The OGF-OGFr axis utilizes the p16INK4a and p21WAF1/CIP1 pathways to restrict normal cell proliferation

Cancer-associated snaR-A noncoding RNA interacts with core splicing machinery and disrupts processing of mRNA subpopulations

RNA polymerase III (Pol III) activity in cancer is linked to the production of small noncoding (nc)RNAs that are otherwise silent in most tissues. snaR-A (small NF90-associated RNA isoform A) - a hominid-specific ncRNA shown to enhance cell proliferation, migration, and invasion - is a cancer-emergent Pol III product that remains largely uncharacterized despite promoting growth phenotypes. Here, we applied a combination of genomic and biochemical approaches to study the biogenesis and subsequent protein interactions of snaR-A and to better understand its role as a putative driver of cancer progression. By profiling the chromatin landscapes across a multitude of primary tumor types, we show that predicted snaR-A upregulation is broadly linked with unfavorable outcomes among cancer patients. At the molecular level, we unexpectedly discover widespread interactions between snaR-A and mRNA splicing factors, including SF3B2 - a core component of the U2 small nuclear ribonucleoprotein (snRNP). We find that SF3B2 levels are sensitive to high snaR-A abundance and that depletion of snaR-A alone is sufficient to decrease intron retention levels across subpopulations of mRNA enriched for U2 snRNP occupancy. snaR-A sensitive genes are characterized by high GC content, close spatial proximity to nuclear bodies concentrated in pre-mRNA splicing factors, and functional enrichment for proteins involved in deacetylation and autophagy. We highlight examples of splicing misregulation and increased protein levels following snaR-A depletion for a wide-ranging set of factors, suggesting snaR-A-driven splicing defects may have far-reaching effects that re-shape the cellular proteome. These findings clarify the molecular activities and consequences of snaR-A in cancer, and altogether establish a novel mechanism through which Pol III overactivity may promote tumorigenesis.

Loss-of-function OGFRL1 variants identified in autosomal recessive cherubism families

Cherubism (OMIM 118400) is a rare craniofacial disorder in children characterized by destructive jawbone expansion due to the growth of inflammatory fibrous lesions. Our previous studies have shown that gain-of-function mutations in SH3 domain-binding protein 2 (SH3BP2) are responsible for cherubism and that a knock-in mouse model for cherubism recapitulates the features of cherubism, such as increased osteoclast formation and jawbone destruction. To date, SH3BP2 is the only gene identified to be responsible for cherubism. Since not all patients clinically diagnosed with cherubism had mutations in SH3BP2, we hypothesized that there may be novel cherubism genes and that these genes may play a role in jawbone homeostasis. Here, using whole exome sequencing, we identified homozygous loss-of-function variants in the opioid growth factor receptor like 1 (OGFRL1) gene in 2 independent autosomal recessive cherubism families from Syria and India. The newly identified pathogenic homozygous variants were not reported in any variant databases, suggesting that OGFRL1 is a novel gene responsible for cherubism. Single cell analysis of mouse jawbone tissue revealed that Ogfrl1 is highly expressed in myeloid lineage cells. We generated OGFRL1 knockout mice and mice carrying the Syrian frameshift mutation to understand the in vivo role of OGFRL1. However, neither mouse model recapitulated human cherubism or the phenotypes exhibited by SH3BP2 cherubism mice under physiological and periodontitis conditions. Unlike bone marrow-derived M-CSF-dependent macrophages (BMMs) carrying the SH3BP2 cherubism mutation, BMMs lacking OGFRL1 or carrying the Syrian mutation showed no difference in TNF-ɑ mRNA induction by LPS or TNF-ɑ compared to WT BMMs. Osteoclast formation induced by RANKL was also comparable. These results suggest that the loss-of-function effects of OGFRL1 in humans differ from those in mice and highlight the fact that mice are not always an ideal model for studying rare craniofacial bone disorders.

Elucidating the mechanism of corneal epithelial cell repair: unraveling the impact of growth factors

The repair mechanism for corneal epithelial cell injuries encompasses migration, proliferation, and differentiation of corneal epithelial cells, and extracellular matrix remodeling of the stromal structural integrity. Furthermore, it involves the consequential impact of corneal limbal stem cells (LSCs). In recent years, as our comprehension of the mediating mechanisms underlying corneal epithelial injury repair has advanced, it has become increasingly apparent that growth factors play a pivotal role in this intricate process. These growth factors actively contribute to the restoration of corneal epithelial injuries by orchestrating responses and facilitating specific interactions at targeted sites. This article systematically summarizes the role of growth factors in corneal epithelial cell injury repair by searching relevant literature in recent years, and explores the limitations of current literature search, providing a certain scientific basis for subsequent basic research and clinical applications.

Design, Synthesis, and Antitumor Evaluation of an Opioid Growth Factor Bioconjugate Targeting Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) presents a formidable challenge with high lethality and limited effective drug treatments. Its heightened metastatic potential further complicates the prognosis. Owing to the significant toxicity of current chemotherapeutics, compounds like [Met5]-enkephalin, known as opioid growth factor (OGF), have emerged in oncology clinical trials. OGF, an endogenous peptide interacting with the OGF receptor (OGFr), plays a crucial role in inhibiting cell proliferation across various cancer types. This in vitro study explores the potential anticancer efficacy of a newly synthesized OGF bioconjugate in synergy with the classic chemotherapeutic agent, gemcitabine (OGF-Gem). The study delves into assessing the impact of the OGF-Gem conjugate on cell proliferation inhibition, cell cycle regulation, the induction of cellular senescence, and apoptosis. Furthermore, the antimetastatic potential of the OGF-Gem conjugate was demonstrated through evaluations using blood platelets and AsPC-1 cells with a light aggregometer. In summary, this article demonstrates the cytotoxic impact of the innovative OGF-Gem conjugate on pancreatic cancer cells in both 2D and 3D models. We highlight the potential of both the OGF-Gem conjugate and OGF alone in effectively inhibiting the ex vivo pancreatic tumor cell-induced platelet aggregation (TCIPA) process, a phenomenon not observed with Gem alone. Furthermore, the confirmed hemocompatibility of OGF-Gem with platelets reinforces its promising potential. We anticipate that this conjugation strategy will open avenues for the development of potent anticancer agents.

The Opioid Growth Factor in Growth Regulation and Immune Responses in Cancer

It has become apparent that endogenous opioids act not only as neurotransmitters and neuromodulators, but have multiple functions in the body. Activation of the opioid system by opiate drugs is associated with a risk of cancer development through direct stimulation of tumor cell proliferation and through immunosuppression. In contrast, the endogenous peptide opioid [Met5]-enkephalin, now commonly referred to as Opioid Growth Factor (OGF), negatively regulates cell proliferation in a wide number of cells during development, homeostasis, and neoplasia. This action is mediated through the opioid growth factor receptor, originally designated the zeta (ζ) opioid receptor. Further, contrary to the traditional notion of opiates as immunosuppressive, endogenous OGF has been shown to possess a number of positive immunomodulatory properties and may provide a beneficial effect in cancer by augmenting the activity of cells involved in both innate and acquired immunity. Taken together, the evidence supports consideration of opioid peptides such as OGF as new strategies for cancer therapy.

Opioid growth factor receptor: Anatomical distribution and receptor colocalization in neurons of the adult mouse brain

The opioid growth factor (OGF) is an endogenous peptide that binds to the nuclear-associated receptor (OGFr), and plays a significant role in the proliferation of developing, renewing, and healing tissues. The receptor is widely expressed in a variety of organs, however its distribution in the brain remains unknown. In this study, we investigated the distribution of OGFr in different brain regions of male heterozygous (-/+ Lepr ^db/J), non -diabetic mice and determined the localization of the receptor in three major brain cell types, astrocytes, microglia, and neurons. Immunofluorescence imaging revealed that the highest number of OGFr was in hippocampal CA3 subregion followed by primary motor cortex, hippocampal CA2, thalamus, caudate and hypothalamus in a descending order. Double immunostaining revealed receptor colocalization with neurons and little or no colocalization in microglia and astrocytes. The highest percentage of OGFr positive neurons was identified in the CA3. Hippocampal CA3 neurons play an important role in memory processing, learning and behavior, and motor cortex neurons are important for muscle movement. However, the significance of the OGFr receptor in these brain regions and its relevance in diseased conditions are not known. Our findings provide a basis for understanding the cellular target and interaction of the OGF- OGFr pathway in neurodegenerative diseases such as Alzheimer's, Parkinson's, and stroke where hippocampus and cortex have an important role. This foundational data may also be useful in drug discovery to modulate OGFr by opioid receptor antagonist in various CNS diseases.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

Methionine enkephalin inhibited cervical carcinoma via apoptosis promotion and reduction of myeloid derived suppressor cell infiltrated in tumor

Immunotherapy for cervical carcinoma is becoming increasingly important recently. In these studies methionine enkephalin (menk) is shown to inhibit cervical tumor cell proliferation in vitro in association with an increase in the expression of apoptosis markers and mediators, including an increase in fas, caspase 8, and caspase 3 expression and intrinsic expression of the signaling pathway mediator bax. In vivo, tumor growth was restrained in mice xenotransplant model with typical pathological features of apoptosis. Furthermore, myeloid derived suppressor cells (MDSCs) had a significant decrease in circulation and in tumor site. In brief, these findings showed menk could inhibit tumor growth in vitro and in vivo, providing direction of further research and clinical application prospect.

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.

Opioids and Ocular Surface Pathology; A Literature Review of New Treatments Horizons

This review discusses the role of opioids in the corneal surface and the different pathways and therapeutic methods of management. A literature review was performed using PubMed database. For the database search, the main searching words “opioid” and “topical opioid treatment” were used with the descriptors “cornea”, “ocular surface”, “neuropathic corneal pain”, “corneal sensitivity” and “naltrexone”; original scientific articles and reviews were included to achieve the purpose of the review. The endogenous opioid system has relevant functions in the organism, and in daily use, opioids are used as painkillers. However, these drugs may be employed for other indications as opioid pathways have a wide spectrum. The corneal surface for topical treatment is easily accessible, hence sparing the side effects of systemic opioids. Instillation of opioid antagonist substances, such as naltrexone, increases corneal healing rates and stimulates the division of corneal epithelium cells without deleterious effects. The natural modulation of endogenous opioids controls different forms of pain, including inflammatory and neuropathic pain, both in the ocular surface and in the central nervous system. There are diverse methods in controlling pain using opioids, especially in refractory forms. This review attempts to collect the literature about corneal surface and opioid pathways to provide an overview image and a possible direction of the news treatments.

Ocular surface complications in diabetes: The interrelationship between insulin and enkephalin

Diabetes is a multi-faceted disorder with increasing prevalence and rising healthcare costs. The burden of diabetes is increased because of associated complications affecting nearly all organs including the eye. The underlying pathophysiology for the onset of these ocular surface disorders is not well known. Enkephalins are endogenous opioids that originate in the brain and have numerous actions in the human body. Opioid growth factor (OGF), chemically termed [Met5]-enkephalin, binds to a novel, nuclear-associated receptor and mediates cellular homeostasis. Serum OGF levels are elevated in diabetic individuals and rodent models of diabetes. Sustained blockade of the OGF receptor (OGFr) with opioid receptor antagonists, such as naltrexone (NTX), reverses many complications of diabetes in the animal model, including delayed cutaneous wound healing, dry eye, altered corneal surface sensitivity, and keratopathy. The increased enkephalin levels observed in diabetes suggest a relationship between endogenous opioid peptides and the pathophysiology of diabetes. It is common for diabetic patients to undergo insulin therapy to restore normal blood glucose levels. However, this restoration does not alter OGF serum levels nor ameliorate ocular surface complications in the animal model of diabetes. Moreover, sex differences in the prevalence of diabetes, response to insulin therapy, and abnormalities in the OGF-OGFr axis have been reported. This review highlights current knowledge on the dysregulation of the OGF-OGFr pathway and possible relationships of insulin and enkephalins to the development of ocular surface defects in diabetes. It proposes that this dysregulation is a fundamental mechanism for the pathobiology of diabetic complications.

Research progress of opioid growth factor in immune-related diseases and cancer diseases

Methionine enkephalin (MENK) has an important role in both neuroendocrine and immune systems. MENK was known as an opioid growth factor (OGF) for its growth regulatory characteristics. OGF interacts with the OGF receptor (OGFr) to inhibit DNA synthesis by upregulating p16 and/or p21, which delays the cell cycle transition from G0/G1 to S phase, and inhibits cell proliferation. In addition, OGF combines with OGFr in immune cells to exert its immunomodulatory activity and regulate immune function. OGF has been studied as an immunomodulator in a variety of autoimmune diseases, including multiple sclerosis, inflammatory bowel disease, diabetes and viral infections, and has been proven to relieve symptoms of certain diseases in animal and in vitro experiments. Also, OGF and OGFr have various anti-tumor molecular mechanisms. OGF can be used as the primary therapy alone or combined with other drugs to treat tumors. This article summarizes the research progress of OGF in immune-related diseases and cancer diseases.

Opioid Growth Factor and its Derivatives as Potential Non-toxic Multifunctional Anticancer and Analgesic Compounds

Despite significant research progress on the pathogenesis, molecular biology, diagnosis, treatment, and prevention of cancer, its morbidity and mortality are still high around the world. The emerging resistance of cancer cells to anticancer drugs remains still a significant problem in oncology today. Furthermore, an important challenge is the inability of anticancer drugs to selectively target tumor cells thus sparing healthy cells. One of the new potential options for efficient and safe therapy can be provided by opioid growth factor (OGF), chemically termed Met-enkephalin. It is an endogenous pentapeptide (Tyr-Gly-Gly-Phe-Met) with antitumor, analgesic, and immune-boosting properties. Clinical trials have demonstrated that OGF therapy alone, as well as in combination with standard chemotherapies, is a safe, non-toxic anticancer agent that reduces tumor size. In this paper, we review the structure-activity relationship of OGF and its analogues. We highlight also OGF derivatives with analgesic, immunomodulatory activity and the ability to penetrate the blood-brain barrier and may be used as safe agents enhancing chemotherapy efficacy and improving quality of life in cancer patients. The reviewed papers indicate that Met-enkephalin and its analogues are interesting candidates for the development of novel, non-toxic, and endowed with an analgesic activity anticancer drugs. More preclinical and clinical studies are needed to explore these opportunities.

Low-dose naltrexone plays antineoplastic role in cervical cancer progression through suppressing PI3K/AKT/mTOR pathway

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LDN inhibited proliferation in cervical cancer.

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LDN inhibited migration and invasion in cervical cancer cells.

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LDN mediated the propagation property in cervical cancer through PI3K/AKT/mTOR signaling pathway.

The incidence of cervical cancer is increasing annually worldwide. Low-dose naltrexone (LDN) has been reported to delay tumor progression, but the mechanism remains unclear. Here, we found that low-dose naltrexone could upregulate the expression of OGFr. Additionally, LDN could suppress the abilities of colony formation, migration and invasion in cervical cancer cells. LDN could also inhibit cervical cancer progression in mice model. Moreover, LDN indirectly reduced the expressions of PI3K, pAKT and mTOR in vitro and in vivo. Therefore, LDN may be considered a potential treatment option for cervical cancer.

Naltrexone as a Novel Therapeutic for Diabetic Corneal Complications

Diabetes is a widespread autoimmune disorder that affects nearly 10% of the adult population in the United States. In addition to the primary disease, there are numerous complications associated with inflammation including abnormalities of the heart, visual system, and peripheral nervous system. More than half of the individuals with diabetes will have one or more ocular related complications such as dry eye disease (DED), keratopathy, or retinopathy. Research over the last 3 decades has focused on the role of the opioid growth factor - opioid growth factor receptor (OGF-OGFr) axis as a regulatory system that maintains homeostasis in corneal epithelialization and tear secretion. In diabetes, OGF appears to be dysregulated resulting in decreased cell replication and increased corneal surface sensitivity. Utilization of naltrexone as a topical therapeutic to block the OGF-OGFr axis results in reversal of dry eye and restoration of corneal sensitivity and rates of corneal re-epithelialization. Naltrexone treatment at dosages that are substantially lower than systemically approved doses appear to be safe and effective therapy for corneal surface abnormalities associated with diabetes.

Naltrexone (NTX) relieves inflammation in the collagen-induced- arthritis (CIA) rat models through regulating TLR4/NFκB signaling pathway

OBJECTIVE

Our aim was to study the efficacy and mechanism by which NTX alleviate arthritis in CIA rat models in vivo.

METHODS

Female Wistar rats were randomly divided into 6 groups, their weights were observed and the severity of arthritis and pathological changes were evaluated by HE staining. T lymphocyte subsets were detected by flow cytometry. The expression of cytokines was detected in peripheral serum by ELISA. Real time PCR, immunohistochemical staining and western blot analysis were utilized to detect the mRNA and protein expression of opioid receptors, TLR4, RANKL and /NF-κB in synovial tissue and the spleen.

RESULTS

The weight of the rats in the 10 mg/kg NTX group decreased the least, and had the least severe arthritis. CD4⁺ T cells, Th1 cells and Treg cells increased, and CD8⁺T cells, Th1 cells and Th17 cells decreased in the splenic lymphocytes. The expression of proinflammatory cytokines decreased, and the expression of anti-inflammatory cytokines increased. MOR and DOR were strongly expressed in the spleen, whereas KOR and DOR were strongly expressed in synovial tissue. The expression of TLR4, NF-κB and RANKL was reduced in the spleen and synovium in the NTX group.

CONCLUSIONS

NTX relieved the severity of arthritis in the CIA rat models at a concentration of 10 mg/kg by regulating T lymphocyte subsets and the expression of cytokines. NTX affected opioid receptors to inhibit the TLR4/NF-κB signaling pathway, regulating the systemic immune response and decreasing osteoclast differentiation, thereby alleviating inflammation and the erosion of articular cartilage along with bone tissue.

Blockade of the OGF-OGFr pathway in diabetic bone

Purpose: This research investigated the presence and integrity of the opioid growth factor (OGF)-opioid growth factor receptor (OGFr) regulatory pathway in type 1 diabetic (T1D) rats, and investigated whether modulation of this axis by naltrexone (NTX) altered the composition of normal bone or fractured femurs. Materials and Methods: Diabetes was induced by streptozotocin; controls rats received buffer. Hyperglycemic animals were subjected to femur osteotomy, with randomized cohorts receiving either topical NTX or sterile saline in calcium carbonate. In experiment 2, hyperglycemic rats were injected daily for 3 weeks with either 30 mg/kg NTX or sterile saline. Expression levels of OGF and OGFr were measured by immunohistochemistry, bone composition was assessed by histomorphometry, and bone integrity was evaluated by µCT and 3-point bending. Results: Relative to normoglycemic bones, OGF and OGFr expression levels were increased 95% and 84%, respectively, in T1D bone; serum levels of OGF in T1D rats were elevated 23%. Hyperglycemia decreased the strength (26%), osteocalcin expression (17%), and number of proliferative (Ki67+) cells (32%) in intact femur. Topical NTX treatment of fractured femurs reduced the percentage of granulation tissue and increased cartilage. Systemic NTX treatment of diabetic rats increased strength by 21% and energy absorbed by105% in bone relative to measurements in saline-treated diabetic rats. Conclusions: The OGF-OGFr pathway appears to be dysregulated in the bone of T1D rats. Topical NTX treatment of T1D fractured bone accelerated some aspects of delayed diabetic fracture repair, and systemic NTX protected against some elements of compromised bone composition.

Prospective oncotarget for gynecological cancer: Opioid growth factor (OGF) - opioid growth factor receptor (OGFr) axis

The standard treatments for neoplasia include surgery, chemotherapy, hormone antagonists and radiotherapy, which can prolong survival, but rarely cure the tumors of gynecological cancer patients. OGF - OGFr expression, in various gynecologic cells and tissues, is an intersection point between cell development, neuroendocrine function and immune modulation. It has been identified that OGF and OGFr expression differs between gynecological tumor and normal cells. Further, exogenous or endogenous OGF and OGFr antagonists have been known to have a role in regulating cell viability and apoptosis. Moreover, the expression of proteins in the OGF - OGFr axis modulate differentiation and membrane expression of immune cells, which can enhance the immune response. In vivo and in vitro assays have shown that OGF and OGFr antagonists inhibit mitosis as well as induce apoptosis in gynecologic cancer cells. Although immune augmentation combination therapies can intensify cytotoxic activity, OGF or OGFr antagonists do not increase toxicities associated with dual-immune regulation. In conclusion, the OGF - OGFr axis provides significant strategies for antitumor efficiency in gynecological cancer.

Long noncoding RNA LINC00673 promotes the proliferation and metastasis of epithelial ovarian cancer by associating with opioid growth factor receptor

Purpose

The long noncoding RNA LINC00673 has emerged as an important regulator of cancer development and progression. However, the clinical significance and biological roles of LINC00673 in epithelial ovarian cancer (EOC) remain unclear. In this study, we aimed to explore the oncogenic roles and underlying molecular mechanisms of LINC00673 in EOC.

Patients and methods

The expression levels of LINC00673 in EOC tissues and cell lines were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Real-time cellular analysis (RTCA), flow cytometry, and transwell assays were conducted to investigate cell proliferation, apoptosis, migration and invasion in vitro. Subcutaneous transplanted tumors were established to explore the oncogenic role of LINC00673 in vivo. Differentially expressed genes were analyzed using transcriptome sequencing. Protein levels were determined by Western blot assays.

Results

LINC00673 was upregulated in EOC tissues and cell lines compared to their corresponding normal controls. High expression of LINC00673 was associated with advanced International Federation of Gynecology and Obstetrics (FIGO) stage, serous histological subtype, lymph node metastasis and poor prognosis in patients with EOC. LINC00673 was also identified as an independent prognostic factor for EOC. In addition, LINC00673 promoted cell migration, invasion and proliferation and inhibited cell apoptosis in vitro and induced tumor growth in vivo. Mechanistically, opioid growth factor receptor (OGFR) was found to be a potential downstream target gene that mediated the oncogenic effect of LINC00673 in EOC.

Conclusion

LINC00673 contributes to EOC proliferation and metastasis and may be a promising prognostic biomarker for EOC patients.

The Use of Naltrexone in Dermatology. Current Evidence and Future Directions

Naltrexone is a competitive opioid receptor antagonist approved as supportive treatment in alcohol dependence and opioid addiction. At a dose of 50-100 mg daily, naltrexone is used off-label in dermatology for the treatment of trichotillomania and different types of pruritus. At a dose as low as 1- 5 mg per day, naltrexone demonstrates immunomodulatory action i.e. modulates Toll-like receptors signaling, decreases release of proinflammatory cytokines (tumor necrosis factor, interleukin-6, interleukin- 12), inhibits T lymphocyte proliferation, down-regulates the expression of chemokine receptors and adhesion molecules. The efficacy of standard and low doses of naltrexone in a variety of dermatological disorders has been reported. These include diseases such as familial benign chronic pemphigus (Hailey-Hailey disease), dermatomyositis, systemic sclerosis, psoriasis and lichen planopilaris. Optimistic preliminary findings, low cost of therapy and good tolerance make naltrexone a promising alternative therapy or adjunct drug in dermatology.

Exogenous OGF enhances the anti-tumor activity of cisplatin on hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma results in high cancer mortality and is difficult to eradicate because of its late stage at the time of diagnosis, multicentricity, and cirrhotic background. It is therefore urgent to explore effective and economical therapeutic methods to treat this disease.

OBJECTIVES

We aimed to investigate the antitumor activity of exogenous opioid growth factor (OGF), as well as the effect of the combination of OGF and cisplatin on hepatocellular carcinoma. The possible underlying mechanisms were also explored.

MATERIALS AND METHODS

RT-PCR and immunohistochemistry were employed to determine the expression of OGF receptor (OGFr) in hepatocellular carcinoma. MTT assays were used to explore the effect of OGF on cell migration and proliferation. Animal experiments were performed to explore the effect of OGF and DDP on tumors.

RESULTS

OGFr is present in human HCC cells and was differentially expressed between HCC tumor and non-tumor tissues. OGF inhibited HCC cell proliferation and migration. The silencing of OGFr blocked the expression of p21 and p53. Treatment using OGF, DDP and OGF+DDP all suppressed the growth of HCC tumors, with the maximum effect in the OGF+DDP group.

CONCLUSION

Our study clarified that OGF inhibits cell migration and proliferation of HCC in animal experiments and that exogenous OGF enhances the anti-tumor activity of cisplatin on HCC by upregulating p21 and p53. These findings may provide a new strategy for future HCC therapeutics.

Intermittent blockade of OGFr and treatment of autoimmune disorders

IMPACT STATEMENT

This mini-review presents information on the intermittent blockade of the opioid growth factor (OGF)-OGF receptor (OGFr) axis by low-dose naltrexone (LDN), and the role of enkephalin (i.e. OGF) in autoimmune disorders, specifically multiple sclerosis, Crohn's, and fibromyalgia. Clinical reports on subjects taking LDN have documented reduced fatigue, few side-effects, and improved overall health. Preclinical studies on mice with experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis, revealed that immunization for EAE reduces serum OGF. Intermittent OGFr blockade with LDN restores serum enkephalin levels that correlate with reduced behavioral and pathological signs of EAE; LDN also increases enkephalin levels in naïve mice. The interplay between LDN, and the onset and treatment of autoimmune diseases, chronic pain, and other addictive behaviors requires further investigation, but highlights a central role for enkephalins and intermittent blockade of the OGF-OGFr pathway in pathogenesis and treatment of these disorders.

Integrated Proteomic and Transcriptomic Analysis Reveals Long Noncoding RNA HOX Transcript Antisense Intergenic RNA (HOTAIR) Promotes Hepatocellular Carcinoma Cell Proliferation by Regulating Opioid Growth Factor Receptor (OGFr)

Long noncoding RNA HOX transcript antisense RNA (HOTAIR) is involved in human tumorigenesis and is dysregulated in hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying HOTAIR functions in HCC are largely unknown. Here, we employed an integrated transcriptomic and quantitative proteomic analysis to systematically explore the regulatory role of HOTAIR in HCC. A total of 673 transcripts and 293 proteins were found to be dysregulated after HOTAIR inhibition. Bioinformatics studies indicated that differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) are involved in many biological processes, especially cancer-related signaling pathways. A set of DEGs and DEPs were validated by quantitative RT-PCR, Western blot and parallel reaction monitoring (PRM) analysis, respectively. Further functional studies of the opioid growth factor receptor (OGFr), a negative biological regulator of cell proliferation in HCC, revealed that HOTAIR exerts its effects on cell proliferation, at least in part, through the regulation of OGFr expression. By correlating the omics data with functional studies, the current results provide novel insights into the functional mechanisms of HOTAIR in HCC cells.

Featured Article: Serum [Met5]-enkephalin levels are reduced in multiple sclerosis and restored by low-dose naltrexone

Low-dose naltrexone is a widely used off-label therapeutic prescribed for a variety of immune-related disorders. The mechanism underlying low-dose naltrexone's efficacy for fatigue, Crohn's disease, fibromyalgia, and multiple sclerosis is, in part, intermittent blockade of opioid receptors followed by upregulation of endogenous opioids. Short, intermittent blockade by naltrexone specifically blocks the opioid growth factor receptor resulting in biofeedback events that increase production of the endogenous opioid growth factor (OGF) (chemically termed [Met5]-enkephalin) facilitating interactions between opioid growth factor and opioid growth factor receptor that ultimately, result in inhibited cell proliferation. Preclinical studies have reported that enkephalin levels are deficient in animal models of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. Our hypothesis is that serum enkephalin levels are diminished in humans with multiple sclerosis and experimental autoimmune encephalomyelitis mice, and that change in serum opioid growth factor levels may serve as a reasonable candidate biomarker for the onset of experimental autoimmune encephalomyelitis and response to therapy. To address this, we designed a two-part study to measure endogenous opioids in multiple sclerosis patients, and to investigate the temporal pattern of decline in serum enkephalin concentrations in mice with chronic progressive experimental autoimmune encephalomyelitis and treated with low-dose naltrexone. For comparison, we investigated whether low-dose naltrexone exposure in normal mice also resulted in altered enkephalin levels. In both animal models, we monitored tactile and heat sensitivity, as well as differential white blood cell counts as indicators of inflammation. Serum [Met5]-enkephalin levels were lower in humans with multiple sclerosis relative to non-multiple sclerosis patients, and low-dose naltrexone restored their levels. In experimental autoimmune encephalomyelitis mice, [Met5]-enkephalin levels were depressed prior to the appearance of clinical disease, and were restored with low-dose naltrexone treatment. Low-dose naltrexone therapy had no effect on serum [Met5]-enkephalin or β-endorphin in normal mice. Thus, [Met5]-enkephalin (i.e. opioid growth factor) may be a reasonable candidate biomarker for multiple sclerosis, and may signal new pathways for treatment of autoimmune disorders. Impact statement This report presents human and animal data identifying a novel biomarker for the onset and progression of multiple sclerosis (MS). Humans diagnosed with MS have reduced serum levels of OGF (i.e. [Met5]-enkephalin) relative to non-MS neurologic patients, and low-dose naltrexone (LDN) therapy restored their enkephalin levels. Serum OGF levels were reduced in mice immunized with MOG35-55 prior to any clinical behavioral sign of experimental autoimmune encephalomyelitis, and LDN therapy restored their serum OGF levels. β-endorphin concentrations were not altered by LDN in humans or mice. Thus, blood levels of OGF may serve as a new, selective biomarker for the progression of MS, as well as response to therapy.

Naltrexone Inhibits IL-6 and TNFα Production in Human Immune Cell Subsets following Stimulation with Ligands for Intracellular Toll-Like Receptors

The opioid antagonist naltrexone hydrochloride has been suggested to be a potential therapy at low dosage for multiple inflammatory conditions and cancers. Little is known about the immune-modulating effects of naltrexone, but an effect on the activity of toll-like receptor 4 (TLR4) has been reported. We analyzed the effects of naltrexone hydrochloride on IL-6 secretion by peripheral blood mononuclear cells (PBMC) in vitro following stimulation with ligands for TLR4 and for the intracellular receptors TLR7, TLR8, and TLR9. Naltrexone did not affect cell viability or induce apoptosis of PBMC. Intracellular staining demonstrated that naltrexone inhibited production of IL-6 and TNFα by monocyte and plasmacytoid dendritic cell subsets within the PBMC population following treatment with ligands for TLR7/8 and TLR9, respectively. No effect of cytokine production by PBMC following stimulation of TLR4 was observed. Additionally, naltrexone inhibited IL-6 production in isolated monocytes and B cells after TLR7/8 and TLR9 stimulation, respectively, but no effect on IL-6 production in isolated monocytes after TLR4 stimulation was observed. These findings indicate that naltrexone has the potential to modulate the secretion of inflammatory cytokines in response to intracellular TLR activity, supporting the hypothesis that it may have potential for use as an immunomodulator.

Morphine Suppresses Lung Cancer Cell Proliferation Through the Interaction with Opioid Growth Factor Receptor: An In Vitro and Human Lung Tissue Study

BACKGROUND

There have been inconsistent reports on whether opioids promote or inhibit lung cancer growth. In this study, we suggest that opioid growth factor receptor (OGFR), a negative regulator of cell proliferation, is a binding site of morphine and is involved in subsequent morphine-induced lung cancer growth suppression.

METHODS

The expression and distribution of OGFR in human lung cancer tissues and cell lines were assessed with immunohistochemistry and real-time reverse transcription polymerase chain reaction. The human lung cancer cell line, H1975 (adenocarcinoma), which overexpressed OGFR but not μ-opioid receptors, was selected for further analysis to verify the interaction between morphine and OGFR and the impact of morphine on cancer cell growth.

RESULTS

OGFR was expressed in lung cancer tissues and all cancer cell lines tested. Adenocarcinoma showed a higher OGFR expression than squamous cell carcinoma (reverse transcription polymerase chain reaction relative quantitation value: median [interquartile range], 13.1 [9.3-20.0] vs 4.3 [2.2-6.6]; P = 0.003). OGFR expression showed an inverse correlation with cell proliferation (r = -0.92, P = 0.0001). Morphine treatment reduced the median H1975 cell number by approximately 23% (P = 0.03). Growth suppression by morphine was attenuated when OGFR was knocked down. A confocal experiment demonstrated binding of morphine to OGFR. Growth suppression by morphine occurred in the S phase of the cell cycle.

CONCLUSIONS

Lung cancer tissues and cell lines express OGFR. Morphine interacts with OGFR and may suppress lung cancer progression.

Developmental Toxicity of Zinc Oxide Nanoparticles to Zebrafish (Danio rerio): A Transcriptomic Analysis

Zinc oxide nanoparticles (ZnO NPs) are being utilized in an increasing number of fields and commercial applications. While their general toxicity and associated oxidative stress have been extensively studied, the toxicological pathways that they induce in developmental stages are still largely unknown. In this study, the developmental toxicity of ZnO NPs to embryonic/larval zebrafish was investigated. The transcriptional expression profiles induced by ZnO NPs were also investigated to ascertain novel genomic responses related to their specific toxicity pathway. Zebrafish embryos were exposed to 0.01, 0.1, 1, and 10 mg/L ZnO NPs for 96 h post-fertilization. The toxicity of ZnO NPs, based on their Zn concentration, was quite similar to that in embryonic/larval zebrafish exposed to corresponding ZnSO₄ concentrations. Pericardial edema and yolk-sac edema were the principal malformations induced by ZnO NPs. Gene-expression profiling using microarrays demonstrated 689 genes that were differentially regulated (fold change >1.5) following exposure to ZnO NPs (498 upregulated, 191 downregulated). Several genes that were differentially regulated following ZnO NP exposure shared similar biological pathways with those observed with ZnSO₄ exposure, but six genes (aicda, cyb5d1, edar, intl2, ogfrl2 and tnfsf13b) associated with inflammation and the immune system responded specifically to ZnO NPs (either in the opposite direction or were unchanged in ZnSO₄ exposure). Real-time reverse-transcription quantitative polymerase chain reaction confirmed that the responses of these genes to ZnO NPs were significantly different from their response to ZnSO₄ exposure. ZnO NPs may affect genes related to inflammation and the immune system, resulting in yolk-sac edema and pericardia edema in embryonic/larval developmental stages. These results will assist in elucidating the mechanisms of toxicity of ZnO NPs during development of zebrafish.

High Level of Fasting Plasma Proenkephalin-A Predicts Deterioration of Kidney Function and Incidence of CKD

High levels of proenkephalin-A (pro-ENK) have been associated with decreased eGFR in an acute setting. Here, we examined whether pro-ENK levels predict CKD and decline of renal function in a prospective cohort of 2568 participants without CKD (eGFR>60 ml/min per 1.73 m²) at baseline. During a mean follow-up of 16.6 years, 31.7% of participants developed CKD. Participants with baseline pro-ENK levels in the highest tertile had significantly greater yearly mean decline of eGFR (P_trend<0.001) and rise of cystatin C (P_trend=0.01) and creatinine (P_trend<0.001) levels. Furthermore, compared with participants in the lowest tertile, participants in the highest tertile of baseline pro-ENK concentration had increased CKD incidence (odds ratio, 1.51; 95% confidence interval, 1.18 to 1.94) when adjusted for multiple factors. Adding pro-ENK to a model of conventional risk factors in net reclassification improvement analysis resulted in reclassification of 14.14% of participants. Genome-wide association analysis in 4150 participants of the same cohort revealed the strongest association of pro-ENK levels with rs1012178 near the PENK gene, where the minor T-allele associated with a 0.057 pmol/L higher pro-ENK level per allele (P=4.67x10^-21). Furthermore, the T-allele associated with a 19% increased risk of CKD per allele (P=0.03) and a significant decrease in the instrumental variable estimator for eGFR (P<0.01) in a Mendelian randomization analysis. In conclusion, circulating plasma pro-ENK level predicts incident CKD and may aid in identifying subjects in need of primary preventive regimens. Additionally, the Mendelian randomization analysis suggests a causal relationship between pro-ENK level and deterioration of kidney function over time.

Antagonism of the Met5-enkephalin-opioid growth factor receptor-signaling axis promotes MSC to differentiate into osteoblasts

Chronic opioid therapy is associated with bone loss. This led us to hypothesize that the opioid antagonists, that include naloxone, would stimulate bone formation by regulating MSC differentiation. The opioid growth factor receptor (OGFR) is a non-canonical opioid receptor that binds naloxone with high affinity whereas the native opioid growth factor, met5-enkephalin (met5), binds both the OGFR and the canonical delta opioid receptor (OPRD). Naloxone and an shRNA OGFR lentivirus were employed to disrupt the OGFR-signaling axis in cultured MSC. In parallel, naloxone was administered to bone marrow using a mouse unicortical defect model. OPRD, OGFR, and the met5-ligand were highly expressed in MSC and osteoblasts. A pulse-dose of naloxone increased mineral formation in MSC cultures in contrast to MSC treated with continuous naloxone or OGFR deficient MSC. Importantly, SMAD1 and SMAD8/9 expression increased after a pulse dose of naloxone whereas SMAD1, SMAD7, and ID1 were increased in the OGFR deficient MSC. Inhibited OGFR signaling decreased proliferation and increased p21 expression. The addition of naloxone to the unicortical defect resulted in increased bone formation within the defect. Our data suggest that novel mechanism through which signaling through the OGFR regulates osteogenesis via negative regulation of SMAD1 and p21. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1195-1205, 2016.

The prostate cancer immunome: In silico functional analysis of antigenic proteins from microarray profiling with IgG

The study of the immunome of prostate cancer (PCa) and characterization of autoantibody signature from differentially reactive antigens can uncover disease stage proteins, reveal enriched networks and even expose aberrant cellular mechanisms during the disease process. By conducting plasma IgG profiling on protein microarrays presenting 5449 unique human proteins expressed in 15 417 E. coli human cDNA expression clones, we elucidated 471 (21 higher reactive in PCa) differentially reactive antigens in 50 PCa versus 49 patients with benign prostate hyperplasia (BPH) at initial diagnosis. Functional analyzes show that the immune-profile of PCa compared to BPH control samples is significantly enriched in features targeting Cellular assembly, Cell death and pathways involved in Cell cycle, translation, and assembly of proteins as EIF2 signaling, PCa related genes as AXIN1 and TP53, and ribosomal proteins (e.g. RPS10). An overlap of 61 (out of 471) DIRAGs with the published 1545 antigens from the SEREX database has been found, however those were higher reactive in BPH. Clinical relevance is shown when antibody-reactivities against eight proteins were significantly (p < 0.001) correlated with Gleason-score. Herewith we provide a biological and pathophysiological characterization of the immunological layer of cancerous (PCa) versus benign (BPH) disease, derived from antibody profiling on protein microarrays.

Featured Article: Nuclear export of opioid growth factor receptor is CRM1 dependent

Opioid growth factor receptor (OGFr) facilitates growth inhibition in the presence of its specific ligand opioid growth factor (OGF), chemically termed [Met(5)]-enkephalin. The function of the OGF-OGFr axis requires the receptor to translocate to the nucleus. However, the mechanism of nuclear export of OGFr is unknown. In this study, endogenous OGFr, as well as exogenously expressed OGFr-EGFP, demonstrated significant nuclear accumulation in response to leptomycin B (LMB), an inhibitor of CRM1-dependent nuclear export, suggesting that OGFr is exported in a CRM1-dependent manner. One consensus sequence for a nuclear export signal (NES) was identified. Mutation of the associated leucines, L217 L220 L223 and L225, to alanine resulted in decreased nuclear accumulation. NES-EGFP responded to LMB, indicating that this sequence is capable of functioning as an export signal in isolation. To determine why the sequence functions differently in isolation than as a full length protein, the localization of subNES was evaluated in the presence and absence of MG132, a potent inhibitor of proteosomal degradation. MG132 had no effect of subNES localization. The role of tandem repeats located at the C-terminus of OGFr was examined for their role in nuclear trafficking. Six of seven tandem repeats were removed to form deltaTR. DeltaTR localized exclusively to the nucleus indicating that the tandem repeats may contribute to the localization of the receptor. Similar to the loss of cellular proliferation activity (i.e. inhibition) recorded with subNES, deltaTR also demonstrated a significant loss of inhibitory activity indicating that the repeats may be integral to receptor function. These experiments reveal that OGFr contains one functional NES, L217 L220 L223 and L225 and can be exported from the nucleus in a CRM1-dependent manner.

Endogenous opioid inhibition of proliferation of T and B cell subpopulations in response to immunization for experimental autoimmune encephalomyelitis

BACKGROUND

Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, is induced by immunization of mice with myelin oligodendrocytic glycoprotein (MOG35-55) injections, and after 9 days, mice develop behavioral signs of chronic progressive EAE. Proliferation of T and B cells located in peripheral lymph tissues such as spleen and inguinal lymph nodes of C57BL/6J mice are stimulated. The opioid growth factor-opioid growth factor receptor (OGF-OGFr) axis has been shown to effectively limit progression of chronic EAE when mice are treated at the time of induction or at time of established disease. In addition to repressed behavioral profiles, spinal cord neuropathology is diminished in mice treated with OGF or low dosages of naltrexone (LDN). However, there is little or no information on peripheral lymphocyte dynamics following immunization of mice with MOG antigen and treatment with OGF or LDN.

METHODS

Six-week old female mice were immunized with MOG35-55 and were injected intraperitoneally with OGF or a low dosage of naltrexone (LDN) beginning at the time of immunization; saline-injected immunized mice served as controls. Normal mice received saline for all injections. Periodically over a 2 week period, spleens and inguinal lymph nodes were removed, total lymphocytes counted, and subpopulations of CD4+ and CD8+ specific T-cells, as well as B lymphocytes, were determined by flow cytometry. On day 15 of treatment, lumbar spinal cord tissue was removed; CNS lymphocytes isolated, and assayed for Th1, Th2, and Th17 markers by flow cytometry.

RESULTS

Exogenous OGF or endogenous OGF following LDN suppressed T and B lymphocyte proliferation in the spleen and inguinal lymph nodes of MOG-immunized mice. Suppression of peripheral immune cell CD4+ and CD8+ T cell proliferation at 5 and 12 days correlated with reductions in clinical behavior. EAE mice treated with OGF for 15 days displayed elevated Th1 and Th17 cells; no subpopulations of Th2-specific T cells were noted.

CONCLUSIONS

OGF or LDN repress proliferation of CD4+ and CD8+T cells and B220+ B lymphocytes in the spleen and lymph nodes of immunized mice within a week of immunization. These data provide novel mechanistic pathways underlying the efficacy of OGF and LDN therapy for MS.

Immune effects of R848: evidences that suggest an essential role of TLR7/8-induced, Myd88- and NF-κB-dependent signaling in the antiviral immunity of Japanese flounder (Paralichthys olivaceus)

The imidazoquinoline compound R848 is a specific agonist of toll-like receptor (TLR) 7/TLR8 that has been used as an immunostimulant in humans against viral diseases. Although R848-induced immune response has been reported in teleost fish, the relevant mechanism is not clear. In this study, we investigated the antiviral potential and the signaling pathway of R848 in a model of Japanese flounder (Paralichthys olivaceus). We found that R848 was able to inhibit the replication of megalocytivirus, stimulated the proliferation of peripheral blood leukocytes (PBL), enhanced the expression of immune genes, and reduced apoptosis of PBL. When endosomal acidification was blocked by chloroquine (CQ), R848-mediated antiviral activity and immune response were significantly reduced. Likewise, inhibition of Myd88 activation markedly impaired the pro-proliferation and anti-apoptosis effect of R848. Cellular study showed that cultured founder cells treated with R848 exhibited augmented NF-κB activity, which, however, was dramatically reduced in the presence of CQ and Myd88 inhibitor. Furthermore, when NF-κB was inactivated, the effect of R848 on cell proliferation and apoptosis was significantly decreased. Taken together, these results indicate that R848 is an immunostimulant with antiviral property in a teleost species, and that the immune response of R848 is mediated by, most likely, TLR7/TLR8 signaling pathway, in which Myd88 and NK-κB play an essential role.

Effect of met-enkephalin on chromosomal aberrations in the lymphocytes of the peripheral blood of patients with multiple sclerosis

Endogenious opiod met-enkephalin throughout previous research manifested cytoprotective and anti-inflammatory effects. Previous research suggests that met-enkephalin has cytogenetic effects. Reducement in the frequency of structural chromosome aberrations as well as a suppressive effect on lymphocyte cell cycle is found. It also reduces apoptosis in the blood samples of the patients with immune-mediated diseases. Met-enkephalin exerts immunomodulatory properties and induces stabilization of the clinical condition in patients with multiple Sclerosis (MS). The goal of the present research was to evaluate met-enkephalin in vitro effects on the number and type of chromosome aberrations in the peripheral blood lymphocytes of patients with MS. Our research detected disappearance of ring chromosomes and chromosome fragmentations in the cultures of the peripheral blood lymphocytes treated with met-enkephalin (1.2 μg/mL). However, this research did not detect any significant effects of met-enkephalin on the reduction of structural chromosome aberrations and disappearance of dicentric chromosomes. Chromosomes with the greatest percent of inclusion in chromosome aberrations were noted as: chromosome 1, chromosome 2 and chromosome 9. Additionally, we confirmed chromosome 14 as the most frequently included in translocations. Furthermore, met-enkephalin effects on the increase of the numerical aberrations in both concentrations applied were detected. Those findings should be interpreted cautiously and more research in this field should be conducted.

Opioids, Neutral Endopeptidase, its Inhibitors and Cancer: Is There a Relationship among them?

The role of endogenous animal opioids in the biology of cancer is widely recognized but poorly understood. This is, among others, because of the short half-life of these peptides, which are quickly inactivated by endopeptidases, e.g., neutral endopeptidase (NEP, CD10). It has been established that NEP is engaged in the modulation of the tumor microenvironment, among others that of colon cancer, by exerting influence on cell growth factors, the extracellular matrix and other biologically active substances. Although there are some discrepancies among the findings on the role of both opioids and NEP in cancer development, authors agree that their role seems to depend on the origin, stage and grade of tumor, and even on the method of examination. Moreover, recently, natural inhibitors of NEP, such as sialorphin, opiorphin and spinorphin have been detected. Their analgesic activity has been established. It is interesting to ask whether there is a relationship among opioid peptides, tumor-associated NEP and its inhibitors.

Impact of lifetime opioid exposure on arterial stiffness and vascular age: cross-sectional and longitudinal studies in men and women

OBJECTIVE

To characterise and compare the potentiation of arterial stiffness and vascular ageing by opioids in men and women.

DESIGN

Cross-sectional and longitudinal studies of 576 clinical controls and 687 opioid-dependent patients (ODP) on 710 and 1305 occasions, respectively, over a total of 2382 days (6.52 years), 2006-2011. Methodology Radial pulse wave analysis with Atcor SphygmoCor system (Sydney).

SETTING

Primary care.

CONTROLS

General practice patients with non-cardiovascular disorders, and university student controls. ODP: Patients undergoing clinical management of their opioid dependence. CONTROLS had lower chronological ages (CAs) than ODP (30.0±0.5 vs 34.5±0.3, mean±SEM, p<0.0001). 69.6% and 67.7% participants were men, and 16% and 92.3% were smokers (p<0.0001) for controls and ODP, respectively. 86.3%, 10.3% and 3.4% of ODP were treated with buprenorphine (6.98±0.21 mg), methadone (63.04±4.01 mg) or implant naltrexone, respectively. Body mass index (BMI) was depressed in ODP.

INTERVENTIONS

Nil.

PRIMARY OUTCOME MEASURES

Vascular Reference Age (RA) and the ratio of vascular age to chronological age (RA/CA).

SECONDARY OUTCOME MEASURES

Arterial stiffness including Augmentation Index.

RESULTS

After BMI adjustment, RA in ODP was higher as a function of CA and of time (both p<0.05). Modelled mean RA in control and ODP was 35.6 and 36.3 years (+1.97%) in men, and 34.5 and 39.2 years (+13.43%) in women, respectively. Changes in RA and major arterial stiffness indices were worse in women both as a factor (p = 0.0036) and in interaction with CA (p = 0.0040). Quadratic, cubic and quartic functions of opioid exposure duration outperformed linear models with RA/CA over CA and over time. The opioid dose-response relationship persisted longitudinally after multiple adjustments from p=0.0013 in men and p=0.0073 in women.

CONCLUSIONS

Data show that lifetime opioid exposure, an interactive cardiovascular risk factor, particularly in women, is related to linear, quadratic, cubic and quartic functions of treatment duration and is consistent with other literature of accelerated ageing in patients with OD.

Topical Naltrexone as Treatment for Type 2 Diabetic Cutaneous Wounds

Objective: Type 2 diabetes (T2D) is associated with impaired cutaneous wound healing and can result in ulceration, infection, and/or amputation. More than 25 million people in the United States have T2D and are vulnerable to epithelial-related complications. Current therapies are limited in their efficacy. New treatments for full-thickness cutaneous wounds that focus on underlying diabetic pathways are needed. Approach: Topical application of the opioid receptor antagonist naltrexone (NTX) dissolved in cream reverses delayed wound closure in type 1 diabetic rat by the acceleration of reepithelialization and enhancement of angiogenesis and remodeling. NTX blocks the opioid growth factor (OGF)-OGF receptor (OGFr) axis and upregulates DNA synthesis and cell proliferation. To investigate whether NTX is an effective therapy for T2D wound closure, genetically obese mice (db/db) and normal C57Bl/6J mice received full-thickness cutaneous wounds. Wounds (5 mm in diameter) were treated topically three times daily with 10-5 M NTX or sterile saline dissolved in cream and photographed every 2 days. Results: Wounds in db/db mice treated with saline were 11-92% larger than those in normal mice throughout the 2-week observation. Topical NTX therapy in T2D mice reduced the residual wound size by 13-30% between days 8 and 14 relative to diabetic mice receiving saline. Reepithelialization and DNA synthesis, as analyzed by epithelial thickness and BrdU labeling indexes, respectively, were accelerated in NTX-treated wounds. Innovation and Conclusion: These data suggest that the OGF-OGFr axis plays a role in epithelial-related complications of T2D and that blockade of this pathway by NTX may be an effective treatment for wound repair.

Impact of opioid pharmacotherapy on arterial stiffness and vascular ageing: cross-sectional and longitudinal studies

Whilst there is a small literature on the cardiovascular toxicity of opiates, there is no detailed antemortem data on non-cardiovascular patient populations. A cross-sectional and longitudinal naturalistic observational study was performed comparing methadone (N = 71)-, buprenorphine (N = 593)-, naltrexone (N = 23)-treated patients with controls (N = 576) on indices of arterial stiffness and vascular age by Pulse Wave Analysis in primary care, 2006-2011. Controls were younger 29.96 ± 0.45 (mean ± SEM) vs. 34.00 ± 0.34-39.22 ± 1.11 years (all P < 0.005) and had fewer smokers (15.9 % vs. 86.9 %-92.96 %, all P < 0.0001). The sex ratio was similar (69.6 vs. 67.7 % male, P = 0.46). These baseline differences were controlled for by multiple regression. Linear regression of vascular age, central augmentation pressure, central augmentation index and other measures against chronologic age showed significant protective effects by treatment group against the treatment standard of methadone, in both sexes in additive and interactive models (all P < 0.02). Interactive terms in treatment type remained significant including all conventional risk factors accounting for differing opiate exposures. The principal findings from multiple regression were confirmed in the time series analysis up to 5 years by repeated measures nonlinear regression. These studies show that the deleterious impact of chronic opiate pharmacotherapy on vascular age and arterial stiffness varies significantly by treatment type.

p38δ regulates p53 to control p21Cip1 expression in human epidermal keratinocytes

PKCδ suppresses keratinocyte proliferation via a mechanism that involves increased expression of p21(Cip1). However, the signaling mechanism that mediates this regulation is not well understood. Our present studies suggest that PKCδ activates p38δ leading to increased p21(Cip1) promoter activity and p21(Cip1) mRNA/protein expression. We further show that exogenously expressed p38δ increases p21(Cip1) mRNA and protein and that p38δ knockdown or expression of dominant-negative p38 attenuates this increase. Moreover, p53 is an intermediary in this regulation, as p38δ expression increases p53 mRNA, protein, and promoter activity, and p53 knockdown attenuates the activation. We demonstrate a direct interaction of p38δ with PKCδ and MEK3 and show that exogenous agents that suppress keratinocyte proliferation activate this pathway. We confirm the importance of this regulation using a stratified epidermal equivalent model, which mimics in vivo-like keratinocyte differentiation. In this model, PKCδ or p38δ knockdown results in reduced p53 and p21(Cip1) levels and enhanced cell proliferation. We propose that PKCδ activates a MEKK1/MEK3/p38δ MAPK cascade to increase p53 levels and p53 drives p21(Cip1) gene expression.

Duration of opiate exposure as a determinant of arterial stiffness and vascular age in male opiate dependence: a longitudinal study

WHAT IS KNOWN AND OBJECTIVE

Despite intriguing initial and associational studies, there remains little research on opiate-related arterial dysfunction and no longitudinal studies. As opiates act potently via P16INK4A/CDKN2A identified on GWAS screens, and as arterial ageing is a surrogate for organismal ageing, this area is of general concern.

METHODS

Thirty-eight male controls compared with 198 opiate-dependent male patients were studied longitudinally using SphygmoCor pulse wave analysis.

RESULTS AND DISCUSSION

Healthy male controls and opiate-dependent male patients were studied on 125 and 625 occasions, respectively. The mean (±SEM) chronological age (CA) was 42·32 ± 2·22 for controls and 35·04 ± 0·61 for opiate dependent (P = 0·0029). 94·4% and 13·2% smoked tobacco (P < 0·0001). Controlling for BMI and CA, there was a significant time: addictive status interaction for vascular age (P = 0·0127) and central augmentation pressure and index (both P < 0·02). Central systolic and diastolic pressures were also worse over time by addictive status (P < 0·005). At repeated measures multiple regression adjusted for classical risk factors, opiate dose and duration of opiate use remained significant. The dose-duration effect was significant in 8 terms and by time. A similar model quadratic in opiate duration was more powerfully predictive, suggesting the salience of the duration of opiate treatment (AIC 191·6898 and 191·5966, P = 0·0116).

WHAT IS NEW AND CONCLUSION

Data suggest that increased length of opiate dependence is associated with advanced vascular stiffness and ageing and are therefore consistent with accelerated ageing organismally. The superiority of power functions of the opiate duration of exposure underscores the significance of the duration of treatment and of putative senescence induction.

Elevation of central arterial stiffness and vascular ageing in opiate withdrawal: cross-sectional and longitudinal studies

The central cardiovascular impacts of clinical opiate withdrawal have not been explored in detail. Pulse Wave Analysis (SphygmoCor) was conducted in healthy controls and opiate-dependent populations. A total of 1,294 patients (69.2 % male) were studied in quintuplicate on 2,089 occasions. Four groups were studied: control (N = 576), buprenorphine stabilized (N = 592), withdrawal (N = 112) and severe withdrawal (N = 14). Control patients were younger than the other groups (29.96 ± 0.45 years v. 32.53 ± 0.74-39.28 ± 3.86) but had similar sex ratios. Multiple regression was used to correct for the effects of age, and significant exacerbations were found in withdrawal in the vascular age (RA), augmentation index, subendocardial perfusion ratio (SEVR <100; R.R. 2.07 95 % C.I. 1.17-3.68, P = 0.02) and central systolic pressure both as factors themselves and in interactions with age (all P < 0.01). The elevation of modelled RA at 60 years was from 69.66 in controls to 97.54 in withdrawal (40.02 %). The effects on RA were found in both sexes and confirmed on longitudinal analysis. The elevation of RA in withdrawal was most marked after 40 years of age (P = 0.027). These results show increased vascular stiffness and cardiovascular age but reduced subendocardial perfusion in opiate withdrawal. Given the daily recurrent nature of withdrawal, these effects are likely cumulative.

Lifetime opiate exposure as an independent and interactive cardiovascular risk factor in males: a cross-sectional clinical study

Introduction

While several studies have identified an increased incidence of cardiovascular disorders in opiate dependence, neither opiates as a cardiovascular risk factor nor their effect on central arterial function has been considered.

Methods

Pulse wave analysis (SphygmoCor, AtCorMedical Pty Limited, Sydney, NSW, Australia) was undertaken on a cohort of controls and opiate dependent patients and the results compared to their lifetime opiate exposure.

Results

Controls (N = 401) were compared with 465 opiate dependent men. The mean (log) ages were different and were found to be 28.80 ± 0.49 years versus 35.02 ± 0.39 years (P < 0.0001), respectively. Of the opiate dependent group, 87.7% were treated with buprenorphine, 8.8% with methadone, and 3.4% with naltrexone. Multiple regression analysis was used to adjust for chronologic age (CA). At CA of 60 years, the modeled age in the controls was 66.40 years, and that in the addicted group was 73.11 years, an advancement of 6.71 years, or 10.10%. Exacerbations of age dependent changes in central arterial stiffness, central pressures, pulse rate, ejection duration, diastolic duration, and subendocardial perfusion ratio by opiate dependence were all noted (P < 0.05). Current heroin dose, heroin duration, and the dose duration interaction were all significantly related to the vascular (or “reference”) age (RA)/CA ratio (all P < 0.006). After multivariate adjustment, the opiate dose duration was independently predictive of RA (P < 0.02). Opiate dose and/or duration were included in a further 25 terms.

Conclusion

These data show that opiate use is not benign for the male cardiovascular system, but has a dose response relationship to central arterial stiffness and thus cardiovascular aging, acting independently and interactively with established cardiovascular risk factors. These findings imply accelerated organismal aging.

Topical treatment with the opioid antagonist naltrexone accelerates the remodeling phase of full-thickness wound healing in type 1 diabetic rats

Wound repair involves a series of overlapping phases that include inflammation, proliferation, and tissue remodeling, with the latter phase requiring months for proper healing. Delays in any of these processes can result in infection, chronic ulceration, and possible amputation. Diabetes is a major risk factor for improper wound repair, and impaired wound healing is a major complication for more than 26 million people in the US diagnosed with diabetes. Previous studies have demonstrated that the opioid antagonist naltrexone (NTX) dissolved in moisturizing cream reverses delays in wound closure in streptozotocin-induced type 1 diabetic (T1D) rats. NTX accelerated DNA synthesis and increased the number of epithelial and mast cells, as well as new blood vessel formation. In this study, remodeling was evaluated in T1D rats up to eight weeks after initial wounding. Twenty days following wounding, diabetic rats treated with vehicle had elevated numbers of MMP-2+ fibroblasts, suggesting delayed healing processes; birefringence of granulation tissue stained with Sirius red revealed diminished collagen formation and maturation. Wound tissue from NTX-treated T1D rats had comparable numbers of MMP-2+ fibroblasts to control specimens, as well as accelerated maturation of granulation tissue. The integrity of wounded skin was evaluated by tensile strength measurements. T1D resulted in delayed wound healing, and wounded skin that displayed reduced tensile strength relative to normal rats. Topical NTX applied to wounds in T1D rats resulted in enhanced collagen formation and maturation over a 60-day period of time. Moreover, the force required to tear skin of NTX-treated T1D rats was elevated relative to the force necessary to tear the skin of vehicle-treated T1D rats, and comparable to that for normal rats. These data reveal that complications in wound healing associated with T1D involve the novel OGF-OGFr pathway, and that topical NTX is an effective treatment to enhance wound healing.