B lymphocytes expressing high levels of PD-L1 are key regulators of diabetes development in non-obese diabetic mice

Overexpression of PD-L1 causes germ cells to slough from mouse seminiferous tubules via the PD-L1/PD-L1 interaction

Spermatogenesis is a cyclical process in which different generations of spermatids undergo a series of developmental steps at a fixed time and finally produce spermatids. Here, we report that overexpression of PD‐L1 (B7 homolog1) in the testis causes sperm developmental disorders and infertility in male mice, with severe malformation and sloughing during spermatid development, characterized by disorganized and collapsed seminiferous epithelium structure. PD‐L1 needs to be simultaneously expressed on Sertoli cells and spermatogonia to cause spermatogenesis failure. After that, we excluded the influence of factors such as the PD‐L1 receptor and humoral regulation, confirming that PD‐L1 has an intrinsic function to interact with PD‐L1. Studies have shown that PD‐L1 not only serves as a ligand but also plays a receptor‐like role in signal transduction. PD‐L1 interacts with PD‐L1 to affect the adhesive function of germ cells, causing malformation and spermatid sloughing. Taken together, these results indicate that PD‐L1 can interact with PD‐L1 to cause germ cell detachment and male infertility.

Canagliflozin impedes ischemic hind-limb recovery in the setting of diabetes

There is a reported increased incidence of lower extremity amputations in individuals with diabetes who are treated with canagliflozin (an SGLT2 receptor inhibitor). It is unclear whether this is an unintended consequence of therapy, or whether canagliflozin can affect peripheral limb perfusion in the setting of underling arterial malperfusion. To evaluate this we explored the effect of canagliflozin on tissue recovery following unilateral hind-limb ischemia (HLI). Adult wildtype (+/+) and diabetic (db/db) mice were maintained on 8 weeks of a regular chow diet, or a chow diet containing canagliflozin (200 mg/kg). Following HLI, hind-limb appearance, function, and Doppler perfusion were serially evaluated. Gastrocnemius muscle fiber size and microvessel density were also evaluated 21 days following HLI. We observed that db/db that received a diet containing canagliflozin had significantly worse hind-limb function and appearance scores compared to both db/db mice that received a regular diet and +/+ mice that received a canagliflozin diet. At post-HLI day 21, db/db mice that received a canagliflozin diet also had decreased Doppler perfusion, gastrocnemius muscle fiber size, and microvessel density compared to +/+ mice that received a canagliflozin diet. These findings indicate that canagliflozin appears to impede ischemic peripheral tissue recovery and warrant further clinical investigation in individuals with diabetes and a history of peripheral artery disease.

PD-1 and PD-L1 Expression in Peripheral CD4/CD8+ T Cells Is Restored in the Partial Remission Phase in Type 1 Diabetes

CONTEXT

Partial remission (PR) in type 1 diabetes (T1D) is accompanied by downregulation of the immune response. Programmed cell death-1 (PD-1) and its ligand (PD-L1) are important immunosuppressive molecules, but their changes in the PR phase are unclear.

OBJECTIVE

We investigated the dynamic changes of PD-1/PD-L1 expression on T cells around the PR phase in T1D.

METHODS

Ninety-eight T1D patients were recruited cross-sectionally and grouped according to PR status into nonremitters (individuals who did not undergo PR during the disease course; n = 39), pre-PR (n = 15), mid-PR (n = 30), and post-PR (n = 14) subgroups. PR was defined according to C-peptide level ≥300 pmol/L or index of insulin-adjusted hemoglobin A1c ≤9 as recommended. Among all the 98 patients, 29 newly diagnosed individuals were prospectively followed up for 1 year. The dynamic changes of PD-1/PD-L1 expression, frequency of regulatory T cells (Tregs) and IL-35+ Tregs among peripheral CD4/CD8+ T cells were determined.

RESULTS

PD-1/PD-L1 on CD4+/CD8+ T cells showed a dynamic change around the PR phase: lowest in pre-PR phase, restored in mid-PR phase, and declined again in post-PR phase. Conversely, this pattern did not occur for nonremitters. Notably, PD-1 expression on CD8+ T cells in mid-PR was positively correlated with the length of the PR phase. The percentages of circulating Tregs and IL-35+ Tregs showed no relation to PR.

CONCLUSIONS

The PR phase is associated with restoration of PD-1/PD-L1 on CD4+ and CD8+ T cells, suggesting that PD-1/PD-L1 may be a potential target for prolonging this phase in T1D.