Vitamin D deficiency exacerbates UV/endorphin and opioid addiction

The current opioid epidemic warrants a better understanding of genetic and environmental factors that contribute to opioid addiction. Here we report an increased prevalence of vitamin D (VitD) deficiency in patients diagnosed with opioid use disorder and an inverse and dose-dependent association of VitD levels with self-reported opioid use. We used multiple pharmacologic approaches and genetic mouse models and found that deficiencies in VitD signaling amplify exogenous opioid responses that are normalized upon restoration of VitD signaling. Similarly, physiologic endogenous opioid analgesia and reward responses triggered by ultraviolet (UV) radiation are repressed by VitD signaling, suggesting that a feedback loop exists whereby VitD deficiency produces increased UV/endorphin-seeking behavior until VitD levels are restored by cutaneous VitD synthesis. This feedback may carry the evolutionary advantage of maximizing VitD synthesis. However, unlike UV exposure, exogenous opioid use is not followed by VitD synthesis (and its opioid suppressive effects), contributing to maladaptive addictive behavior.

Reduced MC4R signaling alters nociceptive thresholds associated with red hair

Humans and mice with natural red hair have elevated basal pain thresholds and an increased sensitivity to opioid analgesics. We investigated the mechanisms responsible for higher nociceptive thresholds in red-haired mice resulting from a loss of melanocortin 1 receptor (MC1R) function and found that the increased thresholds are melanocyte dependent but melanin independent. MC1R loss of function decreases melanocytic proopiomelanocortin transcription and systemic melanocyte-stimulating hormone (MSH) levels in the plasma of red-haired (Mc1re/e ) mice. Decreased peripheral α-MSH derepresses the central opioid tone mediated by the opioid receptor OPRM1, resulting in increased nociceptive thresholds. We identified MC4R as the MSH-responsive receptor that opposes OPRM1 signaling and the periaqueductal gray area in the brainstem as a central area of opioid/melanocortin antagonism. This work highlights the physiologic role of melanocytic MC1R and circulating melanocortins in the regulation of nociception and provides a mechanistic framework for altered opioid signaling and pain sensitivity in red-haired individuals.

Tanning as a substance abuse

While few people would deny the appeal of a day in the sun there are some who seem to take it too far. In recent years the concept of ‘tanning addiction’ has become popular and several studies have supported the notion of viewing exposure to UV radiation as a form of substance abuse. In this article we will review some of the literature on sun seeking behavior.

Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study

IMPORTANCE

The RAS/RAF/mitogen-activated protein kinase and extracellular signal-regulated kinase (ERK) kinase/ERK cascade plays a crucial role in melanoma cell proliferation and survival. Sildenafil citrate (Viagra) is a phosphodiesterase (PDE) 5A inhibitor commonly used for erectile dysfunction. Recent studies have shown that BRAF activation down-regulates PDE5A levels, and low PDE5A expression by BRAF activation or sildenafil use increases the invasiveness of melanoma cells, which raises the possible adverse effect of sildenafil use on melanoma risk.

OBJECTIVE

To evaluate the association between sildenafil use and risk of incident melanoma among men in the United States.

DESIGN, SETTING, AND PARTICIPANTS

Our study is a prospective cohort study. In 2000, participants in the Health Professionals' Follow-up Study were questioned regarding sildenafil use for erectile dysfunction. Participants who reported cancers at baseline were excluded. A total of 25,848 men remained in the analysis.

MAIN OUTCOMES AND MEASURES

The incidence of skin cancers, including melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC), was obtained in the self-reported questionnaires biennially. The diagnosis of melanoma and SCC was pathologically confirmed.

RESULTS

We identified 142 melanoma, 580 SCC, and 3030 BCC cases during follow-up (2000-2010). Recent sildenafil use at baseline was significantly associated with an increased risk of subsequent melanoma with a multivariate-adjusted hazard ratio (HR) of 1.84 (95% CI, 1.04-3.22). In contrast, we did not observe an increase in risk of SCC (HR, 0.84; 95% CI, 0.59-1.20) or BCC (1.08; 0.93-1.25) associated with sildenafil use. Moreover, erectile function itself was not associated with an altered risk of melanoma. Ever use of sildenafil was also associated with a higher risk of melanoma (HR, 1.92; 95% CI, 1.14-3.22). A secondary analysis excluding those reporting major chronic diseases at baseline did not appreciably change the findings; the HR of melanoma was 2.24 (95% CI, 1.05-4.78) for sildenafil use at baseline and 2.77 (1.32-5.85) for ever use.

CONCLUSIONS AND RELEVANCE

Sildenafil use may be associated with an increased risk of developing melanoma. Although this study is insufficient to alter clinical recommendations, we support a need for continued investigation of this association.

A polymorphism in IRF4 affects human pigmentation through a tyrosinase-dependent MITF/TFAP2A pathway

Sequence polymorphisms linked to human diseases and phenotypes in genome-wide association studies often affect noncoding regions. A SNP within an intron of the gene encoding Interferon Regulatory Factor 4 (IRF4), a transcription factor with no known role in melanocyte biology, is strongly associated with sensitivity of skin to sun exposure, freckles, blue eyes, and brown hair color. Here, we demonstrate that this SNP lies within an enhancer of IRF4 transcription in melanocytes. The allele associated with this pigmentation phenotype impairs binding of the TFAP2A transcription factor that, together with the melanocyte master regulator MITF, regulates activity of the enhancer. Assays in zebrafish and mice reveal that IRF4 cooperates with MITF to activate expression of Tyrosinase (TYR), an essential enzyme in melanin synthesis. Our findings provide a clear example of a noncoding polymorphism that affects a phenotype by modulating a developmental gene regulatory network.

Lineage-specific transcriptional regulation of DICER by MITF in melanocytes

DICER is a central regulator of microRNA maturation. However, little is known about mechanisms regulating its expression in development or disease. While profiling miRNA expression in differentiating melanocytes, two populations were observed: some upregulated at the pre-miRNA stage, and others upregulated as mature miRNAs (with stable pre-miRNA levels). Conversion of pre-miRNAs to fully processed miRNAs appeared to be dependent upon stimulation of DICER expression--an event found to occur via direct transcriptional targeting of DICER by the melanocyte master transcriptional regulator MITF. MITF binds and activates a conserved regulatory element upstream of DICER's transcriptional start site upon melanocyte differentiation. Targeted KO of DICER is lethal to melanocytes, at least partly via DICER-dependent processing of the pre-miRNA-17 approximately 92 cluster thus targeting BIM, a known proapoptotic regulator of melanocyte survival. These observations highlight a central mechanism underlying lineage-specific miRNA regulation which could exist for other cell types during development.

Arrhythmia and prognosis in infants, children and adolescents with hypertrophic cardiomyopathy

In adults with hypertrophic cardiomyopathy, the annual mortality rate from sudden death is 2 to 3%, and the finding of nonsustained ventricular tachycardia during electrocardiographic (ECG) monitoring provides a marker of the patient who is at increased risk. In the young, the annual mortality rate from sudden death is even higher, approximately 6%, but the prognostic significance of arrhythmia is unknown. To determine the prevalence of arrhythmia and its relation to prognosis, 2 days of ECG monitoring was performed in 6 infants, 14 children and 33 adolescents with hypertrophic cardiomyopathy receiving no cardioactive medications. An additional 1 to 9 days (median 2) of monitoring was performed in 29 patients. All patients had sinus rhythm; 4 adolescents had episodes of paroxysmal supraventricular tachycardia, a child with the Wolff-Parkinson-White syndrome had symptomatic reentrant atrioventricular tachycardia and 5 adolescents had asymptomatic nonsustained ventricular tachycardia. During follow-up of 1 week to 7 years (median 3 years), five patients died suddenly and two had successful resuscitation from out-of-hospital ventricular fibrillation; none of these seven patients had ventricular arrhythmias during 2 to 7 days (median 3) of ECG monitoring. The two patients with ventricular fibrillation, the five with ventricular tachycardia, the one with Wolff-Parkinson-White syndrome and the seven with recurrent syncope or adverse family history, or both, received low dose amiodarone. None of these "high risk" patients died during 6 months to 6 years (median 3 years) of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of free fatty acids on glycogen recovery in rat heart after exercise

Glycogen supercompensation is the term used to denote the abnormally high levels of glycogen found in the heart shortly after an exercise-induced reduction of the substrate. Using rats, we tested whether this condition was linked to the use of plasma free fatty acids (FFA), which normally rise with exercise. Before a 1-h swim, animals received an injection of either saline (S) or nicotinic acid (NA). The nicotinic acid treatment dramatically suppressed the rise in plasma FFA observed in the S-group. Exercise caused a significant but similar reduction (35-38%) of the myocardial glycogen content in both groups. After 1 h of recovery in the S-group, myocardial glycogen reached a value of 30.3 +/- 1.7 mumol x g-1 or 113% of that measured before the exercise began. In contrast, the value for hearts from the NA-group with reduced FFA levels was 24.0 +/- 1.9 mumol x g-1 or only 91% of that measured before exercise. After 2 h the values were 33.8 +/- 1.4 and 29.0 +/- 1.9 mumol x g-1 respectively. These data indicate that glycogen repletion in rat heart after exercise is related to the amount of FFA present in the plasma. We suggest that carbohydrate metabolism is diverted towards synthesis and storage as a result of the glycolytic inhibition exerted by the increased use of fat as an energy source as previously observed in hearts from fasted or diabetic animals.