Acupuncture promotes tear secretion by up-regulating VIP/cAMP/PKA/AQP5 signaling in guinea pigs with aqueous tear deficiency dry eye. / 基于VIP/cAMP/PKA/AQP5信号通路探讨针刺治疗水液缺乏型干眼的作用机制.

OBJECTIVES: To observe the effect of acupuncture on the ocular surface symptoms and the protein expression of vasoactive intestinal peptide (VIP) / cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) / aquaporin 5(AQP5) signaling pathway in lacrimal gland tissue of aqueous tear deficiency (ATD) type dry eye model, so as to investigate its mechanism underlying improvement of ATD. METHODS: British shorthair guinea pigs were randomly divided into blank control, model, acupuncture, sham-acupuncture and medication group, with 8 guinea pigs in each group. The ATD model was established by subcutaneous injection of scopolamine hydrobromide (0.6 mg/dose, 4 times/d for 10 days). For guinea pigs of the acupuncture group, filiform needles were inserted into bilateral "Jingming"(BL1), "Cuanzhu"(BL2), "Sizhukong"(TE23), "Taiyang"(EX-HN5), and "Tongziliao"(GB1) for 15 min. For guinea pigs of the sham-acupuncture group, a blunt filiform needle was used to repeatedly prick (not pierce) the skin of the same acupoints mentioned above. The treatment in the above two groups was conducted once daily for 14 days. The guinea pigs in the medication group received administration of sodium hyaluronate eye drops in both eyes, three times a day for 14 days. The objective tests of tear film break-up time (BUT), corneal fluorescein staining score (FLS) and phenol red thread (PRT) test were conducted before and after modeling and after the intervention. After the intervention, the lacrimal index (weight of lacrimal gland/body weight) was calculated. Histopathological changes of the lacrimal gland were observed after H.E. staining. The expression of AQP5 in the lacrimal gland were detected by immunofluorescence, and the contents of VIP and AQP5 in the lacrimal gland were measured by ELISA, the protein expression levels of VIP, cAMP, PKA, p-PKA and AQP5 in the lacrimal gland were detected by Western blot. RESULTS: In comparison with the blank control group, the PRT, BUT, lacrimal index, AQP5 immunoactivity, contents of VIP and AQP5, and protein expression levels of VIP, cAMP, PKA, p-PKA and AQP5 were significantly decreased(P<0.01, P<0.05), and FLS was obviously increased (P<0.01) in the model group . Compared to the model group, the PRT, BUT, lacrimal index, AQP5 immunoactivity, contents of VIP and AQP5, and expression levels of VIP and AQP5 in both acupuncture and medication groups, and the expression levels of cAMP, PKA, p-PKA in the acupuncture group were considerably increased (P<0.01, P<0.05), while the FLS was markedly decreased in both acupuncture and medication groups (P<0.01, P<0.05). Compared with the medication group, the acupuncture group had increased PRT (P<0.05). CONCLUSIONS: Acupuncture intervention is effective in reducing ocular surface damage and promoting tear secretion in guinea pigs with ATD, which may be related to its function in activating VIP/cAMP/PKA signaling, and promoting the expression of AQP5 in the lacrimal gland.

[Acupuncture mitigates ocular surface inflammatory response via α7nAChR/NF-κB p65 signaling in dry eye guinea pigs].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on the ocular surface inflammation and α7 nicotinic acetylcholine receptor (α7nAChR) / nuclear factor kappa-B (NF-κB) p65 signal pathway in guinea pigs with dry eye, so as to explore its underlying mechanism. METHODS: A total of 32 male British tricolor short haired guinea pigs were randomized into blank control, model, EA and sham acupuncture groups, with 8 guinea pigs in each group. The dry eye model was established by subcutaneous injection of scopolamine hydrobromide solution (0.6 mg/0.2 mL each time, 4 times a day for 10 days). Guinea pigs of the EA group was treated with EA at bilateral "Cuanzhu" (BL2) and "Taiyang" (HN5), and manual acupuncture at bilateral "Jingming" (BL1), "Sizhukong" (SJ23), "Tongziliao" (GB1) for 15 min, once daily for 14 days. For animals of the sham acupuncture group, a blunt needle was used to prick the skin surface of the acupoints, the acupoint selection and stimulation time were the same as those in the EA group. Before and after modeling and after the intervention, the breakup time (BUT) of lacrimal film, sodium fluorescein coloring (Fl) state of corneal epithelium and phenol red thread (PRT) moist length were recorded for assessing the severity of dry eye. The density of activated immune cells around the corneal epithelial stromal cells was determined by corneal confocal microscopy. The contents of interleukin-4 (IL-4), IL-6, IL-10, tumor necrosis factor α (TNF-α) in the cornea and lacri-mal gland tissues were determined by ELISA, and the expression levels of α7nAChR and NF-κB p65 in the cornea and lacrimal gland were detected by immunohistochemistry and Western blot, separately. RESULTS: Compared with the blank control group, the corneal Fl, density of activated immune cells of corneal epithelium, contents of IL-6, IL-10 and TNF-α in both corneal and lacrimal gland tissues, NF-κB p65 cell positive rate and protein expression of lacrimal gland and corneal tissues were significantly increased (P<0.01, P<0.05), while the BUT, PRT and lacrimal gland α7nAChR cell positive rate considerably decreased (P<0.01) in the model group. In comparison with the model group, the level of corneal Fl, density of the activated immune cells of corneal epithelium, contents of corneal and lacrimal IL-6 and TNF-α, and corneal and lacrimal NF-κB p65 cell positive rates and protein expressions were remarkably down-regulated in the EA group (P<0.01, P<0.05), rather than in the sham acupuncture group (P>0.05) except content of corneal IL-10, lacrimal NF-κB p65 cell positive rate and lacrimal α7nAChR protein expression, whereas the levels of BUT, PRT, corneal and lacrimal IL-10 and corneal and lacrimal α7nAChR cell positive rates and protein expressions significantly up-regulated in the EA group (P<0.01, P<0.05), rather than in the sham acupuncture group (P>0.05) except corneal TNF-α and corneal NF-κB p65 protein expression. CONCLUSION: EA can improve corneal and lacrimal function in dry eye guinea pigs, which may be associated with its actions in increasing the expression of α7nAChR, inhibiting the nuclear translocation of NF-κB, and reducing the activated immune cells and inflammatory reaction.

Capsanthin from Capsicum annum fruits exerts anti-glaucoma, antioxidant, anti-inflammatory activity, and corneal pro-inflammatory cytokine gene expression in a benzalkonium chloride-induced rat dry eye model.

Dry eye disease (DED) is a complex ocular surface inflammatory disease. Its occurrence varies widely over the world, ranging from 5% to 34%. The use of preservatives, specifically benzalkonium chloride, in the ocular drops worsens the DED conditions. Furthermore, the Covid-19 pandemic increased screen time and the use of face masks and shields. As a result, the number of people suffering from dry eye disease (DED) has increased significantly in recent years. The main objective of our study is to find a solution to manage the dry eye disease (DED) preferably from natural source without any adverse events. In this study, the beneficial effects of capsanthin from Capsicum annum (CCA) were evaluated on benzalkonium chloride (BAC)-induced dry eye disease (DED) in Albino Wistar rats. Oral supplementation of CCA resulted in a statistically significant decrease in intraocular pressure (IOP) (p < .0001), increase in tear break-up time (TBUT) (p < .01), decline in Schirmer test results (p < .01), and decrease in corneal surface inflammation (p < .01). Capsanthin ameliorated in reducing oxidative stress by increasing serum antioxidant levels such as glutathione peroxidase (GPX), nitric oxide (NO), and lactoferrin (LTF) and inhibiting matrix metalloproteinases 2 and 9 (MMP2 and MMP9) (p < .0001). Capsanthin treatment significantly inhibited the expression of inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), interleukins (IL-2, IL-4, IL-6), and pro-inflammatory mediator, matrix metalloproteinase-9 (MMP9). Furthermore, the lacrimal gland expressed vascular cell adhesion molecule (VCAM-1), and prostaglandin-endoperoxide synthase 2 (PTGS2) was suppressed by CCA treatment. PRACTICAL APPLICATIONS: Benzalkonium chloride (BAC), a preservative widely used in the topical ocular drug delivery system (ODDS), causes undesirable effects such as dry eye disease as well as ameliorating intraocular pressure leading to optical nerve damage and irreversible vision loss. Capsanthin from Capsicum annum (CCA) can be used to treat symptoms related to dry eye disease such as inflammation, eye irritation, visual disturbance, ocular discomfort with potential damage to the ocular surface. The CCA may be beneficial in the treatment of glaucoma, an elevated intraocular pressure. Capsanthin from C. annum can be useful in managing DED by increasing tear break-up time (TBUT), declining in Schirmer test results and decreasing in corneal surface inflammation.

[Effect of electroacupuncture on ocular surface sensory neuralgia and expression of P2X3 receptor and PKC in cornea and trigeminal ganglion of dry eye guinea pigs].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on ocular surface sensory neuralgia and the expression of P2X3 receptor (P2X3R) and protein kinase C(PKC)in cornea and trigeminal ganglion (TG) in dry eye disease (DED) guinea pigs, so as to explore its mechanism underlying improvement of ocular surface sensory neuralgia in DED. METHODS: Male British tricolor short haired guinea pigs were randomly divided into control, model, medication (pranoprofen), EA and sham acupuncture groups, with 8 guinea pigs in each group. The dry eye model was induced by subcutaneous injection of scopolamine hydrobromide solution (0.6 mg/0.2 mL,once daily) for 10 d. Guinea pigs in the medication group were treated by applying pranoprofen eye drops to eyes, 1 drop for one eye each time, three times a day. Guinea pigs of the EA group received EA stimulation (4 Hz/20 Hz,1 mA) of bilateral "Cuanzhu" (BL2) and "Taiyang" (HN5) and acupuncture at "Jingming" (BL1) "Sizhukong" (TE23), "Tongziliao" (GB1) for 15 min, once a day. Guinea pigs in the sham acupuncture group received blunt stimu-lation at the surface of the same acupoint with the tip of the acupuncture needle, once a day. All the treatments were conducted for 14 d. The corneal epithelium fluorescein staining score (0-3 points) was given according to the number of fluorescence-positive dots and flake-like coloration, the corneal mechanical perception thread (CMPT) detected using a corneal perception meter, and the palpebral fissure height measured. The number of sensory neurons in the cornea and TG was determined by using cholera toxin subunit B conjugated with Alexa Fluor 488 fluorescence labelling, and the expression levels of P2X3R and PKC in the cornea and TG detected by using immunohistochemistry and Western blot, separately. RESULTS: Compared with the control group, the corneal fluorescein staining score, immunoactivity and expression of P2X3R proteins in both cornea and TG, PKC proteins in TG were significantly increased (P<0.01), whereas the CMPT and the height of palpebral fissure and the number of TG neurons significantly decreased in the model group (P<0.05,P<0.01). In comparison with the model group, the fluorescein staining score in the medication and EA groups, the immunoactivity and expression of P2X3R in cornea and TG in the EA group, and that of TG PKC in the EA group and the sham acupuncture groups were significantly decreased (P<0.05, P<0.01), while the height of palpebral fissure and CMPT after EA and the number of labelling TG sensory neurons were remarkably increased in the EA group (P<0.01) rather than in the medication and sham acupuncture groups (P>0.05). CONCLUSION: EA can alleviate the damage of corneal epithelium and sensory neurons in dry eye model guinea pigs, which may be related to its functions in down-regu-lating the expression of P2X3R and PKC in the cornea and TG.

Electroacupuncture inhibits the corneal ROS/TXNIP/NLRP3 signaling pathway in a rat model of dry eye syndrome.

BACKGROUND: Electroacupuncture (EA) treatment has been found to ameliorate clinical symptoms in patients with dry eye, but its mechanisms are still not entirely clear. OBJECTIVE: To study the regulation of EA on ocular surface function and the corneal reactive oxygen species (ROS)/thioredoxin-interacting protein (TXNIP)/Nod-like receptor protein 3 (NLRP3) inflammatory signaling pathway in dry eye syndrome (DES) model rats. METHODS: Male Sprague-Dawley (SD) rats were randomly divided into five groups: Normal, Model, Model + EA, Model + NAC (N-actetylcysteine) and Model + NS (normal saline). The DES model was developed by subcutaneous injection of scopolamine hydrobromide with exposure to an air draft in the latter four groups. After intervention, the Schirmer I test (SIT), tear film break-up time (BUT) and ROS content were measured, the histopathological changes of corneal tissues were observed, and the mRNA and protein expression levels of TXNIP, NLRP3, apoptosis-associated Speck-like protein containing CARD (ASC), caspase-1, interleukin (IL)-1ß and IL-18 were detected. RESULTS: Compared with the Model group, the SIT and BUT increased significantly in the Model + EA group after intervention (p < 0.05), and the corneal injury was improved. Corneal ROS content declined in both Model + EA and Model + NAC groups (p < 0.05), and mRNA expression of TXNIP, NLRP3, ASC and caspase-1 also decreased (p < 0.01). Corneal protein expression of TXNIP, NLRP3, IL-1ß and IL-18 decreased significantly in the Model + EA group (p < 0.01). CONCLUSION: Inhibiting the ROS/TXNIP/NLRP3 signaling pathway may be the mechanism underlying the role of EA in improving corneal injury in DES model rats.

[Effect of acupuncture on expression of transfer growth factor-ß1 in lacrimal gland of rabbits with dry eye].

OBJECTIVE: To observe the effect of acupuncture on expression of transforming growth factor-ß1(TGF-ß1) in lacrimal gland of rabbits with dry eye, so as to explore its underlying mechanism in improving dry eye. METHODS: Healthy male New Zealand rabbits were randomly assigned to 5 groups (n=6 in each group), namely, blank group, model group, western medicine group, acupuncture group and sham acupuncture group. The dye eye rabbit model was estabilished by subcutaneous injection of Scopolamine Hydrobromide solution for 21 days. After modeling, rabbits in the western medicine group were treated with Flumirone eye drops in their eyes 3 times a day, one drop each time. Rabbits of the acupuncture group reveived electroacupuncture(4 Hz/20 Hz, 1 mA) at "Cuanzhu"(BL2) and "Tongziliao"(GB1) for 15 min, and received acupuncture at "Jingming"(BL1), "Taiyang" (EX-HN5) and "Sizhukong"(TE23) for 15 min, once a day. Rabbits of the sham acupuncture group received blunt acupuncture at the surface of the same acupoints once a day. All the treatments were conducted for 14 days. The changes of tear flow, tear film break-up time (BUT) and lacrimal gland morphology in each group were observed. The expression of TGF-ß1 protein and mRNA in lacrimal gland were detected by Western blot and quantitative real-time fluorescence PCR respectively. RESULTS: Following modeling, except for the blank group, the tear flow and BUT in other 4 groups decreased significantly (P<0.01). Compared with their own pretreatment, the tear flow and BUT in western medicine group and acupuncture group increased after the treatment (P<0.05). Compared with the model group, the tear flow and BUT increased in the western medicine group and the acupuncture group(P<0.05). Atrophic lacrimal epithelial cells and the stroma of mucous membrane infiltrated by lymphocytes and plasma cells were found in rabbits of the model group and the sham acupuncture group. By contrast, in the western medicine group and the acupuncture group, the structure of lacrimal epithelial cells was basically normal, and the infiltration of lymphocytes and plasma cells were scattered in the stroma of mucous membrane. In comparison with the blank group, the expression of TGF-ß1 protein and mRNA in lacrimal gland were significantly up-regulated in the model and sham acupuncture groups (P<0.01). Compared with the model group, the expression of TGF-ß1 protein and mRNA were significantly down-regulated in the western medicine and acupuncture groups (P<0.01, P<0.05). CONCLUSION: Acupuncture intervention can increase tear flow and BUT in rabbits with dry eye, which may be related to the regulation of TGF-ß1 expression in lacrimal gland.

The Effect of the Aqueous Extract of Bidens Pilosa L. on Androgen Deficiency Dry Eye in Rats.

BACKGROUND/AIMS: Bidens pilosa L. (Bp) is widely distributed in China and has been widely used as a traditional Chinese medicine. The aim of this study was to examine the effect of the extract of Bp on androgen deficiency dry eye and determine its possible mechanisms. METHODS: Twenty-four rats were randomly divided into four groups: Group Con (control), Group Sal (physiological saline), Group Fin (oral finasteride), and Group Bp (oral finasteride and Bp). The dry eye model was established in group Fin and group Bp. Aqueous tear quantity was measured with phenol red-impregnated cotton threads with anesthesia. Tear film breakup time (BUT) and corneal epithelial damage were evaluated by fluorescein staining. Animals were sacrificed at 28 days, and ocular tissues (lacrimal gland and cornea) were evaluated with light microscopy; gene microarray analysis for inflammatory cytokines and Western blot were also performed. RESULTS: Finasteride administration effectively induced dry eye in rats by 14 days after administration. Group Fin rats had significantly higher fluorescein staining scores and lower aqueous tear quantity and BUT than the group Con rats, and notable inflammatory cell infiltrates were observed in the lacrimal gland of group Fin rats. The fluorescein staining score, aqueous tear quantity and BUT significantly improved with Bp treatment in the group Bp rats, and the structures of the lacrimal gland were well maintained without significant lymphocyte infiltration. Cytokine antibody array data identified the cytokines B7-2/Cd86, IL-1ß, IL-4, IL-6, IL-10, MMP-8, FasL, TNF-α and TIMP-1 as candidates for validation by Western blot. Expression levels of pro-inflammatory cytokines, including IL-1ß, IL-6, and TNF-α, in group Fin were upregulated compared with group Con. Levels of anti-inflammatory cytokines, such as IL-4 and IL-10, in group Fin were also upregulated compared with those in group Con. Compared with group Fin, IL-1ß, FasL, and TNF-α were significantly decreased in group Bp. CONCLUSION: The extract of Bp appears to be effective for the treatment of androgen deficiency dry eye in rats by improving aqueous tear quantity, maintaining tear film stability, and inhibiting the inflammation of the lacrimal gland.

IL-13 Stimulates Proliferation and Expression of Mucin and Immunomodulatory Genes in Cultured Conjunctival Goblet Cells.

PURPOSE: To investigate the effects of IL-13 on goblet cell proliferation, differentiation, and expression of mucin and immunomodulatory genes. METHODS: Explants were excised from the conjunctiva of young C57BL/6 mice. Cultures received 200 µL per week of either Keratinocyte media (KSFM) or KSFM supplemented with 10 ng/mL IL-13 and were incubated for 3 (D3), 7 (D7), or 14 (D14) days. Subsequently, cell proliferation was assessed or cultures were immunostained, collected for dot blot, or for reverse transcription (RT) and quantitative real-time PCR (qPCR) or for RT-PCR gene array. RESULTS: The cultured conjunctival epithelium expressed goblet cell associated keratin 7 and mucins MUC5AC and MUC2 and when stimulated with IL-13 showed increased proliferation at D3 and D7 (P < 0.05) compared with control. MUC5AC expression was increased in the IL-13-treated group at D3 and D14 (P < 0.05). IL-13-treated cultures showed increased chemokine ligand 26 (CCL26), chloride channel calcium activated channel 3 (CLCA3), fas ligand (FasL), and Relm-ß at D7. All conjunctival cultures expressed MUC2, and its expression was decreased at D3 (P < 0.05) and increased at D14 (P < 0.05) with IL-13 treatment. CONCLUSIONS: This study demonstrated that conjunctival goblet cells are IL-13 responsive cells that produce factors known to maintain epithelial barrier, stimulate mucin production, and modulate immune response in nonocular mucosa when treated with IL-13. The functional significance of IL-13-stimulated factors remains to be determined.

Osmoprotective effects of supplemental epidermal growth factor in an ex vivo multilayered human conjunctival model under hyperosmotic stress.

BACKGROUND: To analyze the effects of supplemental epidermal growth factor (EGF) and the roles of inflammatory cytokines (interleukin [IL]-6) in an ex vivo dry-eye model under hyperosmotic stress using a multilayered culture of human conjunctival epithelial cells (HCECs). METHODS: Multilayered cultures of HCECs were exposed to hyperosmotic stress (400 mOsm/L) for 24 h in addition to 0.5 ng/mL EGF (low-EGF group) or 25 ng/mL EGF (high-EGF group). Apoptosis was analyzed using the TUNEL assay. Cell proliferation was measured using the [3H]-thymidine incorporation assay. The expression of IL-6, EGF, EGF receptor (EGFR), and phosphorylated extracellular signal-regulated kinase (p-ERK) was measured by western blot analysis. The secretion of IL-6 was measured using ELISA. Western blot analysis was also performed using antibodies against cleaved caspase-3. RESULTS: The percentage of apoptotic cells was lower in the high-EGF group (6.7%) than in the low-EGF group (10.3%). The high-EGF group demonstrated increased proliferation (323.7 counts/min in the low-EGF group vs 649.1 counts/min in the high-EGF group). EGF induced higher phosphor-EGFR expression and upregulated p-ERK in HCECs. In addition, EGF significantly decreased the secretion of IL-6 and cleaved caspase-3 in HCECs. CONCLUSIONS: The level of IL-6 was increased in the ex vivo HCEC dry-eye model that was under hyperosmotic stress. Supplemental EGF reduces the level of IL-6, decreases apoptosis, and increases proliferation. These findings indicate that EGF has potential as a therapeutic agent for the treatment of dry eyes.