Propentofylline, phosphodiesterase and adenosine reuptake inhibitor modulates lymphocyte subsets and lymphocyte activity after in-vivo administration in non-immunized and SRBC-immunized mice

Evaluation of Immunotropic Activity of Iridoid-Anthocyanin Extract of Honeysuckle Berries (Lonicera caerulea L.) in the Course of Experimental Trichinellosis in Mice

Our experiment determined the immunotropic activity of a natural, iridoid-anthocyanin extract from honeysuckle berry (Lonicera caerulea L.) (LC). The extract was administered to mice infected with Trichinella spiralis, orally at a dose of 2 g/kg bw, six times at 24 h intervals (from day 3 prior to the infection to day 3 post-infection (dpi) with T. spiralis. At 5, 7, 14, and 21 dpi, samples of blood, spleen, and mesenteric lymph nodes (MLN) were collected, and isolated lymphocytes were analyzed by flow cytometry. The splenocyte proliferation was estimated with MTT testing, and the intensity of intestinal and muscle infection was also studied. LC stimulated the local immune system by inducing lymphocyte proliferation in the spleen 7 dpi and altered the percentage and absolute count of B (CD19⁺) and T (CD3⁺, CD8⁺) cells 7, 14, and 21 dpi in the peripheral blood. LC extract affected the dynamics of expulsion of adult Trichinella from the intestines and prolonged the intestinal phase of the infection but did not change the number of larvae in the muscles. These results suggest that Lonicera caerulea L. fruit extract modulates murine cellular immune response during intestinal phase of T. spiralis infection but shows no antiparasitic activity.

Selegiline and clomipramine effects on lymphocyte subsets, regulatory T cells and sheep red blood cell (SRBC)-induced humoral immune response after in vivo administration in mice

We aimed at investigating the influence of clomipramine and selegiline administered in vivo in mice on lymphocyte subsets in lymphoid organs and SRBC-induced humoral immune response. Balb/c mice were given 7 or 14 oral doses (1 mg/kg) of selegiline or clomipramine. Lymphocyte B and T subsets and splenic regulatory T cell (Treg) subset were determined in non-immunized mice 24 and 72 h after the last dose of the drugs. Some mice treated with 7 doses were immunized with sheep red blood cells (SRBC) 2 h after the last dose, and their number of antibody forming cells, haemagglutinin titers and splenocyte subsets were determined. An increase in T lymphocytes and a decrease in B cells were visible in peripheral lymphoid organs, especially after 14 doses of selegiline or clomipramine in non-immunized mice, as well as in spleens of SRBC-immunized mice. The most pronounced change was a decrease in CD4⁺/CD8⁺ ratio resulting mainly from an increase in CD8⁺ subset after seven doses of the drugs in the non-immunized mice. However, it was of a transient nature, as it disappeared after 14 doses of the drugs. The tested drugs only slightly affected thymocyte maturation and did not alter Treg subset. Selegiline and clomipramine transiently stimulated IgG production in SRBC-immunized mice. Both selegiline and clomipramine administered in vivo modulated lymphocyte subsets. This immunomodulatory effect depended on the drug as well as duration of administration.

Role of Phosphodiesterase 7 (PDE7) in T Cell Activity. Effects of Selective PDE7 Inhibitors and Dual PDE4/7 Inhibitors on T Cell Functions

Phosphodiesterase 7 (PDE7), a cAMP-specific PDE family, insensitive to rolipram, is present in many immune cells, including T lymphocytes. Two genes of PDE7 have been identified: PDE7A and PDE7B with three or four splice variants, respectively. Both PDE7A and PDE7B are expressed in T cells, and the predominant splice variant in these cells is PDE7A1. PDE7 is one of several PDE families that terminates biological functions of cAMP—a major regulating intracellular factor. However, the precise role of PDE7 in T cell activation and function is still ambiguous. Some authors reported its crucial role in T cell activation, while according to other studies PDE7 activity was not pivotal to T cells. Several studies showed that inhibition of PDE7 by its selective or dual PDE4/7 inhibitors suppresses T cell activity, and consequently T-mediated immune response. Taken together, it seems quite likely that simultaneous inhibition of PDE4 and PDE7 by dual PDE4/7 inhibitors or a combination of selective PDE4 and PDE7 remains the most interesting therapeutic target for the treatment of some immune-related disorders, such as autoimmune diseases, or selected respiratory diseases. An interesting direction of future studies could also be using a combination of selective PDE7 and PDE3 inhibitors.

Phosphodiesterase Inhibitors for Alzheimer's Disease: A Systematic Review of Clinical Trials and Epidemiology with a Mechanistic Rationale

BACKGROUND

Preclinical studies, clinical trials, and reviews suggest increasing 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP) with phosphodiesterase inhibitors is disease-modifying in Alzheimer's disease (AD). cAMP/protein kinase A (PKA) and cGMP/protein kinase G (PKG) signaling are disrupted in AD. cAMP/PKA and cGMP/PKG activate cAMP response element binding protein (CREB). CREB binds mitochondrial and nuclear DNA, inducing synaptogenesis, memory, and neuronal survival gene (e.g., brain-derived neurotrophic factor) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α). cAMP/PKA and cGMP/PKG activate Sirtuin-1, which activates PGC1α. PGC1α induces mitochondrial biogenesis and antioxidant genes (e.g.,Nrf2) and represses BACE1. cAMP and cGMP inhibit BACE1-inducing NFκB and tau-phosphorylating GSK3β.

OBJECTIVE AND METHODS

We review efficacy-testing clinical trials, epidemiology, and meta-analyses to critically investigate whether phosphodiesteraseinhibitors prevent or treat AD.

RESULTS

Caffeine and cilostazol may lower AD risk. Denbufylline and sildenafil clinical trials are promising but preliminary and inconclusive. PF-04447943 and BI 409,306 are ineffective. Vinpocetine, cilostazol, and nicergoline trials are mixed. Deprenyl/selegiline trials show only short-term benefits. Broad-spectrum phosphodiesterase inhibitor propentofylline has been shown in five phase III trials to improve cognition, dementia severity, activities of daily living, and global assessment in mild-to-moderate AD patients on multiple scales, including the ADAS-Cogand the CIBIC-Plus in an 18-month phase III clinical trial. However, two books claimed based on a MedScape article an 18-month phase III trial failed, so propentofylline was discontinued. Now, propentofylline is used to treat canine cognitive dysfunction, which, like AD, involves age-associated wild-type Aβ deposition.

CONCLUSION

Phosphodiesterase inhibitors may prevent and treat AD.