Placenta-anchored tadalafil liposomes rescues intrauterine growth restriction through continuous placental blood perfusion improvement

Physiological or pathological hypoperfusion of the placenta is one of the main causes of intrauterine growth restriction (IUGR) which poses a significant risk to the health of the fetus and newborn. Tadalafil, a 5-type phosphodiesterase inhibitor, has previously been found to improve the symptoms of IUGR in various clinical studies. Unfortunately, its clinical utility is hindered by its limited water solubility, rapid metabolism, and lack of specific distribution in target tissues rendering tadalafil unable to maintain long-term placental perfusion. In this study, iRGD-modified tadalafil-loaded liposomes (iRGD-lipo@Tad) featuring a size of approximately 480 nm were designed to rectify the shortcomings of tadalafil. The prepared iRGD-lipo@Tad exhibited superior stability, sustained drug release capacity, and low cytotoxicity. The fluorescence study, tissue slice study, and drug biodistribution study together demonstrated the placenta-anchored ability of iRGD-modified liposomes. This was achieved by a dual approach consisting of the iRGD-mediated placenta-targeting effect and special particle size-mediated placenta resident effect. The pharmacokinetic study revealed a significant improvement in the in vivo process of tadalafil encapsulated by the iRGD-modified liposomes. In comparison to the tadalafil solution, the peak plasma concentration of iRGD-lipo@Tad was significantly increased, and the area under the curve was increased by about 7.88 times. In the pharmacodynamic study, iRGD-lipo@Tad achieved a continuous and efficient improvement of placental blood perfusion. This was achieved by decreasing the ratio of plasma soluble fms-like tyrosine kinase to placental growth factor and increasing the levels of cyclic guanosine monophosphate and nitric oxide. Consequently, iRGD-lipo@Tad resulted in a significant increase in embryo weight and a reduction in the miscarriage rate of N-Nitro-L-arginine methyl ester-induced IUGR pregnant mice without detectable toxicity. In summary, the nanotechnology-assisted therapy strategy presented here not only overcomes the limitations of tadalafil in the clinical treatment of IUGR but also offers new avenues to address the treatment of other placenta-originated diseases.

The effects of prophylactic tadalafil use on VEGF expression in the rabbit model of steroid-induced femoral head avascular necrosis

OBJECTIVE

The purpose of this study was to examine the effect of prophylactic tadalafil use on a steroid-induced femoral head avascular necrosis model in terms of microscopic, imaging, and molecular biological changes.

METHODS

Twenty-four New Zealand rabbits were divided into 3 equal groups. Eight rabbits were designated as the control group and did not receive treatment. Rabbits in group 1 (G1) received 0.1 mg/kg Escherichia coli lipopolysaccharide (LPS) intravenously and 40 mg/ kg methylprednisolone sodium succinate (MP) was administered intramuscularly for 3 days consecutively. Rabbits in group 2 (G2) were given 5 mg/kg tadalafil orally for 10 consecutive days. Starting on the eighth day, 0.1 mg/kg LPS was given, and following this 40 mg/kg MP injections were administered for 3 days. All animals were sacrificed 3 weeks after the final MP injection. Magnetic resonance imaging was performed, and bilateral femora were harvested. Half of the femoral head was stored for Vascular Endothelial Growth Factor (VEGF) examination with Western blot analysis. The other half was examined microscopically for the presence of osteonecrosis.

RESULTS

In G1, 15 out of 16 hips (93%) of the 8 rabbits had osteonecrosis compared to 8 out of 12 hips (67%) of 6 rabbits in G2 (P > .05). The VEGF expression in G2 was significantly higher than in the control group and G1 (P < .05 and P < .001, respectively). There was no significant difference in VEGF expression between the control group and G1 (P > .05).

CONCLUSION

This study has shown us that femoral head osteonecrosis can be reliably induced with LPS and corticosteroid, as described in the literature. Prophylactic tadalafil use did not decrease the occurrence of osteonecrosis significantly. However, it significantly increased VEGF expression in the femoral head independent of the effects of steroids and LPS.

Inhibition of phosphodiesterase 5A by tadalafil improves SIRT1 expression and activity in insulin-resistant podocytes

A decrease in intracellular levels of 3',5'-cyclic guanosine monophosphate (cGMP) has been implicated in the progression of diabetic nephropathy. Hyperglycemia significantly inhibits cGMP-dependent pathway activity in the kidney, leading to glomerular damage and proteinuria. The enhancement of activity of this pathway that is associated with an elevation of cGMP levels may be achieved by inhibition of the cGMP specific phosphodiesterase 5A (PDE5A) using selective inhibitors, such as tadalafil. Hyperglycemia decreased the insulin responsiveness of podocytes and impaired podocyte function. These effects were associated with lower protein amounts and activity of the protein deacetylase sirtuin 1 (SIRT1) and a decrease in the phosphorylation of adenosine monophosphate-dependent protein kinase (AMPK). We found that PDE5A protein levels increased in hyperglycemia, and PDE5A downregulation improved the insulin responsiveness of podocytes with reestablished SIRT1 expression and activity. PDE5A inhibitors potentiate nitric oxide (NO)/cGMP signaling, and NO modulates the activity and expression of SIRT1. Therefore, we investigated the effects of tadalafil on SIRT1 and AMPK in the context of improving the insulin sensitivity in podocytes and podocyte function in hyperglycemia. Our study revealed that tadalafil restored SIRT1 expression and activity and activated AMPK by increasing its phosphorylation. Tadalafil also restored stimulating effect of insulin on glucose transport in podocytes with high glucose-induced insulin resistance. Additionally, tadalafil improved the function of podocytes that were exposed to high glucose concentrations. Our results display novel mechanisms involved in the pathogenesis of glomerulopathies in diabetes, which may contribute to the development of more effective treatment strategies for diabetic nephropathy.

Tadalafil Reverses the Effect of Three-Dimensional Cell Culture System on Stem Cell Features in A549 and SK-MES-1

Background: Non-small cell lung cancer is the most common type of lung cancer and is a frequent cause of death. In our research, A549 and SK-MES-1 were used to assess the effect of three-dimensional (3D) culture compared to that of two-dimensional (2D) monolayers in cell proliferation, migration, and invasion, response to chemotherapy, as well as the expression of epithelial to mesenchymal transition (EMT) and cancer stem cell (CSC)-related markers. As tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor with the potential to target CSC maintenance in multiple cancer cell lines, we assessed its function in 3D culture and detected the downstream pathway genes. Methods: We compared the viability and proliferation capacity of A549 and SK-MES-1 cells in 2D and 3D culture by cell counting kit (CCK)-8, foci formation, and Live/Dead double stain (Operetta CLS High content screening). Migration, invasion, and other functions were also assessed. To elucidate the underlying mechanisms, the expression of EMT and CSC markers was analyzed by quantitative real-time PCR (qPCR) and Western blot. Results: A549 and SK-MES-1 cells formed spheroids heterogeneous in shape and size. In our 3D spheroid systems, cells went through EMT, and were also capacitated with higher stemness and chemoresistance. Combination use of tadalafil and cisplatin showed higher chemotherapy efficiency in the 3D model, compared to that of the 2D cell culture. Conclusion: Our research aims at the notable differences between these two cellular systems in terms of cell functions, EMT, and stemness-associated gene expression and chemo-response. We showed that a commonly used drug, tadalafil, showed more pronounced inhibitory effects when cells were cultured in the 3D model. Since the 3D culture system could imitate the in vivo behavior of cancer cells within the tumor, we advocate that this system is superior to traditional 2D culture and should be used in the investigation of new therapeutic compounds.

Cyclic guanosine monophosphate modulates accumulation of phosphodiesterase 5 inhibitors in human platelets

Sildenafil and tadalafil are widely-used phosphodiesterase 5 (PDE5) inhibitors for which no clear dose-response relationship could be established. Using isolated and/or recombinant PDE5, it has been demonstrated that cGMP can increase the affinity of this enzyme for sildenafil and tadalafil. We thus hypothesized that in cells expressing the nitric oxide - soluble guanylyl cyclase - cyclic guanosine monophosphate - PDE5 (NO-sGC-cGMP-PDE5) pathway such as platelets, the presence of NO increases the intracellular cGMP content and thus promotes the intracellular accumulation of sildenafil or tadalafil. As a cell model, isolated and washed human platelets were used. Platelet suspensions were incubated with sildenafil or tadalafil at different concentrations and for various time intervals with or without an NO donor to increase intraplatelet cGMP concentrations. Intracellular sildenafil or tadalafil was quantified by ultra-performance liquid chromatography tandem mass spectrometry and intracellular cGMP by an enzyme-linked immunosorbent assay. Sildenafil accumulated in platelets with an up to 4-fold higher accumulation when platelets were pretreated with an NO donor (p < .0001). Accumulation of tadalafil in platelets was even higher, whereas the increase was 2-fold when an NO donor was present (p < .001). This accumulation was time-dependent and happened concomitantly with a rise in intracellular cGMP. Our data demonstrate that intracellular cGMP increases intracellular PDE5 inhibitor concentrations most likely by raising the affinity of these compounds for PDE5. These findings suggest that PDE5 inhibitor action in humans is critically influenced by modulators of the activity of the NO pathway.