Norepinephrine Signals Through Astrocytes To Modulate Synapses.

Locus coeruleus (LC)-derived norepinephrine (NE) drives network and behavioral adaptations to environmental saliencies by reconfiguring circuit connectivity, but the underlying synapse-level mechanisms are elusive. Here, we show that NE remodeling of synaptic function is independent from its binding on neuronal receptors. Instead, astrocytic adrenergic receptors and Ca2+ dynamics fully gate the effect of NE on synapses as the astrocyte-specific deletion of adrenergic receptors and three independent astrocyte-silencing approaches all render synapses insensitive to NE. Additionally, we find that NE suppression of synaptic strength results from an ATP-derived and adenosine A1 receptor-mediated control of presynaptic efficacy. An accompanying study from Chen et al. reveals the existence of an analogous pathway in the larval zebrafish and highlights its importance to behavioral state transitions. Together, these findings fuel a new model wherein astrocytes are a core component of neuromodulatory systems and the circuit effector through which norepinephrine produces network and behavioral adaptations, challenging an 80-year-old status quo.

Long-Term Health Outcomes of Limb Salvage Compared with Amputation for Combat-Related Trauma.

BACKGROUND: There are little long-term health data, particularly in terms of body composition and development of metabolic syndromes, to help surgeons to guide the decision between limb salvage and amputation in patients with limb-threatening trauma. The purpose of this study was to compare long-term health outcomes after high-energy lower-extremity trauma between patients who underwent attempted flap-based limb salvage or amputation. METHODS: We performed a retrospective review of servicemembers with a minimum 10-year follow-up who underwent flap-based limb salvage followed by unilateral amputation or continued limb salvage after combat-related, lower-extremity trauma between 2005 and 2011. Patient demographic characteristics, injury characteristics, and health outcomes including body mass index (BMI) and development of metabolic disease (e.g., hyperlipidemia, hypertension, heart disease, and diabetes) were compared between treatment cohorts. Adjusted BMIs were calculated for the amputation cohort to account for lost surface area. We performed multivariable and propensity score analysis to determine the likelihood of developing obesity or metabolic disease. RESULTS: In this study, 110 patients had available long-term follow-up (mean, 12.2 years) from the time of the injury. Fifty-six patients underwent limb salvage and 54 patients underwent unilateral amputation. There was no difference in preinjury BMI (p = 0.30). After adjusting for limb loss, the amputation cohort had a trend toward higher BMIs at ≥1 years after the injury, a higher rate of obesity, and a greater increase in BMI from baseline after the injury. The development of metabolic comorbidities was common after both amputation (23 [43%] of 54) and limb salvage (27 [48%] of 56). With the numbers available, we were unable to demonstrate a difference in risk for the development of hypertension, hyperlipidemia, diabetes, heart disease, or any comorbidity other than obesity (p > 0.05). CONCLUSIONS: Amputations may be medically necessary and may decrease pain, improve mobility, and/or expedite return to activity compared with limb salvage after similar injuries. However, limb loss may negatively impact metabolic regulation and may contribute to a higher risk of obesity despite beneficial effects on mobility. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Severe blistering eruptions induced by immune checkpoint inhibitors: a multicentre international study of 32 cases.

Among dermatologic adverse events induced by immune checkpoint inhibitors (ICI), bullous life-threatening reactions are rare. To better define the clinical and histological features, treatment, and prognosis of ICI-related severe blistering cutaneous eruptions. This retrospective case series was conducted between 2014/05/15 and 2021/04/15 by the dermatology departments of four international registries involved in drug reactions. Inclusion criteria were age ≥18 years old, skin eruption with blisters with detachment covering ≥1% body surface area and at least one mucous membrane involved, available pictures, and ICI as suspect drug. Autoimmune bullous disorders were excluded. Each participant medical team gave his own diagnosis conclusion: epidermal necrolysis (EN), severe lichenoid dermatosis (LD), or unclassified dermatosis (UD). After a standardized review of pictures, cases were reclassified by four experts in EN or LD/UD. Skin biopsies were blindly reviewed. Thirty-two patients were included. Median time to onset was 52 days (3-420 days). Cases were originally diagnosed as EN in 21 cases and LD/UD in 11 cases. After review by experts, 10/21 EN were reclassified as LD/UD. The following manifestations were more frequent or severe in EN: fever, purpuric macules, blisters, ocular involvement, and maximal detachment. Most patients were treated with topical with or without systemic corticosteroids. Eight patients (25%) died in the acute phase. The culprit ICI was not resumed in 92% of cases. In three patients, another ICI was given with a good tolerance. Histology did not reveal significant differences between groups. Severe blistering cutaneous drug reactions induced by ICI are often overdiagnosed as EN. Consensus for management is pending.

Palbociclib versus abemaciclib in HR+/HER2- advanced breast cancer: an indirect comparison of patient-reported end points.

Aim: To assess the relative impact of palbociclib plus fulvestrant (PAL + FUL) and abemaciclib plus fulvestrant (ABEM + FUL) on patient-reported outcomes in patients with hormone receptor-positive, HER2-negative (HR+/HER2-) advanced breast cancer. Patients & methods: Anchored matching-adjusted indirect comparisons were conducted using individual patient data from PALOMA-3 (PAL + FUL) and summary-level data from MONARCH-2 (ABEM + FUL). Outcomes included the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 items (EORTC QLQ-C30) and its breast cancer-specific module (QLQ-BR23). Results: Significantly different changes from baseline favoring PAL + FUL compared with ABEM + FUL were observed in global quality of life (6.95 [95% CI: 2.19-11.71]; p = 0.004) and several functional/symptom scales, including emotional functioning, nausea/vomiting, appetite loss, diarrhea and systemic therapy side effects. Conclusion: PAL + FUL was associated with more favorable patient-reported outcomes than ABEM + FUL in patients with HR+/HER2- advanced breast cancer.

Assessment of Treatment Approaches and Outcomes in Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: Insights From a Pan-European Multicenter Study.

IMPORTANCE: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe drug reactions associated with a high rate of mortality and morbidity. There is no consensus on the treatment strategy. OBJECTIVE: To explore treatment approaches across Europe and outcomes associated with the SJS/TEN disease course, as well as risk factors and culprit drugs. DESIGN, SETTING, AND PARTICIPANTS: A retrospective pan-European multicenter cohort study including 13 referral centers belonging to the ToxiTEN ERN-skin subgroup was conducted. A total of 212 adults with SJS/TEN were included between January 1, 2015, and December 31, 2019, and data were collected from a follow-up period of 6 weeks. MAIN OUTCOMES AND MEASURES: Risk factors for severe acute-phase complications (acute kidney failure, septicemia, and need for mechanical ventilation) and mortality 6 weeks following admission were evaluated using a multivariable-adjusted logistic regression model. One tool used in evaluation of severity was the Score of Toxic Epidermal Necrolysis (SCORTEN), which ranges from 0 to 7, with 7 the highest level of severity. RESULTS: Of 212 patients (134 of 211 [63.7%] women; mean [SD] age, 51.0 [19.3] years), the mean (SD) body surface area detachment was 27% (32.8%). In 176 (83.0%) patients, a culprit drug was identified. Antibiotics (21.2%), followed by anticonvulsants (18.9%), nonsteroidal anti-inflammatory drugs (11.8%), allopurinol (11.3%), and sulfonamides (10.4%), were the most common suspected agents. Treatment approaches ranged from best supportive care only (38.2%) to systemic glucocorticoids (35.4%), intravenous immunoglobulins (23.6%), cyclosporine (10.4%), and antitumor necrosis factor agents (3.3%). Most patients (63.7%) developed severe acute-phase complications. The 6-week mortality rate was 20.8%. Maximal body surface area detachment (≥30%) was found to be independently associated with severe acute-phase complications (fully adjusted odds ratio [OR], 2.49; 95% CI, 1.21-5.12; P = .01) and SCORTEN greater than or equal to 2 was significantly associated with mortality (fully adjusted OR, 10.30; 95% CI, 3.82-27.78; P < .001). Cyclosporine was associated with a higher frequency of greater than or equal to 20% increase in body surface area detachment in the acute phase (adjusted OR, 3.44; 95% CI, 1.12-10.52; P = .03) and an increased risk of infections (adjusted OR, 7.16; 95% CI, 1.52-33.74; P = .01). Systemic glucocorticoids and intravenous immunoglobulins were associated with a decreased risk of infections (adjusted OR, 0.40; 95% CI, 0.18-0.88; P = .02). No significant difference in 6-week mortality was found between treatment groups. CONCLUSIONS AND RELEVANCE: This cohort study noted differences in treatment strategies for SJS/TEN in Europe; the findings suggest the need for prospective therapeutic studies to be conducted and registries to be developed.

A scoping review of physical activity interventions for older adults.

BACKGROUND: To inform implementation and future research, this scoping review investigates the volume of evidence for physical activity interventions among adults aged 60+. Our research questions are: (1) what is the evidence regarding interventions designed to increase total physical activity in adults aged 60+ years, in accordance with three of the four strategic objectives of GAPPA (active societies, active environments, active people); (2) what is the current evidence regarding the effectiveness of physical activity programmes and services designed for older adults?; and (3) What are the evidence gaps requiring further research? METHODS: We searched PEDro, MEDLINE, CINAHL and Cochrane from 1 January 2010 to 1 November 2020 for systematic reviews and meta-analyses of physical activity interventions in adults aged 60+. We identified interventions designed to: (1) increase physical activity; and (2) deliver physical activity programmes and services in home, community or outpatient settings. We extracted and coded data from eligible reviews according to our proposed framework informed by TIDieR, Prevention of Falls Network Europe (PROFANE), and WHO's International Classification of Functioning, Disability and Health (ICF). We classified the overall findings as positive, negative or inconclusive. RESULTS: We identified 39 reviews of interventions to increase physical activity and 342 reviews of programmes/services for older adults. Interventions were predominantly structured exercise programmes, including balance strength/resistance training, and physical recreation, such as yoga and tai chi. There were few reviews of health promotion/coaching and health professional education/referral, and none of sport, workplace, sociocultural or environmental interventions. Fewer reported outcomes of total physical activity, social participation and quality of life/well-being. We noted insufficient coverage in diverse and disadvantaged samples and low-middle income countries. CONCLUSIONS: There is a modest but growing volume of evidence regarding interventions designed to increase total physical activity in older adults, although more interventional studies with long term follow-up are needed, particularly for GAPPA 1. Active Societies and GAPPA 2. Active Environments. By comparison, there is abundant evidence for GAPPA 3. specific programmes and services, but coverage of sport and workplace interventions, and diverse samples and settings is lacking. Comprehensive reviews of individual studies are now needed as well as research targeting neglected outcomes, populations and settings.

High Frequency Spectral Ultrasound Imaging Detects Early Heterotopic Ossification in Rodents.

Heterotopic ossification (HO) is a devastating condition in which ectopic bone forms inappropriately in soft tissues following traumatic injuries and orthopedic surgeries as a result of aberrant mesenchymal progenitor cell (MPC) differentiation. HO leads to chronic pain, decreased range of motion, and an overall decrease in quality of life. While several treatments have shown promise in animal models, all must be given during early stages of formation. Methods for early determination of whether and where endochondral ossification/soft tissue mineralization (HO anlagen) develop are lacking. At-risk patients are not identified sufficiently early in the process of MPC differentiation and soft tissue endochondral ossification for potential treatments to be effective. Hence, a critical need exists to develop technologies capable of detecting HO anlagen soon after trauma, when treatments are most effective. In this study, we investigate high frequency spectral ultrasound imaging (SUSI) as a noninvasive strategy to identify HO anlagen at early time points after injury. We show that by determining quantitative parameters based on tissue organization and structure, SUSI identifies HO anlagen as early as 1-week postinjury in a mouse model of burn/tenotomy and 3 days postinjury in a rat model of blast/amputation. We analyze single cell RNA sequencing profiles of the MPCs responsible for HO formation and show that the early tissue changes detected by SUSI match chondrogenic and osteogenic gene expression in this population. SUSI identifies sites of soft tissue endochondral ossification at early stages of HO formation so that effective intervention can be targeted when and where it is needed following trauma-induced injury. Furthermore, we characterize the chondrogenic to osteogenic transition that occurs in the MPCs during HO formation and correlate gene expression to SUSI detection of the HO anlagen.

Development of Gene-Targeted Polypyridyl Triplex-Forming Oligonucleotide Hybrids.

In the field of nucleic acid therapy there is major interest in the development of libraries of DNA-reactive small molecules which are tethered to vectors that recognize and bind specific genes. This approach mimics enzymatic gene editors, such as ZFNs, TALENs and CRISPR-Cas, but overcomes the limitations imposed by the delivery of a large protein endonuclease which is required for DNA cleavage. Here, we introduce a chemistry-based DNA-cleavage system comprising an artificial metallo-nuclease (AMN) that oxidatively cuts DNA, and a triplex-forming oligonucleotide (TFO) that sequence-specifically recognises duplex DNA. The AMN-TFO hybrids coordinate CuII ions to form chimeric catalytic complexes that are programmable - based on the TFO sequence employed - to bind and cut specific DNA sequences. Use of the alkyne-azide cycloaddition click reaction allows scalable and high-throughput generation of hybrid libraries that can be tuned for specific reactivity and gene-of-interest knockout. As a first approach, we demonstrate targeted cleavage of purine-rich sequences, optimisation of the hybrid system to enhance stability, and discrimination between target and off-target sequences. Our results highlight the potential of this approach where the cutting unit, which mimics the endonuclease cleavage machinery, is directly bound to a TFO guide by click chemistry.

Osseointegrated prostheses for the rehabilitation of amputees (OPRA): results and clinical perspective.

Introduction: Patients who undergo extremity amputation have historically used socket prosthetics to ambulate and perform daily functions; however, these prosthetics can be limited by poor terminal control and wear issues. In patients who have difficulty wearing their prostheses or with upper extremity amputations, osseointegrated implants may offer better function and quality of life. The Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA) was the first such device to become commercially available. Clinical trials have demonstrated benefit in patient gait, prosthetic use, and overall well-being, and new implants may be applied for various amputation levels.Areas covered: The OPRA, the most studied osseointegrated prosthetic stem, is reviewed, presenting indications, surgical procedure, complications, and results of clinical studies.Expert commentary: Osseointegration for amputees is an expanding field that has the potential to enhance rehabilitative potential. The OPRA implant is an effective device with a long life-span and low complication profile.

Acute dietary zinc deficiency in rats exacerbates myocardial ischaemia-reperfusion injury through depletion of glutathione.

Zn plays an important role in maintaining the anti-oxidant status within the heart and helps to counter the acute redox stress that occurs during myocardial ischaemia and reperfusion. Individuals with low Zn levels are at greater risk of developing an acute myocardial infarction; however, the impact of this on the extent of myocardial injury is unknown. The present study aimed to compare the effects of dietary Zn depletion with in vitro removal of Zn (N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN)) on the outcome of acute myocardial infarction and vascular function. Male Sprague-Dawley rats were fed either a Zn-adequate (35 mg Zn/kg diet) or Zn-deficient (<1 mg Zn/kg diet) diet for 2 weeks before heart isolation. Perfused hearts were subjected to a 30 min ischaemia/2 h reperfusion (I/R) protocol, during which time ventricular arrhythmias were recorded and after which infarct size was measured, along with markers of anti-oxidant status. In separate experiments, hearts were challenged with the Zn chelator TPEN (10 µm) before ischaemia onset. Both dietary and TPEN-induced Zn depletion significantly extended infarct size; dietary Zn depletion was associated with reduced total cardiac glutathione (GSH) levels, while TPEN decreased cardiac superoxide dismutase 1 levels. TPEN, but not dietary Zn depletion, also suppressed ventricular arrhythmias and depressed vascular responses to nitric oxide. These findings demonstrate that both modes of Zn depletion worsen the outcome from I/R but through different mechanisms. Dietary Zn deficiency, resulting in reduced cardiac GSH, is the most appropriate model for determining the role of endogenous Zn in I/R injury.

Developing a Novel Model to Improve Research and care for Cancer Survivors: a Feasibility Study.

Despite a growing number of clinical trials and supportive care programs for cancer survivors, recruitment of patients for these opportunities during the survivorship phase of care is challenging. We piloted a novel process to systematically educate patients about available research studies and supportive care programs as part of a survivorship care visit. Between 3/2015 and 8/2015, patients seen in the Adult Survivorship Program who had not previously received a treatment summary and survivorship care plan (TS/SCP) were provided with one accompanied by a list of survivorship research studies and care programs tailored to their diagnosis. Survivorship providers discussed the opportunities and recorded whether the patient was interested in relevant studies and placed referrals to study staff. Following the visit, we tracked study enrollment and surveyed patients about their experience. Fifty of 56 (89%) pilot participants completed the survey. Almost all (98%) reported that the TS/SCP visit and document helped with knowledge of research opportunities and supportive care interventions. Following receipt of the TS/SCP, 44% were interested in at least one study and in further follow-up with research staff. Of the 30 survivors eligible for at least one study, 6 (20%) have enrolled in at least one study to date. This pilot program demonstrates that the systematic sharing of available clinical studies and supportive care programming as part of a survivorship care plan visit is feasible and well received by cancer survivors and may facilitate and enhance accrual to clinical trials in the survivorship phase of care.

GPR55 deficiency is associated with increased adiposity and impaired insulin signaling in peripheral metabolic tissues.

Emerging evidence indicates that G-protein coupled receptor 55 (GPR55), a nonclassic receptor of the endocannabinoid system that is activated by L-α-lysophosphatidylinositol and various cannabinoid ligands, may regulate endocrine function and energy metabolism. We examined how GPR55 deficiency and modulation affects insulin signaling in skeletal muscle, adipose tissue, and liver alongside expression analysis of proteins implicated in insulin action and energy metabolism. We show that GPR55-null mice display decreased insulin sensitivity in these tissues, as evidenced by reduced phosphorylation of PKB/Akt and its downstream targets, concomitant with increased adiposity and reduced physical activity relative to wild-type counterparts. Impaired tissue insulin sensitivity coincided with reduced insulin receptor substrate-1 abundance in skeletal muscle, whereas in liver and epididymal fat it was associated with increased expression of the 3-phosphoinoistide lipid phosphatase, phosphatase and tensin homolog. In contrast, GPR55 activation enhanced insulin signaling in cultured skeletal muscle cells, adipocytes, and hepatocytes; this response was negated by receptor antagonists and GPR55 gene silencing in L6 myotubes. Sustained GPR55 antagonism in 3T3-L1 adipocytes enhanced expression of proteins implicated in lipogenesis and promoted triglyceride accumulation. Our findings identify GPR55 as a positive regulator of insulin action and adipogenesis and as a potential therapeutic target for countering obesity-induced metabolic dysfunction and insulin resistance.-Lipina, C., Walsh, S. K., Mitchell, S. E., Speakman, J. R., Wainwright, C. L., Hundal, H. S. GPR55 deficiency is associated with increased adiposity and impaired insulin signaling in peripheral metabolic tissues.

Fluorogenic thiazole orange TOTFO probes stabilise parallel DNA triplexes at pH 7 and above.

The instability of DNA triplexes particularly at neutral pH and above severely limits their applications. Here, we demonstrate that the introduction of a thiazole orange (TO) intercalator onto a thymine nucleobase in triplex forming oligonucleotides (TFOs) resolves this problem. The stabilising effects are additive; multiple TO units produce nanomolar duplex binding and triplex stability can surpass that of the underlying duplex. In one example, a TFO containing three TO units increased the triplex melting temperature at pH 7 by a remarkable 50 °C relative to the unmodified triplex. Notably, TO intercalation promotes TFO binding to target sequences other than pure polypurine tracts by the use of 5-(1-propynyl)cytosine (pC) against C:G inversions. By overcoming the instability of triplexes across a broad range of pH and sequence contexts, these very simple 'TOTFO' probes could expand triplex applications into many areas including diagnostics and cell imaging.

A review of the musculoskeletal manifestations of sarcoidosis.

Sarcoidosis is a systemic disease of unknown aetiology that is characterized by granulomatous inflammation that can develop in almost any organ system. Musculoskeletal manifestations are seen in up to one-third of patients, ranging from arthralgia through to widespread destructive bone lesions. Inflammatory tendon lesions and periarticular swelling are more common than true joint synovitis. Despite advances in our understanding of the pathophysiology of the disease, diagnosis remains challenging. Definitive diagnosis, irrespective of organ site involvement, hinges on histological confirmation of non-caseating granuloma combined with an appropriate clinical syndrome. Musculoskeletal involvement usually develops early in the disease course. Imaging modalities, particularly fluorodeoxyglucose PET, are helpful in delineating the extent of involvement and measuring disease activity. Bone involvement may only become apparent following isotope imaging. Corticosteroids remain the cornerstone of treatment. MTX is the steroid-sparing agent of choice unless there is renal involvement. Biologic therapies are sometimes used in severe disease, although the evidence base for efficacy is inconsistent.

Oncofertility: Fertile Ground for Conflict Between Patient Autonomy and Medical Values.

Oncofertility is a unique, multidisciplinary field that serves to bridge the gap between available fertility resources and the special reproductive needs of cancer patients. Oncofertility is a growing field due to the increasing number of survivors, development of new oncologic therapies, extension of duration of therapies, and development and refinement of reproductive therapies. While the technologies and demand for services expand, clinicians need to be appropriately prepared for dealing with various clinical scenarios that may require ethical deliberation. Three real cases are presented in which the patient wishes to pursue reproductive assistance, but her decision is met with hesitance or uncertainty by her care team. Discussion of these clinical scenarios highlights ethical implications of oncofertility practice and serves to highlight the need for the establishment of multidisciplinary care teams and guidelines to support both clinicians and patients. IMPLICATIONS FOR PRACTICE: The growing field of oncofertility is ripe for conflict between patient autonomy and medical values due to the nature of cancer and associated threat on an individual's health and survival, as well as the personal significance of childbearing. Cases are presented and ethical implications are discussed to further explore the inherent difficulties in oncofertility practice and guide clinicians in similar situations. Developing guidelines and establishing multidisciplinary teams to facilitate oncofertility discussions and care, as well as training of clinical team members, may improve patient safety, well-being, and satisfaction within the context of fertility decision making, care, and outcomes.

Feasibility and Acceptability of a Web Site to Promote Survivorship Care in Survivors of Hodgkin Disease.

PURPOSE: Evaluate rates of enrollment, completion, and patient-reported acceptability of an educational survivorship-care Web site for survivors of Hodgkin disease (HD). PATIENTS AND METHODS: The study was a mixed-method evaluation design. Eligible participants were adults who had completed treatment of a primary diagnosis of HD ≥ 2 years before enrollment. Patients were recruited through postal mail and telephone and were asked to review a Web site, complete an adapted version of the Acceptability E-scale (total score of 24 or greater indicates acceptability), and respond to a structured telephone or e-mail interview to discuss experiences with the Web site. RESULTS: Of 259 potentially eligible participants identified by medical record review, 124 survivors had confirmed contact with study staff and were invited to participate; 63 people (50.8%; 90% CI, 43% to 59%) enrolled; 37 participants (58.7%) were men. The median age at time of enrollment was 51.0 years (range, 29.3 to 80.0 years), and the median time since completion of treatment of HD was 14.9 years (range, 3 to 38.75 years). Overall, 82.5% of those enrolled viewed all Web site content. Forty-eight participants completed the acceptability survey, which resulted in a mean acceptability score of 26.5 (standard deviation, 3.5). The majority of enrollees (67%) completed a follow-up interview. CONCLUSION: Overall, HD survivor participants viewed the content and reviewed it favorably. A Web-based intervention is a promising way to provide survivors of HD with information about how to manage the long-term and late effects from cancer and treatment, and provide trusted survivorship resources.

[Nle3,d-Phe6 ]-γ2 -melanocyte-stimulating hormone possesses the renal excretory but not the cardiovascular actions of the native γ2 -melanocyte-stimulating hormone in anaesthetized rats.

The present study compared the cardiovascular and renal actions of γ(2) -melanocyte-stimulating hormone (γ(2) MSH) with those of the synthetic analogue [Nle(3) ,d-Phe(6) ]-γ(2) MSH (NDP-γ(2) MSH) and explored the effects of high dietary salt intake on the renal actions of NDP-γ(2) MSH. Both peptides were infused systemically (3-1000 nmol/kg) and intrarenally (500 fmol/min) into innervated and renally denervated rats fed either a normal (0.4% NaCl) or high-salt (4% NaCl; HS) diet. Mean arterial pressure (MAP), glomerular filtration rate (GFR), urinary sodium excretion (U(N) (a) V), urinary output (UV) and fractional sodium excretion were determined, as was expression of the melanocortin MC(3) receptor in inner medullary collecting duct (IMCD) epithelial cells. Both renal and systemic infusion of γ(2) MSH increased MAP by 23 ± 2% and 54 ± 4%, respectively, but equivalent doses of NDP-γ(2) MSH had no significant pressor effects. Both peptides had similar natriuretic and diuretic effects in rats fed a normal salt diet. However, NDP-γ(2) MSH increased U(N) (a) V and UV by two- to threefold in rats fed the normal salt diet and by six- to sevenfold in rats fed the HS diet. Furthermore, NDP-γ(2) MSH induced a 3.5-fold increase in GFR only in rats fed the HS diet. These renal effects of NDP-γ(2) MSH were not abolished by prior renal denervation. Rats fed the HS diet also exhibited a 4.5-fold increase in MC(3) receptor expression in IMCD epithelial cells. Intrarenal infusion of NDP-γ(2) MSH induced the natriuretic but not the cardiovascular effects exhibited by γ(2) MSH. The renal activities may be attributed to a direct binding of NDP-γ(2) MSH to MC(3) receptors expressed in IMCD cells, leading to a potent natriuretic effect that is independent of renal innervation.