Aloe vera and Streptozotocin-Induced Diabetes Mellitus

Diabetes mellitus is defined as prolonged hyperglycemia, which can harm the eyes, kidneys, and cardiovascular and neurological systems. Herbal agents and their derived supplements have been used for treatment of diabetes mellitus as a part of integrated complementary medicine for centuries. Numerous studies have considered Aloe vera (L.) Burm.f, Xanthorrhoeaceae, as an alternative medicine due to its abundant bioactive chemicals, such as alkaloids, anthraquinones, and enthrones, with therapeutical properties including antioxidant, anti-inflammatory, neuro-protective, and anti-diabetic effects. Aloe vera has received considerable attention in traditional medicine for the treatment of several diseases including diabetes mellitus. Numerous studies have investigated the effects of herbal agents on diabetes mellitus using a streptozotocin-induced diabetic model. Thereby, this article reviews the effects of Aloe vera prescription on streptozotocin-induced diabetes mellitus to provide a clear insight into the role of this medicinal plant in several biological functions, such as antioxidant, wound healing, anti-inflammatory, anti-hyperglycemic, and anti-hyperlipidemic in diabetic models.

α-Melanocyte-Stimulating Hormone Triggers Melanogenesis Via Activation of the Aryl Hydrocarbon Receptor Pathway in B16F10 Mouse Melanoma Cells

Melanin is a group of natural pigments that determines the human skin color and provides fundamental protection against the harmful impacts of physical and chemical stimuli. The aim of this study was to establish the regulatory role of aryl hydrocarbon receptor (AhR) in α-melanocyte-stimulating hormone (α-MSH) induced melanogenesis. In the present study, following knockdown of AhR, murine B16F10 cells were treated with α-MSH (200 nM) and tyrosinase activities, cellular melanin content, mRNA levels of several important genes involved in melanogenesis including AhR, CTNNB1, TYR2, and microphthalmia-associated transcription factor (MITF) were measured as endpoints. Exposure to α-MSH led to elevated expression of AhR, CTNNB1, MITF, and TYR in accordance with increased tyrosinase enzyme activity as well as a significant rise in the total melanin content. Our results suggest that AhR plays a regulatory role in α-MSH-stimulated melanogenesis.

Anti-androgenic effect of 6-formylindolo[3,2-b]carbazole (FICZ) in LNCaP cells is mediated by the aryl hydrocarbon-androgen receptors cross-talk

The factual impact of endogenously activated AHR by 6-formylindolo[3,2-b]carbazole (FICZ), an endogenous ligand of AHR on androgen receptor (AR) was aim of this study. In this study, LNCaP cells were exposed to FICZ, CH223191 and flutamide (Flu) alone or in combination in the presence and absence of testosterone. CYP1A1 enzyme activity, cell viability, cellular prostate-specific antigen (PSA) and dihydrotestosterone (DHT) production, mRNA levels of PSA, KLK2, TMPRSS2, and AR genes were measured as endpoints. A declining in the expression of androgen- responsive target genes was seen by either Flu or FICZ in the presence of testosterone. Furthermore, the forced decrease in the expression of AR target genes resulted in 41% and 31% decline in the DHT and PSA concentrations respectively. Taken together, endogenously activated AHR plays a regulatory role on AR. Therefore, FICZ might be an effective chemical in treating prostate cancer.

Anti-androgenic effect of astaxanthin in LNCaP cells is mediated through the aryl hydrocarbon-androgen receptors cross talk

The aim of this study was to investigate the anti-androgenic effects of astaxanthin (AST) on human prostatic cancer cell growth, and its impact on androgen receptor (AR) signaling using prostate cancer (PCa) cell line LNCaP. LNCaP cells were treated with AST alone and in combination with CH223191 and flutamide (Flu) in the presence and absence of testosterone. MTT assay, cellular prostate-specific antigen (PSA) and dihydrotestosterone (DHT) production, mRNA levels of CYP1A1, PSA, Kallikrein-Related Peptidase 2 (KLK2), Transmembrane Serine Protease 2 (TMPRSS2), and AR genes were measured as endpoints. The expression of CYP1A1, PSA, KLK2, TMPRSS2, and AR mRNA levels was decreased which results in reducing the production of PSA and DHT in the presence of testosterone. Our data clearly demonstrate that AST has a potential ability to suppress the human prostate LNCaP cells growth at high concentrations. AST was able to repress the testosterone-induced transcription of AR-target genes. PRACTICAL APPLICATIONS: Astaxanthin is a natural compound with the most potent antioxidant activity among other antioxidants. In the current study, ASX suppressed the LNCaP cells at high concentrations. Furthermore, AST inhibited testosterone-induced transcriptional activation of androgen-related genes. AST induced the expression of CYP1A1, which is able to metabolize the steroid hormones. It seems that AST can act as AhR exogenous ligand by induction of CYP1A1, which results in testosterone metabolism and consequent suppression of AR genes. So that, AST could prevent the growth of testosterone-dependent PCa cells, downregulate downstream genes in testosterone pathways, and enhance the metabolism of testosterone via AhR pathway. Collectively, AST could be considered as a potential candidate for the treatment of PCa.

Involvement of Nrf2 Signaling in Lead-induced Toxicity

Nuclear factor erythroid 2-related factor 2 (Nrf2) is used as one of the main protective factors against various pathological processes, as it regulates cells resistant to oxidation. Several studies have extensively explored the relationship between environmental exposure to heavy metals, particularly lead (Pb), and the development of various human diseases. These metals have been reported to be able to, directly and indirectly, induce the production of reactive oxygen species (ROS) and cause oxidative stress in various organs. Since Nrf2 signaling is important in maintaining redox status, it has a dual role depending on the specific biological context. On the one hand, Nrf2 provides a protective mechanism against metal-induced toxicity; on the other hand, it can induce metalinduced carcinogenesis upon prolonged exposure and activation. Therefore, the aim of this review was to summarize the latest knowledge on the functional interrelation between toxic metals, such as Pb and Nrf2 signaling.

Influence of cellular redox environment on aryl hydrocarbon receptor ligands induced melanogenesis

Many environmental pollutants, natural compounds, as well as endogenous chemicals exert their biological/toxicological effects by reacting with the aryl hydrocarbon receptor (AhR). Previous evidence shed new light on the role of AhR in skin physiology by regulating melanin production. In this study, we investigated the effect of oxidative imbalance induced by AhR ligands on the melanogenesis process in B16 murine melanoma cells. Exposure to 6-formylindolo[3,2-b] carbazole (FICZ) or benzo-α-pyrene (BαP) led to enhanced expression of CTNNB1, MITF, and TYR genes following increased tyrosinase enzyme activity and melanin content in an AhR-dependent manner. Analysis of the presence of reactive oxygen species (ROS) as well as reduced glutathione (GSH) / oxidized glutathione (GSSG) ratio revealed that treatment with AhR ligands is associated with oxidative stress which can be ameliorated with NAC (N-acetyl cysteine) or diphenyleneiodonium chloride (DPI). On the other hand, NAC and DPI enhanced melanogenesis induced by AhR ligands by reducing the level of ROS. We have shown for the first time that a cellular redox status is a critical event during AhR ligand-induced melanogenesis.