The main cause of dry eye disease is the evaporation of water from the tear film, leading to insufficient tear production. Increased tear osmolarity, which is linked to ocular surface damage, plays a role in the development of dry eye syndrome. Impairment of ocular surface homeostasis can occur when there is damage or dysfunction of the functional units of the lacrimal gland. The decreased secretion of tears can cause hyperosmotic stress, which in turn triggers the recruitment of immune cells in the lacrimal gland and cornea. This immune response leads to inflammation and damage within these tissues.

Dry eye disease can be treated with a range of eye drops, which encompass anti-inflammatory drugs, immunosuppressants, and steroids. These include artificial tears, lubricants, and steroid eye drops. Although these treatments effectively alleviate the symptoms of dry eye disease, they do not tackle the root cause of the condition.

The purpose of this blog is to provide you with information on the study titled “The Effects of Sargassum horneri Extract and Fucoidan on Tear Hyposecretion and Ocular Surface Injury in Rats with Dry Eye Diseases” conducted by Su-Bin Park et al. The study aimed to explore the potential of Sargassum extract (AB_SH) and its active component Fucoidan in preventing dry eye disease.

The first step involved investigating the prevention of dry eye disease in rats. This was done by removing corneal epithelial cells and lacrimal glands located outside the eye socket. AB_SH (250 mg/kg and 500 mg/kg) and Fucoidan  (100 mg/kg) were orally administered for 7 days.

The administration of AB_SH or Fucoidan showed a dose-dependent reduction in corneal epithelial cell injury caused by hyperosmotic stress, as shown in Figure 1B. The researchers conducted TUNEL staining to assess how AB_SH and Fucoidan influenced hyperosmotic stress-induced apoptosis of corneal epithelial cells. The number of apoptotic cells in corneal epithelial cells was reduced by AB_SH and Fucoidan, with the effect being dependent on their concentration. When exposed to hyperosmolar conditions, the survival of corneal epithelial cells is primarily reduced by apoptosis. However, both AB_SH and Fucoidan demonstrate cytoprotective properties by inhibiting apoptosis.

The expression levels of apoptosis-related proteins in corneal epithelial cells were assessed to determine the effects of AB_SH and Fucoidan. The levels of pro-apoptotic proteins Bax, cleaved caspase-3, and cleaved PARP increased under hyperosmolar conditions, while the levels of the anti-apoptotic protein Bcl-2 decreased. On the other hand, it was observed that the changes in expression of apoptosis-related proteins were significantly reduced by both AB_SH and Fucoidan treatments in a dose-dependent manner, as indicated by Figures 2A and B.

In order to examine the impact of AB_SH and Fucoidan on dry eye disease, the researcher conducted a surgical procedure where he removed the extra-orbital lacrimal gland from one side of the rat model. Figure 3A illustrates a significant decrease in tear volume in rats that had undergone lachrymectomy compared to the normal control rats. AB_SH and Fucoidan were able to reverse the decrease in tear secretion in a manner that depended on the dosage.

The objective of the study was to examine the potential anti-apoptotic properties of AB_SH and Fucoidan  on corneal cells and lacrimal gland cells in rats with dry eye disease, which we accomplished through the use of TUNEL staining. The number of apoptotic cells in the corneal epithelium and lacrimal gland was notably higher in rats that were exposed to tear gas compared to rats in the control group. However, the administration of AB_SH and Fucoidan effectively reversed the apoptosis that was observed.

An exploration of apoptotic pathways has revealed potential therapeutic targets that could be utilized for the treatment of dry eye disease. The findings suggest that the administration of AB_SH may be a promising approach to prevent tissue damage caused by apoptosis, ultimately benefiting patients with dry eye disease.

The extract of Sargassum horneri and Fucoidan have the ability to shield corneal cells from apoptosis caused by hyperosmotic stress, as well as enhance tear secretion and reduce apoptosis in the corneal epithelium and lacrimal gland. Sargassum horneri extract and Fucoidan could potentially provide benefits for individuals suffering from dry eye disease.

Source: Curr Issues Mol Biol. 2023 Aug; 45(8):
6583–6592. doi: 10.3390/cimb45080415