3.3 IL-35 protein therapy relieved the symptoms of psoriasis
models
We stimulated HaCaT cells using M5 together with IL-35 to observe the
effect of IL-35 on the expression of CXCL8 and IL-6. We found consistent
lower levels of CXCL8 and IL-6 in the IL-35-treated group than in the
control group (Supplementary Fig. 1A, B). The results suggest that
IL-35 suppresses the expression of
CXCL8 and IL-6 in stimulated HaCaT cells.
We explored whether IL-35 could exhibit a therapeutic effect in
K14-VEGF-A-Tg mice. Therefore, we injected K14-VEGF-A-Tg mice (10 weeks
old) with IL-35 (5 μg) recombinant protein, as shown in Supplementary
Figure 2A. We found that mice in the control group showed increased ear
thickening; however, mice in the IL-35-treated group were healthy
(Supplementary Fig. 2B). Pathological features, such as erythema,
scaling, and thickness based on PASI scores are shown in Supplementary
Figure 2C.
Concomitantly,
we obtained the cumulative scores of these two groups (Supplementary
Fig. 2C).
In
addition, we observed that the IL-35-treated group had lower cumulative
scores
than the control group. H&E staining of lesioned tissues revealed the
severity of psoriatic disease in the control (PBS) group (Supplementary
Fig. 2D, left panel). In contrast, we observed the reversal in ear
thickness and reduction in leukocyte infiltration in the dermis and
epidermis in the IL-35-treated group (Supplementary Fig. 2D, right
panel). Moreover, we demonstrated that the IL-35-treated group exhibited
a lower disease score based on the Baker scoring system compared to the
control group (Supplementary Fig. 2E).
The
IMQ-induced
psoriasis mouse model is the most common model of psoriasis (Shih et
al., 2020).
Experimental
procedures and the acquisition of mouse back skin images are shown in
Supplementary Figures 3A and 3B. Based on the PASI scoring evaluation of
erythema, scaling, and thickness, we examined the cumulative scores for
different groups in the IMQ-induced psoriasis mouse model
(Supplementary
Fig. 3C). In particular, we noticed that the IMQ model group exhibited
higher cumulative scores than the control group. We then used flow
cytometry to detect any changes in the population of MDSCs in the spleen
and skin tissues of mice in the IMQ-induced model; we found that the
number of MDSCs in the spleen and skin tissues of mice was significantly
higher than that in the control group
(Supplementary
Fig. 3D, p < 0.001 and p < 0.01, respectively). The
results were consistent with those obtained using clinical samples.
We determined whether IL-35 exerts
a therapeutic effect on the IMQ-induced psoriasis mouse model. The
schedule
of the delivery of IL-35 for the therapy of mice with IMQ-induced
psoriasis is shown in Figure 3A. After treatment, we found that the
control group had serious inflammation and skin flaking, which worsened
by the end of the experiment (Fig. 3B. Based on the PASI scoring
evaluation of erythema, scaling, and thickness (Fig. 3C),
we
calculated the cumulative scores of different groups (Fig. 3C).
IL-35
group showed lower cumulative scores relative to the control group. In
addition, H&E-stained skin sections showed less epidermal thickening in
the IL-35 group compared with the control group (Fig. 3D). The Baker
system-based disease score in the IL-35 treated group was significantly
lower than that in the control group (Fig. 3E, p < 0.001).
3.4 IL-35 regulates inflammatory cytokine production in systemic
and local immune microenvironment in IMQ-induced mice .
Inflammatory cytokines play important roles in the progression of
psoriasis (Liang, Xu, Peng, Pan & Ye, 2014). ELISA was used to measure
the levels of cytokines in serum and dorsal skin. Tissue cytokines from
supernatants of extracted tissue protein were assayed and are presented
in terms of picograms cytokine per milligram tissue (pg/mg). IL-17A
(Fig. 4A), IL-23 (Fig. 4B), IL-1β(Fig. 4C) and IL-6 (Fig. 4D) were
detected in serum and skin tissue. Data are representative of three
independent experiments. These results showed that, in addition to no
significant difference in serum IL-6, other cytokines were significantly
different in serum and skin tissue. Columns represent mean; bars
represent SD. *p < 0.05, **p < 0.01, ***p
< 0.001. ns, no significance.
3.5 Treatment with IL-35