Identification and characterization of novel TRPM1 autoantibodies from serum of patients with melanoma-associated retinopathy

Paraneoplastic vision loss

Paraneoplastic vision loss, which represents a small percentage of paraneoplastic neurologic syndromes, can be a blinding disease. Presenting visual symptoms are variable, making diagnosis challenging. History of the presenting illness, ocular examination, and utilization of various modalities, such as automated perimetry, ocular coherence tomography, and electroretinogram allow for localization of vision loss to the optic nerves or retina, guiding in diagnosis and management. Paraneoplastic vision loss is often painless, bilateral, and subacute, and accompanies other neurologic symptoms but can be the first presenting symptom. Paraneoplastic optic neuropathy has been described in association with several antibodies, but most commonly anti-CRMP5. Cancer-associated retinopathy is the most common paraneoplastic autoimmune retinopathy; however, melanoma-associated retinopathy and bilateral diffuse uveal melanocytic proliferation have also been described to be associated with a paraneoplastic process affecting the retina. Paraneoplastic visual loss is an expanding field and advances in research have improved phenotypic characterization; however, further work is needed to identify more reliable biomarkers of disease and to better understand the underlying mechanisms and management.

Blue light exposure collapses the inner blood-retinal barrier by accelerating endothelial CLDN5 degradation through the disturbance of GNAZ and the activation of ADAM17

Blue light is part of the natural light spectrum that emits high energy. Currently, people are frequently exposed to blue light from 3C devices, resulting in a growing incidence of retinopathy. The retinal vasculature is complex, and retinal vessels not only serve the metabolic needs of the retinal sublayers, but also maintain electrolyte homeostasis by forming the inner blood-retinal barrier (iBRB). The iBRB, which is primarily composed of endothelial cells, has well-developed tight junctions. However, with exposure to blue light, the risks of targeting retinal endothelial cells are currently unknown. We found that endothelial claudin-5 (CLDN5) was rapidly degraded under blue light, coinciding with the activation of a disintegrin and metalloprotease 17 (ADAM17), even at non-cytotoxic lighting. An apparently broken tight junction and a permeable paracellular cleft were observed. Mice exposed to blue light displayed iBRB leakage, conferring attenuation of the electroretinogram b-wave and oscillatory potentials. Both pharmacological and genetic inhibition of ADAM17 remarkably alleviated CLDN5 degradation induced by blue light. Under untreated condition, ADAM17 is sequestered by GNAZ (a circadian-responsive, retina-enriched inhibitory G protein), whereas ADAM17 escapes from GNAZ by blue light illuminance. GNAZ knockdown led to ADAM17 hyperactivation, CLDN5 downregulation, and paracellular permeability in vitro, and retinal damage mimicked blue light exposure in vivo. These data demonstrate that blue light exposure might impair the iBRB by accelerating CLDN5 degradation through the disturbance of the GNAZ-ADAM17 axis.

Relation between ocular paraneoplastic syndromes and Immune Checkpoint Inhibitors (ICI): review of literature

PURPOSE

To describe different ocular paraneoplastic syndromes in patients treated with Immune Checkpoint Inhibitors (ICI), its relation with different types of ICI and different types of tumors, and its implications for treatment.

METHODS

A comprehensive review of the literature was performed.

RESULTS

Patients treated with ICI can present with different ocular paraneoplastic syndromes, such as Carcinoma Associated Retinopathy (CAR), Melanoma Associated Retinopathy (MAR) and paraneoplastic Acute Exudative Polymorphous Vitelliform Maculopathy (pAEPVM). In literature, the different types of paraneoplastic retinopathy are mostly related to different types of primary tumors, with MAR and pAEPVM seen in melanoma, and CAR in carcinoma. Visual prognosis is limited in MAR and CAR.

CONCLUSION

Paraneoplastic disorders result from an antitumor immune response against a shared autoantigen between the tumor and ocular tissue. ICI enhance the antitumor immune response, which can lead to increased cross-reaction against ocular structures and unmasking of a predisposed paraneoplastic syndrome. Different types of primary tumors are related to different cross-reactive antibodies. Therefore, the different types of paraneoplastic syndromes are related to different types of primary tumors and are probably unrelated to the type of ICI. ICI-related paraneoplastic syndromes often lead to an ethical dilemma. Continuation of ICI treatment can lead to irreversible visual loss in MAR and CAR. In these cases overall survival must be weighed against quality of life. In pAEPVM however, the vitelliform lesions can disappear with tumor control, which may involve continuation of ICI.

Shedding light on myopia by studying complete congenital stationary night blindness

Myopia is the most common eye disorder, caused by heterogeneous genetic and environmental factors. Rare progressive and stationary inherited retinal disorders are often associated with high myopia. Genes implicated in myopia encode proteins involved in a variety of biological processes including eye morphogenesis, extracellular matrix organization, visual perception, circadian rhythms, and retinal signaling. Differentially expressed genes (DEGs) identified in animal models mimicking myopia are helpful in suggesting candidate genes implicated in human myopia. Complete congenital stationary night blindness (cCSNB) in humans and animal models represents an ON-bipolar cell signal transmission defect and is also associated with high myopia. Thus, it represents also an interesting model to identify myopia-related genes, as well as disease mechanisms. While the origin of night blindness is molecularly well established, further research is needed to elucidate the mechanisms of myopia development in subjects with cCSNB. Using whole transcriptome analysis on three different mouse models of cCSNB (in Gpr179^-/-, Lrit3^-/- and Grm6^-/-), we identified novel actors of the retinal signaling cascade, which are also novel candidate genes for myopia. Meta-analysis of our transcriptomic data with published transcriptomic databases and genome-wide association studies from myopia cases led us to propose new biological/cellular processes/mechanisms potentially at the origin of myopia in cCSNB subjects. The results provide a foundation to guide the development of pharmacological myopia therapies.

Unilateral Melanoma-Associated Retinopathy Case Report

In this report, we present a case of unilateral melanoma-associated retinopathy in a 72-year-old woman. The patient's main symptoms were decreased vision and positive dysphotopsia. Unilateral electronegative electroretinogram (ERG) was suggestive for melanoma retinopathy. PET-CT discovered metastatic disease, 3 years after the initial melanoma. A prompt treatment with corticosteroids was started, followed by immunotherapy. The central and peripheral vision of the patient improved, and the ERG showed normalization of the responses. This case highlights the importance of early recognition and individualized treatment strategies for melanoma-associated retinopathy.

Melanoma-associated retinopathy with anti-TRPM1 autoantibodies showing concomitant Off-bipolar cell dysfunction

BACKGROUND

To report the clinical features of a patient with melanoma-associated retinopathy (MAR) with anti-transient receptor potential cation channel, subfamily M, member 1 (TRPM1) autoantibodies showing concomitant Off-bipolar cell dysfunction.

METHODS

We evaluated a patient with a past history of scalp melanoma presented with sudden-onset shimmering photopsia in both eyes. MAR was confirmed with complete ophthalmic examinations, electronegative electroretinogram (ERG), and the presence of anti-TRPM1 autoantibodies by Western blot analysis. S-cone ERG and photopic On-Off ERG were studied in this patient as well.

RESULTS

The patient's best-corrected visual acuity was 6/30 in the right eye and 6/8.6 in the left eye. Fundus and OCT findings were unremarkable. Visual field test showed severe constriction in both eyes. His full-field ERG was electronegative. S-cone ERG recorded preservation of L/M-cone-mediated response and undetectable S-cone-mediated response. Photopic On-Off ERG disclosed attenuated On- and Off-response. Western blot analysis confirmed immunoreactivity of the patient's serum to a 30 kDa TRPM1 recombinant protein. Whole-body positron emission tomography scan detected lymph node metastases in the neck.

CONCLUSIONS

Anti-TRPM1 autoantibody-positive MAR varies greatly in its presentation and clinical course. We present a case of anti-TRPM1 autoantibody-positive MAR with atypical feature of Off-bipolar cell involvement. A complete electroretinographic study together with identification of the pathogenic antiretinal autoantibodies may help better understand and subclassify the disease in the future.

Electronegative electroretinogram in the modern multimodal imaging era

Background

The electronegative electroretinogram (ERG) reflecting inner retinal dysfunction can assist as a diagnostic tool to determine the anatomical location in eye disease. The aim of this study is to determine the frequency and aetiology of electronegative ERG in a tertiary ophthalmology centre and to develop a clinical algorithm to assist patient management.

Methods

Retrospective review of ERGs performed at the Save Sight Institute from January 2011 to December 2020. ERGs were performed according to ISCEV standard. The b:a ratio was analysed in dark adapted (DA) 3.0 or 12.0 recordings. Patients with ratio of ≤1.0 were included.

Results

A total of 4421 patients had ERGs performed during study period, of which 139 patients (3.1%) had electronegative ERG. The electronegative ERG patients' median age at referral time was 37 (0.7–90.6) years. The causative aetiologies were photoreceptor dystrophy (48, 34.5%), Congenital Stationary Night Blindness (CSNB) (33, 23.7%), retinal ischemia (18, 12.9%), retinoschisis (15, 10.8%), paraneoplastic autoimmune retinopathy (PAIR) and nonPAIR (14, 10.1%), batten disease (4, 2.9%), and inflammatory retinopathy (4, 2.9%). There were three patients with an unclassified diagnosis. Thirty‐two patients (23%) had good vision and a normal fundus appearance. Eleven patients (7.9%) had good vision and normal results in all multimodal imaging.

Conclusions

The frequency of electronegative ERG in our referral centre was 3.1% with photoreceptor dystrophy as the main aetiology. A significant number of the cases had good vision with normal fundus or normal multimodal imaging. This further highlights the value of an ERG in this modern multimodal imaging era.

Minireview: Insights into the role of TRP channels in the retinal circulation and function

Consistent with their wide distribution throughout the CNS, transcripts of all transient receptor potential (TRP) cation channel superfamily members have been detected in both neuronal and non-neuronal cells of the mammalian retina. Evidence shows that members of the TRPC (canonical, TRPC1/4/5/6), TRPV (vanilloid, TRPV1/2/4), TRPM (melastatin, TRPM1/2/3/5), TRPA (ankyrin, TRPA1), and TRPP (polycystin, TRPP2) subfamilies contribute to retinal function and circulation in health and disease, but the relevance of most TRPs has yet to be determined. Their principal role in light detection is far better understood than their participation in the control of intraocular pressure, retinal blood flow, oxidative stress, ion homeostasis, and transmitter signaling for retinal information processing. Moreover, if the therapeutic potential of targeting some TRPs to treat various retinal diseases remains speculative, recent studies highlight that vision restoration strategies are very likely to benefit from the thermo- and mechanosensitive properties of TRPs. This minireview focuses on the evidence of the past 5 years about the role of TRPs in the retina and retinal circulation, raises some possibilities about the function of TRPs in the retina, and discusses the potential sources of endogenous stimuli for TRPs in this tissue, as a reflection for future studies.

Ocular Paraneoplastic Syndromes

Ocular-involving paraneoplastic syndromes present a wide variety of clinical symptoms. Understanding the background pathophysiological and immunopathological factors can help make a more refined differential diagnosis consistent with the signs and symptoms presented by patients. There are two main pathophysiology arms: (1) autoimmune pathomechanism, which is presented with cancer-associated retinopathy (CAR), melanoma-associated retinopathy (MAR), cancer-associated cone dysfunction (CACD), paraneoplastic vitelliform maculopathy (PVM), and paraneoplastic optic neuritis (PON), and (2) ectopic peptides, which is often caused by tumor-expressed growth factors (T-exGF) and presented with bilateral diffuse uveal melanocytic proliferation (BDUMP). Meticulous systematic analysis of patient symptoms is a critical diagnostic step, complemented by multimodal imaging, which includes fundus photography, optical coherent tomography, fundus autofluorescence, fundus fluorescein angiography, electrophysiological examination, and sometimes fundus indocyjanin green angiography if prescribed by the clinician. Assessment of the presence of circulating antibodies is required for diagnosis. Antiretinal autoantibodies are highly associated with visual paraneoplastic syndromes and may guide diagnosis by classifying clinical manifestations in addition to monitoring treatment.

Melanoma-associated retinopathy during pembrolizumab treatment probably controlled by intravitreal injections of dexamethasone

PURPOSE

Melanoma-associated retinopathy (MAR) is a rare paraneoplastic syndrome due to antibodies targeting bipolar retinal cells. Its evolution, particularly in patients treated with immune checkpoint inhibitors (ICI), is currently poorly understood. In the few cases published, patients' visual function got worse when these molecules were prescribed. Here, we present a case of a patient with severe MAR treated with an ICI for melanoma progression.

METHODS

A 68-year-old woman with a history of melanoma of the palpebral conjunctiva presented with sudden and gradually worsening visual disturbances. Simultaneously, a metastatic evolution of the melanoma was diagnosed and surgically treated exclusively. Visual acuity assessment, static automated perimetry and ERG results lead to the diagnosis of MAR. Since systemic corticosteroid therapy did not improve her symptoms, repeated intraocular corticosteroid injections were performed with a positive outcome. Later on, metastatic progression of the patient's melanoma led to the introduction of pembrolizumab, an ICI targeting PD-1. Immunotherapy has changed the prognosis of patient affected by metastatic melanoma, but these molecules may induce various immune-related adverse effects. In our case, intraocular corticosteroid injections were still performed simultaneously. Visual acuity assessment, static automated perimetry and ERG were performed during the course of this treatment.

RESULTS

Full-field ERGs results suggested the possibility that the ophthalmologic treatment might restore the patient's retinal function despite the continued immunotherapy.

CONCLUSION

We report the first case of MAR with a positive outcome after 1 year of ICI, possibly thanks to intravitreal corticosteroid therapy.