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The light leptophilic gauge boson Zx predicted by the U(1)Lx models can contribute to the lepton flavor universality (LFU) parameter Rℓ/ℓ′P and the leptonic decays P→ℓνℓℓ′ℓ′¯ via the process P→ℓνℓZx with Zx decaying into a pair of neutrinos or charged leptons, where P denotes the charged pseudoscalar mesons π±, K±, D(s)± or B±. Using the corresponding experimental data, we obtain the constraints on different U(1)Lx models. The most strict constraints on the U(1)Lx models come from the decay K+→μ+νμe+e−.