Fu Tu Sheng Jin Rehabilitation Formula Mitigate Airway Inflammation, Mucus Secretion and Immune Dysfunction Induced by SARS-CoV-2 Spike Protein.

Objective: To evaluate the effects of Fu Tu Sheng Jin Rehabilitation Formula (FTSJRF) on airway inflammation, mucus secretion, and immunoreaction in a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein-induced mouse model.

Methods: Forty-two mice were randomly divided into seven groups: normal, D1, D3, D10, D10H, D10M and D10L, according to the days of modeling and different dosages of FTSJRF. D1, D3, D10, D10H, D10M and D10L group mice were intratracheally administered with 15 µg SARS-CoV-2 spike protein; mice in the D10H, D10M, and D10L groups were intragastrically administered FTSJRF (46, 23 and 11.5 g/kg, respectively). Observe the pathological changes in lung tissues, expression of inflammatory factors, and mucins in different groups of mice using HE and PAS staining methods, as well as ELISA and RT-qPCR. Flow cytometry was used to detect T helper 17 (Th17)/regulatory T (Treg) cells and T helper 1(Th1)/T helper 2 (Th2) lymphocyte ratios and the proportions of conventional myeloid dendritic cells (cDCs), plasma cell-like DCs, CD80 and CD86 cells in mouse spleens.

Results: HE and PAS staining showed that, compared to that in the normal group, the lung tissue of the D1 group mice showed a significant inflammatory damage response, whereas the D3 and D10 groups showed a gradual recovery trend. Groups D1 and D3 showed mild mucus secretion, whereas the D10 group had excessive mucus secretion. The D10 group of mice displayed increased levels of IL-4, TNF-α, IL-33 and mucin genes such as MUC1, MUC4, etc, and FTSJRF inhibited the expression of these molecules, mucus secretion and lung damage in SARS-CoV-2 spike protein-induced mouse model. Flow cytometry results showed a decrease in the number of cDCs and an abnormal recovery of DC mature cells in the D10 group. FTSJRF increased the number of cDCs and promoted DC maturation. A higher Th17/Treg ratio was observed in the D3 and D10 groups than in the normal group, whereas this ratio decreases under the effect of FTSJRF. D10 had significantly lower Th1/Th2 ratio than normal, D1 and D3 groups, and high doses of FTSJRF increased it.

Conclusion: FTSJRF mitigates airway inflammation and mucus secretion induced by SARS-CoV-2 spike protein. Additionally, FTSJRF regulates immune functions by promoting DC maturation and Th17/Treg and Th1/Th2 cell homeostasis.