Leveraging melanocortin pathways to treat glomerular diseases

The melanocortin receptor signaling system and its role in neuroprotection against neurodegeneration: Therapeutic insights

The melanocortin signaling system consists of the melanocortin peptides, their distinctive receptors, accessory proteins, and endogenous antagonists. Melanocortin peptides are small peptide hormones that have been studied in a variety of physiological and pathological conditions. There are five types of melanocortin receptors, and they are distributed within the central nervous system and in several tissues of the periphery. The G protein-coupled melanocortin receptors typically signal through adenylyl cyclase and other downstream signaling pathways. Depending on the ligand, surface expression of melanocortin receptor, receptor occupancy period, related proteins, the type of cell, and other parameters, the signaling pathways are complicated and pleiotropic. While it is known that all five melanocortin receptors are coupled to Gs, they can also occasionally couple to Gq or Gi. Both direct and indirect neuroprotection are induced by the melanocortin signaling system. Targeting several of the components of the melanocortin signaling system (ligands, receptors, accessory proteins, signaling effectors, and regulators) may provide therapeutic opportunities. Activation of the melanocortin system improves different functional traits in neurodegenerative diseases. There is a potential for additional melanocortin system interventions by interfering with dimerization or dissociation. This review aims to discuss the melanocortin receptor signaling system and its role in neuroprotection, as well as its therapeutic potential.

Melanocortin/MC5R axis regulates the proliferation of hematopoietic stem cells in mice after ionizing radiation injury

Hematopoietic stem cells (HSCs) possess great self-renewal and multidirectional differentiation abilities, which contribute to the continuous generation of various blood cells. Although many intrinsic and extrinsic factors have been found to maintain HSC homeostasis, the precise regulation of hematopoiesis under stress conditions is poorly understood. In this study, we show that melanocortin receptor 5 (MC5R) is abundantly expressed in hematopoietic stem progenitor cells (HSPCs). Using an MC5R knockout mouse model, we observed that it is not essential for steady-state hematopoiesis. Interestingly, the levels of α-melanocyte stimulating hormone (α-MSH), an important subtype of melanocortin, were elevated in the serum and bone marrow, and the expression of MC5R was upregulated in HSPCs from mice after irradiation. MC5R deficiency aggravates irradiation-induced myelosuppression because of impaired proliferation and reconstitution of HSCs. Further investigation revealed that the melanocortin/MC5R axis regulates the proliferation of HSCs by activating the PI3K/AKT and MAPK pathways. More importantly, α-MSH treatment can significantly accelerate hematopoietic recovery in irradiated mice. In conclusion, our data demonstrate that the melanocortin/MC5R axis plays a crucial role in regulating HSC proliferation under stress, thus providing a promising strategy to promote hematopoietic regeneration when suffering from injury.

Negative Modulation of B Cell Activation by Melanocortin 1 Receptor Signaling Protects against Membranous Nephropathy

SIGNIFICANCE STATEMENT

Emerging evidence suggests that melanocortin neuropeptides-specifically adrenocorticotropic hormone-offer a novel, steroidogenic-independent therapeutic modality for membranous nephropathy (MN). The molecular mechanism underlying this beneficial effect, however, remains largely elusive. To investigate whether melanocortins modulate humoral immunity, the authors induced passive Heymann nephritis, a model of human MN, in wild-type and melanocortin 1 receptor (MC1R) knockout rats and treated them with melanocortin agents. Additional rats received adoptive transfer of bone marrow-derived cells beforehand from wild-type or MC1R knockout rats. The findings indicate that MC1R signaling plays a key role in negative modulation of B-cell activation and thereby suppresses humoral immune responses in passive Heymann nephritis, and suggest that MC1R signaling might offer a novel B cell-targeted therapeutic strategy for MN.

BACKGROUND

Emerging evidence suggests that the pituitary neuropeptide melanocortins-specifically, adrenocorticotropic hormone-offer a novel nonsteroidogenic therapeutic modality for membranous nephropathy (MN). However, the mechanism(s) of action remains elusive.

METHODS

To investigate whether melanocortins modulate humoral immunity, we induced passive Heymann nephritis (PHN), a model of MN, in wild-type (WT) and melanocortin 1 receptor (MC1R) knockout (KO) rats. We treated the animals with melanocortin agents-repository corticotropin injection, the nonsteroidogenic pan-melanocortin receptor agonist [Nle 4 , DPhe 7 ]-α-melanocyte stimulating hormone, the selective MC1R agonist MS05, vehicle gel, or phosphate-buffered saline-and evaluated kidney function, histology, and molecular changes. Additional rats received adoptive transfer of syngeneic bone marrow-derived cells beforehand from WT or MC1R KO rats.

RESULTS

KO of MC1R worsened PHN and this was associated with increased deposition of autologous immunoglobulin G (IgG) and complement C5b-9 in glomeruli and higher circulating levels of autologous IgG-evidence of a sensitized humoral immune response. Melanocortin therapy ameliorated PHN in WT rats, coinciding with reduced glomerular deposition of autologous IgG and C5b -9. The beneficial efficacy of melanocortins was blunted in KO rats but restored by adoptive transfer of syngeneic bone marrow-derived cells derived from WT rats. Mechanistically, MC1R was expressed in B lymphocytes and was negatively associated with B cell activation. MC1R agonism triggered the expression of microphthalmia-associated transcription factor in activated B cells in a cAMP-dependent mode and also repressed the expression of interferon regulatory factor 4 (a lymphoid transcription factor essential for B-cell development and maturation), resulting in suppressed plasma cell differentiation and IgG production.

CONCLUSIONS

MC1R signaling negatively modulates B cell activation and suppresses humoral immune responses in PHN, suggesting that MC1R signaling might offer a novel therapeutic target for MN.

Hematopoietic-specific melanocortin 1 receptor signaling protects against nephrotoxic serum nephritis and mediates the beneficial effect of melanocortin therapy

The melanocortin hormone system has emerged as a novel therapeutic target for treating refractory glomerular diseases. However, the role of hematopoietic melanocortin 1 receptor (MC1R) signaling remains unknown. Upon insult by rabbit nephrotoxic serum, MC1R null-mutant mice developed more severe crescentic glomerulonephritis than wild-type mice, marked by aggravated proteinuria, kidney dysfunction and histologic lesions. Melanocortin therapy, using Repository Corticotropin Injection (Acthar Gel), the pan-melanocortin receptor agonist NDP-MSH, or the MC1R agonist MS05, ameliorated experimental nephritis in wild-type mice but this effect was blunted in null mice. Exacerbated experimental nephritis in null mice was associated with increased glomerular deposition of autologous IgG and C5b-9, in parallel with higher circulating levels of autologous IgG2c and IgG3. Additionally, the Th1 immune response was potentiated in null mice with experimental nephritis, accompanied by diminished kidney FoxP3+ regulatory T cells. Kidney infiltration of macrophages was also augmented by MC1R deficiency with an enhanced M1 polarization. Moreover, adoptive transfer of syngeneic bone marrow-derived cells from wild-type mice mitigated experimental nephritis in null mice and restored the beneficial efficacy of melanocortins. Mechanistically, MC1R was expressed by diverse subsets of kidney leukocytes, including macrophages, T and B lymphocytes, and was inversely associated with the NFκB pathway, a key player in immune responses. MS05 attenuated the production of rabbit IgG-specific IgG2c and IgG3 in cultured wild-type splenocytes, and promoted M2 polarization in M1-primed wild-type macrophages, associated with NFκB inhibition. In contrast, in null splenocytes or macrophages, this effect of MS05 was barely detectable, but was mimicked by an NFκB inhibitor. Thus, hematopoietic MC1R signaling attenuates experimental nephritis and mediates the beneficial effect of melanocortin therapy via, in part, regulating the immune response.

Real-word adrenocorticotropic hormone treatment for childhood-onset nephrotic syndrome

Background

Current first-line anti-proteinuric treatments do not produce a satisfactory therapeutic effect in a considerable number of patients with nephrotic syndrome (NS). Interest in adrenocorticotropic hormone (ACTH) for the treatment of NS has recently been revived. The present study investigated the efficacy and safety of ACTH treatment in children with frequent relapsing NS (FRNS), steroid-dependent NS (SDNS), and steroid-resistant NS (SRNS).

Method

The ACTH treatment group was comprised of NS patients receiving ACTH treatment. Patients with serum cortisol concentrations <85.3 nmol/L and who had not received ACTH treatment previously were enrolled in the control group from January 2018 to January 2021. The maintenance dose of prednisone, the number of disease recurrences, the time of first disease relapse, immunosuppressant use, serum cortisol levels, and adverse events were recorded in both groups.

Results

Fifty-one patients were included in the ACTH group, and twenty-one patients were enrolled in the control group. Concurrent treatment with one or more immunosuppressive and/or cytotoxic treatments occurred in 92.2% and 85.7% of patients in the ACTH and control groups, respectively, throughout the study period. A greater reduction in the prednisone maintenance dose was observed in the ACTH group compared with the control group after 1 year of follow up (0.603 ± 0.445 mg/kg vs. 0.267 ± 0.500 mg/kg, p = 0.006). During the one-year study period, fewer participants experienced one or more disease relapses in the ACTH group (45.1%) compared to the control group (76.2%, odds ratio = 3.896, p = 0.016). The number of disease recurrences per patient in the ACTH group was less than that in the control group (median difference = -1, p = 0.006). The mean length of remission was 8.902 m and 7.905 m in the ACTH group and control group, respectively. A log-rank test showed a longer relapse free survival for patients in the ACTH group (p = 0.046), but the Breslow test showed no significant difference between groups (p = 0.104). Ten patients in the ACTH group successfully discontinued all drug therapies. No patients in the control group were able to discontinue drug therapy as of February 2022.

Conclusion

ACTH, combined with multiple drugs, is effective at reducing the prednisone maintenance dose and may effectively prevent disease relapses in childhood NS.

How immunosuppressive drugs may directly target podocytes in glomerular diseases

Podocytes are the direct target of immunologic injury in many immune-mediated glomerular diseases, leading to proteinuria and subsequent kidney failure. Immunosuppressive agents such as steroids, calcineurin inhibitors, and rituximab are the commonly used treatment strategies in this context for their immunotherapeutic or anti-inflammatory properties. However, in recent years, studies have demonstrated that immunosuppressive agents can have a direct effect on podocytes, introducing the concept of the non-immunologic mechanism of kidney protection by immunomodulators. In this review, we focus on the mechanisms by which these agents may directly target the podocyte independent of their systemic effects and examine their clinical significance.

Pharmacological Melanocortin 5 Receptor Activation Attenuates Glomerular Injury and Proteinuria in Rats With Puromycin Aminonucleoside Nephrosis

Clinical evidence indicates that the melanocortin peptide ACTH is effective in inducing remission of nephrotic glomerulopathies like minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS), including those resistant to steroids. This suggests that a steroid-independent melancortinergic mechanism may contribute. However, the type of melanocortin receptor (MCR) that conveys this beneficial effect as well as the underlying mechanisms remain controversial. Burgeoning evidence suggests that MC5R is expressed in glomeruli and may be involved in glomerular pathobiology. This study aims to test the effectiveness of a novel highly selective MC5R agonist (MC5R-A) in puromycin aminonucleoside (PAN) nephrosis. Upon PAN injury, rats developed evident proteinuria on day 5, denoting an established nephrotic glomerulopathy. Following vehicle treatment, proteinuria continued to persist on day 14 with prominent histologic signs of podocytopathy, marked by ultrastructural glomerular lesions, including extensive podocyte foot process effacement. Concomitantly, there was loss of podocyte homeostatic markers, such as synaptopodin and podocin, and de novo expression of the podocyte injury marker desmin. Treatment with MC5R-A attenuated urine protein excretion and mitigated the loss of podocyte marker proteins, resulting in improved podocyte ultrastructural changes. In vitro in cultured podocytes, MC5R-A prevented the PAN-induced disruption of actin cytoskeleton integrity and apoptosis. MC5R-A treatment in PAN-injured podocytes also reinstated inhibitory phosphorylation and thus averted hyperactivity of GSK3β, a convergent point of multiple podocytopathic pathways. Collectively, pharmacologic activation of MC5R by using the highly selective small-molecule agonist is likely a promising therapeutic strategy to improve proteinuria and glomerular injury in protenuric nephropathies.

Synthetic ACTH for Treatment of Glomerular Diseases: A Case Series

Rationale:

Synthetic adrenocorticotropic hormone (Tetracosactide) has been used in the treatment of refractory glomerular diseases. Literature surrounding the use of this medication is limited to small case series and there is conflicting data on the rate of adverse events associated with this medication.

Presenting concerns of the patient:

Glomerulonephritis not in remission after at least 6 months of treatment with conservative care. Stable doses of concurrent immunosuppression were permitted.

Diagnoses:

Membranous nephropathy, IgA nephropathy, minimal change disease, and focal and segmental glomerulosclerosis.

Intervention:

Intramuscular synthetic adrenocorticotropic hormone (Tetracosactide, Synacthen Depot) with doses of either 1 mg weekly or 1 mg twice weekly.

Outcomes:

Five of 12 patients had at least a partial remission with Tetracosactide. Median time to response was 6 months for responders. Five of the 12 patients had adverse events documented, 2 of which led to treatment discontinuation. No patients with focal and segmental glomerulosclerosis responded to treatment.

Lessons Learned:

Higher rate of adverse events than previously reported with synthetic adrenocorticotropic hormone and uncertain treatment efficacy.

Advances in pediatric acute kidney injury

The objective of this study was to inform the pediatric nephrologists of recent advances in acute kidney injury (AKI) epidemiology, pathophysiology, novel biomarkers, diagnostic tools, and management modalities. Studies were identified from PubMed, EMBASE, and Google Scholar for topics relevant to AKI. The bibliographies of relevant studies were also reviewed for potential articles. Pediatric (0-18 years) articles from 2000 to May 2020 in the English language were included. For epidemiological outcomes analysis, a meta-analysis on data regarding AKI incidence, mortality, and proportion of kidney replacement therapy was performed and an overall pooled estimate was calculated using the random-effects model. Other sections were created highlighting pathophysiology, novel biomarkers, changing definitions of AKI, evolving tools for AKI diagnosis, and various management modalities. AKI is a common condition seen in hospitalized children and the diagnosis and management have shown to be quite a challenge. However, new standardized definitions, advancements in diagnostic tools, and the development of novel management modalities have led to increased survival benefits in children with AKI. IMPACT: This review highlights the recent innovations in the field of AKI, especially in regard to epidemiology, pathophysiology, novel biomarkers, diagnostic tools, and management modalities.

Adrenocorticotropic hormone: An expansion of our current understanding of the treatment for nephrotic syndrome

In clinical practice, we may encounter a treatment dilemma where in some patients with nephrotic syndrome are resistant to glucocorticoids or immunosuppressive agents. Thus, we currently lack viable treatment options and eagerly await the availability of new drugs. Adrenocorticotropic hormone (ACTH) had earlier been used to treat nephrotic syndrome in children, but has now become less popular owing to the advent of oral glucocorticoids. However, in recent studies, ACTH was reportedly used again for treating nephrotic syndrome, reducing proteinuria and protecting renal function, indicating a possibility for its use in the treatment of refractory nephrotic syndrome. This review analysed the validity of ACTH in these studies, focusing on the mechanism of action, application in both paediatric and adult patients with nephrotic syndrome, particularly in children, and possible side effects. We anticipate that our findings will help clinicians in treatment decision-making.

Repository Corticotropin in Treating de novo C3 Glomerulonephritis after Transplantation

Introduction

De novo C3 glomerulonephritis (C3GN) after transplant is uncommon. Although eculizumab has been used successfully in several cases, the response is heterogeneous, and treatment strategies remain undefined. The use of repository corticotropin in C3GN has not been described in the literature.

Case Report

A 48-year-old African American male with kidney transplantation secondary to presumed diabetic nephropathy presented 6 years after transplant with lower extremity edema and nephrotic range proteinuria. His urine protein to creatinine ratio (UPCR) was 8.2 g/g. Renal allograft biopsy confirmed the diagnosis of C3GN. He was treated with eculizumab (Solaris®) 900 mg IV once weekly for 4 weeks and repository corticotropin (H.P. Acthar® gel) 80 units SQ twice weekly for 6 months with a near-complete resolution of proteinuria within 3 months of the treatment. The patient presented again 6 months after completing the therapy with a recurrence of proteinuria, which peaked at 11.6 g/g of UPCR. Repeat kidney allograft biopsy was consistent with C3GN. He was started on repository corticotropin 80 units SQ twice weekly, which resulted in a reduction of proteinuria to >50% within 2 months of therapy. When eculizumab 900 mg IV weekly for 4 weeks was added with repository corticotropin, the proteinuria resolved within 10 weeks of treatment. The patient was maintained on monotherapy of repository corticotropin and has been in complete remission of proteinuria for more than a year until his last follow-up.

Conclusion

This is the first case report describing the role of repository corticotropin as an effective therapy in reducing proteinuria and maintaining patients with C3GN in proteinuria remission.

Mechanisms of Scarring in Focal Segmental Glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a histologic pattern characterized by focal glomerular scarring, which often progresses to systemic and diffuse glomerulosclerosis. Previous studies have emphasized that the initiation of classic FSGS occurs in podocytes. The dysfunction and loss of podocytes have been associated with the development of proteinuria and the progression of various diseases. In addition, primary, secondary, and genetic FSGS are caused by different mechanisms of podocyte injury.

SUMMARY

The potential sources and mechanism of podocyte supplementation are the focus of our current research. Increasing attention has been paid to the role played by parietal epithelial cells (PECs) during the progression of FSGS. PECs are not only the primary influencing factors in glomerulosclerosis lesions but also have repair abilities, which remain a focus of debate. Notably, other resident glomerular cells also play significant roles in the progression of this disease.

KEY MESSAGE

In this review, we focus on the mechanism of scarring in FSGS and discuss current and potential therapeutic strategies.

Melanocortin System in Kidney Homeostasis and Disease: Novel Therapeutic Opportunities

Melanocortin peptides, melanocortin receptors, melanocortin receptor accessory proteins, and endogenous antagonists of melanocortin receptors are the key components constituting the melanocortin hormone system, one of the most complex and important hormonal systems in our body. A plethora of evidence suggests that melanocortins possess a protective activity in a variety of kidney diseases in both rodent models and human patients. In particular, the steroidogenic melanocortin peptide adrenocorticotropic hormone (ACTH), has been shown to exert a beneficial effect in a number of kidney diseases, possibly via a mechanism independent of its steroidogenic activity. In patients with steroid-resistant nephrotic glomerulopathy, ACTH monotherapy is still effective in inducing proteinuria remission. This has inspired research on potential implications of the melanocortin system in glomerular diseases. However, our understanding of the role of the melanocortinergic pathway in kidney disease is very limited, and there are still huge unknowns to be explored. The most controversial among these is the identification of effector cells in the kidney as well as the melanocortin receptors responsible for conveying the renoprotective action. This review article introduces the melanocortin hormone system, summarizes the existing evidence for the expression of melanocortin receptors in the kidney, and evaluates the potential strategy of melanocortin therapy for kidney disease.

IgA Nephropathy: An Interesting Autoimmune Kidney Disease

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. It is a leading cause of chronic kidney disease and progresses to end-stage kidney disease in up to 40% of patients about 20 years after diagnosis. Additionally, IgAN is associated with significant mortality. The diagnosis currently necessitates a kidney biopsy, as no biomarker sufficiently specific and sensitive is available to supplant the procedure. Patients display significant heterogeneity in the epidemiology, clinical manifestations, renal progression, and long-term outcomes across diverse racial and ethnic populations. Recent advances in understanding the underlying pathophysiology of the disease have led to the proposal of a four-hit hypothesis supporting an autoimmune process. To date, there is no disease-specific treatment but, with a better understanding of the disease pathogenesis, new therapeutic approaches are currently being tested in clinical trials. In this review, we examine the multiple facets and most recent advances of this interesting disease.

Therapeutic Options for Recurrence of Primary Focal Segmental Glomerulonephritis (FSGS) in the Renal Allograft: Single-Center Experience

Focal Segmental Glomerulosclerosis (FSGS) recurrence after kidney transplantation (KTx) is relatively frequent and is associated with poor graft survival. The aim of this study was to investigate which management strategies were associated with better outcomes in our cohort of KTx recipients with primary FSGS. We retrospectively collected data on patients with primary FSGS who received a KTx between 1993 and 2019. A history of biopsy proven FSGS in native kidneys and new onset of significant proteinuria early post-KTx led to the diagnosis of recurrence, which was confirmed by graft biopsy. From 1993 to 2019 we performed 46 KTxs in patients with primary FSGS. We identified 26 episodes of recurrence in 25 patients, 67% of them occurring in males. They were younger at the time of KTx (33.8 vs. 41.1 years old, p = 0.067) and had progressed to end stage renal disease (ESRD) faster after FSGS diagnosis (61.4 vs. 111.2 months, p = 0.038), while they were less likely to have received prophylactic plasmapheresis (61.5% vs. 90%, p = 0.029). 76.7% of recurrences were found early, after a median of 0.5 months (IQR 0.1-1) with a median proteinuria was 8.5 (IQR 4.9-11.9) g/day. All patients with recurrence were treated with plasmapheresis, while 8 (30.7%) additionally received rituximab, 1 (3.8%) abatacept, and 4 (15.4%) ACTH. 7 (27%) patients experienced complete and 11 (42.3%) partial remission after a mean time of 3 (±1.79) and 4.4 (±2.25) months, respectively. Prognosis was worse for patients who experienced a recurrence. Eleven (42.3%) patients lost their graft from FSGS in a median time of 33 (IQR 17.5-43.3) months. In this series of patients, primary FSGS recurred frequently after KTx. Prophylacic plasmapheresis was shown efficacious in avoiding FSGS recurrence, while timely diagnosis and plasmapheresis-based regimens induced remission in more than half of the patients.

ACTH Treatment for Management of Nephrotic Syndrome: A Systematic Review and Reappraisal

BACKGROUND

In recent years, the use of adrenocorticotropic hormone (ACTH) therapy for treatment of proteinuria due to nephrotic syndrome (NS) has been heavily explored. ACTH therapy, which comes in the natural (H. P. Acthar Gel) or synthetic (tetracosactide) form, has resulted in remission in patients with immunosuppressive and steroid-resistant NS. However, the exact efficacy of ACTH therapy in the NS etiologies, such as membranous nephropathy (MN), focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), lupus nephritis (LN), IgA nephropathy (IgAN), and membranoproliferative glomerulonephritis (MPGN), has not been determined.

OBJECTIVE

This systematic review analyzed the published literature on ACTH therapy in various NS etiologies to determine its efficacy.

METHODS

A comprehensive search of MEDLINE, EMBASE, and Cochrane databases was conducted for articles through June 2019. An additional search was performed on clinicaltrials.gov to search for additional trials and cross reference the results of our database search. The literature which studied synthetic or natural ACTH treatment in patients with known etiologies of NS was included. Studies were excluded when they consisted of a single case report or did not analyze the lone effect of ACTH in NS.

RESULTS

The initial search yielded a total of 411 papers, and 22 papers were included. In 214 MN patients, there was an overall remission of 40% (85/214) and an overall remission of 43% (42/98) in FSGS patients. In other etiologies, there were overall remissions of 78% (11/14), 31% (5/16), 40% (16/40), and 62% (8/13) in MCD, LN, IgAN, and MPGN patients, respectively.

CONCLUSION

ACTH showed benefits in proteinuria reduction across all etiologies of NS. However, more randomized controlled studies with larger population sets and longer follow-ups are imperative to establish causal benefits. New studies into its efficacy in children are also necessary.

Melanocortin therapy ameliorates podocytopathy and proteinuria in experimental focal segmental glomerulosclerosis involving a podocyte specific non-MC1R-mediated melanocortinergic signaling

The clinical effectiveness of adrenocorticotropin in inducing remission of steroid-resistant nephrotic syndrome points to a steroidogenic-independent anti-proteinuric activity of melanocortins. However, which melanocortin receptors (MCR) convey this beneficial effect and if systemic or podocyte-specific mechanisms are involved remain uncertain. In vivo, wild-type (WT) mice developed heavy proteinuria and kidney dysfunction following Adriamycin insult, concomitant with focal segmental glomerulosclerosis (FSGS) and podocytopathy, marked by loss of podocin and synaptopodin, podocytopenia and extensive foot process effacement on electron microscopy. All these pathologic findings were prominently attenuated by NDP-MSH, a potent non-steroidogenic pan-MCR agonist. Surprisingly, MC1R deficiency in MC1R-null mice barely affected the severity of Adriamycin-elicited injury. Moreover, the beneficial effect of NDP-MSH was completely preserved in MC1R-null mice, suggesting that MC1R is likely non-essential for the protective action. A direct podocyte effect seems to contribute to the beneficial effect of NDP-MSH, because Adriamycin-inflicted cytopathic signs in primary podocytes prepared from WT mice were all mitigated by NDP-MSH, including apoptosis, loss of podocyte markers, de novo expression of the podocyte injury marker desmin, actin cytoskeleton derangement and podocyte hypermotility. Consistent with in vivo findings, the podoprotective activity of NDP-MSH was fully preserved in MC1R-null podocytes. Mechanistically, MC1R expression was predominantly distributed to glomerular endothelial cells in glomeruli but negligibly noted in podocytes in vivo and in vitro, suggesting that MC1R signaling is unlikely involved in direct podocyte protection. Ergo, melanocortin therapy protects against podocyte injury and ameliorates proteinuria and glomerulopathy in experimental FSGS, at least in part, via a podocyte-specific non-MC1R-mediated melanocortinergic signaling.

Melanocortin 5 receptor signaling pathway in health and disease

Melanocortin hormone system plays a key role in maintaining the homeostasis of our body via their neuro-immune-endocrine activities and regulates a diverse array of physiological functions, including melanogenesis, inflammation, immunomodulation, adrenocortical steroidogenesis, hemodynamics, natriuresis, energy homeostasis, sexual function, and exocrine secretion. The pathobiologic actions of all melanocortins are conveyed by melanocortin receptors. As the last melanocortin receptor to be cloned and characterized, melanocortin receptor 5 (MC5R) is widely expressed in both central nervous system and a number of peripheral organ systems in man. However, the exact effect of the MC5R mediated melanocortinergic signaling remains largely uncertain. Owing to the recent advances in developing highly selective peptidomimetic agonists and antagonists of MC5R and also to studies in MC5R knockout animals, our understanding of MC5R pathobiology has been greatly expanded and strengthened. Evidence suggests that MC5R plays a key role in governing immune reaction and inflammatory response, and is pivotal for the regulation of sexual behavior, thermoregulation, and exocrine secretion, like sebogenesis, lacrimal secretion and release of sex pheromones. As such, recent translational efforts have focused on developing novel sebum-suppressive therapies for seborrhoea and acne vulgaris based on antagonizing MC5R. Conversely, selective MC5R agonists have demonstrated promising beneficial effects in immune-mediated diseases, metabolic endocrinopathies and other disease conditions, such as glomerular diseases and dry eyes, skin and mouth. Thus, MC5R-mediated signaling is essential for health. Therapeutic targeting of MC5R represents a promising and pragmatic therapeutic strategy for diverse diseases. This review article delineates the biophysiology of MC5R-mediated biophysiology of the melanocortin hormone system, discusses the existing data on MC5R-targeted therapy in experimental disease models, and envisages the translational potential for treating human diseases.

Treatment of nephrotic syndrome: going beyond immunosuppressive therapy

It is indisputable that immunosuppressive therapy and pathological diagnosis of renal biopsy have greatly improved the prognosis of childhood nephrotic syndrome. Unfortunately, there is no "one-size-fits-all" approach for precise patient stratification and treatment when facing the huge challenges posed by steroid-resistant nephrotic syndrome (SRNS). But genomic medicine has brought a glimmer of light, and the cognition of SRNS has entered a new stage. Based on this, identification of single genetic variants of SRNS has recognized the key role of podocyte injury in its pathogenesis. Targeted treatment of podocyte injury is paramount, and immunosuppressant with podocyte-targeted therapy seems to be more suitable as the first choice for SRNS, that is, we need to pay attention to their additional non-immunosuppressive effects. In the same way, other effect factors of nephrotic syndrome and the related causes of immunosuppressive therapy resistance require us to select reasonable and targeted non-immunosuppressive therapies, instead of only blindly using steroids and immunosuppressants, which may be ineffective and bring significant side effects. This article provides a summary of the clinical value of identification of genetic variants in podocytes and non-immunosuppressive therapy for nephrotic syndrome in children.

Relapse of Nephrotic Syndrome after Adrenocorticotropic Hormone-Induced Remission: Implications of Adrenocorticotropic Hormone Antibodies

BACKGROUND

Prolonged use of corticosteroids continues to be the mainstay in the management of most proteinuric glomerulopathies, but is limited by extensive side effects. Alternative medications such as adrenocorticotropic hormone (ACTH) have been recently used to treat refractory glomerulopathies and have shown superior outcomes when compared with steroids. However, the clinical responsiveness to ACTH therapy varies considerably with a number of patients exhibiting de novo or acquired resistance. The underlying mechanism remains unknown.

METHODS

A patient with steroid-dependent focal segmental glomerulosclerosis (FSGS) developed severe steroid side effects impacting quality of life and was converted to repository porcine ACTH therapy. Immediate response in the form of remission of nephrotic syndrome was noted followed by relapse in 10 weeks. Suspecting the role of some ACTH-antagonizing factors, the patient's serum was examined.

RESULTS

Immunoblot-based antibody assay revealed high titers of de novo IgG antibodies in the patient's serum that were reactive to the porcine corticotropin with negligible cross-reactivity to human corticotropin. In vitro, in cultured B16 melanoma cells that express abundant melanocortin receptors, addition of the patient's serum substantially abrogated the porcine corticotropin triggered signaling activity of the melanocortinergic pathway, marked by phosphorylation of glycogen synthase kinase 3β, thus suggesting a mitigating effect on the biological functionality of porcine corticotropin.

CONCLUSION

ACTH is a useful alternative therapeutic modality for refractory proteinuric glomerulopathies like FSGS. However, as quintessential therapeutic biologics, natural ACTH, regardless of purity and origin, is inevitably antigenic and may cause the formation of neutralizing antibodies in some sensitive patients, followed by resistance to ACTH therapy. It is imperative to develop ACTH analogues with less immunogenicity for improving its responsiveness in patients with glomerular diseases.

Adrenocorticotropic Hormone in the Treatment of Focal Segmental Glomerulosclerosis Following Kidney Transplantation

This retrospective study examined the effect of adrenocorticotropic hormone therapy on remission of recurrent focal segmental glomerulosclerosis (FSGS) in patients with history of kidney transplant (KT) treated at 2 transplant centers. Patients with biopsy-confirmed FSGS following KT who received Acthar Gel (Mallinckrodt ARD, Bedminster, New Jersey, United States) treatment for ≥1 month were eligible. A total of 14 patients with idiopathic FSGS were included. Acthar Gel treatment resulted in complete remission of FSGS in 3 patients and partial remission in 2 patients for a total treatment response rate of 36% (5/14) of patients. Among patients showing complete or partial remission, Acthar Gel treatment duration ranged from 6 months to 2 years and 60% (3/5 patients) had serum creatinine ≤ 2 mg/dL at the start of Acthar Gel treatment. Patient outcomes suggest Acthar Gel may be an effective and tolerable treatment for recurrent FSGS in patients with history of KT. Early initiation of Acthar Gel treatment and therapy duration of at least 6 months may be needed for optimal response to Acthar Gel in patients with history of KT and recurrent FSGS.

New strategies and perspectives on managing IgA nephropathy

IgA nephropathy is an inflammatory renal disease characterised by the deposition of IgA in the glomerular mesangium and is the most commonly reported primary glomerulonephritis worldwide. Thirty to forty percent of patients with the disease develop progressive renal function decline, requiring renal replacement therapy within two decades of diagnosis. Despite this, accurate individual risk stratification at diagnosis and predicting treatment response remains a challenge. Furthermore, there are currently no disease specific treatments currently licensed to treat the condition due to long standing challenges in the nature and prevalence of the disease. Despite this, there have been exciting recent advances in the field that may represent paradigm shifts in the way IgA nephropathy is managed in the near future. In this review, we explore the evidence base informing current approaches to management and explore new strategies and future directions in the diagnosis and management of IgA nephropathy.

Use of Repository Corticotropin Gel (Acthar) in Progressive Nephrotic Syndrome Secondary to Transplant Glomerulopathy: A Report of Three Cases

Transplant glomerulopathy is a feared complication of kidney transplantation, often resulting in rapid loss of kidney function and ultimate graft failure. The underlying cause is unclear, with both antibody and cell-mediated immune mechanisms postulated, as well as intrinsic glomerular factors. At the present time, there is no known therapy. We report here 3 cases in which corticotropin gel (Acthar) was used with varying response of proteinuria and stabilization of graft function with continued graft survival as long as 10 years following the diagnosis. Future randomized controlled trials are warranted to examine the efficacy and safety of ACTH gel therapy in nephrotic patients with transplant glomerulopathy.

Management of steroid-resistant nephrotic syndrome in children and adolescents

More than 85% of children and adolescents (majority between 1-12 years old) with idiopathic nephrotic syndrome show complete remission of proteinuria following daily treatment with corticosteroids. Patients who do not show remission after 4 weeks' treatment with daily prednisolone are considered to have steroid-resistant nephrotic syndrome (SRNS). Renal histology in most patients shows presence of focal segmental glomerulosclerosis, minimal change disease, and (rarely) mesangioproliferative glomerulonephritis. A third of patients with SRNS show mutations in one of the key podocyte genes. The remaining cases of SRNS are probably caused by an undefined circulating factor. Treatment with calcineurin inhibitors (ciclosporin and tacrolimus) is the standard of care for patients with non-genetic SRNS, and approximately 70% of patients achieve a complete or partial remission and show satisfactory long-term outcome. Additional treatment with drugs that inhibit the renin-angiotensin axis is recommended for hypertension and for reducing remaining proteinuria. Patients with SRNS who do not respond to treatment with calcineurin inhibitors or other immunosuppressive drugs can show declining kidney function and are at risk for end-stage renal failure. Approximately a third of those who undergo renal transplantation show recurrent focal segmental glomerulosclerosis in the allograft and often respond to combined treatment with plasma exchange, rituximab, and intensified immunosuppression.

Targeting Regulatory T Cells for Transplant Tolerance: New Insights and Future Perspectives

Background

Organ transplantation is considered the ultimate therapy for end-stage organ disease. While pharmacologic immunosuppression is the mainstay of therapeutic strategies to prolong the survival of the graft, long-term use of immunosuppressive medications carries the risk of organ toxicity, malignancies, serious opportunistic infections, and diabetes. Therapies that promote recipient tolerance in solid organ transplantation are able to improve patient outcomes by eliminating the need for long-term immunosuppression.

Summary

Establishing tolerance to an allograft has become an area of intense study and would be the ideal therapy in clinical practice. The discovery of a subset of T cells naturally committed to perform immunoregulation has led to further investigation into their role in the immunopathogenesis of transplantation. Evidence suggests that regulatory T cells (Tregs) are fundamentally involved in promoting allograft tolerance. Efforts to characterize specific markers for Tregs, while challenging, have identified Foxp3 gene expression as a crucial step in promoting the tolerance-inducing features of Tregs. A number of approaches, including those based on targeting the glycogen synthase kinase 3β signaling pathway or activating the melanocortinergic pathway, have been tested as a way to promote Treg lineage commitment and maintenance as well as to facilitate immune tolerance. In order to be effective in clinical practice, Tregs must be allospecific and possess a specific phenotype to avoid suppression of other aspects of the immune system or increasing the risk of malignancy or infections. Multiple experimental and clinical studies have demonstrated the impact of currently used immunosuppressants on the immunoregulatory activities of Tregs and their Foxp3 expression status. Pharmacological induction of tolerogenic Tregs for inducing transplant tolerance, including epigenetic therapies, is in the ascendant.

Key Messages

Therapies that promote Treg function and survival may represent a novel strategy for achieving immune tolerance in transplant patients.

Repository corticotropin injection in multiple sclerosis: an update

Relapse management is a crucial component of multiple sclerosis care. Acute relapses are defined as new neurological symptoms or worsening of existing symptoms persisting for >24 h that are not attributable to heat, overexertion, or infection. The most commonly used treatment for multiple sclerosis relapse is a 3-5-day course of corticosteroids, primarily intravenous methylprednisolone with or without oral steroid taper. Repository corticotropin injection is also the US FDA-approved option for managing acute relapse, particularly in the patients with inadequate response, intolerability or allergy to corticosteroid treatment; poor venous access; or limited ability to receive home or clinic infusions.

G Protein-Coupled Receptors as Targets for Approved Drugs: How Many Targets and How Many Drugs?

Estimates vary regarding the number of G protein-coupled receptors (GPCRs), the largest family of membrane receptors that are targeted by approved drugs, and the number of such drugs that target GPCRs. We review current knowledge regarding GPCRs as drug targets by integrating data from public databases (ChEMBL, Guide to PHARMACOLOGY, and DrugBank) and from the Broad Institute Drug Repurposing Hub. To account for discrepancies among these sources, we curated a list of GPCRs currently targeted by approved drugs. As of November 2017, 134 GPCRs are targets for drugs approved in the United States or European Union; 128 GPCRs are targets for drugs listed in the Food and Drug Administration Orange Book. We estimate that ∼700 approved drugs target GPCRs, implying that approximately 35% of approved drugs target GPCRs. GPCRs and GPCR-related proteins, i.e., those upstream of or downstream from GPCRs, represent ∼17% of all protein targets for approved drugs, with GPCRs themselves accounting for ∼12%. As such, GPCRs constitute the largest family of proteins targeted by approved drugs. Drugs that currently target GPCRs and GPCR-related proteins are primarily small molecules and peptides. Since ∼100 of the ∼360 human endo-GPCRs (other than olfactory, taste, and visual GPCRs) are orphan receptors (lacking known physiologic agonists), the number of GPCR targets, the number of GPCR-targeted drugs, and perhaps the types of drugs will likely increase, thus further expanding this GPCR repertoire and the many roles of GPCR drugs in therapeutics.

Multiple Targets for Novel Therapy of FSGS Associated with Circulating Permeability Factor

A plasma component is responsible for altered glomerular permeability in patients with focal segmental glomerulosclerosis. Evidence includes recurrence after renal transplantation, remission after plasmapheresis, proteinuria in infants of affected mothers, transfer of proteinuria to experimental animals, and impaired glomerular permeability after exposure to patient plasma. Therapy may include decreasing synthesis of the injurious agent, removing or blocking its interaction with cells, or blocking signaling or enhancing cell defenses to restore the permeability barrier and prevent progression. Agents that may prevent the synthesis of the permeability factor include cytotoxic agents or aggressive chemotherapy. Extracorporeal therapies include plasmapheresis, immunoadsorption with protein A or anti-immunoglobulin, or lipopheresis. Oral or intravenous galactose also decreases P_alb activity. Studies of glomeruli have shown that several strategies prevent the action of FSGS sera. These include blocking receptor-ligand interactions, modulating cell reactions using indomethacin or eicosanoids 20-HETE or 8,9-EET, and enhancing cytoskeleton and protein interactions using calcineurin inhibitors, glucocorticoids, or rituximab. We have identified cardiotrophin-like cytokine factor 1 (CLCF-1) as a candidate for the permeability factor. Therapies specific to CLCF-1 include potential use of cytokine receptor-like factor (CRLF-1) and inhibition of Janus kinase 2. Combined therapy using multiple modalities offers therapy to reverse proteinuria and prevent scarring.

Clinical and Economic Evaluation of Repository Corticotropin Injection: A Narrative Literature Review of Treatment Efficacy and Healthcare Resource Utilization for Seven Key Indications

INTRODUCTION

Repository corticotropin injection (RCI; H.P. Acthar® Gel; Mallinckrodt Pharmaceuticals Inc., Hampton, NJ) is a highly purified, prolonged-release porcine preparation of adrenocorticotropic hormone (ACTH) analogue that is FDA-approved for treatment of 19 autoimmune and inflammatory disorders. The diverse physiological actions of RCI at the melanocortin receptors (MCRs) affect processes involved in inflammation, pigmentation, steroidogenesis, and immunomodulation. Although RCI has been approved to treat inflammatory and autoimmune diseases for more than 60 years, recent progress in understanding both MCRs and the effects of RCI in modulating immune responses has led to increased interest in RCI as a therapeutic choice. The objective of this narrative literature review is to summarize key clinical and economic data on RCI treatment of seven disorders: infantile spasms (IS), multiple sclerosis (MS) relapses, proteinuria in nephrotic syndrome, rheumatoid arthritis (RA), dermatomyositis/polymyositis (DM/PM), systemic lupus erythematosus (SLE), and symptomatic sarcoidosis based on published literature and product information. An extended report is available as the Academy of Managed Care Pharmacy (AMCP) Formulary dossier for H.P. Acthar® Gel.

METHODS

Key studies of clinical efficacy and healthcare utilization and cost from 1956 to 2016 are summarized.

RESULTS

The evidence supports the efficacy of RCI across the seven indications. RCI is effective as a first-line therapy for IS. For the other six conditions, RCI may improve clinical outcomes during exacerbations or when the condition is resistant to conventional treatments. Use of RCI is associated with reduced use of biologics, corticosteroids, and disease-modifying antirheumatic drugs. Initiation of RCI therapy in patients with IS, MS, RA, SLE, or DM/PM has been associated with lower post-therapy healthcare utilization and medical costs, including decreases in hospitalizations, hospital length of stay, outpatient visits, and emergency department visits.

CONCLUSION

The evidence suggests that RCI may improve inflammatory and autoimmune disease control and patient quality of life, particularly in complex patients, and yield healthcare cost savings that demonstrate the medicine's value.

FUNDING

Mallinckrodt Pharmaceuticals Inc.

Acquired Resistance to Corticotropin Therapy in Nephrotic Syndrome: Role of De Novo Neutralizing Antibody

There is increasing evidence supporting the use of corticotropin as an alternative treatment of refractory proteinuric glomerulopathies. The efficacy of short-acting corticotropin, however, remains unknown and was tested here in an adolescent with steroid-dependent nephrotic syndrome caused by minimal change disease. After developing Cushing syndrome and recently being afflicted with severe cellulitis, the patient was weaned off all immunosuppressants, including corticosteroids. This resulted in a relapse of generalized anasarca, associated with massive proteinuria and hypoalbuminemia. Subsequently, mono-therapy with short-acting animal-derived natural corticotropin was initiated and resulted in a rapid response, marked by substantial diuresis, reduction in body weight, and partial remission of proteinuria. Ten days later, the patient developed mild skin rash and subcutaneous nodules at injection sites. A relapse followed despite doubling the dose of corticotropin, consistent with delayed-onset resistance to treatment. Immunoblot-based antibody assay revealed de novo formation of antibodies in the patient's serum that were reactive to the natural corticotropin. In cultured melanoma cells known to express abundant melanocortin receptors, addition of the patient's serum strikingly mitigated dendritogenesis and cell signaling triggered by natural corticotropin, denoting neutralizing properties of the newly formed antibodies. Collectively, short-acting natural corticotropin seems effective in steroid-dependent nephrotic syndrome. De novo formation of neutralizing antibodies is likely responsible for acquired resistance to corticotropin therapy. The proof of concept protocols established in this study to examine the anticorticotropin neutralizing antibodies may aid in determining the cause of resistance to corticotropin therapy in future studies.

Sex-specific effects of LiCl treatment on preservation of renal function and extended life-span in murine models of SLE: perspective on insights into the potential basis for survivorship in NZB/W female mice

Considerable research effort has been invested in attempting to understand immune dysregulation leading to autoimmunity and target organ damage. In systemic lupus erythematosus (SLE), patients can develop a systemic disease with a number of organs involved. One of the major target organs is the kidney, but patients vary in the progression of the end-organ targeting of this organ. Some patients develop glomerulonephritis only, while others develop rapidly progressive end organ failure. In murine models of SLE, renal involvement can also occur. Studies performed over the past several years have indicated that treatment with LiCl of females, but not males of the NZB/W model, at an early age during the onset of disease, can prevent development of end-stage renal disease in a significant percentage of the animals. While on Li treatment, up to 80 % of the females can exhibit long-term survival with evidence of mild glomerulonephritis which does not progress to renal failure in spite of on-going autoimmunity. Stopping the treatment led to a reactivation of the disease and renal failure. Li treatment of other murine models of SLE was less effective and decreased survivorship in male BxSB mice, exhibited little effect on male MRL-lpr mice, and only modestly improved survivorship in female MRL-lpr mice. This perspective piece discusses the findings of several related studies which support the concept that protecting target organs such as the kidney, even in the face of continued immune insults and some inflammation, can lead to prolonged survival with retention of organ function. Some possible mechanisms for the effectiveness of Li treatment in this context are also discussed. However, the detailed mechanistic basis for the sex-specific effects of LiCl treatment particularly in the NZB/W model remains to be elucidated. Elucidating such details may provide important clues for development of effective treatment for patients with SLE, ~90 % of which are females.

Adrenocorticotropic hormone analog use for podocytopathies

BACKGROUND

Adrenocorticotropic hormone is being increasingly studied for treatment of various glomerulopathies, most notably membranous nephropathy. Less data are available regarding its use in idiopathic nephrotic syndrome (INS) secondary to minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). We report here our experience with H.P. Acthar(®) Gel (repository corticotropin injection) as first-line or subsequent therapy in patients with INS.

METHODS

Data were taken from three patients with MCD and ten patients with FSGS from around the US, who were treated with Acthar Gel as initial or subsequent therapy. Treatment was solely at the discretion of the primary nephrologist without a specific protocol. A complete response (CR) was defined as final urine protein-to-creatinine ratio <500 mg/g and a partial response (PR) as 50% decrease without rise of serum creatinine. Side effects and tolerability were noted.

RESULTS

All three patients with MCD received Acthar Gel as second-line or later immunosuppressive (IS) therapy and all responded (one CR and two PRs). Two of the ten patients with FSGS received Acthar Gel as first-line IS therapy, while the other eight had failed multiple agents. Four of the ten patients with FSGS had responses, including two CRs and two PRs. The three patients with MCD tolerated therapy well without side effects. Five patients with FSGS tolerated therapy well, while five had various steroid-like side effects, resulting in therapy discontinuation in two patients.

CONCLUSION

Acthar Gel is a viable alternative IS agent for treatment of INS in patients intolerant or resistant to conventional therapy. More data are needed to better define its appropriate place.

Efficacy and safety of adrenocorticotropic hormone treatment in glomerular diseases: a systematic review and meta-analysis

BACKGROUND

There is growing evidence that adrenocorticotropic hormone (ACTH) may be effective in treating various forms of glomerular diseases. However, the efficacy of treatment and frequency of adverse effects associated with the use of ACTH in glomerular diseases are unknown. A systematic review and meta-analysis of the literature was performed.

METHODS

A literature search was performed using Medline, Embase, Google Scholar and the Cochrane Database of Systematic Reviews from inception through 18 July 2015. Studies assessing the efficacy and safety of ACTH treatment in adults with glomerular diseases were included.

RESULTS

Of the 343 identified citations, 18 evaluated the drug efficacy and 12 evaluated the adverse effects. The most common glomerular diseases were membranous nephropathy (MN), primary focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD). The overall rate of complete remission in MN was 80% at 0-6 months, 69% at >6-12 months, 90% at >12-24 months and 95% beyond 24 months of follow-up. Fifty percent of primary FSGS and MCD patients treated with ACTH were in remission at 6 months, but the relapse rate was high after ACTH discontinuation (17%). Evidence of ACTH efficacy for other glomerular diseases was scarce. Edema was the most commonly reported adverse effect {incidence rate [IR] 0.10 [95% confidence interval (CI) 0.04-0.18]} followed by insomnia [IR 0.08 (95% CI 0.03-0.15)]. The dropout rate due to adverse events was 7%, mostly due to edema and weight gain.

CONCLUSIONS

ACTH is a well-tolerated therapy and is most promising when treating patients with MN. There may be a potential role for ACTH in patients with MCD and FSGS, but data are lacking.

The podocyte as a direct target for treatment of glomerular disease?

The Centers for Disease Control and Prevention estimates more than 10% of adults in the United States, over 20 million Americans, have chronic kidney disease (CKD). A failure to maintain the glomerular filtration barrier directly contributes to the onset of CKD. The visceral epithelial cells, podocytes, are integral to the maintenance of this renal filtration barrier. Direct podocyte injury contributes to the onset and progression of glomerular diseases such as minimal change disease (MCD), focal segmental glomerular sclerosis (FSGS), diabetic nephropathy, and HIV-associated nephropathy (HIVAN). Since podocytes are terminally differentiated with minimal capacity to self-replicate, they are extremely sensitive to cellular injury. In the past two decades, our understanding of the mechanism(s) by which podocyte injury occurs has greatly expanded. With this newfound knowledge, therapeutic strategies have shifted to identifying targets directed specifically at the podocyte. Although the systemic effects of these agents are important, their direct effect on the podocyte proves to be essential in ameliorating glomerular disease. In this review, we highlight the mechanisms by which these agents directly target the podocyte independent of its systemic effects.

Adrenocorticotropic hormone therapy for the treatment of idiopathic nephrotic syndrome in children and young adults: a systematic review of early clinical studies with contemporary relevance

Adrenocorticotropic hormone (ACTH) as a treatment for proteinuria due to nephrotic syndrome (NS) has re-emerged over the last decade. Current clinical data are primarily limited to adults with treatment-resistant NS. Largely unknown to today's clinicians is the existence of early clinical studies, following ACTH's introduction in the late 1940s, showing sustained proteinuria response in idiopathic NS in predominantly pediatric, treatment-naïve patients. Before ACTH, patients suffered severe edema and high mortality rates with no reliable or safe treatment. ACTH dramatically altered NS management, initially through recognition of diuresis effects and then through sustained proteinuria remission. This review synthesizes early clinical literature to inform current NS patient management. We undertook a MEDLINE search using MeSH terms "adrenocorticotropic hormone" and "nephrotic syndrome," with limits 1945-1965 and English. Sixty papers totaling 1137 patients were found; 14 studies (9 short-term, five long-term, N = 419 patients) met inclusion criteria. Studies were divided into two groups: short-term (≤28 days) and long-term (>5 weeks; short-term initial daily treatment followed by long-term intermittent)ACTH therapy and results were aggregated. An initial response, defined as a diuresis, occurred in 74 % of patients/treatment courses across nine short-term ACTH studies. Analyzed in eight of these studies, proteinuria response occurred in 56 % of patients/treatment courses. Across five long-term ACTH studies, proteinuria response was shown in 71 % of patients and was sustained up to 4.7 years following treatment. The inventory and re-evaluation of early clinical data broadens the evidence base of clinical experiences with ACTH for implementation of current treatment strategies and aiding the design of future studies.

Acthar gel in the treatment of nephrotic syndrome: a multicenter retrospective case series

Background

Current first-line anti-proteinuric treatments for nephrotic syndrome (NS) do not produce an effective response in all patients and are not tolerated by some patients. Additional effective and tolerable treatment options in NS are strongly needed. This retrospective case series is the largest to date to examine Acthar gel (adrenocorticotropic hormone, ACTH) in patients with varied-etiology NS.

Methods

This multicenter retrospective case series included adult patients with NS (N = 44) treated with Acthar gel at 6 clinical practices. NS etiologies included idiopathic focal segmental glomerulosclerosis (FSGS, 15), idiopathic membranous nephropathy (iMN, 11), IgA nephropathy (IgAN, 5), diabetic nephropathy (DN, 4), systemic lupus erythematosus class V membranous lupus nephritis (MLN, 2), minimal change disease (MCD, 2), membranoproliferative glomerulonephritis (MPGN, 1), fibrillary glomerulonephritis (FGN, 1), and unbiopsied NS (3). Proteinuria response was assessed as percent reduction from baseline and percent of patients meeting complete remission (final proteinuria <500 mg/d), partial remission (≥50 % reduction in proteinuria from baseline and final proteinuria 500–3500 mg/d), clinical response (≥30 % reduction in proteinuria from baseline that did not meet criteria for complete or partial remission), and no response (failed to meet remission or clinical response criteria) following Acthar gel therapy. Safety and tolerability were examined using adverse event (AE) frequency reported by patients or treating nephrologists and frequency of early discontinuation of treatment due to AEs.

Results

68.2 % (30/44) of patients had received prior NS treatment with immunosuppressive or cytotoxic therapies. Thirty-seven patients completed Acthar gel treatment. Seven patients (15.9 %) had early termination due to AEs, including weight gain (2), hypertension (2), edema (1), fatigue (1), seizures (1) and for reasons not stated (2). Proteinuria reduction ≥30 % was shown in 81.1 % (30/37) of patients and 62.2 % (23/37) showed ≥50 % proteinuria reduction. Proteinuria responses were greatest in MCD (n = 2/2 complete remission), MLN (n = 2/2 partial remission), MPGN (n = 1/1 partial remission), FSGS (n = 12/15 [80.0 %] partial remission or clinical response), and iMN (n = 8/11 [72.7 %] complete remission, partial remission, or clinical response).

Conclusions

Acthar gel may meet an important treatment need in patients with treatment-resistant NS in response to first-line therapies, patients unable to tolerate first-line therapies, and in patients with advanced disease.

Melanocortin 1 receptor agonist protects podocytes through catalase and RhoA activation

Drugs containing adrenocorticotropic hormone have been used as therapy for patients with nephrotic syndrome. We have previously shown that adrenocorticotropic hormone and a selective agonist for the melanocortin 1 receptor (MC1R) exert beneficial actions in experimental membranous nephropathy with reduced proteinuria, reduced oxidative stress, and improved glomerular morphology and function. Our hypothesis is that MC1R activation in podocytes elicits beneficial effects by promoting stress fibers and maintaining podocyte viability. To test the hypothesis, we cultured podocytes and used highly specific agonists for MC1R. Podocytes were subjected to the nephrotic-inducing agent puromycin aminonucleoside, and downstream effects of MC1R activation on podocyte survival, antioxidant defense, and cytoskeleton dynamics were studied. To increase the response and enhance intracellular signals, podocytes were transduced to overexpress MC1R. We showed that puromycin promotes MC1R expression in podocytes and that activation of MC1R promotes an increase of catalase activity and reduces oxidative stress, which results in the dephosphorylation of p190RhoGAP and formation of stress fibers through RhoA. In addition, MC1R agonists protect against apoptosis. Together, these mechanisms protect the podocyte against puromycin. Our findings strongly support the hypothesis that selective MC1R-activating agonists protect podocytes and may therefore be useful to treat patients with nephrotic syndromes commonly considered as podocytopathies.

Melanocortin peptides: potential targets in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease resulting in loss of self-tolerance with multiple organs, such as the kidney, skin, joints, and the central nervous system (CNS), being targeted. Numerous immunosuppressant therapies are currently being used for the treatment of SLE, but their clinical utility is somewhat variable because of the clinical heterogeneity. Melanocortins are a family of peptides derived from the common precursor protein pro-opiomelanocortin. These multifunctional peptides activate five subtypes of melanocortin receptors expressed on immune, skin, muscle, bone, and kidney cells and cells within the CNS. Melanocortin peptides have demonstrated a variety of biologic actions including immunomodulation, melanogenesis, and renoprotection. This review aims to introduce the melanocortin system and explore the mechanisms by which they may be beneficial in diseases such as SLE.

Repository corticotropin injection in a patient presenting with focal segmental glomerulosclerosis, rheumatoid arthritis, and optic neuritis: a case report

Background

Focal segmental glomerulosclerosis (FSGS) causes scarring or sclerosis of glomeruli that act as tiny filters in the kidneys, damage to which results in diminished ability to properly filter blood, resulting in the urinary loss of plasma proteins and subsequent proteinuria.

Case presentation

A 60-year-old, white female with a history of intermittent proteinuria was referred by her primary care physician for renal dysfunction. Biopsy confirmed FSGS and she was treated with an angiotensin-converting enzyme inhibitor. She also had rheumatoid arthritis (RA) but no active synovitis and was maintained on prednisone 5 mg/d. She also complained of worsening vision in her right eye and was diagnosed with optic neuritis (ON). She remained stable for about 8 months when examination indicated FSGS relapse, and she reported painful RA flares. She was treated with Acthar^® Gel (40 mg biweekly) for 6 months, after which proteinuria and urine protein-to-creatinine ratio decreased to about half. Her ON improved, and she reported that she had fewer RA flares and pain improved by 50%. This case of confirmed FSGS showed an improved response to treatment with Acthar Gel for FSGS with concomitant RA and ON.

Conclusion

This referral case is relevant to primary care practitioners who treat disorders that may be responsive to corticosteroid therapy. The antiproteinuric effects and ancillary improvement in RA and ON symptoms during treatment with Acthar Gel are not entirely explained by its steroidogenic actions. ACTH is a bioactive peptide that, together with α-melanocyte-stimulating hormone, exhibits biologic efficacy by modulating proinflammatory cytokines and subsequent leukocyte extravasation and may have autocrine/paracrine effects in joints. While Acthar Gel was primarily administered in this case to treat proteinuria, it also showed ancillary benefits in patients with concomitant inflammatory disease states.

Low-dose synthetic adrenocorticotropic hormone-analog therapy for nephrotic patients: results from a single-center pilot study

INTRODUCTION

This report describes our experience using a low-dose synthetic adrenocorticotropic hormone (ACTH) analog for patients affected by nephrotic syndrome who had not responded to or had relapsed after steroid and immunosuppressive treatments.

PATIENTS AND METHODS

Eighteen adult nephrotic patients with an estimated glomerular filtration rate >30 mL/min were recruited. Histological pictures included ten of membranous nephropathy, three of membranous proliferative glomerulonephritis, three of minimal change, and two of focal segmental glomerular sclerosis. All patients received the synthetic ACTH analog tetracosactide 1 mg intramuscularly once a week for 12 months. Estimated glomerular filtration rate, proteinuria, serum lipids, albumin, glucose, and potassium were determined before and during the treatment.

RESULTS

One of the 18 patients discontinued the treatment after 1 month because of severe fluid retention, and two patients were lost at follow-up. Complete remission occurred in six cases, while partial remission occurred in four cases (55.5% responder rate). With respect to baseline, after 12 months proteinuria had decreased from 7.24±0.92 to 2.03±0.65 g/day (P<0.0001), and serum albumin had increased from 2.89±0.14 to 3.66±0.18 g/dL (P<0.0001). Total and low-density lipoprotein cholesterol had decreased from 255±17 to 193±10 mg/dL (P=0.01), and from 168±18 to 114±7 mg/dL (P=0.03), respectively. No cases of severe worsening of renal function, hyperglycemia, or hypokalemia were observed, and no admissions for cardiovascular or infectious events were recorded.

CONCLUSION

Tetracosactide administration at the dosage of 1 mg intramuscularly per week for 12 months seems to be an acceptable alternative for nephrotic patients unresponsive or relapsing after steroid-immunosuppressive regimens. Further studies should be planned to assess the effect of this low-dose ACTH regimen also in nephrotic patients not eligible for kidney biopsy or immunosuppressive protocols.

Back to the Future: Therapies for Idiopathic Nephrotic Syndrome

Background: Roughly 20-40% of individuals with idiopathic nephrotic syndrome will fail to respond to standard therapies and have a high risk of progression to end stage kidney disease (ESKD). In the last 50 years, no new therapies have been approved specifically for the treatment of these individuals with recalcitrant disease. Summary: Recent in vitro, translational, and clinical studies have identified novel targets and pathways that not only expand our understanding of the complex pathophysiology of proteinuric disease but also provide an opportunity to challenge the tradition of relying on histologic classification of nephrotic diseases to make treatment decisions. Key Messages: The traditional methods of directing the care of individuals with nephrotic syndrome by histological classification or deciding second line therapies on the basis of steroid-responsiveness may soon yield customizing therapies based on our expanding understanding of molecular targets. Important non-immunologic mechanisms of widely used immunosuppressive therapies may be just as important in palliating proteinuric disease as proposed immunologic functions.