of opioid exposure on wound healing is poorly understood. The purpose of this study was to investigate the association between opioid exposure and wound outcome in the Wound Etiology and Healing study. This longitudinal observational study was conducted on 450 subjects enrolled in the Wound Etiology and Healing biorepository. Data were collected prospectively including baseline characteristics, pain score, longitudinal opioid exposure, and total wound surface area (tWSA). Data were analyzed using static multivariate models, fixed-effects mixed models, and time to event analysis. Using fixed-effects models, opioid dose was significantly associated with tWSA after accounting for the effects of pain score and baseline co-variates (p < 0.0001). For each 1-unit increase in ln(opioid dose + 1) the ln(tWSA + 1) increased by 0.16 units (95% confidence interval 0.13-0.19, p < 0.0001). Visits where opioids were present had ln(tWSA + 1) 0.48 units larger (95% confidence interval 0.38-0.58, p < 0.0001) than visits with no opioid exposure. Using time-to-event analysis, patients who never received opioids healed faster than those who received opioids (log-rank chi-square 11.00, p  = 0.0009). Using Cox regression analysis, patients with mean opioid dose ≥10 mg were significantly less likely to heal than those with no opioid (HR 0.67 [0.49-0.91], p = 0.011) after adjusting for wound size. Patients with opioid dose >0 to <10 mg had a similar hazard of not healing as those with no opioid exposure (HR 0.88 [0.65-1.19], p = 0.40). In conclusion, opioid analgesics are commonly prescribed to patients with chronic wounds; however, the data presented suggest that opioid exposure is associated with reduced likelihood of healing in patients with chronic wounds. Whether this is a causal relationship will require further study.

β-Endorphin enhances the phospholipase activity of the dandruff causing fungi Malassezia globosa and Malassezia restricta

β-Endorphin is known to stimulate phospholipase production by Malassezia pachydermatis during canine dermatoses. The role of β-endorphin in Malassezia infection in humans is not well studied. The present study compares the influence of β-endorphin on Malassezia globosa and Malassezia restricta isolated from patients with seborrhoeic dermatitis/dandruff (SD/D) and healthy controls. Malassezia isolates (five each of the two species from patients and healthy controls) were grown on modified Dixon's agar with or without 100 nmol/L β-endorphin. Phospholipase activity was quantified based on its ability to hydrolyze L-α-phosphatidylcholine dimyristoyl (phospholipid substrate). Free fatty acid was measured by a colorimetry method. In isolates from patients, the phospholipase activity significantly increased after exposure to β-endorphin (M. globosa, P = .04; M. restricta, P = .001), which did not occur in isolates from healthy controls. Moreover, after β-endorphin exposure the patient isolates had significantly higher (P = .0004) phospholipase activity compared to the healthy control isolates. The results suggest that isolates of M. globosa and M. restricta from patients may differ from those of healthy humans.

[Pruritus in psoriasis : Profile and therapy]

Psoriasis is a common chronic inflammatory disease with an incidence of about 0.5-3 %. Previously psoriasis was not primarily regarded to be associated with pruritus; however, this perception has changed in recent years. Meanwhile data conclusively show that between 64 and 97 % of patients report about pruritus that can be severe in a number of cases. Apart from suffering from psoriasis, the presence of pruritus causes additional stress and leads to a significant impairment of health-related quality of life. Neurogenic inflammation at least in part contributes to the development of pruritus in psoriasis skin lesions. A number of neuropeptides including substance P and calcitonin gene related peptide can act as pro-inflammatory mediators. There is evidence for a dysbalance between κ‑ and µ‑opioid receptors in lesional skin favoring inflammation and pruritus. After clearing of psoriasis lesions, pruritus is relieved as well. Therefore, specific treatment of pruritus is not necessary in general. In cases where severe pruritus is a prominent symptom, targeted therapy with mirtazapin or doxepin or neuroleptic compounds such as pregabalin or gabapentin or drugs affecting the κ‑ und µ‑opioid receptor balance can be administered. Today the importance of pruritus as a prominent symptom of psoriasis lesions has been widely accepted. In recent and running clinical trials with new drugs, pruritus at baseline and the effect of these drugs on pruritus is always assessed. This awareness also fuels basic research about pruritus in psoriasis.