β-Adrenoreceptors as Therapeutic Targets for Ocular Tumors and Other Eye Diseases-Historical Aspects and Nowadays Understanding

β-adrenoreceptors (ARs) are members of the superfamily of G-protein-coupled receptors (GPCRs), and are activated by catecholamines, such as epinephrine and norepinephrine. Three subtypes of β-ARs (β₁, β₂, and β₃) have been identified with different distributions among ocular tissues. Importantly, β-ARs are an established target in the treatment of glaucoma. Moreover, β-adrenergic signaling has been associated with the development and progression of various tumor types. Hence, β-ARs are a potential therapeutic target for ocular neoplasms, such as ocular hemangioma and uveal melanoma. This review aims to discuss the expression and function of individual β-AR subtypes in ocular structures, as well as their role in the treatment of ocular diseases, including ocular tumors.

Isolated juxtapapillary retinal capillary haemangioblastoma and exudative maculopathy in an elderly patient without von Hippel-Lindau syndrome: combined proton beam radiotherapy and intravitreal anti-VEGF

A 71-year-old Caucasian man presented with an isolated juxtapapillary retinal capillary haemangioblastoma on the superior and temporal left optic disc with active exudation resulting in macular intraretinal and subretinal fluid, reduced vision, scotoma and distortion with progression over 6 weeks. He did not have von Hippel-Lindau syndrome. After proton beam radiotherapy (PBR), the tumour size remained unchanged, but did not stop the exudation. Three anti-vascular endothelial growth factor (VEGF) (ie, bevacizumab) injections at monthly intervals resulted in reduced macular oedema. Combined therapy with PBR and anti-VEGF injections sustained our patient's vision at 12 months follow-up.

Propranolol suppresses infantile hemangioma cell proliferation and promotes apoptosis by upregulating miR-125b expression

Propranolol could repress infantile hemangioma cell growth and induce apoptosis. miR-125b could inhibit cell proliferation in some tumors. However, whether propranolol exerts its proliferation inhibition and apoptosis-promoting effect by regulating the expression of miR-125b needs to be further investigated. In tumor tissue and endothelial cells isolated from infantile hemangioma patients, we found that the expression levels of miR-125b were significantly decreased. In-vitro analysis revealed that propranolol increased the expression of miR-125b in hemangioma cells in a dose-dependent and time-dependent manner. Interestingly, it was observed that regression of miR-125b expression by its inhibitor could abrogate the effect of propranolol on hemangioma cell growth and apoptosis. In addition, our data further identified TFAP4 as a direct target of miR-125b. Collectively, our data provided evidence that propranolol may repress infantile hemangioma cell growth and promote apoptosis through upregulating the miR-125b expression, which exerted its suppression of tumor development by targeting TFAP4.

Successful treatment of an exudative choroidal hemangioma with oral propranolol in a 10-year-old boy

A 10-year-old boy was referred for a circumscribed choroidal hemangioma with underlying exudative detachment of the left eye. To avoid general anesthetics required for laser-based therapy in a child, we began a trial of oral propranolol. The patient's exudative detachment resolved, with resulting improvement in visual acuity, and remained quiescent for 3 years.

Difficulties in the management of retinal capillary haemangiomas associated with von Hippel Lindau disease

CLINICAL CASE

A 29-year-old female with bilateral retinal capillary haemangiomas (RCH). A genetic analysis was carried out due to the suspicion of von Hippel-Lindau (VHL) disease, with negative results on 2occasions. There was progression of the RCH in the left eye, leading to a macular epiretinal membrane. The patient was treated with laser, intravitreal ranibizumab, and vitrectomy. Finally, a third genetic test detected a de novo mutation in the VHL gene, and led to the genetic diagnosis.

DISCUSSION

VHL syndrome causes a complex ocular disease with a difficult diagnosis that requires early treatment of the RCH in order to modify its visual prognosis.