Catalpol, the active ingredient in a medicinal herb often used for Sjögren’s syndrome treatment, eases disease symptoms by altering the balance and communication of specific immune cells, a study in mice suggests.
The study, “Catalpol ameliorates Sjögren’s Syndrome by modulating interplay of T and B cells,” was published in the journal Biomedicine & Pharmacotherapy.
The herbal plant Rehmanniae Radix is frequently used to treat Sjögren’s syndrome in traditional Chinese medicine, but the therapeutic effects of its active ingredient, catalpol, have never been assessed in Sjögren’s.
In the study, researchers at the Nanjing University of Chinese Medicine set out to investigate if catalpol can reduce the signs and symptoms associated with the condition, and the mechanisms used to achieve such benefits.
Experiments were performed on non-obese and diabetic (NOD) mice, a strain that spontaneously develops symptoms of Sjögren’s syndrome — salivary infections, immune cell infiltration, reduced saliva flow, and autoantibodies — which mimic the condition in humans.
In the study, eight-week-old female mice were randomly divided into three groups that received a low or high dose of oral catalpol, or a saline solution. Treatment was administered once daily for eight weeks.
Looking at water intake and salivary flow rates, which are overall measures for symptom severity, the researchers found that catalpol significantly protected mice from disease symptoms.
By the end of treatment, the animals receiving catalpol had normal water intake and saliva production, while control animals were drinking significantly more water and their saliva flow had decreased significantly.
Similarly, salivary infection was severe in the control mice after eight weeks, while mice receiving the higher dose of catapol showed almost no sign of infection, and those receiving the lowest dose showed signs of mild infection.
Together, these findings indicate that catalpol can successfully alleviate symptoms that are indicative of Sjögren’s syndrome.
Attempting to determine how catalpol prevented disease symptoms, the researchers examined the mice more closely to monitor for any changes in immune system activity. They found that administering catalpol altered the balance of specific immune system cell types in mice, called T follicular regulatory (Tfr) cells and T follicular helper (Tfh) cells, and the ratio between these two immune subtypes.
These immune changes decreased the abnormal formation of structures, called germinal centers, that act as hubs for immune system activity in salivary glands and other atypical locations.
Two key inflammatory molecules produced in germinal centers, IFN-γ and BAFF, were also reduced in catalpol-treated mice compared to controls, also indicating reduced autoimmune activity in the presence of catalpol.
“Our work indicates that catalpol might be a potential substance to ameliorate primary Sjogren’s Syndrome in a NOD mice model by modulating Tfr and Tfh cells,” the researchers said.
Nevertheless, they noted that additional research is needed to determine how catalpol influences T-cells and inflammatory molecules, and suggest that transgenic mice (that have human DNA) would be a logical next step.
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