Photochemotherapy inhibits angiogenesis and induces apoptosis of endothelial cells in vitro

Psoralen: a narrative review of current and future therapeutic uses

Psoralen is a family of naturally occurring photoactive compounds found in plants that acquire potential cytotoxicity when activated by specific frequencies of electromagnetic waves. Psoralens penetrate the phospholipid cellular membranes and insert themselves between the pyrimidines of deoxyribonucleic acid (DNA). Psoralens are initially biologically inert and acquire photoreactivity when exposed to certain classes of electromagnetic radiation, such as ultraviolet light. Once activated, psoralens form mono- and di-adducts with DNA, leading to marked cell apoptosis. This apoptotic effect is more pronounced in tumor cells due to their high rate of cell division. Moreover, photoactivated psoralen can inhibit tyrosine kinase signaling and influence the immunogenic properties of cells. Thus, the cytotoxicity of photoactivated psoralen holds promising clinical applications from its immunogenic properties to potential anti-cancer treatments. This narrative review aims to provide an overview of the current understanding and research on psoralen and to explore its potential future pharmacotherapeutic benefits in specific diseases.

Mechanisms of UV-induced human lymphocyte apoptosis

The article reviews the results of the studies of marker parameters (indicators) of various pathways and mechanisms of apoptosis of lymphocytes in donor peripheral blood induced by UV light (240-390 nm) in doses of 151, 1510, and 3020 J/m2. The article analyses the processes of DNA fragmentation, distortion of the structural asymmetry of the cell membranes, changes in the degree of DNA damage (single-strand breaks), transcriptional factor р53, cytochrome с, Fas receptors (CD95), caspase-3, caspase-8, and caspase-9, reactive oxygen species, and calcium ions in UV modified cells. The study determined that programmed cell death of lymphocytes after UV irradiation with 1510 J/m2 involves the р53-dependent pathway of the nuclear mechanism, as well as receptor-mediated caspase mechanism, mitochondrial mechanism, and the mechanism associated with the defects in calcium homeostasis. Cell death is mediated by reactive oxygen and calcium ions. The article suggests a scheme of possible intracellular events resulting in the apoptotic death of lymphocytes after UV irradiation.

A novel personalised treatment approach for psoriasis: anti-VEGF-A therapy

Chronic plaque psoriasis is an inflammatory skin disease in which genetic predisposition along with environmental factors lead to the development of the disease, which affects 2% of the UK’s population and is associated with extracutaneous morbidities and a reduced quality of life. A complex crosstalk between innate and adaptive immunity, the epithelia and the vasculature maintain the inflammatory milieu in psoriasis. Despite the development of promising treatment strategies, mostly targeting the immune system, treatments fail to fulfil every patient’s goals. Vascular endothelial growth factor‐A (VEGF‐A) mediates angiogenesis and is upregulated in the plaques and plasma of patients with psoriasis. Transgenic expression of VEGF‐A in experimental models led to the development of skin lesions that share many psoriasis features. Targeting VEGF‐A in in vivo models of psoriasis‐like inflammation resulted in disease clearance. Anti‐angiogenesis treatments are widely used for cancer and eye disease and there are clinical reports of patients treated with VEGF‐A inhibitors who have experienced Psoriasis Area and Severity Index improvement. Existing psoriasis treatments downregulate VEGF‐A and angiogenesis as part of their therapeutic effect. Pharmacogenetics studies suggest the existence of different genetic signatures within patients with psoriasis that correspond with different treatment responsiveness and disease severity. There is a subset of patients with psoriasis with an increased predisposition to produce high levels of VEGF‐A, who may be most likely to benefit from anti‐VEGF‐A therapy, offering an opportunity to personalize treatment in psoriasis. Anti‐VEGF‐A therapies may offer an alternative to existing anticytokine strategies or be complementary to standard treatments for the management of psoriasis.

Vascular endothelial growth factor-A as a promising therapeutic target for the management of psoriasis

Vascular endothelial growth factor-A (VEGF-A), the main angiogenic mediator, plays a critical role in the pathogenesis of several inflammatory immune-mediated diseases, including psoriasis. Even though anti-angiogenic therapies, such as VEGF inhibitors, are licensed for the treatment of various cancers and eye disease, VEGF-targeting interventions are not part of current psoriasis therapy. In this viewpoint essay, we argue that the existing preclinical research evidence on the role of VEGF-A in the pathogenesis of psoriasis as well as clinical observations in patients who have experienced psoriasis remission during oncological anti-VEGF-A therapy strongly suggests to systematically explore angiogenesis targeting also in the management of psoriasis. We also point out that some psoriasis therapies decrease circulating levels of VEGF-A and normalise the psoriasis-associated vascular pathology in the papillary dermis of plaques of psoriasis and that a subset of patients with constitutionally high levels of VEGF-A may benefit most from the anti-angiogenic therapy we advocate here. Given that novel, well-targeted personalised medicine therapies for the development of psoriasis need to be developed, we explore the hypothesis that VEGF-A and signalling through its receptors constitute a promising target for therapeutic intervention in the future management of psoriasis.

Novel investigational vascular endothelial growth factor (VEGF) receptor antagonists for psoriasis

INTRODUCTION

Affecting 1 million people in the UK, psoriasis is a commonly diagnosed inflammatory disease arising from autoimmune processes that are triggered by environmental factors in genetically susceptible individuals. The pathophysiology of psoriasis has been widely studied and there is evidence that angiogenesis is a key component.

AREAS COVERED

In this review the role of vascular endothelial growth factor-A (VEGF), as a key angiogenic mediator in psoriasis pathogenesis is discussed. VEGF is found in higher levels in plaques, normal skin and plasma of patients with psoriasis. The level of VEGF also fluctuates in accordance with disease activity and in response to conventional treatments. There are several VEGF inhibitors currently licenced for use; primarily in the fields of oncology and there are case reports of patients being treated with these therapies for metastatic cancer who have demonstrated significant improvement in their psoriasis. VEGF inhibitory agents have suggested promising utility for the treatment of psoriasis following animal studies.

EXPERT OPINION

VEGF may represent a novel treatment target in psoriasis. However, VEGF inhibitors can cause significant side effects such as hypertension and left ventricular dysfunction. The risks of treatment must be carefully evaluated before VEGF inhibitors are trialled or advocated for psoriasis.

Antiangiogenic effect of methotrexate and PUVA on psoriasis

Vascular endothelial growth factor (VEGF) is important factor for angiogenesis in psoriasis. Methotrexate and psoralen and ultraviolet light A (PUVA) mainly target the T cell-mediated immunopathology of psoriasis. Our work aimed at estimating VEGF mRNA in psoriatic patients and investigating whether the standard therapeutic modalities (methotrexate and PUVA) exert their antiangiogenic activity through altering VEGF levels. Twenty-four chronic plaque psoriasis patients were enrolled. Patients were divided into two groups (12 patients each); group A received intramuscular methotrexate and group B was treated by PUVA three times/week in a PUVA 1000 cabin for 10 weeks each. Twelve healthy volunteers served as controls. A skin biopsy was taken from lesional skin before and after treatment for RT-PCR detection of VEGF mRNA. Capillary perfusion scanning using LASER Doppler perfusion imaging was performed on the same psoriatic plaque before and after treatment and was also done for the controls. Following both methotrexate and PUVA, a significant reduction in the amount of VEGF mRNA (P < 0.001 and P = 0.002, respectively) and capillary perfusion (P = 0.002) occurred. These reductions were significantly higher in the methotrexate group (P < 0.001 and  P = 0.001, respectively) than in the PUVA group. The percentage of clinical improvement in the examined psoriatic plaque was significantly positively correlated with the percentage of reduction in the amount of VEGF mRNA (r = 0.850, P < 0.001) and the percentage of reduction in the capillary perfusion (r = 0.684, P < 0.001). Both modalities may exert an antiangiogenic effect. Methotrexate appears to have possibly a more potent antiangiogenic effect than PUVA.

Vascular endothelial growth factor inhibitors: investigational therapies for the treatment of psoriasis

Psoriasis is a common inflammatory autoimmune condition in which environmental factors and genetic predisposition contribute to the development of disease in susceptible individuals. Angiogenesis is known to be a key pathogenic feature of psoriasis. Local and systemic elevation of vascular endothelial growth factor (VEGF)-A has been demonstrated in the skin and plasma of patients with psoriasis and is known to correlate with improvement following some traditional psoriasis treatments. A number of VEGF inhibitors are licensed for the treatment of malignancies and eye disease and isolated case reports suggest that some individuals with psoriasis may improve when exposed to these agents. The small number of cases and lack of unified reporting measures makes it difficult to draw generalizations and underline the heterogeneity of psoriasis as a disease entity. Though not yet licensed for the treatment of psoriasis in humans, experimental data supports the potential of VEGF inhibitors to influence relevant aspects of human cell biology (such as endothelial cell differentiation) and to improve animal models of skin disease. Given the multi-factorial nature of psoriasis it is unlikely that VEGF inhibitors will be effective in all patients, however they have the potential to be a valuable addition to the therapeutic arsenal in selected cases. Current VEGF inhibitors in clinical use are associated with a number of potentially serious side effects including hypertension, left ventricular dysfunction, and gastrointestinal perforation. Such risks require careful consideration in psoriasis populations particularly in light of growing concerns linking psoriasis to increased cardiovascular risk.

UV Light and Its Interaction with Cutaneous Receptors

Phototherapy (UV-A and UV-B) has become one of the most commonly used modalities for the treatment of a variety of skin diseases, although the action mechanisms have not been fully understood. Inhibition of DNA synthesis by UV radiation may be one of the therapeutic effects in proliferating skin diseases; however, phototherapy is also used for the treatment of allergic or autoimmune diseases.

Vascular endothelial growth factor gene polymorphisms increase the risk to develop psoriasis

We investigated the relationship between eight polymorphisms in the gene encoding for vascular endothelial growth factor (VEGF) (-1540C > A, -1512Ins18, -1451C > T, -460T > C, -160C > T, -152G > A, -116G > A and +405G > C) and plaque-type psoriasis stratified for age at onset, gender and family history of dermatosis. For this purpose, 117 patients with chronic plaque-type psoriasis and 215 healthy subjects were enrolled. We found that being homozygous -1540AA, -1512InsIns, -1451TT, -460CC and -152AA conferred a significant risk in developing psoriasis compared with heterozygous (-1540CA, -1512 + Ins, -1451CT, -460CT and -152AG) and homozygous genotypes (-1540CC, -1512 + +-1451CC, -460TT and -152GG) grouped together [odds ratio (ORs) = 1.73, 1.73, 1.73, 1.77 and 1.87, respectively]. Conversely, having the -116AA or +405GG genotype did not significantly increase the risk of disease expression compared with other genotypes of the same loci. Interestingly, we found that -1540AA, -1512InsIns, -1451TT, -460CC and -152AA homozygous genotypes have a significant two-fold increased risk in developing psoriasis after the age of 40 years (late-onset psoriasis) (ORs = 2.19, 2.19, 2.19, 2.05 and 2.26; P = 0.02, 0.02, 0.02, 0.04 and 0.02, respectively) as compared with controls. On the contrary, we found no phenotype-genotype association of the same magnitude among the patients in whom psoriasis developed at or before the age of 40 years (early-onset psoriasis) compared with controls. Genotype distributions were not significantly different when cases and controls were stratified either by gender or family history of psoriasis. Finally, VEGF plasma concentration was not significantly different between patients and controls and was not correlated with the severity of the disease.