Association of Angiotensin-Converting Enzyme (ACE) Gene Polymorphism with Inflammation and Cellular Cytotoxicity in Vitiligo Patients

The Renin-Angiotensin System: The Challenge behind Autoimmune Dermatological Diseases

Autoimmune dermatological diseases (AIDD) encompass a diverse group of disorders characterized by aberrant immune responses targeting the skin and its associated structures. In recent years, emerging evidence suggests a potential involvement of the renin-angiotensin system (RAS) in the pathogenesis and progression of these conditions. RAS is a multicomponent cascade, primarily known for its role in regulating blood pressure and fluid balance. All of the RAS components play an important role in controlling inflammation and other immune responses. Angiotensin II, the main effector, acts on two essential receptors: Angiotensin Receptor 1 and 2 (AT1R and AT2R). A disturbance in the axis can lead to many pathological processes, including autoimmune (AI) diseases. AT1R activation triggers diverse signaling cascades involved in inflammation, fibrosis and tissue remodeling. Experimental studies have demonstrated the presence of AT1R in various cutaneous cells and immune cells, further emphasizing its potential contribution to the AI processes in the skin. Furthermore, recent investigations have highlighted the role of other RAS components, beyond angiotensin-converting enzyme (ACE) and Ang II, that may contribute to the pathophysiology of AIDD. Alternative pathways involving ACE2, Ang receptors and Ang-(1-7) have been implicated in regulating immune responses and tissue homeostasis within the skin microenvironment. Understanding the intricate involvement of the RAS in AIDD may provide novel therapeutic opportunities. Targeting specific components of the RAS, such as angiotensin receptor blockers (ARBs), ACE inhibitors (ACEIs) or alternative RAS pathway modulators, could potentially ameliorate inflammatory responses, reduce tissue damage and lessen disease manifestations. Further research is warranted to outline the exact mechanisms underlying RAS-mediated immune dysregulation in AIDD. This abstract aims to provide a concise overview of the intricate interplay between the RAS and AIDD. Therefore, we elaborate a systematic review of the potential challenge of RAS in the AIDD, including psoriasis, systemic sclerosis, vitiligo, lupus erythematosus and many more.

Inducible Nitric Oxide Synthase iNOS-954-G>C and Ex16+14-C>T Gene Polymorphisms and Susceptibility to Vitiligo in the Saudi Population

Objective

Vitiligo is an acquired pigmentary skin disorder with regional disappearance of melanocytes. Multigenic inheritance has been proposed in the pathogenesis of vitiligo. The present study aimed to investigate the possible association of inducible nitric oxide synthase polymorphisms iNOS-954-G/C (rs1800482 G>C) and iNOS-Ex16+14-C/T (rs2297518 C>T) with vitiligo in the Saudi population, if any.

Methods

We included 120 vitiligo cases and an equal number of age matched healthy controls. Polymerase chain reaction with restriction fragment length polymorphism method was used for the analysis of genetic polymorphisms.

Results

The heterozygous (GC), (GC + CC) combined genotype and variant allele; C allele of rs1800482 G>C were associated significantly (p < 0.005, after Bonferroni correction) with increased risk of vitiligo (OR = 3.46, 95% CI = 1.99–6.01, p = 0.001), (OR = 3.30, 95% CI= 1.93–5.65, p = 0.001) and (OR = 1.94, 95% CI = 1.31–2.87, p = 0.001) respectively. When GC genotype of rs1800482 G>C was co-inherited with common genotype (CC) and heterozygous genotype (CT) of rs2297518 C>T, the risk of vitiligo was significantly increased ((OR = 4.51, 95% CI = 2.18–9.33, p = 0.001) and (OR = 3.60, 95% CI = 1.61–8.01, p = 0.001)) respectively. None of the rs1800482 G>C and rs2297518 C>T genotypes and alleles have been associated with non-segmental vitiligo in terms of gender, age of onset, and types of vitiligo.

Conclusion

The heterozygous (GC), (GC+CC) combined genotype and variants allele; C allele of rs1800482 G>C, may cause overproduction of NO, which has been linked to melanocyte loss by increasing oxidative stress and decreasing melanocyte adhesion to the extracellular matrix components, and thus could be an associative risk factor for vitiligo.

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

Age and genotype dependent erythropoietin protection in COVID-19

Erythropoietin (EPO) is the main mediator of erythropoiesis and an important tissue protective hormone that appears to mediate an ancestral neuroprotective innate immune response mechanism at an early age. When the young brain is threatened-prematurity, neonatal hyperbilirubinemia, malaria- EPO is hyper-secreted disproportionately to any concurrent anemic stimuli. Under eons of severe malarial selection pressure, neuroprotective EPO augmenting genetic determinants such as the various hemoglobinopathies, and the angiotensin converting enzyme (ACE) I/D polymorphism, have been positively selected. When malarial and other cerebral threats abate and the young child survives to adulthood, EPO subsides. Sustained high ACE and angiotensin II (Ang II) levels through the ACE D allele in adulthood may then become detrimental as witnessed by epidemiological studies. The ubiquitous renin angiotensin system (RAS) influences the α-klotho/fibroblast growth factor 23 (FGF23) circuitry, and both are interconnected with EPO. Here we propose that at a young age, EPO augmenting genetic determinants through ACE D allele elevated Ang II levels in some or HbE/beta thalassemia in others would increase EPO levels and shield against coronavirus disease 2019, akin to protection from malaria and dengue fever. Human evolution may use ACE2 as a “bait” for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to gain cellular entry in order to trigger an ACE/ACE2 imbalance and stimulate EPO hypersecretion using tissue RAS, uncoupled from hemoglobin levels. In subjects without EPO augmenting genetic determinants at any age, ACE2 binding and internalization upon SARS-CoV-2 entry would trigger an ACE/ACE2 imbalance, and Ang II oversecretion leading to protective EPO stimulation. In children, low nasal ACE2 Levels would beneficially augment this imbalance, especially for those without protective genetic determinants. On the other hand, in predisposed adults with the ACE D allele, ACE/ACE2 imbalance, may lead to uncontrolled RAS overactivity and an Ang II induced proinflammatory state and immune dysregulation, with interleukin 6 (IL-6), plasminogen activator inhibitor, and FGF23 elevations. IL-6 induced EPO suppression, aggravated through co-morbidities such as hypertension, diabetes, obesity, and RAS pharmacological interventions may potentially lead to acute respiratory distress syndrome, cytokine storm and/or autoimmunity. HbE/beta thalassemia carriers would enjoy protection at any age as their EPO stimulation is uncoupled from the RAS system. The timely use of rhEPO, EPO analogs, acetylsalicylic acid, bioactive lipids, or FGF23 antagonists in genetically predisposed individuals may counteract those detrimental effects.

Defining IL-6 levels in healthy individuals: A meta-analysis

BACKGROUND

Interleukin-6 (IL-6) is produced by and impacts different cell types in human. IL-6 is associated with different diseases and viral infections, including COVID-19. To our knowledge, no normal values were reported for IL-6 in the blood of healthy individuals. We have reviewed and performed a meta-analysis on a total of 140 studies, including 12,421 values for IL-6 in the blood of healthy adult donors. Among these studies, 83 did not report a mean value and the standard deviation. Therefore, for the statistical analysis, we used the values reported in 57 studies, which included 3166 values for IL-6.

RESULTS

The reported values for IL-6 in the blood of healthy donors varied between 0 and 43.5 pg/ml. The pooled estimate of IL-6 was 5.186 pg/ml (95% confidence interval [CI]: 4.631, 5.740). As the age increased by 1 year, IL-6 values increased by 0.05 pg/ml (95% CI: 0.02, 0.09; p < .01). Though the heterogenicity, as determined by I2 statistics, was high in our study, the differences in IL-6 values are still at the level of a few pg/ml, which might be related to the differences in the conditions that influence IL-6 production in the healthy population.

CONCLUSIONS

This is the first meta-analysis reporting the levels of IL-6 in the blood of healthy donors based on a large number of studies and donors. Therefore the 95% CI values determined in our study could well serve as a reference range for quick decision-making in clinical interventions, particularly those aiming to inhibit IL-6, especially urgent interventions, for example, COVID-19.

Deleterious effect of angiotensin-converting enzyme gene polymorphism in vitiligo patients

Vitiligo is a rare skin condition caused by an immune reaction. Vitiligo can occur anywhere on the body. This proposed explanation of vitiligo makes it clear that vitiligo is not linked to any other autoimmune diseases. The polymorphisms of some genes present in the immune system play a major function in susceptibility of vitiligo. Meta-analysis studies have shown that the Angiotensin converting enzyme (ACE) gene insertion and deletion polymorphism is closely associated with vitiligo in many ethnicities. The connection between ACE gene and vitiligo is connected through the auto immune diseases and there are no genetic polymorphism studies have been carried out with ACE gene with vitiligo in the Saudi population. Previous studies show that vitiligo patients are more likely to also have an autoimmune disorder. The current study aims to investigate the I/D polymorphism in the ACE gene with diagnosed patients with vitiligo subjects. This is a case-control study carried out in the Saudi population with 100 vitiligo cases and 100 healthy controls. Genotyping was performed through polymerase chain reaction followed by 3% agarose gel electrophoresis. Genotype and allele frequencies were carried out with genetic mode of inheritances. Statistical analysis was performed considering p < 0.05 as significant association. There was a substantial difference in allele frequency distribution between vitiligo patients and healthy controls (OR-1.70 (95%CI: 1.14-2.53); p = 0.008). Additionally, DD genotype (OR-4.71 (95%CI: 1.42-15.61); p = 0.008) and recessive model (OR-2.66 (95%CI: 1.41-5.02); p = 0.002) was strongly associated. Both dominant and co-dominant showed the negative association (p > 0.05) when compared between the vitiligo cases and controls. The correlation between age and genotyping was performed with Anova analysis and current study results confirmed the substantial link between 11 and 20 years (p = 0.01) and 31-40 years (p = 0.04) with the defined age groups. In conclusion, in Saudi populations, the ACE gene I/D polymorphism was identified as being correlated with vitiligo. This is the first study in Saudi Arabia to report the risk factors of vitiligo with the ACE gene polymorphism.

Associations of Angiotensin-Converting Enzyme Gene Insertion/Deletion (ACE Gene I/D) Polymorphism With Vitiligo: An Updated Systematic Review and Meta-Analysis

Objective

The objective of the article is to summarize the current evidence regarding the association between angiotensin-converting enzyme insertion/deletion (ACE I/D) gene polymorphism and vitiligo disease.

Methods

A computerized search was performed through four electronic databases (PubMed, Scopus, Cochrane Central Register of Controlled Trials [CENTRAL], and Web of Science) with the relevant keywords. Included studies comprised of papers examining the association of ACE gene polymorphisms with vitiligo. Data were pooled as an odds ratio (OR) in random- and fixed-effect models using the Mantel-Haenszel (M-H) method. Review Manager 5.3 software (clicktime.com, Inc., San Francisco, US) was utilized in the meta-analysis. 

Results

Ten studies (n=2,740) matching the inclusion criteria were included in the systematic review and meta-analysis. Results showed no significant difference between individuals carrying deletion/deletion (D/D) genotype and individuals with deletion/insertion (D/I) + insertion/insertion (I/I) genotypes in terms of vitiligo risk (odds ratio [OR]=1.13, 95% confidence interval [CI]: 0.78 to 1.64, p=0.53). However, vitiligo risk was higher in the individuals carrying the I/D genotype when compared with individuals with D/D + I/I genotypes (OR=1.29, 95% CI: 1.10 to 1.52, p=0.001). Moreover, the increased risk was observed in individuals carrying D/D when compared with I/I (OR=1.67, 95% CI: 1.33 to 2.09, p<0.0001). D allele was associated with significant risk when compared with the I allele (OR=1.29, 95% CI: 1.15 to 1.45, p<0.0001).

Conclusion

The current evidence suggests that there is a significant association between ACE I/D gene polymorphism and vitiligo. These findings support the use of ACE polymorphism in the prediction of vitiligo as a biomarker.

Therapeutic effects of iNOS inhibition against vitiligo in an animal model

Nitric oxide (NO) is involved in several biological processes, but its role in human melanogenesis and vitiligo need further studies. Previous studies revealed that exposure to UVA and UVB were capable of the inducing nitric oxide production in keratinocytes and melanocytes through the activation of constitutive nitric oxide synthase, whereas inducible nitric oxide synthase overexpression has been reported to play an important role in hyperpigmentary disorders. The aim of this study was to evaluate iNOS inhibitor aminoguanidine (AG) as a therapeutic agent in our mouse model of vitiligo. In this study, male C57BL/6J Ler-vit/vit mice were purchased to evaluate the effect of iNOS inhibitor (aminoguanidine) (50 and 100 mg/kg) and L-arginine (100 mg/kg) in a mouse model of vitiligo induced by monobenzone 40%. Moreover, we used phototherapy device to treat the mice with NBUVB as a gold standard.The findings revealed that monobenzone was capable of inducing depigmentation after 6 weeks. However, aminoguanidine in combination with monobenzone was decrease the effect of monobenzone, while L-arginine play a key role in promoting the effect of monobenzone (P<0.001). Based on the phototherapy, the efficacy of phototherapy significantly increased by adding L-arginine (P<0.05). Taken together, we suggest that iNOS inhibitor can be a novel treatment for the prevention and treatment of vitiligo by combination of NBUVB therapy, furthermore; NO agents like L-arginine could also increase the effectiveness of phototherapy. Taken together, this pilot study showed significant repigmentation of vitiligous lesions treated with iNOS inhibitor plus NBUVB therapy, where other aspect including expression of an inducible iNOS, NO and TNF levels remained to be evaluated in mice model.

Alterations in ACE and ABCG2 expression levels in the testes of rats subjected to atropine-induced toxicity

Atropine-induced damage is associated with enzyme and protein alterations. The aim of the present study was to investigate atropine‑induced alterations in testicular expression levels of angiotensin‑converting enzyme (ACE) and adenosine 5'-triphosphate binding cassette sub‑family G member 2 (ABCG2) following atropine treatment. Male Wistar rats received 15 mg/kg/day atropine for 7 days; control rats received an identical volume of saline, Following treatment, the testes were harvested for immunohistochemistry and in situ hybridization to examine the protein and gene expression levels of ACE and ABCG2 by digital image analysis. ACE gene and protein expression levels were significantly reduced in the testes of atropine‑treated rats, compared with control rats (P=0.0001 and P<0.001, respectively). In addition, ABCG2 gene and protein expression levels were significantly increased in the testes of atropine‑treated rats, compared with control rats (P=0.0017 and P<0.001, respectively). Thus, the results of the present study demonstrate that testicular protein and gene expression levels of ACE and ABCG2 were altered as a result of atropine‑induced toxicity in the rats. These alterations may result in abnormal testicular function, and the proteins and genes identified in the present study may be useful to elucidate the mechanisms underlying atropine‑induced toxicity and provide a direction for further studies.