Fig 2: An outline of the mechanisms that intercede linagliptin’s amelioration of cadmium-evoked testicular impairment. According to the current findings, the proposed mechanisms are: (A,A′) Curbing the inflammatory responses, including HMGB1/TLR4/NF-κB and NLRP3/caspase-1/IL-1β pathways in the testes of cadmium-intoxicated rats. (B) Stimulation of the autophagy response with activation of AMPK/mTOR pathway in the testes of cadmium-intoxicated rats. (C) Interference with the pro-apoptotic responses, including Bax downregulation, Bcl2 upregulation, and caspase 3 inhibition in the testes of cadmium-intoxicated rats. Of note, the beneficial outcomes of linagliptin are mainly due to DPP-4 inhibition, which has been linked to marked anti-inflammatory/immune-modulatory actions [21,22]. DPP-4 inhibition triggers several downstream targets, including the upregulated protein expression of SDF-1α, which prompts intensified testicular repair and regeneration [21,33]. Moreover, the beheld activation of autophagy may suppress the pro-inflammatory responses/NLRP3 inflammasome activation [12,20] and limit the proapoptotic responses [12,17,19] in the testes of cadmium-intoxicated rats. Activation is represented by solid arrows, whereas inhibition is depicted by blunt arrows. The question marks denote unknown mechanisms.

Fig 3: A summary of the molecular mechanisms that support the ameliorative impact of topiramate against cadmium-triggered testicular damage in rats. The observed improvement of testicular impairment and disrupted spermatogenesis were mediated by (A) Suppression of the NLRP3/caspase-1/IL-1β axis and curbing of NF-κB activation. (B) Inhibition of the pro-apoptotic events by lowering Bax protein expression and caspase-3 activity alongside upregulating the anti-apoptotic Bcl-2. (C) Stimulation of AMPK/mTOR-driven autophagy in the testicular tissues of rats. Notably, the observed autophagy stimulation is likely engaged in the suppression of NLRP3 inflammasome and associated pro-inflammatory events [7,15] and attenuation of the pro-apoptotic responses [13,15,21] in the testicular tissues of animals. Solid arrows demonstrate activation while blunt arrows depict inhibition.

Fig 4: Effect of cadmium and/or topiramate on AMPK/mTOR pathway in testes of rats. The co-treatment with topiramate activated the testicular pro-autophagy AMPK/mTOR pathway that was inhibited by cadmium administration. This was manifested by increased p-AMPK (Ser487)/total AMPK ratio [H (3, 20) = 5.71, p = 0.0054] (A) and lowered p-mTOR (Ser2448)/total mTOR ratio [H (3, 20) = 18.83, p < 0.0001] (B). Results are demonstrated as the mean ± standard error of the mean (SEM) for six rats in each experimental group. * p < 0.05, ** p < 0.01, **** p < 0.0001 signifies statistical significance versus the control group; # p < 0.05, ## p < 0.01 signifies statistical significance versus cadmium chloride-treated group. AMPK, AMP-activated protein kinase; mTOR, mammalian target of rapamycin. TPM, topiramate; Cd, cadmium chloride.

Fig 5: A concise outline for the molecular events underpinning dapagliflozin’s mitigating impact against the testicular damage triggered by Cd in rats. The testicular impairment and spermatogenesis derangement were improved with dapagliflozin by (A) Stimulation of the testicular SIRT1/Nrf2/HO-1 cytoprotective cascade, augmentation of antioxidants, and curtailment of oxidative events. (B) Activation of AMPK/mTOR pathway, as evidenced by the decrease in the p-mTOR/total mTOR ratio and the concurrent increase in the p-AMPK/total AMPK ratio. These events were associated with an enhancement of autophagy that was manifested by a lowering in SQSTM-1/p62 accumulation and an increase in Beclin 1. (C) Suppression of testicular apoptotic machinery, as evidenced by caspase-3 activity inhibition, Bax downregulation, and Bcl2 upregulation. Activation is illustrated by a solid arrow, while inhibition is illustrated by a blunt arrow.