4.2 The effect of SGLT-2i’s on angiogenesis
The effect of SGLT-2i’s on angiogenesis is still controversial. Previously, Zhou et al. demonstrated that EMPA promoted angiogenesis of CMECs in diabetic mice, thus improving myocardial microcirculatory perfusion and cardiac function (Zhou et al. , 2018). This study showed that EMPA preserved angiogenetic capacity of isolated CMECs through stabilization of F-actin. The effect of EMPA was nearly abolished when EMPA was combined with FCCP, a mitochondrial fission activator to promote mtROS generation (Zhou et al. , 2018). Excessive ROS arrested the cell cycle transition from G0/G1 to S and interrupted CMECs proliferation, which was re-established by EMPA and mdivi1 (an inhibitor for mitochondrial fission) (Zhou et al. , 2018). Taken together, prevention of mitochondrial fission and subsequent oxidative stress by EMPA was involved in its pro-angiogenetic effects on CMECs. Correspondingly, a recent study from Nikolaou et al. showed that chronic administration (6 weeks) of EMPA reduced myocardial infarct size after ischemia-reperfusion in non-diabetic mice, and this cardioprotective effect of EMPA could be partially explained by the improved CMECs survival (Nikolaou et al. , 2021). An in vitro study with human ECs exposed to hypoxia/reoxygenation stress also proved that EMPA increased cellular viability via activating signal transducer and activator of transcription 3 pathway (Nikolaou et al. , 2021). Using human aortic endothelial cells (HAECs), another study revealed that the autophagy is also involved in the pro-angiogenic effect of EMPA. The anti-leukemia agent ponatinib (PON) induces vasculotoxicity via mitochondrial damage, while the autophagy-mediated removal of injured mitochondria represents a cardiovascular protective mechanism against the toxic insult of PON. HAECs exposed to PON showed decreases in autophagy marker expression (LC3-I/II), tube formation as well cell viability, which were reverted by EMPA (Madonna et al. , 2021).
In contrast, Behnammanesh et al. reported a robust anti-proliferative and anti-migration effect of CANA in HUVECs and HAECs (Behnammaneshet al. , 2019). In clinically relevant dosages, CANA (5 µM and 10 µM) inhibited the proliferation of HUVECs by reducing the expression of cyclin A, as well as by reducing phosphorylation of the retinoblastoma protein, while EMPA and DAPA barely influenced the proliferative capacity of ECs in their physiological dosage (1-2 µM) (Behnammaneshet al. , 2019; Devineni et al. , 2016; Tomlinson et al. , 2017). The anti-proliferative effect of CANA could also be beneficial: CANA suppressed the increased proliferation and tubular formation of HUVECs during co-culture with Huh7 and HepG2 (hepatocyte-derived carcinoma cell lines), as well the enhanced production of angiogenic cytokines (e.g. IL-8), thus inhibiting the growth of liver cancer (Kaji et al. , 2018). More recently, another study showed that CANA had a dosage-dependent inhibitory effect on the VEGF-A expression and angiogenesis of HUVECs co-cultured with HepG2 cell line (Luo et al. , 2021).
Several factors might explain the observed opposite effects of CANA and EMPA on angiogenesis. Firstly, these studies were performed with ECs under different “stress” conditions. Cells in the EMPA studies were activated with pathological stimuli (diabetes, hypoxia/reoxygenation and PON) that impaired their cellular viability and angiogenesis capacity (Zhou et al. , 2018; Nikolaou et al. , 2021; Madonnaet al. , 2021), while the anti-angiogenic effect of CANA was reported in “non-stimulated” cells or ECs co-cultured with cancer cells (Behnammanesh et al. , 2019; Kaji et al. , 2018; Luoet al. , 2021). The potential involvement of SGLT-1 is also of importance, considering that anti-proliferating effect seems to be compound-specific for CANA (Behnammanesh et al. , 2019). Compared with EMPA and DAPA, CANA is relatively less selective for SGLT-2 over SGLT-1, and the latter is highly expressed in human ECs (Ohgaki et al. , 2016). However, in a HepG2 and ECs co-culture model, CANA reduced glucose uptake and growth of liver cancer cells via inhibiting SGLT-2 rather than SGLT-1 (Kaji et al. , 2018). Moreover, the effect of SGLT-2i’s on ECs proliferation and migration might vary among different organs/tissues, and more research is required to explain these existing differences.