PART TWO Cistanche Deserticola Polysaccharide Induces Melanogenesis in Melanocytes And Reduces Oxidative Stress
Mar 07, 2022
Contact: joanna.jia@wecistanche.com
4 | DISCUSSION AND CONCLUSIONS
In this study, we investigated the role of CDP in HEMs and B16F10 cells. For the first time, we found Cistanche that CDP could promote melanogenesis in melanocytes and promote pigmentation in zebrafish. A subsequent experiment showed that the MAPK signaling pathway was activated under CDP treatment. We further investigated its role in oxidative stress and found that CDP could attenuate H2O2- induced cytotoxicity and apoptosis in melanocytes; meanwhile, CDP could activate the NRF2/HO-1 antioxidant pathway and scavenge intracellular ROS under oxidative stress conditions.
cistanche is a tyrosinase inhibitor
Mitogen-activated protein kinase is a vital pathway involved in Cistanche in the regulation of MITF, a key transcription factor that promotes the expression of melanogenesis-related genes and subsequently affects melanin synthesis and transport.26,27 In our study, the ac- activation of ERK, JNK, and p38 in melanocytes was increased significantly after CDP treatment; meanwhile, the expressions of MITF/p-MITF and MITF-driven TYR, TRP1, TRP2 and RAB27A were up-regulated accordingly. Thus, we suggest that CDP can promote melanogenesis via activating the MAPK pathway, but how CDP activates MAPKs remains Cistanche unknown. According to recent studies, toll-like receptor 4 (TLR4) is highly expressed in melanocytes and involved in melanogenesis.28,29 TLR4 is an important transmembrane protein that can specifically bind lipopolysaccharide (LPS)30; studies reported that LPS can induce melanogenesis.29 Interestingly, several polysaccharides extracted from plants or mushrooms reportedly activated TLRs and downstream signaling pathways such as MAPK and nuclear factor kappa beta (NF-κB).31,32 Therefore, we suspect that CDP can be recognized and bound by TLRs, then activates the downstream MAPK signal-ling pathway and promotes melanogenesis. Furthermore, nucleotide-binding oligomerization domain-like receptors (NLRs) are known to recognize intracellular ligands and drive the activation of MAPK and NF-κB signaling pathways.33,34 As reported, poly- saccharides extracted from Ganoderma lucidum and Astragalus can enter cells and affect NLRs.35,36 Thus, it is possible that CDP can enter melanocytes and regulate the MAPK signaling pathway via NLRs. However, further studies are needed to verify this hypothesis.
Some studies to date reported the application of herbal polysaccharides in melanogenesis to inhibit melanin production.37,38 However, in this study, CDP promoted melanogenesis in
melanocytes, and this effect was further confirmed after comparison with α-MSH. CDP is also a kind of polysaccharide extracted from herbs, we suspect that the opposite effect of CDP may be related to the structural differences between CDP and other polysaccharides. Polysaccharides are formed by polymerization of monosaccharides but are variable in monosaccharide type, mono-saccharide composition, glycosidic bond, side-chain structure, and molecular weight39,40; these factors are thought to determine their biological functions.41 Existing studies have proposed the structure of CDP and suggested that CDP structure subsequently influences its function.42 Thus, more proof is needed to fully understand CDP and confirm our hypothesis.
Melanogenesis is an important protective mechanism of resisting Cistanche ultraviolet damage and maintaining body homeostasis43; at the same time, melanocytes are easily exposed to unfavorable environments such as ROS overload.11 It is known that ROS participate in promoting melanogenesis, one of the mechanisms is activating MAPKs.44 But studies also revealed that this effect exists only within a certain ROS level, while ROS overload impairs melanogenesis significantly.45 The relationship between ROS, MAPK, and melanogenesis is variable under different conditions, thus, the balance between pro-and anti-oxidant systems is obviously important. In depigmentation diseases such as vitiligo, an imbalanced antioxidant system and uncontrollable ROS overload will damage melanocytes and decrease cell viability.11,46 In this study, we used different concentrations of H2O2 to simulate the ROS overload in cells, and HEMs showed poorer tolerance to H2O2 than B16F10 cells. When melanocytes were subjected to H2O2 treatment, their viability and apoptosis rate got worse, but
Phenylethanoid Glycosides in cistanche can anti-inflammatory
CDP pretreatment could partially reverse the trend. At the same time, ROS was scavenged. As reported, NRF2/ARE antioxidation pathway activation is a major method of ROS scavenging in skin cells.14 In our experiments, the protein levels of NRF2 and HO-1 in melanocytes were up-regulated after H2O2 treatment without CDP; this means that H2O2-induced oxidative stress can activate the NRF2/HO-1 pathway, but it is insufficient for maintaining a redox balance and protecting the cell from injury. However, CDP pretreatment enhanced the NRF2/HO-1 antioxidation pathway and restored the balance. Thus, we suggest that CDP can protect melanocytes from oxidative stress injury via activating the NRF2/HO-1 antioxidation pathway and scavenging ROS.
We found that CDP treatment alone has no influence on ROS or NRF2/HO-1 in melanocytes. This result suggests that CDP can affect redox balance under oxidative stress, but not normal conditions. Moreover, the NRF2/HO-1 antioxidation pathway is reportedly regulated by the PI3K, NF-κB, and MAPK signaling pathways.47,48 In our study, CDP was able to activate the MAPK signaling pathway. It is possible that CDP can activate the NRF2/HO-1 pathway via up-regulating MAPKs. As Slominski reported, melanocytes are stress sensors involved in a regulatory network, and their functions can change rapidly in response to the environment.49 We suggest that the role of CDP is influenced by melanocytes status, it can pro-mote melanogenesis without affecting the antioxidant system under normal conditions but restore the redox balance under oxidative stress conditions. Therefore, the melanocyte function and survival can be maintained in two different ways by CDP. CDP helps melanocytes maintain homeostasis, which is also an important function of melanogenesis.50,51
In conclusion, CDP can promote the melanogenesis of melanocytes
via activating the MAPK signaling pathway. CDP can improve melanocyte survival via activating the NRF2/HO-1 antioxidant pathway and scavenging intracellular ROS under oxidative stress conditions. Our findings are meaningful because they demonstrate that CDP can both promote melanogenesis and protect melanocytes from oxidative stress injury, which is possibly responsible for melanocyte dysfunction and loss. This study's findings indicate that CDP could be a novel drug in the treatment of depigmentation diseases.
cistanche whitening effect on the skin to anti-oxidation
ACKNOWLEDGMENTS
This work was supported by the National Natural Science Foundation of China (No. 81703101), the New Xiangya Talent Projects of the Third Xiangya Hospital of Central South University (No. JY201623 and No. 20170301), the Natural Science Foundation of Hunan Province (No. 2018JJ3788 and No. 2018JJ3793) and the Project of Hunan health commission (No. C2019173). Dr. Yibo Hu performed the main part of the study and wrote the manuscript; Professor Jing Chen and Qinghai Zeng designed the study and guided the manuscript writing; Professor Jinhua Huang, Lihua Huang, and Hong Xiang provided technical support and analyzed the data; Dr. Yixiao Li, Ling Jiang, Yujie Ouyang, Yumeng Li, Lun Yang, and Xiaojiao Zhao contributed to part of the experiments.
CONFLICT OF INTEREST
The authors confirm that there are no conflicts of interest.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.
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